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As body size increases, some predators eliminate small prey from their diet exhibiting an ontogenetic shift toward larger prey. In contrast, some predators show a telescoping pattern of prey size in which both large and small prey are consumed with increasing predator size. To explore a functional explanation for the two feeding patterns, I examined feeding effort as both handling time and number of upper jaw movements during ingestion of fish of consistent size. I used a range of body sizes from two snake species that exhibit ontogenetic shifts in prey size ( Nerodia fasciata and N. rhombifer ) and a species that exhibits telescoping prey size with increased body size ( Thamnophis proximus ). For the two Nerodia species, individuals with small or large heads exhibited greater difficulty in feeding effort compared to snakes of intermediate size. However, for T. proximus measures of feeding effort were negatively correlated with head length and snout–vent length (SVL). These data indicate that ontogenetic shifters of prey size develop trophic morphology large enough that feeding effort increases for disproportionately small prey. I also compared changes in body size among the two diet strategies for active foraging snake species using data gleaned from the literature to determine if increased change in body size and thereby feeding morphology is observable in snakes regardless of prey type or foraging habitat. Of the 30 species sampled from literature, snakes that exhibit ontogenetic shifts in prey size have a greater magnitude of change in SVL than species that have telescoping prey size patterns. Based upon the results of the two data sets above, I conclude that ontogenetic shifts away from small prey occur in snakes due, in part, to growth of body size and feeding structures beyond what is efficient for handling small prey. [ABSTRACT FROM AUTHOR]

During aquatic feeding salamanders use the hyobranchial apparatus to capture prey. The hyobranchial apparatus depresses the floor of the mouth, effectively expanding the oropharyngeal cavity and generating suction. Within the family Salamandridae, there is a wide range of ecological diversity, with salamanders being terrestrial, semi-aquatic, or aquatic as adults. The purpose of this research was to quantify the diverse morphology and suction feeding performance of aquatically feeding salamandrids. We hypothesized that a more robust hyobranchial apparatus morphology would yield increased aquatic feeding performance. When compared to semi-aquatic newts, the fully aquatic species Paramesotriton labiatus had greater mineralization of the hyobranchial apparatus, as well as relatively more narrow basibranchial and wider ceratobranchial I + II complexes. These morphological differences coincide with greater aquatic feeding performance. Kinematics from high-speed videography revealed that maximum mouth opening velocity and acceleration were approximately two and five times greater, respectively, in Paramesotriton , and hyobranchial depression acceleration was found to be approximately three times greater than in the semi-aquatic species Pleurodeles waltl, Notophthalmus viridescens, Triturus dobrogicus, and Cynops cyanurus . Using digital particle image velocimetry, peak and average fluid velocity generated in Paramesotriton during suction feeding events were found to be 0.5 m s −1 and 0.2 m s −1 , respectively, doubling that of all semi-aquatic species. These findings reveal that specialized morphology increases aquatic feeding performance in a fully aquatic newt. [ABSTRACT FROM AUTHOR]

Adult green turtles (Chelonia mydas) are unusual relative to other sea turtles in that they are predominately herbivorous. This herbivorous diet is reflected in the serrated morphology of their beak, bite performance and the relative morphometrics of their heads. Recent bite performance data in loggerhead turtles (Caretta caretta), which are known for their durophagous capability, have demonstrated that bite force is correlated with head morphometrics. The objective of this study was to characterize bite force in green turtles and correlate bite performance with head and carapace morphometrics. We predicted that maximum bite force in green turtles would be less in magnitude relative to loggerheads, but would be positively correlated with head morphometrics. Therefore, mass, straight carapace length, straight carapace width, greatest head width, height, and length were collected with bite force from free-ranging green turtles from Punta Abreojos, Baja California Sur, Mexico and Otsuchi, Japan. Subjects ranged from 10.9 to 48kg, with straight carapace length and width ranged from 40.6cm to 71.9cm (mean=56.3±8.5cm) and from 33.5cm to 55.9cm (mean=44.8±5.7cm), respectively. A bite force apparatus was used to collect bite performance from subjects. The maximum bite force was 303N. Mean head width, head height, and head length were 8.7±1.2, 8.2±1.1, and 11.5±1.5cm, respectively. Bite force was lower in magnitude than reported for loggerhead turtles as predicted but still strong enough to process algal and plant matter, as well as crush many hard prey items. Simultaneous measurements of body and head size, and the use of non-linear reduced major axis regression, show that bite force scaled isometrically relative to body size and head size. Simple correlation showed that all logged transformed morphometrics were good predictors of logged bite performance, but an AICc-based weighted regression showed that body mass, followed by head width and head height, were better predictors of bite force than carapace size. [ABSTRACT FROM AUTHOR]

Abstract: Evaluations of bite force, either measured directly or calculated theoretically, have been used to investigate the maximum feeding performance of a wide variety of vertebrates. However, bite force studies of fishes have focused primarily on small species due to the intractable nature of large apex predators. More massive muscles can generate higher forces and many of these fishes attain immense sizes; it is unclear how much of their biting performance is driven purely by dramatic ontogenetic increases in body size versus size-specific selection for enhanced feeding performance. In this study, we investigated biting performance and feeding biomechanics of immature and mature individuals from an ontogenetic series of an apex predator, the bull shark, Carcharhinus leucas (73–285cm total length). Theoretical bite force ranged from 36 to 2128N at the most anterior bite point, and 170 to 5914N at the most posterior bite point over the ontogenetic series. Scaling patterns differed among the two age groups investigated; immature bull shark bite force scaled with positive allometry, whereas adult bite force scaled isometrically. When the bite force of C. leucas was compared to those of 12 other cartilaginous fishes, bull sharks presented the highest mass-specific bite force, greater than that of the white shark or the great hammerhead shark. A phylogenetic independent contrast analysis of anatomical and dietary variables as determinants of bite force in these 13 species indicated that the evolution of large adult bite forces in cartilaginous fishes is linked predominantly to the evolution of large body size. Multiple regressions based on mass-specific standardized contrasts suggest that the evolution of high bite forces in Chondrichthyes is further correlated with hypertrophication of the jaw adductors, increased leverage for anterior biting, and widening of the head. Lastly, we discuss the ecological significance of positive allometry in bite force as a possible “performance gain” early in the life history of C. leucas. [Copyright &y& Elsevier]

Abstract: The present study aimed to determine the effects of different concentrations of the toxic dinoflagellate Gymnodinium catenatum on the feeding performance, survival rates, and PSP toxin profiles of Euterpina acutifrons Dana and Acartia grani Sars. Each of the three different experiments was conducted in order to determine the feeding rates of adult female copepod species. Feeding experiments were performed in four 75-ml vessels each containing five copepods and different concentrations of cells (C1=2.68×102, C2=5.36×102 cellsml−1). Initial and final cell concentrations were estimated using a Coulter counter, while the carbon and nitrogen content were determined using a CHN analyzer. High-performance liquid chromatography was used to determine the composition of the PSP toxins, and estimate their concentrations in the tissue of the copepods. In experiment 1, significantly higher (p <0.05) ingestion rates were recorded for A. grani when feeding on the second concentration of cells (C2). Filtration rates were also significantly higher (p <0.05) for C2. A similar pattern was recorded for ingestion rates in E. acutifrons. By contrast, filtration rates were apparently higher for the lower concentration (C1). In experiment 2, A. grani ingestion rates were significantly higher (p <0.05) for the higher concentration (C2) in all three time phases. However, filtration rates for C2 were significantly higher (p <0.05) at 12 and 18h. E. acutifrons also presented significantly higher ingestion rates (p <0.05) for C2 at 12 and 18h. Filtration rates were significantly higher (p <0.05) for C2 only in the 12-h phase. In experiment 3, both copepods presented significantly lower (p <0.05) ingestion and filtration rates following exposure to G. catenatum for 24h. Carbamoyl toxins in the chromatograms were dominated by GTX1 and STX, followed by GTX2 and GTX3. Total cell toxicity was 2.58 and 2.34pgSTXeqcell−1 for cells harvested at the beginning and the end of the experiments, respectively. Total toxicity in the tissues of E. acutifrons and A. grani was 11.51 and 7.56(gSTXeqg−1, respectively. Survival rates in A. grani and E. acutifrons fed on C2 were 0% after 168 and 192h, respectively. Overall, the present study indicates that the copepods E. acutifrons and A. grani can not only ingest G. catenatum toxic cells, but also transfer their PSP toxins to other trophic levels. However, G. catenatum PSP toxins were shown to have had a deterrent and negative time-dependent effect on the feeding and survival rates, respectively, of E. acutifrons and A. grani. [Copyright &y& Elsevier]

Abstract: To assist haematophagy, Rhodnius prolixus produces several bioactive molecules in its saliva which it injects into the host skin. The most abundant of these molecules are the nitrophorins (NPs). In this work, we reduced the expression of NP1–4 in the saliva of R. prolixus by RNAi and evaluated the subsequent feeding performance of the bugs using the cibarial pump electromyogram either on the dorsal skin or on the tail vein of the mice. NPs salivary mRNA was reduced by >99% in comparison to controls. Saliva from knockdown nymphs also presented 82% less haemproteins while the total protein was not reduced. Knockdown nymphs feeding on the skin had lower ingestion rates mainly due to the longer cumulative probing time and lower cibarial pump frequency. Another difference was that knockdown insects bit ∼5 times more. No differences were observed between groups fed on the tail vein. When the feeding sites were compared, nymphs fed on the tail vein had higher effective ingestion rates. These findings endorse the importance of the NPs for the ability of bugs to complete the meal in a short total contact time with a low number of bites, decreasing the perception of the insect by the host. [Copyright &y& Elsevier]

Abstract: It has been documented in the many-lined sun skink (Mabuya multifasciata) that pregnant females select lower body temperatures (27.6–30.8°C) than do nonpregnant females and adult males (29.7–35.7°C). We therefore used the skink to test the hypothesis that the maximization of reproductive benefits should be achieved in pregnant females by shifting thermal preferences towards the levels optimal for embryonic development but entailing relatively small costs of reproduction. Data on adult males showed that temperatures maximizing swimming stamina (indicative of locomotor endurance) fell within the range of body temperatures selected by nonpregnant females and adult males. Data on swimming stamina and feeding performance of pregnant females, nonpregnant females and adult males measured at 26 and 30°C showed that: (1) pregnancy impaired locomotor and feeding performances, but such impairments did not persist after parturition; (2) the degree of locomotor impairment during pregnancy was greater at 26°C than at 30°C, but the degree of feeding impairment during pregnancy was greater at 30°C than at 26°C. Pregnant females of M. multifasciata selecting body temperatures at about 29°C could not only produce good-quality offspring in a relatively short gestation length but also reduce reproductive costs associated with locomotor and feeding impairments to some extent. Thus, data from M. multifasciata validate the above hypothesis. [Copyright &y& Elsevier]

Abstract: We compared intraoral prey transport in venomous snake species from four families (two atractaspidids, nine elapids, three colubrids, 44 viperids) with that in eight non-venomous colubrid species, most feeding on similar mammalian prey. The morphology of the venom delivery system suggests that intraoral prey transport performance should be slightly decreased in atractaspidids, unmodified in most elapids and venomous colubrids, and increased or unmodified in vipers, as compared to that in non-venomous colubrid snakes. Our measurements of relative intraoral prey transport performance show that differences among families do not match expectations based on morphology or past studies. Decreased performance in Atractaspis results from reduction and loss of teeth on the medial palatal elements and dentaries, but affects only early phases of ingestion. Although joint and bone features of elapids and colubrids are similar, intraoral prey transport performance is significantly lower in elapids than in colubrids. Predicted enhancement of intraoral prey transport performance in vipers as compared to colubrids was not borne out by measurements, presumably because palatopterygoid movement during intraoral prey transport is reduced in many viper species to limit fang erection. Absence of significant performance differences between colubrids and viperids might suggest that evolution of the viperid venom delivery system was subject to little selection pressure from intraoral prey transport. Another possibility is that there are trade-offs between intraoral prey transport and strike performance in vipers related to relative skull mass and jaw fragility. Immobilizing prey prior to intraoral transport places less demand on transport performance in vipers. In this model, the conservative kinesis and greater robustness of the colubrid palate has greater potential for transporting live prey with less risk of injury. [Copyright &y& Elsevier]

• Climate change is driving poleward range extensions in tropical fishes. • This did not affect proxies of body condition in tropical or temperate fishes. • Reduced temperatures decreased performance in tropical fishes. • Increased temperatures did not alter performance in temperate fishes. • Tropical fishes trade-off growth for body maintenance in their novel climate range. As ocean waters warm due to climate change, tropical species are shifting their ranges poleward to remain within their preferred thermal niches. As a result, novel communities are emerging in which tropical species interact with local temperate species, competing for similar resources, such as food and habitat. To understand how range-extending coral reef fish species perform along their leading edges when invading temperate ecosystems, we studied proxies of their fitness, including somatic growth (length increase), feeding rates, and body condition, along a 730-km latitudinal gradient situated in one of the global warming hotspots. We also studied co-occurring temperate species to assess how their fitness is affected along their trailing edges under ocean warming. We predicted that tropical fishes would experience reduced performance as they enter novel communities with suboptimal environmental conditions. Our study shows that although tropical fish maintain their body condition (based on three proxies) and stomach fullness across all invaded temperate latitudes, they exhibit decreased in situ growth rates, activity levels, and feeding rates in their novel temperate environment, likely a result of lower metabolic rates in cooler waters. We posit that tropical fishes face a growth–maintenance trade-off under the initial phases of ocean warming (i.e. at their leading edges), allowing them to maintain their body condition in cooler temperate waters but at the cost of slower growth. Temperate fish exhibited no distinct patterns in body condition and performance along the natural temperature gradient studied. However, in the face of future climate change, when metabolism is no longer stymied by low water temperatures, tropical range-extending species are likely to approach their native-range growth rates along their leading edges, ultimately leading to increased competitive interactions with local species in temperate ecosystems. [ABSTRACT FROM AUTHOR]

Sesamia nonagrioides , commonly known as the Mediterranean corn stalk borer, is one of the most important pests of the sweet sorghum in the circum Mediterranean countries. In the present study, the feeding performance of larvae, post treatment with the entomopathogenic fungi Beauveria bassiana , Metarhizium robertsii and Isaria fumosorosea , was first evaluated in laboratory experiments. The efficacy of the three entomopathogens in protecting the sorghum from its pest was then examined in a tritrophic field experiment in a farm, under natural conditions. The fungi, efficiently induced the mortality of larvae and reduced their relative growth rate (RGR), with the virulence of I. fumosorosea being relatively higher (90–93%). The feeding performance of larvae was significantly affected by the three entomopathogens. Reduced food consumption (39–64%), relative food consumption rate (15–38%) and the feces produced (48–81%) compared to untreated larvae, resulted in slight changes of digestibility. The weight of treated larvae remained almost unchanged while ECD and ECI increased in infected larvae compared to control. The infected larvae were also sluggish and static, and unwieldy on the food surface. The impact of infection should be rather attributed to their altered behaviour than to disturbed digestion. The tritrophic field experiment confirmed the efficacy of entomopathogens which were experimentally introduced into the plants as endophytes, against larvae of S.nonagrioides under natural conditions. In fact, they reduced infestation by 20–30% and the tunnelling length by 19–43%, and increased larval mortality by 57–82%, without affecting sorghum growth. Consequently, the three fungi could be used for the control of S. nonagrioides in sorghum crops, at least in areas with a Mediterranean-like climate. Image 1 • Three endophytes of the sorghum evaluated against Sesamia nonagrioides. • Larval mortality increased at all conidial concentrations, though dose-dependent. • Larval relative growth rate and feeding performance decreased. • Virulence of Isaria fumosorosea was relatively higher. • Efficacy of the three endophytes was corroborated in field conditions. [ABSTRACT FROM AUTHOR]