Journal articles: 'Insects - Metamorphosis'

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Belles, Xavier. "The innovation of the final moult and the origin of insect metamorphosis." Philosophical Transactions of the Royal Society B: Biological Sciences 374, no. 1783 (August 26, 2019): 20180415. http://dx.doi.org/10.1098/rstb.2018.0415.

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The three modes of insect postembryonic development are ametaboly, hemimetaboly and holometaboly, the latter being considered the only significant metamorphosis mode. However, the emergence of hemimetaboly, with the genuine innovation of the final moult, represents the origin of insect metamorphosis and a necessary step in the evolution of holometaboly. Hemimetaboly derives from ametaboly and might have appeared as a consequence of wing emergence in Pterygota, in the early Devonian. In extant insects, the final moult is mainly achieved through the degeneration of the prothoracic gland (PG), after the formation of the winged and reproductively competent adult stage. Metamorphosis, including the formation of the mature wings and the degeneration of the PG, is regulated by the MEKRE93 pathway, through which juvenile hormone precludes the adult morphogenesis by repressing the expression of transcription factor E93, which triggers this change. The MEKRE93 pathway appears conserved in extant metamorphosing insects, which suggest that this pathway was operative in the Pterygota last common ancestor. We propose that the final moult, and the consequent hemimetabolan metamorphosis, is a monophyletic innovation and that the role of E93 as a promoter of wing formation and the degeneration of the PG was mechanistically crucial for their emergence. This article is part of the theme issue ‘The evolution of complete metamorphosis’.

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Rolff, Jens, Paul R. Johnston, and Stuart Reynolds. "Complete metamorphosis of insects." Philosophical Transactions of the Royal Society B: Biological Sciences 374, no. 1783 (August 26, 2019): 20190063. http://dx.doi.org/10.1098/rstb.2019.0063.

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The majority of described hexapod species are holometabolous insects, undergoing an extreme form of metamorphosis with an intercalated pupal stage between the larva and adult, in which organs and tissues are extensively remodelled and in some cases completely rebuilt. Here, we review how and why this developmental strategy has evolved. While there are many theories explaining the evolution of metamorphosis, many of which fit under the hypothesis of decoupling of life stages, there are few clear adaptive hypotheses on why complete metamorphosis evolved. We propose that the main adaptive benefit of complete metamorphosis is decoupling between growth and differentiation. This facilitates the exploitation of ephemeral resources and enhances the probability of the metamorphic transition escaping developmental size thresholds. The evolution of complete metamorphosis comes at the cost of exposure to predators, parasites and pathogens during pupal life and requires specific adaptations of the immune system at this time. Moreover, metamorphosis poses a challenge for the maintenance of symbionts and the gut microbiota, although it may also offer the benefit of allowing an extensive change in microbiota between the larval and adult stages. The regulation of metamorphosis by two main players, ecdysone and juvenile hormone, and the related signalling cascades are now relatively well understood. The mechanics of metamorphosis have recently been studied in detail because of the advent of micro-CT and research into the role of cell death in remodelling tissues and organs. We support the argument that the adult stage must necessarily have preceded the larval form of the insect. We do not resolve the still contentious question of whether the larva of insects in general originated through the modification of existing preadult forms or through heterochrony as a modified embryonic stage (pronymph), nor whether the holometabolous pupa arose as a modified hemimetabolous final stage larva. This article is part of the theme issue ‘The evolution of complete metamorphosis’.

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Ogilvie, Brian W. "Attending to insects: Francis Willughby and John Ray." Notes and Records of the Royal Society 66, no. 4 (October 10, 2012): 357–72. http://dx.doi.org/10.1098/rsnr.2012.0051.

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Francis Willughby and John Ray were at the forefront of the natural history of insects in the second half of the seventeenth century. Willughby in particular had a deep interest in insects' metamorphosis, behaviour and diversity, an interest that he passed on to his friend and mentor Ray. By examining Willughby's contributions to John Wilkins's Essay towards a Real Character (1668) and Ray's Methodus insectorum (1705) and Historia insectorum (1710), which contained substantial material from Willughby's manuscript history of insects, one may reconstruct how the two naturalists studied insects, their innovative use of metamorphosis in insect classification, and the sheer diversity of insect forms that they described on the basis of their own collections and those of London and Oxford virtuosi. Imperfect as it was, Historia insectorum was recognized by contemporaries as a significant contribution to the emerging field of entomology.

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Nicholson, David B., Andrew J. Ross, and Peter J. Mayhew. "Fossil evidence for key innovations in the evolution of insect diversity." Proceedings of the Royal Society B: Biological Sciences 281, no. 1793 (October 22, 2014): 20141823. http://dx.doi.org/10.1098/rspb.2014.1823.

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Explaining the taxonomic richness of the insects, comprising over half of all described species, is a major challenge in evolutionary biology. Previously, several evolutionary novelties (key innovations) have been posited to contribute to that richness, including the insect bauplan , wings, wing folding and complete metamorphosis, but evidence over their relative importance and modes of action is sparse and equivocal. Here, a new dataset on the first and last occurrences of fossil hexapod (insects and close relatives) families is used to show that basal families of winged insects (Palaeoptera, e.g. dragonflies) show higher origination and extinction rates in the fossil record than basal wingless groups (Apterygota, e.g. silverfish). Origination and extinction rates were maintained at levels similar to Palaeoptera in the more derived Polyneoptera (e.g. cockroaches) and Paraneoptera (e.g. true bugs), but extinction rates subsequently reduced in the very rich group of insects with complete metamorphosis (Holometabola, e.g. beetles). Holometabola show evidence of a recent slow-down in their high net diversification rate, whereas other winged taxa continue to diversify at constant but low rates. These data suggest that wings and complete metamorphosis have had the most effect on family-level insect macroevolution, and point to specific mechanisms by which they have influenced insect diversity through time.

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Hammer, Tobin J., and Nancy A. Moran. "Links between metamorphosis and symbiosis in holometabolous insects." Philosophical Transactions of the Royal Society B: Biological Sciences 374, no. 1783 (August 26, 2019): 20190068. http://dx.doi.org/10.1098/rstb.2019.0068.

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Many animals depend on microbial symbionts to provide nutrition, defence or other services. Holometabolous insects, as well as other animals that undergo metamorphosis, face unique constraints on symbiont maintenance. Microbes present in larvae encounter a radical transformation of their habitat and may also need to withstand chemical and immunological challenges. Metamorphosis also provides an opportunity, in that symbiotic associations can be decoupled over development. For example, some holometabolous insects maintain the same symbiont as larvae and adults, but house it in different tissues; in other species, larvae and adults may harbour entirely different types or numbers of microbes, in accordance with shifts in host diet or habitat. Such flexibility may provide an advantage over hemimetabolous insects, in which selection on adult-stage microbial associations may be constrained by its negative effects on immature stages, and vice versa. Additionally, metamorphosis itself can be directly influenced by symbionts. Across disparate insect taxa, microbes protect hosts from pathogen infection, supply nutrients essential for rebuilding the adult body and provide cues regulating pupation. However, microbial associations remain completely unstudied for many families and even orders of Holometabola, and future research will undoubtedly reveal more links between metamorphosis and microbiota, two widespread features of animal life. This article is part of the theme issue ‘The evolution of complete metamorphosis’.

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Reynolds, Stuart. "Cooking up the perfect insect: Aristotle's transformational idea about the complete metamorphosis of insects." Philosophical Transactions of the Royal Society B: Biological Sciences 374, no. 1783 (August 26, 2019): 20190074. http://dx.doi.org/10.1098/rstb.2019.0074.

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Aristotle made important contributions to the study of developmental biology, including the complete metamorphosis of insects. One concept in particular, that of the perfect or complete state, underlies Aristotle's ideas about metamorphosis, the necessity of fertilization for embryonic development, and whether morphogenesis involves an autonomous process of self-assembly. Importantly, the philosopher erroneously views metamorphosis as a necessary developmental response to lack of previous fertilization of the female parent, a view that is intimately connected with his readiness to accept the idea of the spontaneous generation of life. Aristotle's work underpins that of the major seventeenth century students of metamorphosis, Harvey, Redi, Malpighi and Swammerdam, all of whom make frequent reference to Aristotle in their writings. Although both Aristotle and Harvey are often credited with inspiring the later prolonged debate between proponents of epigenesis and preformation, neither actually held firm views on the subject. Aristotle's idea of the perfect stage also underlies his proposal that the eggs of holometabolous insects hatch ‘before their time’, an idea that is the direct precursor of the much later proposals by Lubbock and Berlese that the larval stages of holometabolous insects are due to the ‘premature hatching’ from the egg of an imperfect embryonic stage. This article is part of the theme issue ‘The evolution of complete metamorphosis’.

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Tariq, K., M. Noor, M. Hori, A. Ali, A. Hussain, W. Peng, C. J. Chang, and H. Zhang. "Blue light-induced immunosuppression in Bactrocera dorsalis adults, as a carryover effect of larval exposure." Bulletin of Entomological Research 107, no. 6 (May 9, 2017): 734–41. http://dx.doi.org/10.1017/s0007485317000438.

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AbstractDetrimental effects of ultraviolet (UV) light on living organisms are well understood, little is known about the effects of blue light irradiation. Although a recent study revealed that blue light caused more harmful effects on insects than UV light and blue light irradiation killed insect pests of various orders including Diptera, the effects of blue light on physiology of insects are still largely unknown. Here we studied the effects of blue light irradiation on cuticular melanin in larval and the immune response in adult stage of Bactrocera dorsalis. We also evaluated the effects of blue light exposure in larval stage on various age and mass at metamorphosis and the mediatory role of cuticular melanin in carryover effects of larval stressors across metamorphosis. We found that larvae exposed to blue light decreased melanin contents in their exoskeleton with smaller mass and delayed metamorphosis than insects reared without blue light exposure. Across metamorphosis, lower melanotic encapsulation response and higher susceptibility to Beauveria bassiana was detected in adults that had been exposed to blue light at their larval stage, thereby constituting the first evidence that blue light impaired adult immune function in B. dorsalis as a carryover effect of larval exposure.

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Liu, Suning, Kang Li, Yue Gao, Xi Liu, Weiting Chen, Wei Ge, Qili Feng, Subba R. Palli, and Sheng Li. "Antagonistic actions of juvenile hormone and 20-hydroxyecdysone within the ring gland determine developmental transitions in Drosophila." Proceedings of the National Academy of Sciences 115, no. 1 (December 18, 2017): 139–44. http://dx.doi.org/10.1073/pnas.1716897115.

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In both vertebrates and insects, developmental transition from the juvenile stage to adulthood is regulated by steroid hormones. In insects, the steroid hormone, 20-hydroxyecdysone (20E), elicits metamorphosis, thus promoting this transition, while the sesquiterpenoid juvenile hormone (JH) antagonizes 20E signaling to prevent precocious metamorphosis during the larval stages. However, not much is known about the mechanisms involved in cross-talk between these two hormones. In this study, we discovered that in the ring gland (RG) of Drosophila larvae, JH and 20E control each other’s biosynthesis. JH induces expression of a Krüppel-like transcription factor gene Kr-h1 in the prothoracic gland (PG), a portion of the RG that produces the 20E precursor ecdysone. By reducing both steroidogenesis autoregulation and PG size, high levels of Kr-h1 in the PG inhibit ecdysteriod biosynthesis, thus maintaining juvenile status. JH biosynthesis is prevented by 20E in the corpus allatum, the other portion of the RG that produces JH, to ensure the occurrence of metamorphosis. Hence, antagonistic actions of JH and 20E within the RG determine developmental transitions in Drosophila. Our study proposes a mechanism of cross-talk between the two major hormones in the regulation of insect metamorphosis.

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Gomez-Orte, E., and X. Belles. "MicroRNA-dependent metamorphosis in hemimetabolan insects." Proceedings of the National Academy of Sciences 106, no. 51 (December 4, 2009): 21678–82. http://dx.doi.org/10.1073/pnas.0907391106.

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KUBOTA, Kohei. "Metamorphosis and Appendicular Development of Insects." Journal of the Society of Mechanical Engineers 113, no. 1099 (2010): 436–37. http://dx.doi.org/10.1299/jsmemag.113.1099_436.

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Johnston, Paul R., Véronique Paris, and Jens Rolff. "Immune gene regulation in the gut during metamorphosis in a holo- versus a hemimetabolous insect." Philosophical Transactions of the Royal Society B: Biological Sciences 374, no. 1783 (August 26, 2019): 20190073. http://dx.doi.org/10.1098/rstb.2019.0073.

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During metamorphosis, holometabolous insects completely replace the larval gut and must control the microbiota to avoid septicaemia. Rapid induction of bactericidal activity in the insect gut at the onset of pupation has been described in numerous orders of the Holometabola and is best-studied in the Lepidoptera where it is under control of the 20-hydroxyecdysone (20E) moulting pathway. Here, using RNAseq, we compare the expression of immune effector genes in the gut during metamorphosis in a holometabolous ( Galleria mellonella ) and a hemimetabolous insect ( Gryllus bimaculatus ). We find that in G. mellonella , the expression of numerous immune effectors and the transcription factor GmEts are upregulated, with peak expression of three antimicrobial peptides (AMPs) and a lysozyme coinciding with delamination of the larval gut. By contrast, no such upregulation was detectable in the hemimetabolous Gr. bimaculatus . These findings support the idea that the upregulation of immune effectors at the onset of complete metamorphosis is an adaptive response, which controls the microbiota during gut replacement. This article is part of the theme issue ‘The evolution of complete metamorphosis’.

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Tettamanti, Gianluca, and Morena Casartelli. "Cell death during complete metamorphosis." Philosophical Transactions of the Royal Society B: Biological Sciences 374, no. 1783 (August 26, 2019): 20190065. http://dx.doi.org/10.1098/rstb.2019.0065.

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In insects that undergo complete metamorphosis, cell death is essential for reshaping or removing larval tissues and organs, thus contributing to formation of the adult's body structure. In the last few decades, the study of metamorphosis in Lepidoptera and Diptera has provided broad information on the tissue remodelling processes that occur during larva–pupa–adult transition and made it possible to unravel the underlying regulatory pathways. This review summarizes recent knowledge on cell death mechanisms in Lepidoptera and other holometabolous insects, highlighting similarities and differences with Drosophila melanogaster , and discusses the role of apoptosis and autophagy in this developmental setting. This article is part of the theme issue ‘The evolution of complete metamorphosis'.

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Reynolds, Stuart E. "Mayfly metamorphosis: Adult winged insects that molt." Proceedings of the National Academy of Sciences 118, no. 38 (September 14, 2021): e2114128118. http://dx.doi.org/10.1073/pnas.2114128118.

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Bellés, Xavier. "The metamorphosis of insects and their regulation." Comptes Rendus Biologies 342, no. 7-8 (September 2019): 254–56. http://dx.doi.org/10.1016/j.crvi.2019.09.009.

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Jindra, Marek. "Where did the pupa come from? The timing of juvenile hormone signalling supports homology between stages of hemimetabolous and holometabolous insects." Philosophical Transactions of the Royal Society B: Biological Sciences 374, no. 1783 (August 26, 2019): 20190064. http://dx.doi.org/10.1098/rstb.2019.0064.

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Insect metamorphosis boasts spectacular cases of postembryonic development when juveniles undergo massive morphogenesis before attaining the adult form and function; in moths or flies the larvae do not even remotely resemble their adult parents. A selective advantage of complete metamorphosis (holometaboly) is that within one species the two forms with different lifestyles can exploit diverse habitats. It was the environmental adaptation and specialization of larvae, primarily the delay and internalization of wing development, that eventually required an intermediate stage that we call a pupa. It is a long-held and parsimonious hypothesis that the holometabolous pupa evolved through modification of a final juvenile stage of an ancestor developing through incomplete metamorphosis (hemimetaboly). Alternative hypotheses see the pupa as an equivalent of all hemimetabolous moulting cycles (instars) collapsed into one, and consider any preceding holometabolous larval instars free-living embryos stalled in development. Discoveries on juvenile hormone signalling that controls metamorphosis grant new support to the former hypothesis deriving the pupa from a final pre-adult stage. The timing of expression of genes that repress and promote adult development downstream of hormonal signals supports homology between postembryonic stages of hemimetabolous and holometabolous insects. This article is part of the theme issue ‘The evolution of complete metamorphosis’.

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Kamsoi, Orathai, and Xavier Belles. "E93-depleted adult insects preserve the prothoracic gland and molt again." Development 147, no. 22 (October 19, 2020): dev190066. http://dx.doi.org/10.1242/dev.190066.

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ABSTRACTInsect metamorphosis originated around the middle Devonian, associated with the innovation of the final molt; this occurs after histolysis of the prothoracic gland (PG; which produces the molting hormone) in the first days of adulthood. We previously hypothesized that transcription factor E93 is crucial in the emergence of metamorphosis, because it triggers metamorphosis in extant insects. This work on the cockroach Blattella germanica reveals that E93 also plays a crucial role in the histolysis of PG, which fits the above hypothesis. Previous studies have shown that the transcription factor FTZ-F1 is essential for PG histolysis. We have found that FTZ-F1 depletion towards the end of the final nymphal instar downregulates the expression of E93, whereas E93-depleted nymphs molt to adults that retain a functional PG. Interestingly, these adults are able to molt again, which is exceptional in insects. The study of insects able to molt again in the adult stage may reveal clues about how nymphal epidermal cells definitively become adult cells, and whether it is possible to reverse this process.

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Montagna, Matteo, K. Jun Tong, Giulia Magoga, Laura Strada, Andrea Tintori, Simon Y. W. Ho, and Nathan Lo. "Recalibration of the insect evolutionary time scale using Monte San Giorgio fossils suggests survival of key lineages through the End-Permian Extinction." Proceedings of the Royal Society B: Biological Sciences 286, no. 1912 (October 9, 2019): 20191854. http://dx.doi.org/10.1098/rspb.2019.1854.

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Insects are a highly diverse group of organisms and constitute more than half of all known animal species. They have evolved an extraordinary range of traits, from flight and complete metamorphosis to complex polyphenisms and advanced eusociality. Although the rich insect fossil record has helped to chart the appearance of many phenotypic innovations, data are scarce for a number of key periods. One such period is that following the End-Permian Extinction, recognized as the most catastrophic of all extinction events. We recently discovered several 240-million-year-old insect fossils in the Mount San Giorgio Lagerstätte (Switzerland–Italy) that are remarkable for their state of preservation (including internal organs and soft tissues), and because they extend the records of their respective taxa by up to 200 million years. By using these fossils as calibrations in a phylogenomic dating analysis, we present a revised time scale for insect evolution. Our date estimates for several major lineages, including the hyperdiverse crown groups of Lepidoptera, Hemiptera: Heteroptera and Diptera, are substantially older than their currently accepted post-Permian origins. We found that major evolutionary innovations, including flight and metamorphosis, appeared considerably earlier than previously thought. These results have numerous implications for understanding the evolution of insects and their resilience in the face of extreme events such as the End-Permian Extinction.

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Truman, James W. "Steroid Receptors and Nervous System Metamorphosis in Insects." Developmental Neuroscience 18, no. 1-2 (1996): 87–101. http://dx.doi.org/10.1159/000111398.

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Schmidt-Loske, Katharina. "Historical sketch Maria Sibylla Merian - Metamorphosis of insects." Deutsche Entomologische Zeitschrift 57, no. 1 (May 25, 2010): 5–10. http://dx.doi.org/10.1002/mmnd.201000001.

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Kamsoi, Orathai, Alba Ventos-Alfonso, Fernando Casares, Isabel Almudi, and Xavier Belles. "Regulation of metamorphosis in neopteran insects is conserved in the paleopteran Cloeon dipterum (Ephemeroptera)." Proceedings of the National Academy of Sciences 118, no. 34 (August 20, 2021): e2105272118. http://dx.doi.org/10.1073/pnas.2105272118.

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In the Paleozoic era, more than 400 Ma, a number of insect groups continued molting after forming functional wings. Today, however, flying insects stop molting after metamorphosis when they become fully winged. The only exception is the mayflies (Paleoptera, Ephemeroptera), which molt in the subimago, a flying stage between the nymph and the adult. However, the identity and homology of the subimago still is underexplored. Debate remains regarding whether this stage represents a modified nymph, an adult, or a pupa like that of butterflies. Another relevant question is why mayflies have the subimago stage despite the risk of molting fragile membranous wings. These questions have intrigued numerous authors, but nonetheless, clear answers have not yet been found. By combining morphological studies, hormonal treatments, and molecular analysis in the mayfly Cloeon dipterum, we found answers to these old questions. We observed that treatment with a juvenile hormone analog in the last nymphal instar stimulated the expression of the Kr-h1 gene and reduced that of E93, which suppress and trigger metamorphosis, respectively. The regulation of metamorphosis thus follows the MEKRE93 pathway, as in neopteran insects. Moreover, the treatment prevented the formation of the subimago. These findings suggest that the subimago must be considered an instar of the adult mayfly. We also observed that the forelegs dramatically grow between the last nymphal instar, the subimago, and the adult. This necessary growth spread over the last two stages could explain, at least in part, the adaptive sense of the subimago.

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Johnson, Kevin P., Christopher H. Dietrich, Frank Friedrich, Rolf G. Beutel, Benjamin Wipfler, Ralph S. Peters, Julie M. Allen, et al. "Phylogenomics and the evolution of hemipteroid insects." Proceedings of the National Academy of Sciences 115, no. 50 (November 26, 2018): 12775–80. http://dx.doi.org/10.1073/pnas.1815820115.

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Hemipteroid insects (Paraneoptera), with over 10% of all known insect diversity, are a major component of terrestrial and aquatic ecosystems. Previous phylogenetic analyses have not consistently resolved the relationships among major hemipteroid lineages. We provide maximum likelihood-based phylogenomic analyses of a taxonomically comprehensive dataset comprising sequences of 2,395 single-copy, protein-coding genes for 193 samples of hemipteroid insects and outgroups. These analyses yield a well-supported phylogeny for hemipteroid insects. Monophyly of each of the three hemipteroid orders (Psocodea, Thysanoptera, and Hemiptera) is strongly supported, as are most relationships among suborders and families. Thysanoptera (thrips) is strongly supported as sister to Hemiptera. However, as in a recent large-scale analysis sampling all insect orders, trees from our data matrices support Psocodea (bark lice and parasitic lice) as the sister group to the holometabolous insects (those with complete metamorphosis). In contrast, four-cluster likelihood mapping of these data does not support this result. A molecular dating analysis using 23 fossil calibration points suggests hemipteroid insects began diversifying before the Carboniferous, over 365 million years ago. We also explore implications for understanding the timing of diversification, the evolution of morphological traits, and the evolution of mitochondrial genome organization. These results provide a phylogenetic framework for future studies of the group.

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Ishimaru, Yoshiyasu, Sayuri Tomonari, Yuji Matsuoka, Takahito Watanabe, Katsuyuki Miyawaki, Tetsuya Bando, Kenji Tomioka, Hideyo Ohuchi, Sumihare Noji, and Taro Mito. "TGF-β signaling in insects regulates metamorphosis via juvenile hormone biosynthesis." Proceedings of the National Academy of Sciences 113, no. 20 (May 2, 2016): 5634–39. http://dx.doi.org/10.1073/pnas.1600612113.

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Although butterflies undergo a dramatic morphological transformation from larva to adult via a pupal stage (holometamorphosis), crickets undergo a metamorphosis from nymph to adult without formation of a pupa (hemimetamorphosis). Despite these differences, both processes are regulated by common mechanisms that involve 20-hydroxyecdysone (20E) and juvenile hormone (JH). JH regulates many aspects of insect physiology, such as development, reproduction, diapause, and metamorphosis. Consequently, strict regulation of JH levels is crucial throughout an insect’s life cycle. However, it remains unclear how JH synthesis is regulated. Here, we report that in the corpora allata of the cricket, Gryllus bimaculatus, Myoglianin (Gb’Myo), a homolog of Drosophila Myoglianin/vertebrate GDF8/11, is involved in the down-regulation of JH production by suppressing the expression of a gene encoding JH acid O-methyltransferase, Gb’jhamt. In contrast, JH production is up-regulated by Decapentaplegic (Gb’Dpp) and Glass-bottom boat/60A (Gb’Gbb) signaling that occurs as part of the transcriptional activation of Gb’jhamt. Gb’Myo defines the nature of each developmental transition by regulating JH titer and the interactions between JH and 20E. When Gb’myo expression is suppressed, the activation of Gb’jhamt expression and secretion of 20E induce molting, thereby leading to the next instar before the last nymphal instar. Conversely, high Gb’myo expression induces metamorphosis during the last nymphal instar through the cessation of JH synthesis. Gb’myo also regulates final insect size. Because Myo/GDF8/11 and Dpp/bone morphogenetic protein (BMP)2/4-Gbb/BMP5–8 are conserved in both invertebrates and vertebrates, the present findings provide common regulatory mechanisms for endocrine control of animal development.

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Rowland, John M., Ian J. Rowland, and Walter G. Goodman. "Teaching Principles of Endocrinology Using the Tobacco Hornworm." American Biology Teacher 79, no. 7 (September 1, 2017): 584–89. http://dx.doi.org/10.1525/abt.2017.79.7.584.

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Insects provide an excellent model for examining concepts in endocrinology in the classroom. They are relatively inexpensive to rear, short-lived, and free from animal welfare regulations. Using the tobacco hornworm (Manduca sexta) as a model, we have developed a simple laboratory experiment to demonstrate the role of hormones in development. In this experiment, students will use a readily available agonist to disrupt insect development, preventing metamorphosis. This exercise fits well into the AP lab curriculum and the NGSS LSB.1 objectives.

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Gallon, Marília Elias, and Leonardo Gobbo-Neto. "Plant Metabolites Involved in the Differential Development of a Heliantheae-Specialist Insect." Metabolites 11, no. 3 (February 25, 2021): 134. http://dx.doi.org/10.3390/metabo11030134.

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Balanced nutritional intake is essential to ensure that insects undergo adequate larval development and metamorphosis. Integrative multidisciplinary approaches have contributed valuable insights regarding the ecological and evolutionary outcomes of plant–insect interactions. To address the plant metabolites involved in the larval development of a specialist insect, we investigated the development of Chlosyne lacinia caterpillars fed on Heliantheae species (Tithonia diversifolia, Tridax procumbens and Aldama robusta) leaves and determined the chemical profile of plants and insects using a metabolomic approach. By means of LC-MS and GC-MS combined analyses, 51 metabolites were putatively identified in Heliantheae species and C. lacinia caterpillars and frass; these metabolites included flavonoids, sesquiterpene lactones, monoterpenoids, sesquiterpenoids, diterpenes, triterpenes, oxygenated terpene derivatives, steroids and lipid derivatives. The leading discriminant metabolites were diterpenes, which were detected only in A. robusta leaves and insects that were fed on this plant-based diet. Additionally, caterpillars fed on A. robusta leaves took longer to complete their development to the adult phase and exhibited a greater diapause rate. Hence, we hypothesized that diterpenes may be involved in the differential larval development. Our findings shed light on the plant metabolites that play roles in insect development and metabolism, opening new research avenues for integrative studies of insect nutritional ecology.

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Kuwano, Eiichi. "Synthesis of chemicals regulating metamorphosis and diapause in insects." Journal of Pesticide Science 36, no. 2 (2011): 322–24. http://dx.doi.org/10.1584/jpestics.w11-09.

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Truman, James W., and Lynn M. Riddiford. "Endocrine Insights into the Evolution of Metamorphosis in Insects." Annual Review of Entomology 47, no. 1 (January 2002): 467–500. http://dx.doi.org/10.1146/annurev.ento.47.091201.145230.

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Mark, Brandon, Liliana Bustos-González, Guadalupe Cascallares, Felipe Conejera, and John Ewer. "The circadian clock gates Drosophila adult emergence by controlling the timecourse of metamorphosis." Proceedings of the National Academy of Sciences 118, no. 27 (June 28, 2021): e2023249118. http://dx.doi.org/10.1073/pnas.2023249118.

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The daily rhythm of adult emergence of holometabolous insects is one of the first circadian rhythms to be studied. In these insects, the circadian clock imposes a daily pattern of emergence by allowing or stimulating eclosion during certain windows of time and inhibiting emergence during others, a process that has been described as “gating.” Although the circadian rhythm of insect emergence provided many of the key concepts of chronobiology, little progress has been made in understanding the bases of the gating process itself, although the term “gating” suggests that it is separate from the developmental process of metamorphosis. Here, we follow the progression through the final stages of Drosophila adult development with single-animal resolution and show that the circadian clock imposes a daily rhythmicity to the pattern of emergence by controlling when the insect initiates the final steps of metamorphosis itself. Circadian rhythmicity of emergence depends on the coupling between the central clock located in the brain and a peripheral clock located in the prothoracic gland (PG), an endocrine gland whose only known function is the production of the molting hormone, ecdysone. Here, we show that the clock exerts its action by regulating not the levels of ecdysone but that of its actions mediated by the ecdysone receptor. Our findings may also provide insights for understanding the mechanisms by which the daily rhythms of glucocorticoids are produced in mammals, which result from the coupling between the central clock in the suprachiasmatic nucleus and a peripheral clock located in the suprarenal gland.

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Romanelli, Davide, Barbara Casati, Eleonora Franzetti, and Gianluca Tettamanti. "A Molecular View of Autophagy in Lepidoptera." BioMed Research International 2014 (2014): 1–11. http://dx.doi.org/10.1155/2014/902315.

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Metamorphosis represents a critical phase in the development of holometabolous insects, during which the larval body is completely reorganized: in fact, most of the larval organs undergo remodeling or completely degenerate before the final structure of the adult insect is rebuilt. In the past, increasing evidence emerged concerning the intervention of autophagy and apoptosis in the cell death processes that occur in larval organs of Lepidoptera during metamorphosis, but a molecular characterization of these pathways was undertaken only in recent years. In addition to developmentally programmed autophagy, there is growing interest in starvation-induced autophagy. Therefore we are now entering a new era of research on autophagy that foreshadows clarification of the role and regulatory mechanisms underlying this self-digesting process in Lepidoptera. Given that some of the most important lepidopteran species of high economic importance, such as the silkworm,Bombyx mori, belong to this insect order, we expect that this information on autophagy will be fully exploited not only in basic research but also for practical applications.

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Gregory, T. Ryan. "Genome size of the northern walkingstick, Diapheromera femorata (Phasmida: Heteronemiidae)." Canadian Journal of Zoology 80, no. 7 (July 1, 2002): 1303–5. http://dx.doi.org/10.1139/z02-106.

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The haploid genome size (C value) of the northern walkingstick, Diapheromera femorata (Say), was estimated to be 1C = 2.55 pg using Feulgen image-analysis densitometry of haemocyte and sperm nuclei. This relatively large genome is similar in size to the genomes of the few other phasmids studied so far, and is consistent with hypotheses regarding an upper limit to the size of many insect genomes imposed by the process of metamorphosis, which is relaxed among hemimetabolous orders. Comments on sperm morphology in D. femorata are also provided, and another possible relationship between genome size and the organismal phenotype in insects is suggested.

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Li, Zhiqian, Lang You, Baosheng Zeng, Lin Ling, Jun Xu, Xu Chen, Zhongjie Zhang, Subba Reddy Palli, Yongping Huang, and Anjiang Tan. "Ectopic expression of ecdysone oxidase impairs tissue degeneration in Bombyx mori." Proceedings of the Royal Society B: Biological Sciences 282, no. 1809 (June 22, 2015): 20150513. http://dx.doi.org/10.1098/rspb.2015.0513.

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Metamorphosis in insects includes a series of programmed tissue histolysis and remolding processes that are controlled by two major classes of hormones, juvenile hormones and ecdysteroids. Precise pulses of ecdysteroids (the most active ecdysteroid is 20-hydroxyecdysone, 20E), are regulated by both biosynthesis and metabolism. In this study, we show that ecdysone oxidase (EO), a 20E inactivation enzyme, expresses predominantly in the midgut during the early pupal stage in the lepidopteran model insect, Bombyx mori . Depletion of BmEO using the transgenic CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/RNA-guided Cas9 nucleases) system extended the duration of the final instar larval stage. Ubiquitous transgenic overexpression of BmEO using the Gal4/UAS system induced lethality during the larval–pupal transition. When BmEO was specifically overexpressed in the middle silk gland (MSG), degeneration of MSG at the onset of metamorphosis was blocked. Transmission electron microscope and LysoTracker analyses showed that the autophagy pathway in MSG is inhibited by BmEO ectopic expression. Furthermore, RNA-seq analysis revealed that the genes involved in autophagic cell death and the mTOR signal pathway are affected by overexpression of BmEO . Taken together, BmEO functional studies reported here provide insights into ecdysone regulation of tissue degeneration during metamorphosis.

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Chanchay, Pornchanan, Wanwipa Vongsangnak, Anchana Thancharoen, and Ajaraporn Sriboonlert. "Reconstruction of insect hormone pathways in an aquatic firefly, Sclerotia aquatilis (Coleoptera: Lampyridae), using RNA-seq." PeerJ 7 (August 2, 2019): e7428. http://dx.doi.org/10.7717/peerj.7428.

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Insect hormones: ecdysteroids and juvenile hormones have crucial functions during the regulation of different developmental pathways in insects. Insect metamorphosis is one of the primary pathways regulated by these hormones. The insect hormone biosynthetic pathway is conserved among arthropods, including insects, with some variations in the form of hormones used among each group of insects. In this study, the candidate genes involved in the insect hormone pathways and their functional roles were assessed in an aquatic firefly, Sclerotia aquatilis using a high-throughput RNA sequencing technique. Illumina next-generation sequencing (NGS) was used to generate transcriptome data for the different developmental stages (i.e., larva, pupa, and adult) of S. aquatilis. A total of 82,022 unigenes were generated across all different developmental stages. Functional annotation was performed for each gene, based on multiple biological databases, generating 46,230 unigenes. These unigenes were subsequently mapped using KEGG pathways. Accordingly, 221 protein-encoding genes involved in the insect hormone pathways were identified, including, JHAMT, CYP15A1, JHE, and Halloween family genes. Twenty potential gene candidates associated with the biosynthetic and degradation pathways for insect hormones were subjected to real-time PCR, reverse transcriptase PCR (RT-PCR) and sequencing analyses. The real-time PCR results showed similar expression patterns as those observed for transcriptome expression profiles for most of the examined genes. RT-PCR and Sanger sequencing confirmed the expressed coding sequences of these gene candidates. This study is the first to examine firefly insect hormone pathways, facilitating a better understanding of firefly growth and development.

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Hironaka, Ken-ichi, and Yoshihiro Morishita. "Adaptive significance of critical weight for metamorphosis in holometabolous insects." Journal of Theoretical Biology 417 (March 2017): 68–83. http://dx.doi.org/10.1016/j.jtbi.2017.01.014.

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Mohorič, Aleš, Janko Božič, Polona Mrak, Kaja Tušar, Chenyun Lin, Ana Sepe, Urša Mikac, Georgy Mikhaylov, and Igor Serša. "In vivo continuous three-dimensional magnetic resonance microscopy: a study of metamorphosis in Carniolan worker honey bees (Apis mellifera carnica)." Journal of Experimental Biology 223, no. 21 (October 6, 2020): jeb225250. http://dx.doi.org/10.1242/jeb.225250.

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ABSTRACTThree-dimensional (3D) magnetic resonance microscopy (MRM) is a modality of magnetic resonance imaging (MRI) optimized for the best resolution. Metamorphosis of the Carniolan worker honey bee (Apis mellifera carnica) was studied in vivo under controlled temperature and humidity conditions from sealed larvae until the emergence of an adult. The 3D images were analyzed by volume rendering and segmentation, enabling the analysis of the body, tracheal system and gastrointestinal tract through the time course of volume changes. Fat content sensitivity enabled the analysis of flight muscles transformation during the metamorphosis by the signal histogram and gray level co-occurrence matrix (GLCM). Although the transformation during metamorphosis is well known, MRM enables an alternative insight to this process, i.e. 3D in vivo, which has relatively high spatial and temporal resolutions. The developed methodology can easily be adapted for studying the metamorphosis of other insects or any other incremental biological process on a similar spatial and temporal scale.

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Takeshima, Mika, Mari H. Ogihara, and Hiroshi Kataoka. "Sterol Characteristics in Silkworm Brain and Various Tissues Characterized by Precise Sterol Profiling Using LC-MS/MS." International Journal of Molecular Sciences 20, no. 19 (September 29, 2019): 4840. http://dx.doi.org/10.3390/ijms20194840.

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Sterols, especially cholesterol (Chl), are fundamental for animal survival. Insects lacking the ability to synthesize Chl are sterol auxotrophic animals and utilize dietary Chl and phytosterols to survive. The sterols obtained from a diet are distributed to the tissues; however, sterol homeostasis in insect tissues remains to be elucidated. This study sought to understand the sterol characteristics of insect tissues through detailed sterol quantification and statistics. The combination of sterol quantification using liquid chromatography tandem mass spectrometry (LC-MS/MS) and principal component analysis (PCA) revealed tissue-specific sterol characteristics in the silkworm, Bombyx mori, a phytophagous insect. We found that insect tissues have tissue-intrinsic sterol profiles. The brain has a unique sterol composition as compared to other tissues—high concentration of Chl and less accumulation of phytosterols. Other tissues also have intrinsic sterol characteristics, which when defined by dietary sterols or Chl metabolites, indicate preference for a sterol and consistently manage their own sterol homeostasis. Though most tissues never change sterol profiles during development, the brain drastically changes its sterol profile at the wandering stage, indicating that it could alter sterol composition in preparation for metamorphosis. These results suggest the existence of tissue- and sterol-specific systems for sterol homeostasis in insects.

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Letsch, Harald O., Karen Meusemann, Benjamin Wipfler, Kai Schütte, Rolf Beutel, and Bernhard Misof. "Insect phylogenomics: results, problems and the impact of matrix composition." Proceedings of the Royal Society B: Biological Sciences 279, no. 1741 (May 23, 2012): 3282–90. http://dx.doi.org/10.1098/rspb.2012.0744.

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In this study, we investigated the relationships among insect orders with a main focus on Polyneoptera (lower Neoptera: roaches, mantids, earwigs, grasshoppers, etc.), and Paraneoptera (thrips, lice, bugs in the wide sense). The relationships between and within these groups of insects are difficult to resolve because only few informative molecular and morphological characters are available. Here, we provide the first phylogenomic expressed sequence tags data (‘EST’: short sub-sequences from a c(opy) DNA sequence encoding for proteins) for stick insects (Phasmatodea) and webspinners (Embioptera) to complete published EST data. As recent EST datasets are characterized by a heterogeneous distribution of available genes across taxa, we use different rationales to optimize the data matrix composition. Our results suggest a monophyletic origin of Polyneoptera and Eumetabola (Paraneoptera + Holometabola). However, we identified artefacts of tree reconstruction (human louse Pediculus humanus assigned to Odonata (damselflies and dragonflies) or Holometabola (insects with a complete metamorphosis); mayfly genus Baetis nested within Neoptera), which were most probably rooted in a data matrix composition bias due to the inclusion of sequence data of entire proteomes. Until entire proteomes are available for each species in phylogenomic analyses, this potential pitfall should be carefully considered.

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Song, Xiaowen, Qisheng Zhong, Guifang Peng, Yanhao Ji, Yuemei Zhang, Jing Tang, Jia Xie, Jingxiu Bi, Fan Feng, and Bin Li. "Functional characterization of a special dicistronic transcription unit encoding histone methyltransferase su(var)3-9 and translation regulator eIF2γ in Tribolium castaneum." Biochemical Journal 477, no. 16 (August 28, 2020): 3059–74. http://dx.doi.org/10.1042/bcj20200444.

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Operons are rare in eukaryotes, where they often allow concerted expression of functionally related genes. While a dicistronic transcription unit encoding two unrelated genes, the suppressor of position-effect variegation su(var)3-9 and the gamma subunit of eukaryotic translation initiation factor 2 (eIF2γ) has been found in insecta, and its significance is not well understood. Here, we analyzed the evolutionary history of this transcription unit in arthropods and its functions by using model Coleoptera insect Tribolium castaneum. In T. castaneum, Tcsu(var)3-9 fused into the 80 N-terminal amino acids of TceIF2γ, the transcription of these two genes are resolved by alternative splicing. Phylogenetic analysis supports the natural gene fusion of su(var)3-9 and eIF2γ occurred in the ancestral line of winged insects and silverfish, but with frequent re-fission during the evolution of insects. Functional analysis by using RNAi for these two genes revealed that gene fusion did not invoke novel functions for the gene products. As a histone methyltransferase, Tcsu(var)3-9 is primarily responsible for H3K9 di-, and tri-methylation and plays important roles in metamorphosis and embryogenesis in T. castaneum. While TceIF2γ plays essential roles in T. castaneum by positively regulating protein translation mediated ecdysteroid biosynthesis. The vulnerability of the gene fusion and totally different role of su(var)3-9 and eIF2γ in T. castaneum confirm this gene fusion is a non-selected, constructive neutral evolution event in insect. Moreover, the positive relationship between protein translation and ecdysteroid biosynthesis gives new insights into correlations between translation regulation and hormonal signaling.

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Nobles, Sarah, and Colin R. Jackson. "Effects of Life Stage, Site, and Species on the Dragonfly Gut Microbiome." Microorganisms 8, no. 2 (January 28, 2020): 183. http://dx.doi.org/10.3390/microorganisms8020183.

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Insects that undergo metamorphosis from juveniles to adults provide an intriguing opportunity to examine the effects of life stage, species, and the environment on their gut microbiome. In this study, we surveyed the gut microbiomes of 13 species of dragonfly collected from five different locations subject to different levels of human impact. Juveniles were collected as nymphs from aquatic habitats while airborne adults were caught at the same locations. The gut microbiome was characterized by next generation sequencing of the bacterial 16S rRNA gene. Life stage was an important factor, with the gut microbiomes of dragonfly nymphs differing from those of adult dragonflies. Gut microbiomes of nymphs were influenced by sample site and, to a lesser extent, host species. Neither sample location nor host species had a strong effect on the gut microbiome of dragonfly adults. Regardless of life stage, gut microbiomes were dominated by members of the Proteobacteria, with members of the Bacteroidetes (especially in adults), Firmicutes, and Acidobacteria (especially in nymphs) also being proportionally abundant. These results demonstrate that different life stages of metamorphosing insects can harbor very different gut microbiomes and differ in how this microbiome is influenced by the surrounding environment.

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Urena, E., C. Manjon, X. Franch-Marro, and D. Martin. "Transcription factor E93 specifies adult metamorphosis in hemimetabolous and holometabolous insects." Proceedings of the National Academy of Sciences 111, no. 19 (April 28, 2014): 7024–29. http://dx.doi.org/10.1073/pnas.1401478111.

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Skowronek, Patrycja, Łukasz Wójcik, and Aneta Strachecka. "Fat Body—Multifunctional Insect Tissue." Insects 12, no. 6 (June 11, 2021): 547. http://dx.doi.org/10.3390/insects12060547.

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The biodiversity of useful organisms, e.g., insects, decreases due to many environmental factors and increasing anthropopressure. Multifunctional tissues, such as the fat body, are key elements in the proper functioning of invertebrate organisms and resistance factors. The fat body is the center of metabolism, integrating signals, controlling molting and metamorphosis, and synthesizing hormones that control the functioning of the whole body and the synthesis of immune system proteins. In fat body cells, lipids, carbohydrates and proteins are the substrates and products of many pathways that can be used for energy production, accumulate as reserves, and mobilize at the appropriate stage of life (diapause, metamorphosis, flight), determining the survival of an individual. The fat body is the main tissue responsible for innate and acquired humoral immunity. The tissue produces bactericidal proteins and polypeptides, i.e., lysozyme. The fat body is also important in the early stages of an insect’s life due to the production of vitellogenin, the yolk protein needed for the development of oocytes. Although a lot of information is available on its structure and biochemistry, the fat body is an interesting research topic on which much is still to be discovered.

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Kayukawa, Takumi, Akiya Jouraku, Yuka Ito, and Tetsuro Shinoda. "Molecular mechanism underlying juvenile hormone-mediated repression of precocious larval–adult metamorphosis." Proceedings of the National Academy of Sciences 114, no. 5 (January 17, 2017): 1057–62. http://dx.doi.org/10.1073/pnas.1615423114.

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Juvenile hormone (JH) represses precocious metamorphosis of larval to pupal and adult transitions in holometabolous insects. The early JH-inducible geneKrüppel homolog 1(Kr-h1) plays a key role in the repression of metamorphosis as a mediator of JH action. Previous studies demonstrated that Kr-h1 inhibits precocious larval–pupal transition in immature larva via direct transcriptional repression of the pupal specifierBroad-Complex(BR-C). JH was recently reported to repress the adult specifier geneEcdysone-induced protein 93F(E93); however, its mechanism of action remains unclear. Here, we found that JH suppressed ecdysone-inducibleE93expression in the epidermis of the silkwormBombyx moriand in aB. moricell line. Reporter assays in the cell line revealed that the JH-dependent suppression was mediated by Kr-h1. Genome-wide ChIP-seq analysis identified a consensus Kr-h1 binding site (KBS, 14 bp) located in theE93promoter region, and EMSA confirmed that Kr-h1 directly binds to the KBS. Moreover, we identified a C-terminal conserved domain in Kr-h1 essential for the transcriptional repression ofE93. Based on these results, we propose a mechanism in which JH-inducible Kr-h1 directly binds to the KBS site upstream of theE93locus to repress its transcription in a cell-autonomous manner, thereby preventing larva from bypassing the pupal stage and progressing to precocious adult development. These findings help to elucidate the molecular mechanisms regulating the metamorphic genetic network, including the functional significance ofKr-h1,BR-C, andE93in holometabolous insect metamorphosis.

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Sleigh, Charlotte. "Jan Swammerdam's frogs." Notes and Records of the Royal Society 66, no. 4 (October 10, 2012): 373–92. http://dx.doi.org/10.1098/rsnr.2012.0039.

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Having discussed insect metamorphosis at length, Jan Swammerdam's Bybel der Natuure (1679/1737) reached its climax with a substantial description of the generation and muscular activity of frogs. This paper explores the rhetorical role of frogs in Swammerdam's ‘great work’, showing how they were the Archimedean point from which he aimed to reorder all of creation—from insects to humans—within one glorious, God-ordained natural history and philosophy. Swammerdam linked insects to frogs through a demonstration that all underwent epigenesis; and frogs were then linked to humans through a demonstration of their identical muscular activity. The success of Swammerdam's strategy required a theological reconstruction of the frog, traditionally an ungodly creature, such that trustworthy knowledge could be obtained from its body. Perhaps surprisingly, this act of theological cleansing is shown to be somewhat prefigured in the distinctly non-experimental natural history of Edward Topsell (1608). The paper also examines Swammerdam's interactions with the mystic Antoinette Bourignon, and his challenges in reconciling a spirituality of meletetics with a material epistemology in natural philosophy. Differences are revealed between the natural analogies given by Swammerdam in his published and unpublished writings, undermining to a certain extent the triumphal insect–frog–human rhetorical structure of the Bybel .

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Truman, James W., and Lynn M. Riddiford. "The evolution of insect metamorphosis: a developmental and endocrine view." Philosophical Transactions of the Royal Society B: Biological Sciences 374, no. 1783 (August 26, 2019): 20190070. http://dx.doi.org/10.1098/rstb.2019.0070.

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Developmental, genetic and endocrine data from diverse taxa provide insight into the evolution of insect metamorphosis. We equate the larva–pupa–adult of the Holometabola to the pronymph–nymph–adult of hemimetabolous insects. The hemimetabolous pronymph is a cryptic embryonic stage with unique endocrinology and behavioural modifications that probably served as preadaptations for the larva. It develops in the absence of juvenile hormone (JH) as embryonic primordia undergo patterning and morphogenesis, the processes that were arrested for the evolution of the larva. Embryonic JH then drives tissue differentiation and nymph formation. Experimental treatment of pronymphs with JH terminates patterning and induces differentiation, mimicking the processes that occurred during the evolution of the larva. Unpatterned portions of primordia persist in the larva, becoming imaginal discs that form pupal and adult structures. Key transcription factors are associated with the holometabolous life stages: Krüppel-homolog 1 ( Kr-h1 ) in the larva, broad in the pupa and E93 in the adult. Kr-h1 mediates JH action and is found whenever JH acts, while the other two genes direct the formation of their corresponding stages. In hemimetabolous forms, the pronymph has low Broad expression, followed by Broad expression through the nymphal moults, then a switch to E93 to form the adult. This article is part of the theme issue ‘The evolution of complete metamorphosis’.

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Perevaryukha, A. Yu. "ON THE TECHNIQUE OF MODELING ONTOGENETIC CHANGES IN FISH AND INSECTS LIFECYCLE." «System analysis and applied information science», no. 1 (May 4, 2017): 12–23. http://dx.doi.org/10.21122/2309-4923-2017-1-12-23.

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The article discusses the approach to modeling of metamorphoses in the development of a number of species in the context of their influence on the success of long-term trends of population dynamics. Changes in survival during early ontogenesis, controlled by important factor – the rate of individual development in a competing group of individuals, can cause unexpected degradation of population with a small excess fishing impact. The theory of nonlinear efficiency of reproduction leads us to the hypothesis that two different nonlinear effects are controlled by similar mechanisms. For insects such fluctuations in survival during metamorphosis can start another process - the rapid outbreak of pests, where actual formalization of the impact of parasites on the first stage of development, depending on the initial concentration of clutches, but limited resources is taken into account at a finishing. The method has been for submission to decline of generations on the basis of dynamic overriding differential equations with discrete-continuous structure of time. To extend the previously proposed model for the formation of generations is formed computing structure for the account mortality depending on the level of competition, complete with trigger functional and a new scheme describing the changes the growth rate for the example of the Caspian Sea sturgeon in three ecological and physiological stages of development. The new model has a non-trivial possibilities parametrically modification of behavior regimes. The coexistence of alternative cycles is explained by the increase in adaptive interspecies differences.

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Strong, L., and T. A. Brown. "Avermectins in insect control and biology: a review." Bulletin of Entomological Research 77, no. 3 (September 1987): 357–89. http://dx.doi.org/10.1017/s0007485300011846.

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AbstractIn a variety of laboratory and field experiments, avermectins have been tested against some 84 species of insects in ten orders, most of which are pests of livestock or horticultural crops or are of general nuisance value. This work is reviewed, comparing doses used, methods of application, and responses of the insects. Avermectins (abamectin and ivermectin) are toxic to almost all insects examined, although tolerance varies and death can be uncommonly slow, taking 24 h to 30 days. There is a marked absence of information on physiological processes that are affected by the pesticides, although at the cellular level they are thought to disrupt receptors for y-aminobutyric acid and glutamic acid in the central nervous system and muscular system. At high doses, treated insects are progressively immobilized, and although initially many can move when stimulated, this ability becomes lost. Some show a disturbed water balance and become distended with fluid, while others show disruption of moulting and metamorphosis. Feeding inhibition is commonly observed at sub-lethal doses. Avermectins affect many aspects of reproduction including mating behaviour, egg development, oviposition and egg hatching. The possibility is raised that these diverse disturbances are not all due to disruption of neuromuscular or central nervous system synapses, and the need for work in this area is stressed. Field studies have shown ivermectin to be most valuable in eradicating insect pests of livestock, but the use of abamectin against horticultural pests has produced less impressive results. The limited work on non-target species is discussed, and attention is drawn to some possible environmental consequences of excreted ivermectin on dung-breeding insects.

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Alnajim, Ihab, Naser Aldosary, Manjree Agarwal, Tao Liu, Xin Du, and Yonglin Ren. "Role of Lipids in Phosphine Resistant Stored-Grain Insect Pests Tribolium castaneum and Rhyzopertha dominica." Insects 13, no. 9 (September 1, 2022): 798. http://dx.doi.org/10.3390/insects13090798.

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Insects rely on lipids as an energy source to perform various activities, such as growth, flight, diapause, and metamorphosis. This study evaluated the role of lipids in phosphine resistance by stored-grain insects. Phosphine resistant and susceptible strains of the two main stored-grain insects, Tribolium castaneum and Rhyzopertha dominica, were analyzed using liquid chromatography-mass spectroscopy (LC-MS) to determine their lipid contents. Phosphine resistant strains of both species had a higher amount of lipids than susceptible stains. Significant variance ratios between the resistant and susceptible strains of T. castaneum were observed for glycerolipids (1.13- to 53.10-fold) and phospholipids (1.05- to 20.00-fold). Significant variance ratios between the resistant and susceptible strains of R. dominica for glycerolipids were 1.04- to 31.50-fold and for phospholipids were 1.04- to 10.10-fold. Glycerolipids are reservoirs to face the long-term energy shortage. Phospholipids act as a barrier to isolate the cells from the surrounding environment and allow each cell to perform its specific function. Thus, lipids offer a consistent energy source for the resistant insect to survive under the stress of phosphine fumigation and provide a suitable environment to protect the mitochondria from phosphine. Hence, it was proposed through this study that the lipid content of phosphine-resistant and phosphine-susceptible strains of T. castaneum and R. dominica could play an important role in the resistance of phosphine.

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Kraus, Johanna M., David M. Walters, Jeff S. Wesner, Craig A. Stricker, Travis S. Schmidt, and Robert E. Zuellig. "Metamorphosis Alters Contaminants and Chemical Tracers in Insects: Implications for Food Webs." Environmental Science & Technology 48, no. 18 (September 2, 2014): 10957–65. http://dx.doi.org/10.1021/es502970b.

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Lee, Gyunghee, and Jae H. Park. "Programmed cell death reshapes the central nervous system during metamorphosis in insects." Current Opinion in Insect Science 43 (February 2021): 39–45. http://dx.doi.org/10.1016/j.cois.2020.09.015.

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Duneau, David F., and Brian P. Lazzaro. "Persistence of an extracellular systemic infection across metamorphosis in a holometabolous insect." Biology Letters 14, no. 2 (February 2018): 20170771. http://dx.doi.org/10.1098/rsbl.2017.0771.

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Organisms with complex life cycles can differ markedly in their biology across developmental life stages. Consequently, distinct life stages can represent drastically different environments for parasites. This difference is especially striking with holometabolous insects, which have dramatically different larval and adult life stages, bridged by a complete metamorphosis. There is no a priori guarantee that a parasite infecting the larval stage would be able to persist into the adult stage. In fact, to our knowledge, transstadial transmission of extracellular pathogens has never been documented in a host that undergoes complete metamorphosis. We tested the hypothesis that a bacterial parasite originally sampled from an adult host could infect a larva, then survive through metamorphosis and persist into the adult stage. As a model, we infected the host Drosophila melanogaster with a horizontally transmitted, extracellular bacterial pathogen, Providencia rettgeri . We found that this natural pathogen survived systemic infection of larvae (L3) and successfully persisted into the adult host. We then discuss how it may be adaptive for bacteria to transverse life stages and even minimize virulence at the larval stage in order to benefit from adult dispersal.

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Agrawal, Rashika, and Seema Keshari. "A study of life cycle of vegetable pests in Ranchi." INTERNATIONAL JOURNAL OF AGRICULTURAL SCIENCES 17, no. 2 (June 15, 2021): 311–17. http://dx.doi.org/10.15740/has/ijas/17.2/311-317.

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The study is done to investigate the different pests found in the vegetables in Ranchi. The pests who damage these vegetables are Plutella xylostella (cauliflower pest), Earias vittella (Okra Pest), Etiella zinckenella (pea pod borer) and Thysanoplusia orichalcea (coriander leaf pest). The pests’ life cycle was studied in detail by culturing the insect in the laboratory. Pest problem is one of the major constarints for getting good yield in the agricultural crops. India also suffers a huge loss in crop yield due to pests and diseases each year. The study of life cycle of the pests show that the insects undergo metamorphosis and the larval stage is the damaging phase of the life cycle. The use of pesticides to kill the pests causes environmental pollution which has become an increasing problem.

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Zheng, J., K. Tian, Y. Yuan, M. Li, and X. Qiu. "Identification and expression patterns of Halloween genes encoding cytochrome P450s involved in ecdysteroid biosynthesis in the cotton bollworm Helicoverpa armigera." Bulletin of Entomological Research 107, no. 1 (August 22, 2016): 85–95. http://dx.doi.org/10.1017/s0007485316000663.

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Abstract20-Hydroxyecdysone (20E) is a key hormone which regulates growth, development and reproduction in insects. Although cytochrome P450 enzymes (P450s) participating in the ecdysteroid biosynthesis of 20E have been characterized in a few model insects, no work has been published on the molecular entity of their orthologs in the cotton bollworm Helicoverpa armigera, a major pest insect in agriculture worldwide. In this study, four cytochrome P450 homologs, namely HarmCYP302A1, HarmCYP306A1, HarmCYP314A1 and HarmCYP315A1 from H. armigera, were identified and evolutional conservation of these Halloween genes were revealed among lepidopteran. Expression analyses showed that HarmCYP302A1 and HarmCYP315A1 were predominantly expressed in larval prothoracic glands, whereas this predominance was not always observed for HarmCYP306A1 and CYP314A1. The expression patterns of Halloween genes indicate that the fat bodies may play an important role in the conversion of ecdysone into 20E in larval–larval molt and in larval–pupal metamorphosis, and raise the possibility that HarmCYP315A1 plays a role in tissue-specific regulation in the steroid biosynthesis in H. armigera. These findings represent the first identification and expression characterization of four steriodogenic P450 genes and provide the groundwork for future functional and evolutionary study of steroid biosynthesis in this agriculturally important pest.

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Journal articles on the topic 'Insects - Metamorphosis'

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