The hellbender (Cryptobranchus alleganiensis) is a salamander that grows over a large range of body sizes (2-74 cm total length) making it an ideal organism for examining the effects of body size on morphology and performance. The goal of this study is to investigate the morphology changes over ontogeny and change in feeding ability. Cryptobranchus feeds on small aquatic insects as juveniles and shifts to crayfish as they get larger. Morphology can be expected to change as an organism grows larger, and because morphology and performance are closely linked, this morphological change can result in a change in feeding ability. Cryptobranchus alleganiensis are primarily aquatic salamanders that utilize both suction feeding and biting behaviors. I hypothesize bite force would increase with positive allometry reflecting a possible dietary shift during ontogeny in which larger Cryptobranchus favor crayfish. Because suction is the primary mode of feeding making it an important aspect of feeding throughout ontogeny, suction index was hypothesized to scale with isometry. Fourteen preserved specimens (11.9-34.5 cm SVL) were used to investigate the effects of scaling on suction potential and estimated bite force. Bite force was calculated using a 3D static equilibrium model and suction potential was calculated as suction index. Bite force scaled with positive allometry allowing the animals to bite harder relative to body mass with increasing body size, and suction index showed no effect of body size. Results of this study indicate that Cryptobranchus alleganiensis maintains suction performance across ontogeny allowing them to generate suction with similar ability ontogenetically, but increases its biting performance to cope with durophagous prey with a possible ontogenetic dietary shift.

Cryptobranchus guildayi is described as an extinct species of large salamander that is closely related to the hellbender, Cryptobranchus alleganiensis. The validity of this extinct taxon has been questioned, so an expanded osteological sample of modern hellbenders was used for comparative purposes with the C. guildayi fossil material. Based on this analysis, all supposed distinguishing morphological characteristics used to define C. guildayi can be observed in specimens of C. alleganiensis, or are based on misidentifications. Therefore, Cryptobranchus guildayi is considered to be conspecific with C. alleganiensis and taxonomically should be considered a junior synonym of the latter. The reassignment of the C. guildayi specimens to C. alleganiensis and examination of undescribed fossil specimens from the same region expands the prehistoric range of the species to the Potomac River and its tributaries and also extends the age of the species to the Irvingtonian North American land mammal age.

<p>  </p> <p>The Eastern Hellbender (<em>Cryptobranchus alleganiensis alleganiensis</em>) is a fully aquatic salamander found throughout the eastern United States. Hellbenders require cool, fast-moving rivers and streams with flat rock substrates for shelter. Due to habitat degradation and anthropogenic changes across landscapes, Hellbenders have required intervention programs to reduce extirpation and extinction risks. Over 5000 Hellbenders are found in captive-rearing and breeding programs throughout 15 different states. However, captive-rearing standards vary from facility to facility. </p> <p>Currently, Hellbender captive-rearing programs are based on established zoo guidelines that recommend rearing in traditional glass aquaria until they reach releasable mass (~60 g) at approximately three years of age. To achieve releasable size, the guidelines provide density and food availability requirements based on the amount of available floor space of the enclosure. Unfortunately, because these guidelines lack empirical data, it is unclear whether these recommendations are optimizing captive-rearing efforts for Hellbenders and, therefore, optimizing conservation potential. </p> <p>There is an overall lack of available information on housing conditions and requirements for Hellbenders outside of intraspecies aggression or cannibalism. Because many facilities use different types of housing conditions, there is substantial variation in the time needed to achieve the release size threshold. Our objectives were to: 1) understand how different raceway sizes impact growth rates of juvenile Hellbenders and 2) understand the effects of density and food availability on larval Hellbender growth. Both of these goals will allow us to develop optimal housing and husbandry standards and optimizing conservation potential within rearing facilities. Our study will build on our current knowledge of Hellbender captive-rearing techniques and provide empirical data to create optimal rearing standards nationwide. </p>