Hellbender

The hellbender (Cryptobranchus alleganiensis), also known as the hellbender salamander, is a species of aquatic giant salamander endemic to eastern North America. A member of the family Cryptobranchidae, the hellbender is the only member of the genus Cryptobranchus, and is joined only by one other genus of salamanders (Andrias, which contains the Japanese and Chinese giant salamanders) at the family level. The hellbender, which is much larger than all other salamanders in its geographic range, employs an unusual means of respiration (which involves cutaneous gas exchange through capillaries found in its dorsoventral skin folds), and fills a particular niche—both as a predator and prey—in its ecosystem, which either it or its ancestors have occupied for around 65 million years. The species is listed as Near Threatened. The origin of the name 'hellbender' is unclear. The Missouri Department of Conservation says: Vernacular names include 'snot otter', 'lasagna lizard', 'devil dog', 'mud-devil', 'grampus', 'Allegheny alligator', 'mud dog', 'water dog', and 'leverian water newt'. The genus name is derived from the Ancient Greek kryptos (hidden) and branchion (gill). The subspecific name, bishopi, is in honor of American herpetologist Sherman C. Bishop. C. alleganiensis has a flat body and head, with beady dorsal eyes and slimy skin. Like most salamanders, it has short legs with four toes on the front legs and five on its back limbs, and its tail is keeled for propulsion. The hellbender has working lungs, but gill slits are often retained, although only immature specimens have true gills; the hellbender absorbs oxygen from the water through capillaries of its side frills. It is blotchy brown or red-brown in color, with a paler underbelly. Both males and females grow to an adult length of 24 to 40 cm (9.4 to 15.7 in) from snout to vent, with a total length of 30 to 74 cm (12 to 29 in), making them the third-largest aquatic salamander species in the world (after the Chinese giant salamander and the Japanese giant salamander, respectively) and the largest amphibian in North America, although this length is rivaled by the reticulated siren of the southeastern United States (although the siren is much leaner in build). An adult weighs 1.5 to 2.5 kg (3.3 to 5.5 lb), making them the fourth heaviest living amphibian in the world after their Chinese and Japanese cousins and the goliath frog, while the largest cane toads may also weigh as much as a hellbender. Hellbenders reach sexual maturity at about five years of age, and may live 30 years in captivity. The hellbender has a few characteristics that make it distinguishable from other native salamanders, including a gigantic, dorsoventrally flattened body with thick folds travelling down the sides, a single open gill slit on each side, and hind feet with five toes each. Easily distinguished from most other endemic salamander species simply by their size, hellbenders average up to 60 cm or about 2 ft in length; the only species requiring further distinction (due to an overlap in distribution and size range) is the common mudpuppy (Necturus maculosus). This demarcation can be made by noting the presence of external gills in the mudpuppy, which are lacking in the hellbender, as well as the presence of four toes on each hind foot of the mudpuppy (in contrast with the hellbender's five). Furthermore, the average size of C. a. alleganiensis has been reported to be 45–60 cm (with some reported as reaching up to 74 cm or 30 in), while N. m. maculosus has a reported average size of 28–40 cm in length, which means that hellbender adults will still generally be notably larger than even the biggest mudpuppies. The genus Cryptobranchus has historically only been considered to contain one species, C. alleganiensis, with two subspecies, C. a. alleganiensis and C. a. bishopi. A recent decline in population size of the Ozark subspecies C. a. bishopi has led to further research into populations of this subspecies, including genetic analysis to determine the best method for conservation.Crowhurst et al., for instance, found that the 'Ozark subspecies' denomination is insufficient for describing genetic (and therefore evolutionary) divergence within the genus Cryptobranchus in the Ozark region. They found three equally divergent genetic units within the genus: C. a. alleganiensis, and two distinct eastern and western populations of C. a. bishopi. These three groups were shown to be isolated, and are considered to most likely be 'diverging on different evolutionary paths'.