Academic literature on the topic 'Gemmules'

Geographic distributions of freshwater sponges are related to the geological and climatic history of the continents, on the presence of gemmules and the morphological complexity of this resistant body to withstand change. Gemmules are characteristic of the freshwater Families Spongillidae, Metaniidae and Potamolepidae. However, Acanthotylotra alvarengai, Echinospongilla brichardi and a number of other species within the genus Potamolepis do not produce gemmules. Potamolepis is endemic to the Afrotropical region with seven valid species. African freshwater sponges however, are mostly known from a single specimen (the holotype), due to the scarcity of material from these freshwater systems. In the present study, we describe two new species of non-gemmule bearing freshwater sponges from the Neotropical and Afrotropical Regions.

Abstract A survey of four selected streams in the Tennessee portion of the Great Smoky Mountains National Park was conducted to document the presence of freshwater sponges. Streams were surveyed by wading and observing rock and log substrates for sponges. Sponges were viewed with a 10X magnifier for gemmules. If gemmules were present a portion of the sponge containing gemmules was collected. Scanning electron microscopy of gemmules and spicules was used for taxonomic identification. Two species, Radiospongilla crateriformis and Trochospongilla horrida, were discovered. Both were found in the Abrams Creek embayment of Chilhowee Lake. These findings represent the first records of freshwater sponges within the Great Smoky Mountains National Park.

Successful dispersal of freshwater sponges depends on the formation of dormant sponge bodies (gemmules) under adverse conditions. Gemmule formation allows the sponge to overcome critical environmental conditions, for example, desiccation or freezing, and to re-establish as a fully developed sponge when conditions are more favorable. A key process in sponge development from hatched gemmules is the construction of the silica skeleton. Silica spicules form the structural support for the three-dimensional filtration system the sponge uses to filter food particles from ambient water. We studied the effect of different hypergravity forces (1, 2.5, 5, 10, and 20 × g for 48 h)—as measure for environmental stress—on the ability of developing sponges to set-up their spiculous skeleton. Additionally, we assessed whether the addition of nutrients (i.e., dissolved 13C- and 15N-labeled amino acids) compensates for this stress. Our results show that freshwater sponges can withstand prolonged periods of hypergravity exposure and successfully set-up their skeleton, even after 48 h under 20 × g. Developing sponges were found to take up and assimilate dissolved food before forming a functional filtering system. However, fed and non-fed sponges showed no differences in skeleton formation and relative surface area growth, suggesting that the gemmules’ intrinsic energy fulfills the processes of skeleton construction. Additionally, non-fed sponges formed oscula significantly more often than fed sponges, especially under higher g-forces. This suggests that the eventual formation of a filtration system might be stimulated by food deprivation and environmentally stressful conditions. These findings indicate that the process of spiculous skeleton formation is energy-efficient and highly resilient. The uptake of dissolved food substances by freshwater sponges may contribute to the cycling of dissolved organic matter in freshwater ecosystems where sponges are abundant.

Gemmules of five species of freshwater sponge found in deposits at Cedar Mountain bog in the southeastern Puget Lowland were used to infer that during the late-glacial period the water was calcareous, was not deficient in SiO2, was aerobic, and had a pH in the range 6.6–8.5. This is consistent with plant fossil data. In view of their paleoenvironmental potential it is worth looking for gemmules when extracting other fossils from lake sediments.

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CAPEs
Corvoheteromeyenia Ezcurra de Drago, 1979 é um gênero endêmico da Região Neotropical, criado para albergar: C. australis (Bonetto & Ezcurra de Drago, 1966) e C. heterosclera (Ezcurra de Drago, 1974). No entanto, devido à confusão na descrição original de C. australis e C. heterosclera, não era clara a distinção entre as espécies. Adicionalmente, o material tipo dessas espécies não foi depositado nas coleções indicadas nos trabalhos originais. Sendo assim, no intuito de elucidar o status específico destes materiais, o presente trabalho apresenta a revisão do gênero e a designação dos neótipos. Um total de 41 espécimes foram analisados e identificados como sendo Corvoheteromeyenia. Baseado na bibliografia e no material examinado foi realizada a redescrição das espécies C. australis e C. heterosclera. A microsclera acantóxea foi apontada como o caráter distintivo entre ambas as espécies, presente apenas em C. heterosclera. Além destas duas espécies, foi descrita C. sanidastosclera Pinheiro, Silva & Calheira, no prelo, que difere das demais por apresentar apenas gemosclera sanidáster. Este trabalho também testou se a fisiologia da eclosão da gêmula poderia influenciar na distribuição das esponjas de águas continentais. Até o presente, apenas a morfologia gemular estava sendo considerados para entender o padrão de distribuição das espécies. Neste trabalho, escolhemos duas espécies (Heteromeyenia cristalina Batista, Volkmer-Ribeiro & Melão, 2007 e Radiospongilla inesi Nicacio & Pinheiro, 2011) para testar se a distribuição da espécie está associada à capacidade de eclosão da gêmula em diferentes tipos de ambientes. Cinco tratamentos foram realizados (T): T1 (água do local da coleta das esponjas); T2 (água do Rio Pirangi); T3 (água da Lagoa Araraquara); T4 (água mineral) e T5 (T1 + gêmulas dessecadas). Para cada tratamento, foram utilizadas 30 gêmulas com três réplicas. As gêmulas foram observadas diariamente, durante 30 dias. Para a análise dos dados foi realizada ANOVA e teste Tukey. O resultado apresentou que as gêmulas de ambas as espécies submetidas ao T3 não eclodiram, provavelmente em virtude da maior condutividade da água. Houve diferença significativa entre os tratamentos (T1, T2, T4) e entre as espécies (F2;12=77,2). A comparação entre T1 e T5 apresentou diferença entre os tratamentos e as espécies (F1;8=27,5), com alta significância para ambos resultados (P<0.001). Foi constatado que R. inesi apresentou um percentual de eclosão elevado nos tratamentos analisados, enquanto que H. cristalina, teve percentual de eclosão elevado apenas na água de sua própria localidade de coleta. Adicionalmente foi observado o desenvolvimento de esponjas em ambas as espécies.
Corvoheteromeyenia Ezcurra de Drago, 1979 is endemic from the Neotropical Region and was created to comprise C. australis (Bonetto & Ezcurra de Drago, 1966) and C. heterosclera (Ezcurra de Drago, 1974). However, due to confusion in the original description of C. australis and C. heterosclera, the distinction between them was not well-established. Additionally, the type material from these species was not deposited in the collections indicated at the original descriptions. Thus, in order to elucidate their specific status, this paper presents a review of the genus and the designation of both neotypes. A total of 41 specimens were analyzed and identified as belonging to Corvoheteromeyenia. Based on the literature and additional specimens, the redescription of C. australis and C. heterosclera is presented. The microsclera acanthoxea was stated as the distinctive character of both, present only in C. heterosclera. Corvoheteromeyenia sanidastosclera Pinheiro, Silva & Calheira, in press, was also described and is distinct from congeners by the presence of gemmoscleres sanidaster. This study also tested whether the physiology of gemmules hatching could affect the distribution of freshwater sponges. Until the present, only the morphology of the gemmule was being considered to understand the pattern of distribution of species. In this work we choose two species (Heteromeyenia cristalina Batista, Volkmer-Ribeiro & Melão, 2007 e Radiospongilla inesi Nicacio & Pinheiro, 2011) to test whether the distribution is associated with the capacity of gemmules hatching in different environments. Five treatments were done (T): T1 (water of sponges site collected); T2 (Pirangi River water); T3 (Araraquara Pond water); T4 (mineral water) and T5 (T1 + drying gemmules). For each treatment 30 gemmules with three replicates were used. The gemmules were observed daily during 30 days. Data analysis was performed using ANOVA and Tukey test. Results showed that gemmules from both species submitted to T3 have not hatched, probably due to its higher conductivity. There was a significant difference between treatments (T1, T2, T4) and between species (F2, 12 = 77.2). Comparison between T1 and T5 showed differences between treatments and species (F1, 8 = 27.5), with high significance for both results (P <0.001). It was found that R. inesi presented a high percentage of hatching at all treatments while H. cristalina had high percentage of hatching only at treatment with water from its natural habitat. Additionally, the development of sponges was observed from both species.