Journal articles: 'Gape size'

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Bremigan, Mary T., and Roy A. Stein. "Gape-dependent Larval Foraging and Zooplankton Size: Implications for Fish Recruitment across Systems." Canadian Journal of Fisheries and Aquatic Sciences 51, no. 4 (April 1, 1994): 913–22. http://dx.doi.org/10.1139/f94-090.

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Small gape of zooplanktivorous larval fish limits their prey size; yet, within constraints set by gape, zooplankton size eaten influences larval growth and ultimately survival. To determine if optimal zooplankton size varied among fish species with different gapes, we conducted foraging trials with larval bluegill (Lepomis macrochirus, 10–26 mm TL) and gizzard shad (Dorosoma cepedianum, 18–31 mm TL). Larvae (n = 10) fed for 1 h on zooplankton assemblages that varied in size, after which all larvae and remaining zooplankton were preserved. Larval gape was measured; both larval gut contents and available zooplankton were quantified. Bluegill, the large-gaped species, fed on larger zooplankton than did gizzard shad with similar gapes. Further, larger bluegill fed on progressively larger zooplankton whereas all gizzard shad ate small prey (< 0.60 mm). As available zooplankton size increased, bluegill prey size increased whereas gizzard shad consistently selected small prey. Therefore, differences in zooplankton size among lakes could differentially affect foraging success of larval fishes. In particular, systems with small zooplankton may represent ideal foraging environments for gizzard shad whereas lakes with large zooplankton may favor larval bluegill. If differential larval foraging translates to differential growth and survival, zooplankton size could influence recruitment success and ultimately fish community composition.

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Graham, Zackary A. "Moving in fast waters: the exaggerated claw gape of the New River crayfish ( Cambarus chasmodactlyus ) aids in locomotor performance." Biology Letters 17, no. 5 (May 2021): 20210045. http://dx.doi.org/10.1098/rsbl.2021.0045.

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Humans are inherently fascinated by exaggerated morphological structures such as elk antlers and peacock trains. Because these traits are costly to develop and wield, the environment in which they are used can select for specific sizes or shapes to minimize such costs. In aquatic environments, selection to reduce drag can constrain the form of exaggerated structures; this is presumably why exaggerated morphologies are less common in aquatic environments compared to terrestrial ones. Interestingly, some crayfish species possess claws with an exaggerated gape between their pinching fingers, but the function of this claw gape is unknown. Here, I describe and test the function of the exaggerated claw gape of the New River crayfish, Cambarus chasmodactylus . Specifically, I test the hypothesis that the claw gape aids in movement against flowing currents. I found that both claw size and gape size were sexually dimorphic in this species and that males have disproportionately larger gapes compared to females. By experimentally covering their claw gape and testing crayfish locomotor performance, I found that individuals with their gape blocked were 30% slower than crayfish with a natural gape. My results highlight a unique adaptation that compensates for wielding an exaggerated structure in aquatic environments.

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Ladds, MA, MH Pinkerton, E. Jones, LM Durante, and MR Dunn. "Relationship between morphometrics and trophic levels in deep-sea fishes." Marine Ecology Progress Series 637 (March 5, 2020): 225–35. http://dx.doi.org/10.3354/meps13243.

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Marine food webs are structured, in part, by predator gape size. Species found in deep-sea environments may have evolved such that they can consume prey of a wide range of sizes, to maximise resource intake in a low-productivity ecosystem. Estimates of gape size are central to some types of ecosystem model that determine which prey are available to predators, but cannot always be measured directly. Deep-sea species are hypothesized to have larger gape sizes than shallower-water species relative to their body size and, because of pronounced adaptive foraging behaviour, show only a weak relationship between gape size and trophic level. Here we present new data describing selective morphological measurements and gape sizes of 134 osteichthyan and chondrichthyan species from the deep sea (200-1300 m) off New Zealand. We describe how gape size (height, width and area) varied with factors including fish size, taxonomy (class and order within a class) and trophic level estimated from stable isotopes. For deep-sea species, there was a strong relationship between gape size and fish size, better predicted by body mass than total length, which varied by taxonomic group. Results show that predictions of gape size can be made from commonly measured morphological variables. No relationship between gape size and trophic level was found, likely a reflection of using trophic level estimates from stable isotopes as opposed to the commonly used estimates from FishBase. These results support the hypothesis that deep-sea fish are generalists within their environment, including suspected scavenging, even at the highest trophic levels.

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Schael, Denise M., Lars G. Rudstam, and John R. Post. "Gape Limitation and Prey Selection in Larval Yellow Perch (Perca flavescens), Freshwater Drum (Aplodinotus grunniens), and Black Crappie (Pomoxis nigromaculatus)." Canadian Journal of Fisheries and Aquatic Sciences 48, no. 10 (October 1, 1991): 1919–25. http://dx.doi.org/10.1139/f91-228.

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We compared prey selection of larval yellow perch (Perca flavescens), freshwater drum (Aplodinotus grunniens), and black crappie (Pomoxis nigromaculatus) in Lake Mendota, Wisconsin. All three species had a diet dominated by copepods and selected progressively larger prey as fish length increased. For a given fish length, freshwater drum selected larger prey and black crappie selected smaller prey than yellow perch. These differences in prey selectivity were partly explainable from differences in gape to length relationships. Freshwater drum did have the largest gape for a given length of the three species, but gape size for black crappie and yellow perch were similar. Gape size predicted 67% of the variability in mean prey size ingested by yellow perch but only 15% for freshwater drum and 8% for black crappie. Although gape size did predict the upper limit of ingestible prey sizes and explained some of the differences in prey selectivity among the three species, both the degree to which the different fishes can ingest prey close to their gape limit and the degree to which gape predicted mean size of ingested prey varied among the three fish species.

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Slaughter, Joe E., and Brad Jacobson. "Gape: Body Size Relationship of Flathead Catfish." North American Journal of Fisheries Management 28, no. 1 (February 2008): 198–202. http://dx.doi.org/10.1577/m06-033.1.

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Johnson, Andrew F., Maria Valls, Joan Moranta, Stuart R. Jenkins, Jan G. Hiddink, and Hilmar Hinz. "Effect of prey abundance and size on the distribution of demersal fishes." Canadian Journal of Fisheries and Aquatic Sciences 69, no. 1 (January 2012): 191–200. http://dx.doi.org/10.1139/f2011-138.

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Many demersal fish species rely on benthic prey as food sources for part of, or in some cases, all of their life history. We investigated the relationships between prey and predator abundance and prey size and predator mouth gape size for nine demersal fish species. Of the species analysed, four showed a significant positive increase in abundance with increasing prey abundance. Prey size is thought to be an important parameter for demersal fish that are limited in their feeding potential by their mouth gape size, as it influences consumption rate and energy expenditure while foraging. The relationship between prey size and mouth gape was investigated using both stomach content data and prey availability data. Stomach content analysis revealed positive relationships between maximum prey size and predator mouth gape size for six of the species. Indications of prey size selectivity were only seen in the environment for European hake ( Merluccius merluccius ), highlighting the potential importance of prey size over prey abundance for this species. The results demonstrate that prey abundance and size are of significance for some demersal fish species feeding primarily on benthos and will help in defining habitat requirements of demersal fish species.

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Arts, Michael T., and D. O. Evans. "Precision Micrometer Measurement of Mouth Gape of Larval Fish." Canadian Journal of Fisheries and Aquatic Sciences 44, no. 10 (October 1, 1987): 1786–91. http://dx.doi.org/10.1139/f87-221.

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A precision micrometer device is described which standardizes measurement of mouth gape of larval fish and provides a greater degree of accuracy and speed than the conventional manual method. We compared gape measurements of larval lake whitefish (Coregonus clupeaformis) and lake herring (Coregonus artedii) using the gape micrometer versus the manual method. The micrometer measurements revealed a greater increase in gape with body length and resulted in a greater proportion of the variance in gape being explained, indicating that the gape micrometer is more sensitive and accurate than the manual method. Coefficient of variation of gape measurements on 238 larval yellow perch (Perca flavescens) decreased with body size from 0.5–4.0% at 0.8–1.2 cm standard length to 0.2–0.5% at 3.0 cm. The device has the added advantage that it could be adapted to connect to a microcomputer for direct data capture.

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Stalwick, Jordyn A., and Karen L. Wiebe. "Prey size and nestling gape size affect allocation within broods of the Mountain Bluebird." Journal of Ornithology 160, no. 1 (November 10, 2018): 145–54. http://dx.doi.org/10.1007/s10336-018-1603-7.

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Puvanendran, Velmurugu, Karine Salies, Benjamin Laurel, and Joseph A. Brown. "Size-dependent foraging of larval Atlantic cod (Gadus morhua)." Canadian Journal of Zoology 82, no. 8 (August 1, 2004): 1380–89. http://dx.doi.org/10.1139/z04-114.

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Most marine fish larvae are thought to be gape-limited predators, and the presence of suitably sized prey at the appropriate time in the foraging environment is a key factor for their growth and survival. Two experiments were carried out: in experiment 1, we investigated feeding of Atlantic cod (Gadus morhua L., 1758) larvae from 5 to 35 days post hatch on prey of three different sizes: two different-sized strains of rotifers, small rotifers (SR) and large rotifers (LR), and Artemia Leach, 1819 nauplii (AN), or an equal mixture of the three types of prey (MIX). In experiment 2, cod larvae were fed SR, LR, or a combination of SR and LR (MIX-R) at concentrations of 1500 and 4000 prey·L–1 from 4 to 20 days post hatch. Feeding incidence, number of prey in the gut, mouth gape, and prey selection were measured. In experiment 1, feeding incidence was initially higher in the SR treatment, while larvae failed to start feeding in either the LR or the AN treatment at 5 dph. Larvae in the LR treatment started feeding at 8 dph, and feeding incidence was comparable to that in the SR treatment, but the total number of prey eaten was higher in the SR than in the LR treatment until 20 dph. Larvae did not start feeding on AN until 26 dph, although they attacked them from 5 dph. In the MIX-R treatment in experiment 2, larvae fed selectively on LR at 4000 prey·L–1, whereas no selection was observed at 1500 prey·L–1. Our results suggest that cod larvae are gape-limited predators and the concentration of prey affects prey selection.

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Hampton, Paul M., and Brad R. Moon. "Gape size, its morphological basis, and the validity of gape indices in western diamond-backed rattlesnakes (crotalus atrox)." Journal of Morphology 274, no. 2 (October 29, 2012): 194–202. http://dx.doi.org/10.1002/jmor.20087.

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López, Pilar, Pilar López, José Martín, Pilar López, José Martín, and Alfredo Salvador. "Flexibility in feeding behaviour may compensate for morphological constraints of fossoriality in the amphisbaenian Blanus cinereus." Amphibia-Reptilia 34, no. 2 (2013): 241–47. http://dx.doi.org/10.1163/15685381-00002879.

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Morphological adaptations for burrowing, such as an elongated body, and a small head may constrain feeding behaviour in fossorial reptiles. We experimentally examined the effect of prey type on prey capture and handling behaviour of the amphisbaenian Blanus cinereus. This amphisbaenian showed four different handling modes according to the characteristics of each prey type. When prey diameter was narrower than gape-size, prey were consumed without prey processing; when prey diameter was wider than gape-size, B. cinereus shifted handling mode to prey processing. Amphisbaenians scraped or tore off bite-sized pieces of large prey and showed longer handling times for some prey types than most epigean saurians. Flexibility in feeding behaviour may allow amphisbaenians to exploit variable underground trophic resources, overcoming constraints of morphological adaptation to fossoriality.

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Montaña, Carmen G., Craig A. Layman, and Kirk O. Winemiller. "Gape size influences seasonal patterns of piscivore diets in three Neotropical rivers." Neotropical Ichthyology 9, no. 3 (September 2, 2011): 647–55. http://dx.doi.org/10.1590/s1679-62252011005000028.

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We examined diets of four piscivores, two in the order Perciformes (Cichla temensis and C. orinocensis) and two in the order Characiformes (Boulengerella cuvieri and B. lucius), from the Cinaruco, La Guardia, and Ventuari rivers in Venezuela throughout the wet-dry seasonal cycle. The four piscivores consumed a phylogenetically and morphologically diverse group of fishes, reflecting the overall diversity of fish species in these rivers. At the start of the falling-water period, Cichla consumed large prey, especially the abundant, migratory, fish of the genus Semaprochilodus. As these relatively large prey became depleted during the dry season, Cichla tended to consume smaller prey. For Boulengerella, gape limitation precluded consumption of larger, seasonally abundant, fishes, and so prey sizes were more consistent throughout the seasonal cycle. Our findings show how prey abundance and gape limitations interact to influence seasonal patterns of predator-prey interactions.

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LORD, JANICE M. "Frugivore gape size and the evolution of fruit size and shape in southern hemisphere floras." Austral Ecology 29, no. 4 (August 2004): 430–36. http://dx.doi.org/10.1111/j.1442-9993.2004.01382.x.

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Wheelwright, Nathaniel T. "Fruit-Size, Gape Width, and the Diets of Fruit-Eating Birds." Ecology 66, no. 3 (June 1985): 808–18. http://dx.doi.org/10.2307/1940542.

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Sethi, Pia, and Henry F. Howe. "Fruit removal by hornbills in a semi-evergreen forest of the Indian Eastern Himalaya." Journal of Tropical Ecology 28, no. 6 (November 2012): 531–41. http://dx.doi.org/10.1017/s0266467412000648.

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Abstract:We tested the hypothesis that seed size influences which frugivores eat fruits, and the size and nature of disperser assemblages in Pakke Tiger Reserve, India. Four tree species had large seeds (> 18 mm width) that could be handled by birds with large gape widths, while two tree species had smaller seeds (< 7 mm width) falling within the gape size range of many frugivores. We tested whether (1) disperser assemblage and activity reflected seed size, and (2) large-gaped hornbills were more effective at fruit removal of tree species with large seeds, than of those with smaller seeds and many dispersers. Day-long watches were conducted in 2005 at trees of Dysoxylum binectariferum (three in 2005 and nine in 2006), Chisocheton cumingianus (nine), Aglaia spectabilis (seven), Polyalthia simiarum (nine), Litsea monopetala (four) and Cinnamomum bejolghota (two in 2005 and six in 2006) to determine which frugivores visited trees and ate fruit. Disperser visitation and species diversity per tree to species with medium-sized seeds averaged 85 visits and 10 species d−1, contrasted with five visits by one frugivore species to large-seeded tree species. Seed removal rates per tree averaged 486 seeds d−1 from medium-seeded tree species, but 10 seeds d−1 from large-seeded species. Hornbills (Bucerotidae) and Ducula badia (Columbidae) removed large seeds from capsules of Aglaia spectabilis, Chisocheton cumingianus and Dysoxylum binectariferum (Meliaceae). Primates, civets and bats also consumed drupes of large-seeded Polyalthia simiarum (Annonaceae). Anthracoceros albirostris hornbills were important dispersers of Litsea monopetala (Lauraceae), a medium-seeded tree with a large disperser assemblage. Conversely, hornbills were quantitatively inconsequential for Cinnamomum bejolghota (Lauraceae), another medium-seeded tree species with several dispersers. Results suggest that the size and activity of disperser assemblages accurately reflects seed size. While hornbills were quantitatively important dispersers of large-seeded tree species, their effectiveness for trees with small- to medium-sized seeds depended on the tree species.

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Skorczewski, Tyler, Angela Cheer, Samson Cheung, and Peter C. Wainwright. "Use of computational fluid dynamics to study forces exerted on prey by aquatic suction feeders." Journal of The Royal Society Interface 7, no. 44 (August 12, 2009): 475–84. http://dx.doi.org/10.1098/rsif.2009.0218.

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Suction feeding is the most commonly used mechanism of prey capture among aquatic vertebrates. Most previous models of the fluid flow caused by suction feeders involve making several untested assumptions. In this paper, a Chimera overset grids approach is used to solve the governing equations of fluid dynamics in order to investigate the assumptions that prey do not interact with the flow and that the flow can be modelled as a one-dimensional flow. Results show that, for small prey, both neglecting the prey and considering prey interaction give similar calculated forces exerted on the prey. However, as the prey item increases in size toward the size of the gape, its effect on the flow becomes more pronounced. This in turn affects both the magnitude of the hydrodynamic forces imparted to the prey and the time when maximum force is delivered. Maximum force is delivered most quickly to intermediate sized prey, about one-third of mouth diameter, and most slowly to prey less than 7 per cent or greater than 67 per cent of mouth diameter. This suggests that the effect of prey size on the timing of suction forces may have substantial consequences for the feeding ecology of suction feeders that are known to prefer prey between 25 and 50 per cent of mouth diameter. Moreover, for a 15 cm fish with a 15 mm gape, assuming a radial one-dimensional flow field can result in underestimating the maximum force exerted on a 5 mm diameter spherical prey 1 gape distance from the mouth by up to 28.7 per cent.

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Bachiller, Eneko, and Xabier Irigoien. "Allometric relations and consequences for feeding in small pelagic fish in the Bay of Biscay." ICES Journal of Marine Science 70, no. 1 (November 21, 2012): 232–43. http://dx.doi.org/10.1093/icesjms/fss171.

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Abstract Bachiller, E. and Irigoien, X. 2013. Allometric relations and consequences for feeding in small pelagic fish in the Bay of Biscay. – ICES Journal of Marine Science, 70:232–243. The body size of fish is an important factor in determining their biology and ecology, as predators eat prey smaller than themselves. Predator mouth size restricts the availability of possible prey. In this paper we provide the allometric relationships of eight common, small pelagic fish species in the Bay of Biscay. In addition, we describe the predator-prey size ratios for different species, and we determine changes in their ratio-based trophic-niche breadth with increasing body size. Results suggest that gape size does not totally determine the predator-prey size ratio distribution, but predators use the entire available prey size range, including the smallest. As they grow they simply incorporate larger prey as their increased gape size permits. Accordingly, a large degree of overlap was found in the diet composition in terms of size and predator-prey ratios, even between fish of different sizes. Of the species studied, only horse mackerels seem to be clearly specialized in relatively large prey.

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Cloyed, Carl S., and Perri K. Eason. "Feeding limitations in temperate anurans and the niche variation hypothesis." Amphibia-Reptilia 38, no. 4 (2017): 473–82. http://dx.doi.org/10.1163/15685381-00003131.

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The niche variation hypothesis (NVH) states that populations with wider niches are more phenotypically variable. The NVH has important ecological and evolutionary implications but has been controversial since its inception. Recent interpretations have supported the NVH by directly comparing among-individual diet variation with population dietary niche breadth. Traditional studies of the NVH focused on morphological traits as proxies of niche variation, with contradictory results. Gape-limited predators may be relatively likely to show effects of morphological variation on diet breadth because gape size can strongly limit diet. We used five anurans to test NVH predictions, including three true frogs, Rana catesbeiana, R. clamitans, and R. sphenocephala, and two toads, Anaxyrus americanus and A. fowleri. We combined recent and traditional approaches by comparing both individual variation in diet and variation in gape width with dietary niche breadth. We found support for the NVH within two species of the three true frogs but not for either toad species, a difference likely driven by greater strength of the feeding limitation caused by gape width in the frogs. Toads had higher gape width to snout-vent length ratios, reducing the strength of the feeding limitation imposed by gape width. We found strong support for the NVH among species; species with more among-individual variation in diet and species with more variation in gape width had broader niches. Our results highlight the circumstances under which the NVH is applicable and demonstrate an example in which the NVH is supported through both traditional and recent interpretations.

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Sardiña, Paula, and Andrea Lopez Cazorla. "Trophic ecology of the whitemouth croaker, Micropogonias furnieri (Pisces: Sciaenidae), in south-western Atlantic waters." Journal of the Marine Biological Association of the United Kingdom 85, no. 2 (March 31, 2005): 405–13. http://dx.doi.org/10.1017/s0025315405011331h.

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Ontogenetic and seasonal diet changes of the juveniles of the marine fish Micropogonias furnieri, a species inhabiting Bahía Blanca estuary (Argentina), were investigated. Two size-related dietary shifts, at 4·00 cm and 7·00 cm total length (LT), respectively, were found. Small juveniles (1·00–3·99 cm LT) ate mostly chaetognaths (Sagitta friderici); medium-sized juveniles (4·00–6·99 cm LT) fed intensively on mysid shrimps (mainly Neomysis americana) and polychaetes, whereas large juveniles (7·00–15·99 cm LT) fed almost exclusively on epibenthic crustaceans (primarily Peisos petrunkevitchi). Increased mouth gape was related to increased size spectrum and mean size of the most important prey items consumed by M. furnieri. Juveniles <510 cm LT ate prey items almost as large as their mouth opening, whereas juveniles >410 cm LT were capable of consuming larger prey items than those found in their stomachs, indicating that the maximum size of prey eaten was not constrained by mouth gape. Seasonal and selectivity dietary analyses showed that M. furnieri can be a highly opportunistic selective feeder. Juveniles relied on S. friderici and P. petrunkevitchi throughout the year, except in summer, when mysids abundance increased in the estuary. Electivity values also showed that prey size and prey relative abundance are important factors in prey selection mechanisms.

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Burress, Edward D., and Peter C. Wainwright. "A peacock bass (Cichla) functional novelty relaxes a constraint imposed by the classic cichlid pharyngeal jaw innovation." Biological Journal of the Linnean Society 130, no. 2 (May 20, 2020): 382–94. http://dx.doi.org/10.1093/biolinnean/blaa050.

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Abstract Innovations may provide access to new resources but often result in significant trade-offs. Pharyngognathy is a classic pharyngeal jaw innovation in which the left and right lower pharyngeal jaw (LPJ) bones are united into a single structure, producing a strong bite but reduced gape. Throughout cichlids, pharyngeal suturing occurs along the entire medial border between LPJ bones, except in peacock bass (Cichla), where these bones are connected by ligaments only in their anterior region. We show that this limited attachment permits the jaw bones to spread apart and we link this feature to an increase in pharyngeal gape that is comparable to non-pharyngognathous species. The capacity of the LPJ bones to spread apart is strongest in juveniles and is mostly lost during development. Juvenile Cichla exhibit size-specific pharyngeal gape similar to non-pharyngognathous percomorphs; however, adults exhibit pharyngeal gape on par with other predatory cichlids. Relaxation of pharyngeal suturing offsets a major deleterious consequence of pharyngognathy by reducing gape limitation and we propose this may accelerate the ontogenetic transition to piscivory. Partial reversal of the classic cichlid pharyngeal jaw innovation highlights the functional trade-offs that often accompany innovations and may be a major cause of variation in their macroevolutionary consequences.

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Forsman, Anders. "Body Size and Net Energy Gain in Gape-Limited Predators: A Model." Journal of Herpetology 30, no. 3 (September 1996): 307. http://dx.doi.org/10.2307/1565167.

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Hampton, Paul M. "Morphological Indicators of Gape Size for Red-Tailed Pipe Snakes (Cylindrophis ruffus)." Journal of Herpetology 52, no. 4 (December 2018): 425–29. http://dx.doi.org/10.1670/18-015.

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Webb, Jonathan K., and Richard Shine. "Prey-size selection, gape limitation and predator vulnerability in Australian blindsnakes (Typhlopidae)." Animal Behaviour 45, no. 6 (June 1993): 1117–26. http://dx.doi.org/10.1006/anbe.1993.1136.

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Vincent, S. E., P. D. Vincent, D. J. Irschick, and J. M. Rossell. "Do juvenile gape-limited predators compensate for their small size when feeding?" Journal of Zoology 268, no. 3 (March 2006): 279–84. http://dx.doi.org/10.1111/j.1469-7998.2005.00014.x.

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Mehner, Thomas, Matthias Plewa, Stephan Hülsmann, and Susanne Worischka. "Gape-size dependent feeding of age-0 perch (Perca fluviatilis) and age-0 zander (Stizostedion lucioperca) on Daphnia galeata." Fundamental and Applied Limnology 142, no. 2 (May 26, 1998): 191–207. http://dx.doi.org/10.1127/archiv-hydrobiol/142/1998/191.

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Bowman, Clive E. "Feeding design in free-living mesostigmatid chelicerae (Acari: Anactinotrichida)." Experimental and Applied Acarology 84, no. 1 (April 30, 2021): 1–119. http://dx.doi.org/10.1007/s10493-021-00612-8.

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AbstractA model based upon mechanics is used in a re-analysis of historical acarine morphological work augmented by an extra seven zoophagous mesostigmatid species. This review shows that predatory mesostigmatids do have cheliceral designs with clear rational purposes. Almost invariably within an overall body size class, the switch in predatory style from a worm-like prey feeding (‘crushing/mashing’ kill) functional group to a micro-arthropod feeding (‘active prey cutting/slicing/slashing' kill) functional group is matched by: an increased cheliceral reach, a bigger chelal gape, a larger morphologically estimated chelal crunch force, and a drop in the adductive lever arm velocity ratio of the chela. Small size matters. Several uropodines (Eviphis ostrinus, the omnivore Trachytes aegrota, Urodiaspis tecta and, Uropoda orbicularis) have more elongate chelicerae (greater reach) than their chelal gape would suggest, even allowing for allometry across mesostigmatids. They may be: plesiosaur-like high-speed strikers of prey, scavenging carrion feeders (like long-necked vultures), probing/burrowing crevice feeders of cryptic nematodes, or small morsel/fragmentary food feeders. Some uropodoids have chelicerae and chelae which probably work like a construction-site mechanical excavator-digger with its small bucket. Possible hoeing/bulldozing, spore-cracking and tiny sabre-tooth cat-like striking actions are discussed for others. Subtle changes lead small mesostigmatids to be predator–scavengers (mesocarnivores) or to be predator–fungivores (hypocarnivores). Some uropodines (e.g., the worm-like prey feeder Alliphis siculus and, Uropoda orbicularis) show chelae similar in design to astigmatids and cryptostigmatids indicating possible facultative saprophagy. Scale matters—obligate predatory designs (hypercarnivory) start for mesostigmatids with chelal gape > 150 μm and cheliceral reach > 350 μm (i.e., about 500–650 μm in body size). Commonality of trophic design in these larger species with solifugids is indicated. Veigaia species with low chelal velocity ratio and other morphological strengthening specialisms, appear specially adapted in a concerted way for predating active soft and fast moving springtails (Collembola). Veigaia cerva shows a markedly bigger chelal gape than its cheliceral reach would proportionately infer suggesting it is a crocodile-like sit-and-wait or ambush predator par excellence. A small chelal gape, low cheliceral reach, moderate velocity ratio variant of the worm-like feeding habit design is supported for phytoseiid pollenophagy. Evidence for a resource partitioning model in the evolution of gnathosomal development is found. A comparison to crustacean claws and vertebrate mandibles is made. Alliphis siculus and Rhodacarus strenzkei are surprisingly powerful mega-cephalics for their small size. Parasitids show a canid-like trophic design. The chelicera of the nematophagous Alliphis halleri shows felid-like features. Glyphtholaspis confusa has hyaena-like cheliceral dentition. The latter species has a markedly smaller chelal gape than its cheliceral reach would suggest proportionately, which together with a high chelal velocity ratio and a high estimated chelal crunch force matches a power specialism of feeding on immobile tough fly eggs/pupae by crushing (durophagy). A consideration of gnathosomal orientation is made. Predatory specialisms appear to often match genera especially in larger mesostigmatids, which may scale quite differently. Comparison to holothyrids and opilioacarids indicates that the cheliceral chelae of the former are cutting-style and those of the latter are crushing-style. A simple validated easy-to-use ‘2:1 on’ predictive algorithm of feeding habit type is included based on a strength-speed tradeoff in chelal velocity ratio for ecologists to test in the field.

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Ramamonjisoa, Noelikanto, and Akira Mori. "Growth, developmental, and size structure responses in tadpole prey under increasing threat from gape-limited newts." Canadian Journal of Zoology 97, no. 12 (December 2019): 1116–21. http://dx.doi.org/10.1139/cjz-2019-0067.

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Size variability within a cohort can have profound effects on community ecology and evolution. Although competition for resources generally increases size variability, the effect of (non-consumptive) predation on this demographic trait remains relatively poorly understood. Existing models suggest a positive correlation between growth rate (mediated by resource level) and expression of size variability (as measured by the coefficient of variation) in prey cohorts. We tested this prediction by exposing the tadpoles of the Japanese Forest Green Treefrog (Rhacophorus arboreus (Okada and Kawano, 1924) = Zhangixalus arboreus (Okada and Kawano, 1924)) to the non-lethal presence of gape-limited Japanese Fire-bellied Newts (Cynops pyrrhogaster (Boie, 1826)) at low and high predator densities in an outdoor mesocosm experiment. Tadpole growth rates and periphyton biomass increased with newt density. But in contrast to prediction, elevated growth rates did not increase but, reversely, decreased cohort size variability in the tadpoles. We discuss two potential mechanisms behind this outcome. First, increased resource availability mediated by predator feeding may have reduced the strength of competition, ultimately leading to more evenly distributed resource gains among individuals; second, if smaller individuals grew relatively faster than larger individuals, as to quicken entry to a size refuge against the gape-limited predator, then inter-individual size differences could diminish over time.

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Maret, Timothy J., and James P. Collins. "Effect of Prey Vulnerability on Population Size Structure of a Gape-Limited Predator." Ecology 77, no. 1 (January 1996): 320–24. http://dx.doi.org/10.2307/2265681.

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Rodríguez-Robles, Javier A., Christopher J. Bell, and Harry W. Greene. "Gape size and evolution of diet in snakes: feeding ecology of erycine boas." Journal of Zoology 248, no. 1 (May 1999): 49–58. http://dx.doi.org/10.1017/s0952836999005051.

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Ward, F. J., and B. R. McCulloch. "Relationship between mouth gape of juvenile walleye (Stizostedion vitreum vitreum) and prey size." SIL Proceedings, 1922-2010 24, no. 4 (September 1991): 2362–64. http://dx.doi.org/10.1080/03680770.1989.11899965.

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Kloepper, Laura, Rebecca Wojciechowicz, and James Simmons. "The effect of mouth gape angle on beam size for echolocating Eptesicus fuscus." Journal of the Acoustical Society of America 137, no. 4 (April 2015): 2335. http://dx.doi.org/10.1121/1.4920528.

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Rodriguez-Robles, Javier A., Christopher J. Bell, and Harry W. Greene. "Gape size and evolution of diet in snakes: feeding ecology of erycine boas." Journal of Zoology 248, no. 1 (May 1999): 49–58. http://dx.doi.org/10.1111/j.1469-7998.1999.tb01021.x.

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33

Van Der Bilt, A., H. W. Van Der Glas, L. W. Olthoff, and F. Bosman. "The Effect of Particle Size Reduction on the Jaw Gape in Human Mastication." Journal of Dental Research 70, no. 5 (May 1991): 931–37. http://dx.doi.org/10.1177/00220345910700051301.

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Garcia, Alexandre M., Ricardo M. Geraldi, and João P. Vieira. "Diet composition and feeding strategy of the southern pipefish Syngnathus folletti in a Widgeon grass bed of the Patos Lagoon Estuary, RS, Brazil." Neotropical Ichthyology 3, no. 3 (September 2005): 427–32. http://dx.doi.org/10.1590/s1679-62252005000300011.

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Pipefish species are poorly known representatives of the family Syngnathidae, which have been increasingly threatened by anthropogenic activities. We describe the diet composition and feeding strategy of southern pipefish Syngnathus folletti inhabiting a Widgeon grass (Ruppia maritima L.) bed in the estuarine zone of Patos Lagoon, southern Brazil. We also investigated whether mouth gape affected the size of prey items consumed and based on indirect evidence, we suggest possible pipefish foraging movements within the bed. Individuals were collected from December 1994 to March 1995 in a Ruppia maritima bed located in the Patos Lagoon Estuary during day and night periods. We analyzed the stomach contents of 108 individuals (54 females and 54 males). Both genders seemed to be diurnal carnivores with diets composed primarily of copepods and isopods. Mixed feeding strategies were evident with varying degrees of specialization on different prey types. Females had a more diverse diet both in prey richness as in prey size range, whereas males fed primarily on smaller prey, the isopod U. peterseni and copepods. Gender-based diet differences suggest that females may be more mobile and active inside the Widgeon grass bed than males. The average size range of the two dominant prey items fitted well to the pipefish mouth gape (0.4 to 1.4mm). However, a few female individuals were able to consume prey three times larger than their maximum gape. A diagram of prey microhabitat suggested that both genders browse and capture invertebrates over the entire vegetated substrate provided by the Widgeon grass bed.

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Grant, Jonathan, Craig W. Emerson, and Sandra E. Shumway. "Orientation, passive transport, and sediment erosion features of the sea scallop Placopecten magellanicus in the benthic boundary layer." Canadian Journal of Zoology 71, no. 5 (May 1, 1993): 953–59. http://dx.doi.org/10.1139/z93-125.

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Passive transport and orientation of sea scallops (Placopecten magellanicus; 27–120 mm shell height) were studied in a laboratory flume to assess flow-mediated control of movement and position on the seabed. Additional experiments were conducted to characterize patterns of sediment transport around the scallop shell in relation to recesses occupied by scallops. The critical shear velocity of scallop transport was not correlated with shell height or other size measures, and most scallops were transported with the ventral shell margin facing downstream. Frontal exposure of scallops to the flow as indicated by fineness (shell height/shell depth) was greater in larger scallops, but when pallial gape was included in fineness (shell height/shell depth + gape)), frontal exposure was not correlated with scallop size. This suggests that variation in the drag component of transport was responsible for the lack of correlation between shell morphometry and critical shear velocity. Sediment transport created a horseshoe-shaped trough around the shell and several smaller erosion–deposition features downstream. The dimensions of sediment transport features were dependent on shell allometry, and it is likely that sediment transport contributes to the formation of scallop recesses typically observed in scallop beds. These results indicate that passive transport of sea scallops has a behavioural component related to gape that is independent of shell size. In contrast, scallop orientation and recessing may be explained by physical processes rather than simply by behaviour. Studies of bivalve hydrodynamics require consideration of living animals in addition to shell specimens and must include conditions of benthic boundary layer flow and sediment transport.

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Sempeski, Philippe, and Philippe Gaudin. "Size-related shift in feeding strategy and prey-size selection in young grayling (Thymallus thymallus)." Canadian Journal of Zoology 74, no. 9 (September 1, 1996): 1597–603. http://dx.doi.org/10.1139/z96-176.

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Observations of feeding behaviour and analysis of prey-size selection by young grayling revealed a shift in feeding strategy coinciding with a shift in habitat occurring between larval (observed in lateral habitats) and juvenile (observed in the river channel) stages of grayling. The mean number of foraging attempts per minute decreased four times between both stages, while in the same time the mean distance travelled during each foraging attempt decreased from 1.5 body lengths to 1 body length. Gape-limited postemergent larvae fed mainly on small chironomid larvae (<0.5 mm3) but larger larvae and pupae (0.5 – 1 mm3) were consumed with increasing size. The diet spectrum of juveniles >40 mm was characterized by the appearance of very large prey (> 10 mm3), such as simuliid and ephemeropteran larvae, but also by a new increase of the contribution of small chironomid larvae. Changes in the feeding strategy of young grayling are discussed in relation to internal (e.g., morphological limitations) and external (e.g., physical characteristics of habitat) constraints.

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Michener, Gail R. "Limits on egg predation by Richardson's ground squirrels." Canadian Journal of Zoology 83, no. 8 (August 1, 2005): 1030–37. http://dx.doi.org/10.1139/z05-094.

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To test the inference, arising from circumstantial evidence, that Richardson's ground squirrels (Spermophilus richardsonii (Sabine, 1822)) frequently depredate eggs of greater sage-grouse (Centrocercus urophasianus (Bonaparte, 1827)), gape size was measured and the response of free-living squirrels to three sizes of eggs was observed. Maximum gape measured on carcasses was 26 mm and functional gape assessed from tooth imprints in artificial clay eggs was 17 mm. Squirrels left imprints in 46 of 110 clay eggs, but whether tested with domestic fowl (Gallus gallus (L., 1758)) or ring-necked pheasant (Phasianus colchicus L., 1758) eggs that approximated the maximum width of sage-grouse eggs or with much smaller Japanese quail (Coturnix japonica Temminck and Schlegel, 1849) eggs that approximated maximum gape, no squirrels (28 adults and at least 28 juveniles) spontaneously depredated eggs, even after multiple exposures. When re-tested with damaged eggs, 15 of 16 adult females scavenged contents, though usually not on their first exposure. After scavenging damaged eggs, 2 of 12 squirrels opened a few intact eggs, but only quail eggs and usually only if the shell was rough. Although Richardson's ground squirrels are potential scavengers of large damaged eggs and likely they could depredate small eggs, the inference from circumstantial evidence that they are major predators of greater sage-grouse eggs remains unsubstantiated.

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Virgl, John A., Shane P. Mahoney, and Kim Mawhinney. "Phenotypic Variation in Skull Size and Shape Between Newfoundland and Mainland Populations of North American Black Bears, Ursus americanus." Canadian Field-Naturalist 117, no. 2 (April 1, 2003): 236. http://dx.doi.org/10.22621/cfn.v117i2.702.

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It is well recognized that differences in environmental selection pressures among populations can generate phenotypic divergence in a suite of morphological characteristics and associated life history traits. Previous analysis of mitochondrial DNA and body size have suggested that Black Bears (Ursus americanus) inhabiting the island of Newfoundland represent a different subspecies or ecotype from mainland populations. Assuming that body size covaries positively with skull size, we predicted that skull size would be greater for bears on the island than the mainland, and the distribution of size-related shape components in multivariate space should show a distinct separation between Newfoundland and mainland populations. Measurements of 1080 specimens from Newfoundland, Alberta, New York, and Quebec did not provide unequivocal support for our prediction that skull size in Newfoundland bears would be larger than bears from the mainland populations. After removing ontogenetic effects of skull size, between-population variation in skull shape was greater in females than males, and the analysis significantly separated Newfoundland bears from mainland populations. Explanations for this pattern are numerous, but currently remain hypothetical. Limited covariation between skull size and body size suggests that genetic traits regulating the size of Black Bear skulls are more heritable (i.e., less influenced by environmental selection pressures) than characteristics affecting body size. We hypothesize that if gape size does not limit prey size in solitary terrestrial carnivores, large degrees of among-population variation in body size should be coupled with little covariation in skull size. In general, sexual dimorphism in skull size and shape was marginal for the phenotypic characters measured in our study. We believe that sexual dimorphism in skull size in Black Bears is primarily driven by intrasexual selection in males for increased gape size display, while similarity in skull shape between sexes is associated with the constraints of a temporally-selective, but similar diet.

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Hodgkison, Simon, and Jean-Marc Hero. "Seasonal, sexual and ontogenetic variations in the diet of the 'declining' frogs Litoria nannotis, Litoria rheocola and Nyctimystes dayi." Wildlife Research 30, no. 4 (2003): 345. http://dx.doi.org/10.1071/wr01008.

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Faecal analyses were used to investigate the diets of the endangered frogs Litoria nannotis, L. rheocola and Nyctimystes dayi in Tully Gorge, North Queensland. Comparisons of diet and food availability indicate that these species feed indiscriminately on a range of terrestrial and aquatic invertebrates. Changes in morphology and foraging behaviour significantly influenced diet composition and created subtle shifts in the degree of selectivity displayed in prey choice. Interspecific differences in numeric and volumetric diet composition were attributed to variations in gape size and microhabitat selection. Within the diets of L. nannotis and L. rheocola, a decline in prey selectivity observed during the dry season reflected a reduction in foraging activity. Differences in the gape size and foraging behaviour of males and females of L. nannotis were responsible for sex-specific differences in diet composition. L. nannotis also diplayed an ontogenetic shift in prey size and type. As snout–vent length increased, L. nannotis consumed fewer, but larger prey and increasingly discriminated against dipterans, dipteran larvae and hemipterans. Importantly, L. nannotis, L. rheocola and N. dayi demonstrated the capacity to compensate for fluctuations in food availability by feeding on less lucrative prey.

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40

Hampton, Paul, and Taylor Kalmus. "The Allometry of Cranial Morphology and Gape Size in Red-Bellied Mudsnakes (Farancia abacura)." Herpetologica 70, no. 3 (September 2014): 290–97. http://dx.doi.org/10.1655/herpetologica-d-13-00067.

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41

Segura, Angel Manuel, Valentina Franco-Trecu, Paula Franco-Fraguas, and Matías Arim. "Gape and energy limitation determine a humped relationship between trophic position and body size." Canadian Journal of Fisheries and Aquatic Sciences 72, no. 2 (February 2015): 198–205. http://dx.doi.org/10.1139/cjfas-2014-0093.

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We found a segmented pattern, increasing for small sizes and decreasing for larger sizes, in the relationship between trophic position and body size. This pattern provides support for a recently developed theoretical model whose derivation was based on consumers’ metabolic requirements and on basic assumptions about feeding relationships. We combined original and published information about stable nitrogen isotopes, a proxy of trophic position, for a broad range of animal body sizes (10−3–105 kg) inhabiting the southwestern Atlantic Ocean. Linear, polynomic, and piecewise segmented models were fit to species trophic position and body mass. The segmented model had the best fit, presenting a positive slope (β1 = 0.33 ± 0.08) for small organisms (<200 kg) and a negative slope (β2 = −1.93 ± 0.16) for larger ones. This suggests that there are morphological restrictions to prey consumption in smaller organisms and energetic constraints to trophic position in larger ones. Furthermore, the predator–prey body mass ratio (BMR = 1.31; 95% CI = 0.9–2.40) estimated here is similar to previous reports of direct observations (BMR = 1.64 and 1.82). However, the trophic position of larger organisms decreases at a faster rate (β2 = −1.93) than expected by metabolic demand (β2expected = −0.16 to −0.82), suggesting that additional processes should be considered. Our results suggest that large species could be more vulnerable to global change than previously thought.

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42

Makrakis, M. C., K. Nakatani, A. Bialetzki, L. C. Gomes, P. V. Sanches, and G. Baumgartner. "Relationship between gape size and feeding selectivity of fish larvae from a Neotropical reservoir." Journal of Fish Biology 72, no. 7 (May 2008): 1690–707. http://dx.doi.org/10.1111/j.1095-8649.2008.01845.x.

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Booth, DJ, GH Pyke, and WJR Lanzing. "Prey detection by the blue-eye Pseudomugil signifer Kner (Atherinidae): analysis of field behaviour by controlled laboratory experiments." Marine and Freshwater Research 36, no. 5 (1985): 691. http://dx.doi.org/10.1071/mf9850691.

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Observations in a brackish creek in eastern Australia indicate that the blue-eye, P. signifer, includes various kinds of insects in its diet in the proportions encountered, provided that they are below a maximum size dictated by the mouth-gape of the fish. Encounter rates are affected by prey body size and water turbidity, but not by hunger level of the fish. Fish fed on insects at rates varying between 0.04 and 0.08 mg s-1.

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44

Persson, Lennart, Jens Andersson, Eva Wahlstrom, and Peter Eklov. "Size-Specific Interactions in Lake Systems: Predator Gape Limitation and prey Growth Rate and Mortality." Ecology 77, no. 3 (April 1996): 900–911. http://dx.doi.org/10.2307/2265510.

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45

Ponton, D., and R. Muller. "Size of prey ingested by whitefish, Coregonus sp., larvae. Are Coregonus larvae gape-limited predators?" Journal of Fish Biology 36, no. 1 (January 1990): 67–72. http://dx.doi.org/10.1111/j.1095-8649.1990.tb03520.x.

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46

Du, Bo, Chang-Jing Liu, and Shi-Jie Bao. "Begging form and growth pattern of nestlings correlate with parental food-allocation patterns in the Horned Lark (Eremophilaalpestris)." Canadian Journal of Zoology 93, no. 4 (April 2015): 273–79. http://dx.doi.org/10.1139/cjz-2014-0235.

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Life-history theory assumes that selection favors parents that can maximize their reproductive success via behavioral strategies. As brood size determines the reproductive value of each nestling, parents may adjust their food-allocation patterns according to brood size. We test this assumption in the Horned Lark (Eremophila alpestris (L., 1758)). Our findings revealed that nestling begging forms varied with brood size, by gaping in one-chick broods and postural activity in two- and three-chick broods. Accordingly, parental food-allocation patterns differed in different-sized broods. In one-chick broods, parents increased feeding rates with the gaping duration of nestling. In two-chick broods, parents did not change food-allocation patterns according to nestlings’ begging. In three-chick broods, however, they fed later-hatched nestlings more even when early-hatched nestlings begged more intensely. Horned Larks exhibited obvious sexual differences in parenting style and ability, which resulted in nestlings from two- and three-chick broods changing their begging intensity according to the sex of the provisioning adult. Furthermore, nestling growth pattern diverged with brood sizes, with body mass growing faster in one-chick broods than in two- and three-chick broods. Growth rate of beak gape and tarsus length did not differ significantly among brood sizes, but beak gape was larger and tarsus length was shorter in one-chick broods than in larger broods at fledging. Our results thus support the idea that parents may use food allocation to regulate sibling rivalry, which in turn cause nestlings to beg food in different forms and grow in different patterns so that their reproductive success can be enhanced.

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Reimchen, T. E., and P. Nosil. "Replicated ecological landscapes and the evolution of morphological diversity among Gasterosteus populations from an archipelago on the west coast of Canada." Canadian Journal of Zoology 84, no. 5 (May 2006): 643–54. http://dx.doi.org/10.1139/z06-036.

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We investigated defence and trophic morphology of 40 freshwater stickleback (Gasterosteus aculeatus L., 1758) populations from the Banks–Estevan archipelago for comparison with the isolated stickleback populations from the nearby Haida Gwaii archipelago. Using 14 size-standardized metric traits and 11 meristic or categorical traits from 1706 individuals (14–54/site), we found that the first principal component (PC1) defined a defence apparatus characterized by high loadings for pelvic spine length, number of forks on the ascending process, number of lateral plates, and overlap between lateral and basal plates. The second component (PC2) defined a trophic apparatus characterized by high loadings for gape length, eye diameter, and body depth. Populations with loss of spines, loss of plates, increased gape, increased body depth, and low gill raker number were most prevalent in ponds and shallow lakes with low conductivity. Most traits were sexually dimorphic, with males exhibiting greater armature and increased benthic trophic adaptations. We observed substantially less morphological variability among Banks–Estevan stickleback populations than among the Haida Gwaii populations and one instance of common ancestry or convergence to the giant black stickleback of Haida Gwaii.

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Denoël, Mathieu, and Pierre Joly. "REGULAR ARTICLES / ARTICLES RÉGULIERSSize-related predation reduces intramorph competition in paedomorphic Alpine newts." Canadian Journal of Zoology 79, no. 6 (June 1, 2001): 943–48. http://dx.doi.org/10.1139/z01-063.

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Evolutionary theory assumes that facultative paedomorphosis in newts and salamanders is adaptive in allowing either a younger age at maturity or resource partitioning between the heterochronic morphs. In newt populations that only take the metamorphic ontogenetic pathway, juveniles are terrestrial and avoid food competition with larvae and breeding adults. In contrast, in populations where paedomorphosis occurs, branchiate newts of all sizes coexist in the aquatic habitats, posing the question of whether intramorph competition exists and its relationship with the evolution of paedomorphosis. We studied size-related predation in such a size-structured community of branchiate Alpine newts (Triturus alpestris) inhabiting a deep alpine lake. Although gape limitation may explain such size-related predation, individuals also exhibited selectivity according to prey size. Amongst small prey that were within the capture range of all newt size classes, smaller newts preyed on smaller items than did larger ones. We assume that such decisions favour the coexistence of different-sized individuals. It is suspected that such size-selective predation on items which are avoided by water-living metamorphs allows the maintenance of facultative paedomorphosis, in favouring resource partitioning between morphs.

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Brassard, Colline, Marilaine Merlin, Claude Guintard, Elodie Monchâtre-Leroy, Jacques Barrat, Nathalie Bausmayer, Stéphane Bausmayer, et al. "Bite force and its relationship to jaw shape in domestic dogs." Journal of Experimental Biology 223, no. 16 (June 25, 2020): jeb224352. http://dx.doi.org/10.1242/jeb.224352.

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ABSTRACTPrevious studies based on two-dimensional methods have suggested that the great morphological variability of cranial shape in domestic dogs has impacted bite performance. Here, we used a three-dimensional biomechanical model based on dissection data to estimate the bite force of 47 dogs of various breeds at several bite points and gape angles. In vivo bite force for three Belgian shepherd dogs was used to validate our model. We then used three-dimensional geometric morphometrics to investigate the drivers of bite force variation and to describe the relationships between the overall shape of the jaws and bite force. The model output shows that bite force is rather variable in dogs and that dogs bite harder on the molar teeth and at lower gape angles. Half of the bite force is determined by the temporal muscle. Bite force also increased with size, and brachycephalic dogs showed higher bite forces for their size than mesocephalic dogs. We obtained significant covariation between the shape of the upper or lower jaw and absolute or residual bite force. Our results demonstrate that domestication has not resulted in a disruption of the functional links in the jaw system in dogs and that mandible shape is a good predictor of bite force.

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Reilly, S. "The ontogeny of aquatic feeding behavior in Salamandra salamandra: stereotypy and isometry in feeding kinematics." Journal of Experimental Biology 198, no. 3 (March 1, 1995): 701–8. http://dx.doi.org/10.1242/jeb.198.3.701.

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To examine the extent to which aquatic prey-capture behavior in salamanders is stereotyped and how feeding kinematics scales with size, the ontogenetic variability of aquatic feeding behavior was examined in eight Salamandra salamandra. Feeding kinematics (seven duration and angular displacement variables), kinematic variance and capture performance were quantified and compared in the first several feedings after birth with a series of feedings 8 weeks later, just prior to metamorphosis. Analysis of variance revealed no statistically significant ontogenetic differences in the kinematic variables, and individual differences were found in only two variables (maximum gape angle and gape cycle time). A comparison of the relative kinematic variance within individuals revealed no significant differences in variance during ontogeny. In addition, capture success rate did not change. The strike is significantly faster than that of other salamanders. These results indicate that the initial prey-capture behavior remains unchanged throughout larval ontogeny. Thus, aquatic strike behavior in S. salamandra is developmentally fixed (innate) and does not appear to be influenced by learning or improvement in 'skill', supporting the hypothesis that aquatic salamander feeding is a highly stereotyped, unmodulated behavior. In addition, the lack of kinematic change through ontogeny indicates that feeding kinematics do not scale with body size, contrary to predictions that movements should be slower in larger animals.

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Journal articles on the topic 'Gape size'

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