Реферат на тему Hellbender Essay Research Paper The Eastern HellbenderCryptobranchus

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Hellbender Essay, Research Paper

The Eastern Hellbender

(Cryptobranchus alleganiensis alleganiensis)

Cryptobranchus alleganiensis alleganiensis is the largest

North American salamander, ranging in length from 30.5 to 74 cm

(Niering 1985). Eastern Hellbenders are members of the order of

tailed amphibians, Caudata and the family, Cryptobranchidae.

Along with C. a. bishopi, the Ozark Hellbender, it is one of the

two subspecies of hellbenders, also known as the Allegheny

alligator or devil-dog.

C. a. alleganiensis is perennially aquatic, preferring clear

fast-moving rivers or large streams with rocky bottoms. Most

are found in water 12 to 46 cm deep and tend to avoid areas with

thick layers of silt (Hillis and Bellis 1971). It ranges from

the Susquehanna River and its tributaries in New York and

Pennsylvania to the Ohio River and its tributaries including the

Allegheny, which gives it its species name, westward to the

Mississippi River and southward to Missouri, Arkansas, and

Georgia. It has also been recorded in Iowa (Bishop 1943).

C. a. alleganiensis has a dorsoventrally flattened body and

a laterally flattened tail. The tail is the main means of

locomotion, but the hellbender can also crawl when seeking refuge

(Hillis and Bellis 1971). C. a. alleganiensis is dark gray or

olive-brown with a mottled or spotted pattern on its dorsal

surface. The ventral surface is a lighter shade with few

markings (Niering 1985). The male and female are similar in

appearance, but the male is broader and heavier than a female of

the same length. Eyelids are absent. It has five toes on its

hind feet and four on the fore feet, most of which develop during

the larval stage (Bishop 1943).

C. a. alleganiensis is nocturnal, spending its days hiding

under rocks with only the tip of its broad head exposed. It

exhibits diurnal behavior only during its mating season which

occurs in late summer or early fall depending on geographic

location. (Hillis and Bellis 1971).

C. a. alleganiensis practices external fertilization. The

male will dig a saucer-shaped nest-like cavity beneath a large,

flat rock or sunken log. The female lays 200-500 yellowish eggs

in long strings. The male assumes a mating position above or

behind the female and sprays the eggs. The male will then remain

in the area to guard the nest (Niering 1985). Evidence has shown

that the male will eat some of these eggs and therefore may

remain more to guard his food supply than from a sense of

parental responsibility (Hillis and Bellis 1971). The larvae

will latch two to three months later. The larva are

approximately 30 mm long and born with gills which they will lose

when they are 100-130 mm long at about 18 months, leaving only a

single pair of gill slits (Bishop 1943).

The hellbenders principle food source appears to be

crayfish, this is most likely for convenience since crayfish hide

in similar locations as the hellbender. The rest of its diet is

composed mainly of other aquatic invertebrates such as molluscs,

worms, and insects. They have also been observed to eat small

fish and animal refuse (Hillis and Bellis 1971).

Bishop, S.C. 1943. Handbook of Salamanders. pp. 59-63. Comstock

Publishing Associates, Ithaca, NY.

Hillis, R.E. and E.D. Bellis. 1971. Some aspects of the ecology

of the hellbender, Cryptobranchus alleganiensis alleganiensis,

in a Pennsylvania stream. Journal of Herpetology, 5:121-126.

Niering, W.A. 1985. National Audubon Society Nature Guides:

Wetlands. pp. 384-385. Alfred A. Knopf, Inc., New York, NY.

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