Taxon Management Account
Hellbender Salamander
Cryptobranchus alleganiensis alleganiensis (Daudin)

Compiled by: William P. Flanagan III
Compilation Date: August 2002

Introduction and Natural History

The family Cryptobranchidae contains three extant species; Andrias japonicus, A. davidianus, and Cryptobranchus alleganiensis. The genus Cryptobranchus contains only one extant species with two subspecies; C. a. alleganiensis and C. a. bishopi. They are the largest salamanders in America, with adult size ranging between 29-51 cm,and a record length of 74cm (Conant and Collins 1991, Fitch 1947). The body form is compressed horizontally with a laterally compressed paddle-like tail. The integument is covered in ridges and folds especially along the lateral surfaces. Ground color is usually brown but ranges between black and bright orange (Conant and Collins 1991, Petranka 1998, Fauth et. Al. 1996). Albinism has been reported (Dyrkacz 1981). Mottling is often present.

C. a. alleganiesis ranges from New York south to Mississippi and west to central Missouri. C. a. bishopi is endemic to the Ozark Mountains of southeastern Missouri and northeastern Arkansas (Conant and Collins 1991). C. alleganiensis are found in fast- moving streams or rivers. Large rocks are utilized as cover and seem to be a requirement (Pfingsten 1990, Siebert 1989). Pfingsten 1990 noted that Ohio hellbender populations concentrated shortly after bends in rivers.

Bishop 1941 describes C. alleganiensis as "A great flat flabby animal…." This fantastic amphibian’s aquatic nature and nocturnal habits (Bishop 1941, Humphries and Pauley 2000, Noeske and Nickerson 1979) have made collecting life-history data difficult. Daylight hours are largely spent under cover, sometimes with their heads partially exposed. Crayfish and fish make up the bulk of the diet, but they will accept a wide variety of prey if the opportunity presents itself. Defenses include cryptic coloration, noxious skin secretions (Brodie 1971), the ability to flee quickly with short bursts of speed, and an intimidating bite (pers. obser.). A variety of fish, snakes, turtles, larger C. alleganiensis, and man have been reported as predators (Nickerson and Mays 1973, Petranka 1998, Minton 2001). Minton 2001 reported an experienced source saying, "They tasted pretty good if you didn’t know what you were eating."

Breeding occurs in the fall (Smith 1907, Bishop 1941, Ingersol 1982, Nickerson and Mays 1973). Breeding season is longer, September – November, in Missouri populations (Dundee and Dundee 1965, Peterson 1988). One winter breeding has been recorded in Missouri (Peterson et. al 1989). In the east, breeding seasons generally last 2-3 weeks, from late August to mid September or September into October (Petranka 1998). Larvae are gilled until approximately 1.5 – 2 years of age, at which point the gills are lost and they resemble miniature versions of the adults. Age at maturity remains somewhat unclear. Smith 1907 estimated age at maturity to be within the range of 3-4 years. Nickerson and Mays 1973 and Peterson 1985 estimated it to be later at, 7-8 years of age. The longevity is recorded as 29 years (Nigrelli 1954), but it is likely they can live longer.

One of the most frequently asked questions regarding C. alleganiensis is the origin of its common name, hellbender. Nickerson and Mays 1973 reference two sources that attribute the name hellbender to early African-American origins. The name is believed to be a reference to the animal’s bending movements being similar to what one must experience during the torments of Hell.

Conservation Status

Currently C. a. alleganiensis and C. a. bishopi are not protected by the Federal Government or CITES. However, C. a. bishopi is currently a candidate for protection from the Federal Government (Federal Register 2002). C. alleganiensis is provided some level of protection or management in Ohio, North Carolina, South Carolina, Arkansas, Missouri, Illinois, Alabama, and Georgia However, this animal does not enjoy protection from New York, Pennsylvania, Kentucky, Mississippi, and West Virginia (Levell 1997, Humphries 2002a). Some states even regulate it as if it were a bait species.

Habitat destruction due to deforestation or pesticide run-off probably represents the greatest threat to C. alleganiensis. Although rarely kept by hobbyists, limited range, specialized habitat, decreased density combine to make hellbenders especially vulnerable to overcollection. Unfortunately, several researchers have encountered examples of collection by the pet trade (Nickerson ?, Wilkinson?) Acquisition of specimens is the most common question posted to a hellbender website (Humphries pers. Com.), possibly indicating an increase in collection pressure.

Recent population data are absent throughout most of the range of C. a. alleganiensis and C. a. bishopi. Dramatic declines in numbers have been observed in Missouri and Arkansas, with little or no observed recruitment (Mathis pers. Com. 2002, Wheeler and Trauth 2002). Microhabitat use makes locating larvae extremely difficult in parts of the hellbender’s range (Nickerson 2001). It is clear that more intensive monitoring throughout the animal’s range is needed.

Captive Management

ISIS online abstracts lists 28 animals in 14 institutions. Five institutions list Cryptobranchus alleganiensis without identifying the subspecies, one C. a. bishopi, and ten list C. a. alleganiensis. Six facilities reported housing only solitary animals or single sex populations. Currently Cryptobranchus alleganiensis is listed as a priority 2 DRP with a recommendation of up grade to -1 PMP if captive reproduction occurs (Wright 2000).

Although there is considerable work done in situ, data collection is time consuming and difficult. Large gaps still exist in our knowledge of their biology. Further research on social interactions, reproductive physiology, and habitat selection may prove critical in the conservation of this species. Low genetic variability between populations (Routman 1993) coupled with the fact that hellbenders have faired well in limited repatriation attempts (Nickerson 1980) make this species a good candidate for re-release programs. Captive management of this species could make significant contributions to the conservation of this species.

Captive reproduction has yet to be achieved. However, only about 30% of the Cryptobranchus reported to ISIS are of known sex, and only two institutions report numbers and sex ratios suitable to make serious propagation attempts. It is important to develop suitable propagation protocol now. Size and structure of den, social groupings, sexing techniques, temperature, lighting, and water quality parameters are all areas of investigation that require further research.

Husbandry Parameters

Since hellbenders tolerate a wide of captive conditions and captive reproduction has proven elusive, a variety of husbandry strategies may be appropriate.

Large aquatic setups with a high flow rate are required. Two or three adults can be maintained in a tank 95"x 25"x 18". It is advisable to design enclosures with removable dividers. This will allow social groupings to be manipulated with relative ease. Hellbenders can be territorial and will eat smaller conspecifics (Nickerson and Mays 1973). Although they are aquatic, there are reports of terrestrial movement (Nickerson and Mays 1973). The author maintained one adult that would routinely crawl onto the land area of the exhibit. Recent captives have been observed making numerous attempts to escape enclosures (John Groves pers. com). Consequently, enclosures should include either a tight fitting lid or an overhang to prevent escapes.

Underwater cover is important. Large flat rocks set at least twice the animal’s height are excellent. Care should be taken to ensure that heavy cover is properly supported on the enclosure bottom. Animals will dig into gravel bottoms and improperly supported cover will shift posing a significant squishing hazard. Since hellbenders are territorial, the number of submerged cover spots should equal or exceed the number of animals housed in the enclosure.

Peagravel is an acceptable substrate; larger gravel with average diameter of 1-3” is best. This will help to prevent animals from accidentally ingesting gravel during feeding.

Water should be filtered to ensure excellent water quality. Flow should be strong and directional. An adjustable standpipe will make it easy to change water levels, which seems to be important in cycling these animals.

Proper water quality and temperature are often to two biggest challenges. NH4, NO2 and NO3 should be monitored weekly. Levels of these nitrogenous wastes should be maintained below 1.0 p.p.m., for NH4, 0.5 p.p.m. for NO2, and 5.0 p.p.m. for NO3. Dissolved Oxygen should be over 90% saturation. Beffa 1976 found that animals increased rocking activity as dissolved oxygen decreased until 20?% at which point animals attempted to leave the aquaria.

Temperatures should be maintained at temperatures that range between 9 and 25?C with the extremes at 1.5 to 2 month intervals in the winter and summer. Smith 1907 recorded breeding season water temps between 14-18?C. Dundee and Dundee 1965 noted spring fed streams had temperatures that rarely varied beyond 17-12?C, whereas non spring fed streams that got as warm as 25?C during the summer months.

Lighting is likely an important cue for reproduction of this species. Riss et. Al. 1963? Suggested that lighting played a significant role in endocrine activity. Hellbenders are usually nocturnal (Bishop 1941, Humphries 2000) with seasonal or occasional diurnal activity (Nickerson and Mays 1973). Like most captive herps they should be offered a natural light cycle, 10hours light and 12dark during the winter December and January and 12 hours of light with 10 hours on dark in the summer June and July. Many popular weather web sites offer local sunrise and sunset data. Using this data with electronic or analog lighting timers would make it easy to closely approximate the collection locality light cycle. A bank of lights hung directly above the tank that goes on one hour after and off one hour before the main room lights will simulate dusk and give the animals a variety of light intensities. Although this author has offered UVB, it is unlikely that this aquatic and largely nocturnal animal will require it in captivity.

Because behavioral data is difficult to collect in situ, this is one area where ex situ programs should be making big contributions. Housing multiple animals in one in enclosure can pose a risk of nasty bite wounds or even cannibalism. Multiple animal enclosures should include lots of space, multiple underwater retreats and removable dividers. Captive animals have been observed both vigorously defending territories and tolerating other adults of both sexes. Situations should be individually evaluated especially during change of seasons or social structure. Keepers should watch for bite wounds, appetite loss, or any other signs of stress.

This is one aspect of the biology of this animal that has been well studied. Crayfish is clearly the most common food item taken by wild hellbenders (Smith 1907, Bishop 1941, Nickerson and Mays 1973). However in captivity the diets of captive hellbenders have often been more reliant on earthworms, fish, shrimp, raw meat, and even mice. Two feeding strategies are common. One is tong feeding each animal food items. This approach allows the keeper to track food intake closely. Unfortunately it also conditions many captives to vigorously strike at any item that is presented towards the mouth including; keepers fingers and potential mates. The second strategy is to keep a number of live food items crayfish or feeder fish available in the enclosure at all times. This fosters a more natural set of feeding behaviors but has several potential dangers. Excessive numbers of crayfish will sometimes pick at captive hellbenders. The threat of introducing disease from the food items is greater when the food items are housed this way. Obtaining frequent weights is important to insure that animals are eating and adjusting well.

If environmental parameters are met, hellbenders tend to be hardy captives. Loss of weight or appetite should be treated as a sign of serious illness. While a certain amount of rocking behavior is normal continuous rocking can be a sign of low dissolved oxygen or stress and should be investigated. Physical restraint can be difficult. Hellbenders seem to have greater patience for handling that occurs under water. Andrias and Cryptobranchus both possess a tacky spot near the tip and towards the top of their laterally compressed tail. Grasping this spot firmly between the thumb and forefinger will allow for limited cautious manipulation and reduce the need for more aggressive restraint. The animals will generally tolerate this condition for several seconds before reacting at which point the animal will vigorously attempt to swim away or bite. In both cases the animal should be released. More aggressive physically restrain may be accomplished by confining the animal to an appropriate sized net. A pant leg made of soft cloth works very well. Opinions vary greatly on the potential danger posed by a bite. A bite from an adult could certainly cause lacerations and caution should be used when handling large specimens.

Reproduction

Hellbenders can be difficult to correctly sex. During the breeding season the glands around the males’ cloacas swell making them easy to identify as males. Absence of this swelling could indicate either a non-sexually active male or a female. This could be especially confusing in captive settings where reproductive cycles may not be functioning properly. Males are broader and heavier than similarly sized females (Bishop 1941). Laproscopy and ultrasound of adults is definitive regardless of reproductive readiness. Ultrasound is less invasive but both require the involvement of a skilled technician or veterinarian.

Any serious attempt to breed these animals should start by simulating natural light and temperature cycles. In addition several authors suggest that rainfall plays an important role in stimulating activity during the breeding season (Nickerson and Mays 1973, Nickerson pers. Com). During the fall water level and frequency of fake rain showers should be increased while temperature and day length decreased. Reproductively active males have swollen cloacas that may even ooze salamander milt and females will have swollen abdomens. Males build a nest that is usually under a large submerged cover object. Nickerson and Tohulka 1986, and Bishop 1941 describe nests and should give the keeper some direction. Active nests may contain large complements of eggs, approximately 2000 eggs(Bishop 1941). This large number represents the reproductive effort of several females. A single female may produce approximately 250 eggs in a season (Smith 1907). There is insufficient data to suggest appropriate structure of breeding groups. Although multiple female breeding groups may be more natural there is risk associated. Larger groupings increase the chances of a detrimental territorial interaction. In addition, hellbenders have been known to cannibalize eggs in the wild (Bishop 1941). Females may selectively target the eggs of competing females. Enclosure size should be strongly considered before attempting larger groupings

Eggs lack pigment and may be light sensitive.

Fertilization is external. Males have been observed fanning the eggs with their tails. This is believed to spread the milt across the surface of the eggs(Smith 1907). Males excavate an underwater nest chamber and will entice several females to oviposit in it. Eggs are laid in the fall(Smith 1907, Siebert 1989, Nickerson and Mays 1973). Males will stay and guard egg filled nests. It is still unclear at what point they stop defending the nests. Length of incubation period is variable. Smith 1912 a &b give excellent accounts of the embryology of Cryptobranchus.

Little is known about neonate husbandry. Johnson 2000 raised larvae from a wild collected captive incubated eggs. He noted that larvae had enough yolk reserves to sustain growth for three months after hatching. The author raised an animal that was approximately 1.5-2.0 years of age at capture using conditions similar to adults.

Comments

In addition to several institutions being poised to make serious breeding attempts Philadelphia Zoo has collaborated to describe the feeding physiology (Cundall et al 1987). Cincinnati Zoo’s CREW has be working with Cryptobranchid reproductive biology. A large number of zoos with amphibian expertise are geographically located within driving distance of the hellbenders range. With many hellbender populations in decline or questionable status now is an excellent time for zoos to make contributions to its conservation beyond captive propagation.

Literature Cited

  • Anonymous Proposed Rules, FEDERAL REGISTER, Vol. 67, No. 114, Thurs. June 13 2002, Pg 40673, 2002.
  • Anonymous SPECIES HOLDINGS, AMPHIBIANS, CRYPTOBRANCHUS.
  • International Species Information System website, https://www.isis.org/abstracts/abs.asp. 26 August 2002
  • Beffa, D. A. RESPONSES OF Cryptobranchus alleganiensis alleganiensis TO DIFFERENT OXYGEN CONCERTRATIONS, TEMPERATURE, AND PHOTOPERIOD. MA Thesis. Southwest Missouri State University. 1976.
  • Bishop, S. C. 1941. THE SALAMANDERS OF NEW YORK. New York State Mus. Bull. No. 324, 365pp
  • Conant, R., Collins, J. T.. A FIELD GUIDE TO THE REPTILES AND AMPHIBIANS OF EASTERN AND CENTRAL NORTH AMERICA. Peterson Field Guides #12. Houghton Mifflin Co., Boston. 1991.
  • Cundall, D., J. Lorenz-Elwood, and J. D.Groves. Asymmetric suction feeding in primitive salamanders. EXPERIENTIA, 43: 1229-1231. 1987
  • Dyrkacz, S. RECENT INSTANCES OF ALBINISM IN NORTH AMERICAN AMPHIBIANS AND RETILES. SSAR, Herpetological Circular 11:1-31, 1981. .
  • Dundee, H.A., and Dundee, D. S.. Observations on the Systemics and Ecology of Cryptobranchus from the Ozark Plateaus of Missouri and Arkansas. COPEIA, 1965(3): 369-370, 1965.
  • Fauth, J. E., Buchanan B. W., Wise S.E., Welter S. M., Komoroski M. J. Caudata: Cryptobranchus alleganiensis alleganiensis (hellbender). Coloration. HERPETOLOGICAL REVIEW, 27(3), Pg. 135, 1996.
  • Fitch, F. W. A record Cryptobranchus alleganiensis. COPEIA, 1947(3): Pg. 210, 1947.
  • Groves, J. 2002 personal communication.
  • Humphries, W. J. THE HELLBENDER HOMEPAGE. http://hellbenders.sanwalddesigns.com/ , 27 August 2002.
  • Humphries, W. J. 2002 personal communication.
  • Humphries, W. J. and Pauley, T.. K. Seasonal Changes in Noctunal Activity of the Hellbender, Cryptobranchus alleganiensis, in West Virginia. JOURNAL OF HERPETOLOGY 34(4): 604-607, 2000.
  • Ingersol, C. A. SEASONAL REPRODUCTIVE CHANGES IN Cryptobranchus alleganiensis. M. S. Thesis, Southwest Missouri State Univ., Springfield 1982.
  • Johnson, T. R. THE AMPHIBIANS AND REPTILES OF MISSOURI, 2nd ed., Conservation Commission of the State of Missouri, Jefferson City, MO., 2000.
  • Levell, J. P. A FIELD GUIDE TO REPTILES AND THE LAW, 2nd ed., Serpent’s Tale Natural History Book Distributers, Lanesboro WS, 1997.
  • Mathis, A. 2002 personal communication July 2002
  • Nickerson, M. A. Return of captive Ozark hellbenders, Cryptobranchus alleganiensis bishopi, to site of capture. COPEIA, 1980: 536-537, 1980.
  • Nickerson, M. A. 2001. ?
  • Nickerson, M. A., and Mays, C. E. THE HELLBENDERS: NORTH AMERICA’S “GIANT SALAMANDERS.”, Pub. Biol. Geol., Milw. Publ. Mus. 1:1-106. 1973.
  • Nickerson, M. A., and Tohulka, M. D. The Nest and Nest Site Selection by Ozark Hellbenders, Cryptobranchus alleganiensis bishopi (Grobman). TRANS. OF KANSAS ACADEMY OF SCIENCE, 89: 66-69, 1986.
  • Noeske, T. A., and Nickerson, M. A. Diel Activity Rhythms in the Hellbender. Cryptobranchus alleganiensis(Caudata: Cryptobranchidae). COPEIA, 1979:92-95, . 1979 .
  • Petranka, J. W. SALAMANDERS OF THE UNITED STATES AND CANADA, Smithsonian Institute Press Washington and London. Pgs. 140-144, 1998.
  • Pfingsten, R. A. The Status and Distribution of the Hellbender, Cryptobranchus alleganiensis in Ohio. HERPETOLOGICAL REVIEW, Vol 21, No. 3, 1990.
  • Routman, E. Mitochondrial DNA variation in Cryptobranchus alleganiensis a salamander with extremely low allozyme diversity. COPEIA, 1993 (2). 1993. 407-416.
  • Seibert, H. C. Cryptobranchus alleganiensis (Daudin) Hellbender. Pp 65-71 in SALAMANDERS OF OHIO. Pfingsten, R. A., and F. L. Downs, eds. Ohio Biol. Surv. Bull. New Series Vol. 7, No. 2, 1989. .
  • Smith, B. G. Life History and Habits of Cryptobranchus allegheniensis BIOLOGICAL BULLETIN, 13: 5-39, 1907.
  • Smith, B. G. The embryology of Cryptobranchus allegheniensis, including comparisons with some other vertebrates. I. Introduction; the history of the egg before cleavage. JOURNAL OF MORPHOLOGY . 23(1): 61-157, 1912.a.
  • Smith, B. G. The embryology of Cryptobranchus allegheniensis including comparisons with some other vertebrates. II. General embryonic and larval development, with special reference to external features. JOURNAL OF MORPHOLOGY, 23(3): 455-579, 1912b.
  • Wheeler B. and S. Trauth 2002 personal communication July 2002.
  • Wright, K. AMERICAN ZOO AND AQUARIUM ASSOCIATION AMPHIBIAN TAXON ADVISORY GROUP REGIONAL COLLECTION PLAN, 1st. ed., AZA ATAG website, http://www.atag2.homestead.com/cplan.html, August 2000.

Appendix

  • A Bibliography of Cryptobranchus alleganiensis (Hellbender Salamander)
  • By William P. Flanagan III, The Detroit Zoological Institute, National Amphibian Conservation Center, 8450 West Ten Mile Rd., Royal Oak, MI 48068.
  • Alexander, W. P. The Allegheny hellbender and its habitat. BUFFALO SOC. SCI., 7(10): 13-18 1927.
  • Baker, C. L. The comparative anatomy of the aortic arches of the urodeles and their relation to respiration and degree of metamorphosis. J. TENN. ACAD. SCI. 24:12-40, 1949 .
  • Baker, C. L. Spermatozoa and spermateleosis in Cryptobranchus and Necturus. J. TENN. ACAD. OF SCI., 38(1): 1-9, 1963.
  • Barbour, R. W. AMPHIBIANS AND REPTILES OF KENTUCKY. Lexington, Ky., Univ. of Kentucky Press, 1971.
  • Barton, B. S. MEMOIR CONERNING AN ANIMAL OF THE CLASS OF REPTILIA OR AMPHIBIA, WHICH IS KNOWN IN THE UNITED STATES, BY THE NAMES ALLIGATOR AND HELL-BENDER. Privately printed for the author in Philadelphia by Griggs and Dickinson, Printers. 26 pp. 1pl., 1812.
  • Beck, R. 1965. The great hellbender. FIELD AND STREAM, 69:65-66,109-111
  • Beffa, D. A. RESPONSE OF Cryptobranchus alleganiensis alleganiensis TO DIFFERENT OXYGEN CONCENTRATIONS, TEMPERATURE, AND PHOTOPERIOD. MA Thesis, Southwest Missouri State University, 1976.
  • Bernstein, H. Structural modifications of the amphibian skin. PENN. ACAD. SCI., 27:204-211, 1953.
  • Bishop, S. C. Records of some salamanders from North Carolina and Pennsylvania. COPEIA 139: 9-12, 1925.
  • Bishop, S. C. The amphibians and reptiles of Allegany State Park. NEW YORK STATE MUSEUM HANDBOOK 3:1-141, 1927.
  • Bishop, S. C. THE SALAMANDERS OF NEW YORK. New York State Mus. Bull. No. 324, 1941.
  • Bishop, S. C. HANDBOOK OF SALAMANDERS OF THE UNITED STATES, OF CANADA, AND OF LOWER CALIFORNIA. Cornell University Pub. 1994, Originally by Comstock Publishing Company, Inc. 1943.
  • Black, J. D., and Dellinger S. C. HERPETOLOGY OF ARKANSAS. PART 2. THE AMPHIBIANS. Occas. Pap. Univ. Ark. Mus. No. 2, 1938.
  • Blatchley, W. S. Notes on the batrachians and reptiles of Vigo County, Indiana. J. CINCINNATI SOC. NAT. HIST. 14:22-35, 1891.
  • Blais, D. P. MOVEMENT, HOME RANGE, AND OTHER ASPECTS OF THE BIOLOGY OF THE EASTERN HELLBENDER (Cryptobranchus alleganiensis). A RADIO TELEMETRIC STUDY. M.S. Thesis, State Univ. of New York at Binghamton, Binghamton, 1996.
  • Bogert, C. M. The hellbenders and giant salamanders. Pgs. 1203-1207 in THE ILLUSTRATED ENCYCLOPEDIA OF ANIMAL LIFE. VOL. 10. F. Drimmer, ed. Greystone Press, New York, 1961.
  • Bond, H. D. Some amphibians and reptiles on Monogalia County, West Virginia. COPEIA 2: 53-54, 1931.
  • Bothner, R. A survey of the New York state populations of the hellbender, Cryptobranchus alleganiensis alleganiensis. UNPUBL. REP. NEW YORK STATE DEPT. OF ENVIRON. CONSERV., 1981
  • Boutilier, R. G., McDonald, D. G., and Toews, D. P. The effects of enforced activity on ventilation, circulation and blood acid base balance in the aquatic gill-less urodele, Cryptobranchus alleganiensis; and comparison with the semi-terrestrial anuran, Bufo marinus. J. EXP. BIOL., 84:289-302, 1980.
  • Boyden, A., and Noble, G. K. The relationships of some common amphibia as determined by serological study. AMER. MUS. NOVITATES, 606:1-24, 1933.
  • Boyer, D. A., and Heinze, A. A. An annotated list of the amphibians and reptiles of Jefferson County, Missouri. TRANS. ACAD. SCI., St. Louis 28(4): 185-201, 1934.
  • Brame, A. H., Jr. A list of the world’s recent and fossil salamanders. HERPETON 2(1):1-26, 1967.
  • Branch, H. E. A LABORATORY MANUAL OF Cryptobranchus alleganiensis DAUDIN. Vantage Press, N. Y., 1933.
  • Brandon, R. A. and Ballard S. R. Cryptobranchus alleganiensis (Hellbender). HERP. REV. 25(1). 1994.
  • Branson, B. A., and Baker, E. C. An ecological study of the queen snake, Regina septemvittata (Say) in Kentucky. TULANE STUDIES ZOOL. BOT., 18:153-171, 1974.
  • Breisch, A. Letter about results of a one day survey for hellbenders. UNPUBL. REP. NEW YORK STATE DEPT. OF ENVION. CONSERV., 1990.
  • Brimley, C. S. The amphibians and reptiles of North Carolina. CAROLINA TIPS, 2(2): 1-8, 1939.
  • Brodie, E. D., Jr. Two more toxic salamanders: Ambystoma maculatum and Cryptobranchus alleganiensis. HERP. REV., 3(1): 8, 1971.
  • Bruner, H. L. The mechanism of pulmonary respiration in amphibians with gill clefts. MORPH. JAHRB., Leipzig, 48:63-82, 1914.
  • Buker, W. E. The Drew Site (36A162). PENN. ARCH., 40(3-4): 21-68, 1970.
  • Cagle, F. R. Herpetological fauna of Jackson and Union Counties, Illinois. AMER. MIDLAND NAT., 28(1): 164-200, 1942.
  • Chermock, R. L. A key to the amphibians and reptiles of Alabama. MUS. PAP. GEOL. SURV. ALABAMA, 33:1-88, 1952.
  • Chezar, H. H. Studies on the lateral line system of amphibia II. Comparative cytology and innervation of the lateral line organs in the urodela. J. COMP. NEUROL., 50(1): 159-176, 1930.
  • Claypole, E. J. Blood of Necturus and Cryptobranchus. PROC. AMER. MICROS. SOC., 15, 1893.
  • Coatney, C. E., Jr. HOME RANGE AND NOCTURNAL ACTIVITY OF THE OZARK HELLBENDER. M. S. Thesis. Southwest Missouri State Univ., Springfield, 1982.
  • Conant, R., and, Collins J. T. REPTILES AND AMPHIBIANS EASTERN AND CENTRAL NORTH AMERICA, PETERSON FIELD GUIDE #12. Houghton Mifflin Co., Boston, 1991.
  • Cope, E. D. On the osseous structures of the types of the urodela. J. ACAD. NAT. SCI., Philadelphia, 2nd series, 6(1): 97-112, 1867.
  • Cope, E. D. On the relations of the hyoid and otic elements of the skeleton in the batrachia. J. MORPHOL., 2(2): 297-310, 1888.
  • Cope, E. D. THE BATRACHIA OF NORTH AMERICA. U. S. Nat. Mus. Bull., 34:1-525, 1889.
  • Craigie, E. H. The blood vessels of the brain substance in some amphibians. PROC. AMER. PHILOS. SOC., 78(4): 615-649, 1938.
  • Cross C. E., Murdaugh, H. V., and Robin, E. D. Aquatic versus aerial gas exchange in the amphibian Cryptobranchus a. alleganiensis. AMER. FED. CLIN. RES., 14(2) 1967.
  • Cox, D. C., and Tanner W. W. Hyobranchial Apparatus of the Cryptobranchoidea Amphibia. GREAT BASIN NATURALIST, 49 (4). 1989. 482-490, 1989.
  • Cundall, D., Lorenz-Elwood, J., and Groves, J. D. Asymmetric suction feeding in primitive salamanders. EXPERIENTIA, 43. 1229-1231, 1987.
  • Daniel. J. C., and, Simpson, R. W. A negative note on antibiotics. HERPETOLOGICA, 10(1): 16, 1954.
  • Daudin, F. M. HISTOIRE NATURELLE des REPTILES. Vol. 8 Paris, 1803.
  • Davis, N. S., Jr., and, Rice F. L. List of batrachia and reptilia of Illinois. BULL. CHICAGO ACAD. SCI., 1(3): 25-32, 1883.
  • Dowling, H. G. Geographic relations of Ozarkian amphibians and reptiles. SOUTHWESTERN NATURIST, 1(4): 174-189, 1956.
  • Dowling, H. G. Amphibians and reptiles in Arkansas. OCCAS. PAP. UNIV. ARK. MUS. 3:1-51, 1957.
  • Dundee, H.A., and Dundee, D. S. Observations on the Systemics and Ecology of Cryptobranchus from the Ozark Plateaus of Missouri and Arkansas. COPEIA, 3: 369-370, 1965.
  • Dundee, H. A. Cryptobranchus and C. alleganiensis. CAT. AMER. AMPHIBIANS AND REPTILES, SSAR: 101.1-101.4, 1971.
  • Dunn, E. R. The collection of amphibia Caudata of the Museum of Comparative Zoology. BULL. MUS. COMP. ZOOL., 62(9): 445-471, 1918.
  • Dunn, E. R. The “opercularis” muscle of salamanders. J. MORPHOL., 69(2): 207-215, 1941.
  • Dyrkacz, S. RECENT INSTANCES OF ALBINISM IN NORTH AMERICAN AMPHIBIANS AND REPTILES. SSAR, Herpetological Circular 11, 1981.
  • Edgeworth, F. H. On the larval hyobranchial skeleton and musculature of Cryptobranchus, Menopoma, Ellipsosglossa. J. ANAT., 57:97-105, 1922.
  • Elwood J. R. L., and Cundall D. Morphology and behavior of the feeding apparatus in Cryptobranchus alleganiensis (Amphibia: Caudata). J. OF MORPH., 220 (1), 47-70, 1994.
  • Endsley, J. R. An annotated listing of the herpetological collection mainly from Tennessee. TENNESSEE ACAD. SCI., 29(1): 36-41, 1954.
  • Estes, R. Fossil vertebrates from the late Cretaceous lance formation eastern Wyoming. UNIV. CAL. PUBL. GEOL. SCI., 49:1-180, 1964.
  • Estes, R. Fossil salamanders and salamander origins. AMER. ZOOL., 5:319-334, 1965.
  • Fauth, J. E., Buchanan B. W., Wise S.E., Welter S. M., Komoroski M. J. Caudata: Cryptobranchus alleganiensis alleganiensis (hellbender). Coloration. HERP. REV., 27(3): 135, 1996.
  • Ferguson, D. The herpetofauna of Tishomingo County, Mississippi, with comments on its zoogeographic affinities. COPEIA, 1961(4): 391-396, 1961.
  • Firschein, L. The range of Cryptobranchus bishopi and remarks on the distribution of the genus Cryptobranchus. AMER. MIDLAND NAT. 45(2): 455-459, 1951.
  • Fitch, F. W. A record Cryptobranchus alleganiensis. COPEIA 1947(3): 210, 1947.
  • Fowler, H. W. Some amphibians and reptiles of Cecil County, Maryland. COPEIA (22): 37-40, 1915.
  • Fox, H. A study of the evolution of the amphibian and dipnoan pronephros by and analysis of its relationship with the anterior spinal nerves. PROC. ZOOL. SOC. LONDON, 138:225-256, 1962.
  • Foxon, G. E. H. Blood and respiration. Pp. 151-209. in PHYSIOLOGY OF AMPHIBIA. J. A. Moore ed., Academic Press New York., 1964.
  • Gage, S. H. Notes on the epithelium lining the mouth of Necturus and Menopoma. PROC. AMER. SOC. MICR., 8:126-127, 1885a.
  • Gage, S. H. The epithelium lining the mouth of Necturus and Menopoma. THE MICROSCOPE, 5:210-211, 1885b.
  • Gage, S. H., and Gage, S. P. Pharyngeal respiratory movements of adult amphibia underwater. SCIENCE, 7(169): 394-395, 1886.
  • Garman, H. A synopsis of the reptiles and amphibians of Illinois. III. LAB. NAT. HIST. BULL., 3(13): 215-388, 1892.
  • Gates, J. E., Hocutt, C. H., Stauffer, J. R., Jr., and Taylor, G. J. The distribution and status of Cryptobranchus alleganiensis in Maryland. HERP. REV., 16:17-18, 1985.
  • Gentry, G. An annotated checklist of the amphibians and reptiles of Tennessee. J TENN ACAD. SCI., 30(2): 168-176, 1955.
  • Goodnight, C. J. A key to the adult salamanders of Illinois. TRANS. ILLINOIS ACAD. SCI., 30(2): 300-302, 1937.
  • Green, N. B. Cryptobranchus alleganiensis in West Virginia. PROC. WEST VIRGINIA ACAD. SCI., 7: 28-30, 1934.
  • Green, N. B. Further notes on the water dog, Cryptobranchus alleganiensis Daudin. PROC. WEST VIRGINIA ACAD. SCI., 9:36, 1935.
  • Green, N. B. The amphibians and reptiles of Randolph County, West Virginia. HERPETOLOGICA, 1:113-116, 1937.
  • Green, N. B. THE AMPHIBIANS AND REPTILES OF WEST VIRGINIA. Huntington, West Virginia, Marshall College, 1954.
  • Green, N. B. Recent developments in herpetology in West Virginia. PROC. WEST VIRGINIA ACAD. SCI., 33:21-27, 1962.
  • Green, N. B. AMPHIBIANS AND REPTILES IN WEST VIRGINIA, THEIR IDENTIFICATION AND DISTRIBUTION. Marshall Univ. Dept. Biol. Sci., Huntington, West Virginia, 1969.
  • Green, N. B., and B. Dowler. Amphibians and reptiles of the Little Kanawha River basin. PROC. WEST VIRGINIA ACAD. SCI., 38:50-57, 1966.
  • Grenell, R. G. The morphogenesis of the hypophysis in Cryptobranchus alleganiensis. ANAT. REC., 73(3): 327-340, 1939.
  • Grobman, A. B. Notes on Salamanders with the Description of a New Species of Cryptobranchus. OCCAS. PAP. MUS ZOOL. UNIV MICH., No. 470, pp. 1-13, 1943.
  • Grote, A. R. A preliminary note on Menopoma alleghaniense of Harlan. AMER. ASSOC. ADV. SCI. PROC., 24:255-257, 1877.
  • Guilday, J.E. 1960. Vertebrate remains from the Varner site. (36-Gr-1). PENN. ARCH., 30(1): 119-124.
  • Guimond, R. W. AERIAL AND AQUATIC RESPIRATION IN FOUR PAEDOMORPHIC SALAMANDERS: Amphiuma means means, Cryptobranchus alleganiensis alleganiensis, Necturus maculosus maculosus, Siren lacertina. Ph.D. Dissertation. Univ. of Rhode Island, 1970.
  • Guimond, R. W., and Hutchison, V. H. Aquatic respiration: An unusual strategy in the Hellbender Cryptobranchus alleganiensis alleganiensis (Daudin). SCIENCE, 182:1263-1265, 1973.
  • Hall, H. H., and Smith, H. M. Selected records of reptiles and amphibians from southeastern Kansas. TRANS. KANSAS ACAD. SCI., 49(4): 447-454, 1947.
  • Hardy, J. D., Jr. Amphibians of the Chesapeake Bay region. CHESAPEAKE SCI., 13:123-128, . 1972.
  • Harlan, R. Observations on the genus Salamandra with the anatomy of Salamandra gigantea (Barton) or S. alleganiensis (Michaux) and two new genera proposed. ANN. LYC. NAT. HIST., 1:222-234, 1825.
  • Harlan, R. GENERA OF NORTH AMERICAN REPTILIA, WITH A SYNOPSIS OF THE SPECIES. Private Printing. Philadelphia, 1827.
  • Harlan, R. A. THE EFFECTS OFDISSOLVED OXYGEN CONTENT OF WATER ON BLOOD Ph, CO2, O2 AND ROCKING ACTIVITY OF Cryptobranchus alleganiensis. M.A. Thesis, Southwest Missouri State Univ. Springfield, 1978.
  • Harlan, R. A., and Wilkinson, R. F. The effects of progressive hypozia and rocking activity on blood oxygen tension for hellbenders, Cryptobranchus alleganiensis. J. OF HERP., Vol. 15(2), 383-387, 1981.
  • Hay, O. P. The batrachians and reptiles of Indiana. INDIANA DEPT. OF GEOLOGY AND NATURAL RESOUCES 17TH ANNUAL REPORT (1891). Indianapolis. pp. 409-602, 1892.
  • Hibbard, C. W. The amphibians and reptiles of Mammoth Cave National Park Proposed. TRANS. KANSAS ACAD. SCI. 39:277-281, 1936.
  • Hillis, R. E. CERTAIN ASPECTS OF THE ECOLOGY OF Cryptobranchus alleganiensis DAUDIN. Thesis D Ed, Penn State Univ., 1969.
  • Hills, R. E., and Bellis, E. D. Some Aspects of the Ecology of the Hellbender, Cryptobranchus alleganiesis alleganiensis in a Pennsylvania Stream. J. OF HERP., 5:121-126, 1971.
  • Hilton, W. A. The vertebrae of salamanders. J. ENT. AND ZOOL., 40(3): 47-65, 1948.
  • Hilton, W. A. Review of the chondrocranium of tailed amphibia. HERPETOLOGICA, 6(5): 125-135, 1950.
  • Hilton, W. A. Teeth of salamanders. HERPETOLOGICA, 7(3): 133-136, 1951.
  • Hilton, W. A. Dural blood vessels of salamanders. BULL. SO. CAL. ACAD. SCI., 51(3):79-85, 1952a.
  • Hilton, W. A. The pulmonary respiratory system of salamanders. HERPETOLOGICA 8(3): 87-92, 1952b.
  • Hilton, W. A. Review of the head muscles of salamanders. Part I. BULL. SO. CAL. ACAD. SCI., 53:133-137, 1959.
  • Hilton, W. A. Shoulder and upper arm muscles of salamanders. BULL. SO. CAL. ACAD. SCI., 61(4): 205-216, 1962.
  • Hoeven, J. vander. Notes on the genus Menopoma and its natural affinities. ANNALS. MAG. NAT. HIST., 18:363-375, 1866.
  • Holbrook, J. NORTH AMERICAN HERPETOLOGY. Philadelphia, J. Dobson, 1842, SSAR Reprint, 1976.,
  • Huheey, J. E. and Stupka, A. AMPHIBIANS AND REPTILES OF THE GREAT SMOKY MOUNTIANS NATIONAL PARK. Univ. of Tenn. Press, Knoxville, Tennessee, 1967.
  • Hulse, A. C., McCoy, C. J., and Censky, E. J. AMPHIBIANS AND REPTILES OF PENNSYLVANIS AND THE NORTHEAST. Cornell Univ. Press, Ithaca and London, 2001.
  • Humphries, W. J. ECOLOGY AND POPULATION DEMOGRAPHY OF THE HELLBENDER, Cryptobranchus alleganiensis, IN WEST VIRGINIA. M. S. Thesis, Marshall Univ., Huntington, West Virginia, 1999.
  • Humphries, W. J. and T.. K. Pauley Seasonal Changes in Noctunal Activity of the Hellbender, Cryptobranchus alleganiensis, in West Virginia. J. OF HERP., 34(4): 604-607, 2000.
  • Hurter, J. A contribution to the herpetology of Missouri. TRANS. ST. LOUIS ACAD. SCI., 7(19):499-503, 1897.
  • Hurter, J. A HERPETOLOGY OF MISSOURI, Trans. St. Louis Acad. Sci. 20(5) 59-274, 1911.
  • Hutchison, V. H. An annotated list of the amphibians and reptiles of Giles County, Virginia. VIRGINIA J. SCI., 72(7-8): 80-86, 1956.
  • Hutchison, V. H., Engletson, G., and Turney, D. Thermal Acclimation and Tolerance in the Hellbender, Cryptobranchus alleganiesis. COPEIA, 1973(4): 805-807, 1973.
  • Huxley, T. H. Structure of skull and heart of Menobranchus lateralis. PROC. ZOOL. SOC., London, Pp. 186-204,
  • Ingersol, C. A. SEASONAL REPRODUCTIVE CHANGES IN Cryptobranchus alleganiensis. M. S. Thesis, Southwest Missouri State Univ., Springfield, 1982.
  • Ingersol, C. A., Wilkinson R. F., Petterson C. L., Ingersol R. H. Histology of the reproductive organs of Cryptobranchus alleganiensis Caudata Cryptobranchidae in Missouri USA. SOUTHWESTERN NATURALIST 36(1), 60-66, 1991.
  • Jerrett, D. P. A COMPARATIVE HEMATOLOGICAL STUDY OF THE HELLBENDER SALAMANDER, GENUS, Cryptobranchus, WITH COMMENTS ON OTHER URODELES. M.S. Thesis, Depauw Univ., Greencastle, Indiana, 1971.
  • Jerrett, D. P., and Mays, C. E. Comparative hematology of the hellbender Cryptobranchus alleganiensis in Missouri. COPEIA, 1973(2): 331-337, 1973.
  • Johnson, R. M. A BIOGEOGRAPHIC STUDY OF THE HERPETOFAUNA OF EASTERN TENNESSEE. PHD, Dissertation. Univ. of Florida, 1958.
  • Johnson, T. R. Notes on the internal anatomy of a hellbender. KENTUCKY HERP., 2(2): 4, 1971.
  • Johnson, T. R. THE AMPHIBIANS AND REPTILES OF MISSOURI, 2ND ed. Conservation Commission of the State of Missouri, Jefferson City, MO., 2000.
  • Keim, T. D. Notes on the fauna about the headwaters of the Allegany, Genesee and Susquenanna Rivers in Pennsylvania. COPEIA 1915(24): 51-52, 1915.
  • Kerr, T. Development and structure of some actinopterygian and urodele teeth. ZOOL. SOC. LONDON PROC., 133:401-422, 1960.
  • King, W. A survey of the herpetology of Great Smoky Mountains National Park. AMER. MIDLAND NAT., 21(3): 531-582, 1939.
  • Kingsbury, B. F., and Reed, H. D. The columella auris in amphibia. J. MORPHOL., 20(4): 549-628, 1909.
  • Kirtland, J. P. A catalogue of the mammalia, birds, reptiles, fishes, testacea, and crustacea of Ohio. 2ND ANN. REPT., GEOL. SUR. OHIO, 159-200, 1838.
  • Krecker, F. H. Filaria cingula parasitic in the skin of Cryptobranchus alleganiensis. PARASITOL. 2:74-79, 1916.
  • Lang, R. W. The natural environment and subsistence economy of the McKees Rocks Village Site. PENN. ARCH., 38(1-4): 50-80, 1968.
  • La Rue, G. R. A new cestode, Ophiotaenia cryptobranchi nov. sec., from Cryptobranchus alleganiensis (Daudin). 16TH REPT. MICH. ACAD. SCI., 11-17, 1914.
  • Low, J. W. Contributions to the development of the pelvic girdles: I. The pelvic girdle in the batrachian Menopoma alleghaniense Harlan. PROC. ZOOL. SOC. LONDON, 2(45): 913-929, 1926.
  • Lucas, F. A. The sacrum of Menopoma. AMER. NAT., 20:561-562, 1886.
  • Luckhardt, A. B., and Carlson, . A. J. Studies on the visceral sensory nervous system. VI. Lung automatism and lung reflexes in Cryptobranchus. AMER. J. PHYSIOL., 55:212-222, 1921.
  • Makino, S. The chromosomes of Cryptobranchus alleganiensis. J. MORPHOL. 58(2): 573-583, 1935.
  • Maldonado-Koerdell, M., and Firschein, I Notes on the ranges of some North American salamanders. COPEIA 1947(2): 140, 1947.
  • Malewitz, T. D. Intestinal Parasitism of some mid-western salamanders. AMER. MIDLAND NAT., 55(2): 434-436, 1955.
  • Martof, B. Observations on the life history and ecology of the amphibians of the Athens area, Georgia. COPEIA 1955(3): 166-170, 1955.
  • Mays, C. E., and Nickerson, M. A. A population study of the Ozark hellbender salamander, Cryptobranchus alleganiensis bishopi. INDIANA ACAD. SCI., 81:339-340., 1971.
  • McCauley, R. H., Jr., and East, C. S. Amphibians and reptiles from Garrett County, Maryland. COPEIA, 1940(2): 120-123, 1940.
  • McCutcheon, F. H., and Hall, F. G. Hemoglobin in the amphibia. J. CELLULAR COMP. PHYSIOL., 9(2):191-197, 1937.
  • McGregor, J. H. Preliminary notes on the cranial nerves of Cryptobranchus alleganiensis. J. COMP. NEUROL., 6:45-53, 1896.
  • McGregor, J. H. An embryo of Cryptobranchus. ABSTRAT. IN ZOOL., Anz., Bd. 20, p. 29, 1897.
  • McGregor, J. H. Cranial nerves of Cryptobranchus alleganiensis. J. COMP. NEUR., 6:45-53, 1901.
  • McGregor, J. H. An embryo of Cryptobranchus. BIOL. BULL., 13(1): 39, 1907.
  • McMullen, D. B., and Roudabush, R. L. A new species of trematode, Cercorchis cryptobranchi, from Cryptobranchus alleganiensis. J. PARASITOL., 22:516-517, 1936.
  • Merkle, D. A. GENE FLOW AND POPULATION DIFFERENTIATION IN THE SALAMANDERS Eurycea lucifuga AND Cryptobranchus alleganiensis. Ph.D. dissertation. Miami Univ., Oxford, Ohio, 1975.
  • Merkle, D. A. , Guttman, S. I., and Nickerson, M.A. Genetic Uniformity Throughout the Range of the Hellbender. Cryptobranchus alleganiensis. COPEIA 1977: 549-553, 1977.
  • Meszoely, C. North American fossil cryptobranchid salamanders. AMER. MIDLAND NAT., 75(2): 495-515, 1966.
  • Minton, S. A. Jr. AMPHIBIANS AND REPTILES OF INDIANA. Rev. 2nd. Ed., Indiana Acad. Sci., Indianapolis, IN., 2001.
  • Mivart, St. G. Notes on the myology of Menopoma alleghaniense. PROC. ZOOL. SOC. LONDON, 1869:254-271, 1869.
  • Mivart, St. G. On the axial skeleton of the urodela. PROC. ZOOL. SOC. LONDON, 1870:260-278, 1870.
  • Moalli, R. , Meyers, R. S., Ultsch, G. R., and Jackson, D. C. Acid-base balance and temperature in the predominantly skin-breathing salamander, Cryptobranchus alleganiensis. RESPIR. PHYSIOL., 43:1-11, 1981.
  • Morse, M. BATRACHIANS AND REPTILES OF OHIO. Ohio State Acad. Sci. 4, Part 3(9): 95-144, 1904.
  • Myers, C. W. Amphibians and reptiles of Montauk State Park and vicinity, Dent County, Missouri. TRANS. KANSAS ACAD. SCI., 62(1): 88-90, 1959.
  • Naylor, B. G. Cryptobranchid salamanders from the Paleocene and Miocene of Saskatchewan. COPEIA, 1981: 76-86, 1981
  • Neill, W. T. Distributional notes on Georgia amphibians and some corrections. COPEIA, 1957(1): 43-47, 1957.
  • Netting, M. G. The food of the hellbender, Cryptobranchus alleganiensis (Daudin). COPEIA, 170: 24-25, 1929.
  • Nickerson, M. A. Return of captive Ozark hellbenders, Cryptobranchus alleganiensis bishopi, to site of capture. COPEIA 1980: 536-537, 1980.
  • Nickerson, M. A., and Hutchison, J. A. The distribution of the fungus Basidiobolus ranarum Eidam in fish, amphibians and reptiles. AMER. MIDLAND NAT., 86(2): 500-502, 1971.
  • Nickerson, M. A., and Mays, C. E. THE HELLBENDERS: NORTH AMERICA’S “GIANT SALAMANDERS.” Pub. Biol. Geol., Milw. Publ. Mus. 1:1-106, 1973a
  • Nickerson, M. A., and Mays, C. E. A Study of the Ozark Hellbender Cryptobranchus alleganiensis bishopi. ECOLOGY, 54: 1164-1165, 1973b
  • Nickerson, M. A., Ashton, R. E., and Braswell, A. L. Lampreys in the diet of hellbender Cryptobranchus alleganiensis (Daudin) and the Neuse River waterdog Necturus lewisi (Brimley). HERP. REV., 14:10, 1983.
  • Nickerson, M. A., and Tohulka, M. D. The Nest and Nest Site Selection by Ozark Hellbenders, Cryptobranchus alleganiensis bishopi (Grobman). TRANS. KANSAS ACAD. SCI. 89: 66-69, 1986.
  • Nigrelli, R. F. Some longevity records of vertebrates. TRANS. NEW YORK ACAD. SCI., Ser. II 16(6): 296-299, 1954.
  • Noble, G. K. The integumentary, pulmonary, and cardiac modifications correlated with increased cutaneous respiration in the amphibia: A solution of the hairy frog problem. J. MORPH. AND PHYSIOL., 40(2): 341-416, 1925.
  • Noble, G. K. THE BIOLOGY OF THE AMPHIBIA. McGraw-Hill Book Co., Inc. New York, 1931.
  • Noble, G. K., and Farris, E. J. A metamorphic change produced in Cryptobranchus by thyroid solutions. ANAT. REC., 42:59, 1929.
  • Noeske, T. A., and Nickerson, M. A. Diel Activity Rhythms in the Hellbender. Cryptobranchus alleganiensis(Caudata: Cryptobranchidae). COPEIA, 1979:92-95, 1979.
  • Oliver, J. A. THE NATURAL HISTORY OF NORTH AMERICAN AMPHIBIANS AND REPTILES. D. Van Nostrand Co., Inc. Princeton, New Jersey, 1955.
  • Osborn, H. F. Preliminary observations upon the brain of Menopoma. PROC. ACAD. NAT. SCI., Philadelphia 1884: 262-274, 1884.
  • Osborn, H. F. Contribution to internal structure of the amphibian brain. J. MORPH., 2:51-96, 1888.
  • Parker, W. K. On the structure and development of the skull in the urodeles. TRANS. ZOOL. SOC., 11:171-214, 1885.
  • Paulmier, F. C. NEW YORK REPTILES AND BATRACHIANS. Bull. New York State Mus. Bull. 51:389-414, 1902.
  • Pearse, A. S. The reactions of amphibians to light. PROC. AMER. ACAD. ARTS AND SCI., 45(6): 160-208, 1910.
  • Peterson, C. L. COMPARATIVE DEMOGRAPHY OF FOUR POPULATIONS OF THE HELLBENDER, Cryptobranchus alleganiensis IN THE OZARKS. Ph.D. Dissertation Univ. of Missouri, Columbia, 1985.
  • Peterson, C. L. Movement and catchability of the hellbender, Cryptobranchus alleganiensis. J. OF HERP., 21:198-204, 1987.
  • Peterson, C. L. Breeding activities of the hellbender salamander in Missouri. HERP. REV., 19(2), 1988.
  • Peterson, C. L., Topping, M. S., Wilkinson Jr. , R. F., and Taber, C. A. An examination of long-term growth of Cryptobranchus alleganiensis predicted by linear regression methods. COPEIA, 1985:2, 492-496, 1985.
  • Peterson, C. L., Metter, D. E., Miller, B. T., Wilkinson Jr., R. F., and Topping, M. S. Demography of the hellbender Cryptobranchus alleganiensis in the Ozarks. AMER. MIDLAND NAT., 119:291-303, 1988.
  • Peterson, C. L., Wilkinson Jr., R. F. , Topping, M. S. and Metter, D. E. Age and growth of the Ozark hellbender (Cryptobranchus alleganiensis bishopi). COPEIA 1983: 225-231, 1983.
  • Peterson, C. L., Ingersol, C. A., and Wilkinson Jr., R. F. Winter breeding of Cryptobranchus alleganiensis bishopi in Arkansas. COPEIA, 1989:1031-1035, 1989.
  • Peterson, C. L., Wilkinson Jr., R. F. Home range size of the hellbender (Cryptobranchus alleganiensis) in Missouri. HERP. REV., 27 (3), 126-127, 1996.
  • Peterson, O. The fossils of the Frankstown Cave, Blair County, Pennsylvania. ANN. CARNEGIE MUS., 16:249-314, 1925.
  • Petranka, J. W. SALAMANDERS OF THE UNITED SATES AND CANADA. Smithsonian Institute Press, Washington and London, Pgs. 140-144, 1998.
  • Pfingsten, R. A., and Downs, F. L. eds. SALAMANDERS OF OHIO. Ohio Biol. Surv. Bull., New Series Vol. 7, No. 2, 1989.
  • Pfingsten, R. A. The Status and Distribution of the Hellbender, Cryptobranchus alleganiensis in Ohio. HERP. REV., Vol 21, No. 3, 1990.
  • Pickens, A. L. Amphibians of upper South Carolina. COPEIA, 1927(165): 106-110, 1927.
  • Powell, R. Updated size records for amphibians and retiles in Missouri. MISSOURI HERP. ASSOC. NEWSL., 7:7-8, 1994.
  • Rafinesque, C. S. On two new salamanders of Kentucky. KENTUCKY GAZETTE, Lexington, Ky., New Series 1(9): 3, 1822.
  • Rafinesque, C. S. Herpetology-On three new water salamanders of Kentucky. ATLANTIC J., 1(3): 121, 1832.
  • Rankin, J. S. AN ECOLOGICAL STUDY OF PARASITES OF SOME NORTH CAROLINA SALAMANDERS. Ecol. Monogr. 7:169-269, 1937.
  • Ratcliff, M. A., Jr. The male urogenital system in Cryptobranchus. J. TENNESSEE ACAD. SCI., 40:52-57, 1965.
  • Reeder, W G. The digestive system. Pp 99-149 in PHYSIOLOGY OF THE AMPHIBIA. Moore, J. A. ed. Academic Press, New York, 1964.
  • Reese, A. M. The habits of the giant salamander. POPULAR SCIENCE MONTHLY, April, 1903.
  • Reese, A. M. The Sexual Elements of the Giant Salamander, Cryptobranchus alleganiensis. BIOL. BULL., 6:220-223, 1904.
  • Reese, A. M. The enteron and integument of Cryptobranchus alleganiensis. TRANS. AMER. MICROS. SOC., 27th Annual Meeting, Vol. XXVI., 1905a.
  • Reese, A. M. The eye of Cryptobranchus. BIOL. BULL. 9(1): 22-26, 1905b.
  • Reese, A. M. Anatomy of Cryptobranchus alleganiensis. AMER. NAT., 40(472): 287-326, 1906a.
  • Reese, A. M. Observations on the reactions of Cryptobranchus and Necturus to light and heat. BIOL. BULL., 11(2): 93-99, 1906b.
  • Reilly, S. M. and Lauder, G. V. Morphology behavior and evolution comparative kinematics of aquatic feeding in salamanders. BRAIN, BEHAVOIR, AND EVOLUTION, 40(4). 182-196, 1992.
  • Rhoads, S. N. Contributions to the zoology of Tennessee. No. 1, reptiles and amphibians. PROC. ACAD. NAT. SCI., Philadelphia, 47:376-407, 1895.
  • Richmond, N. Fossil amphibians and reptiles of Frankstown Cave, Pennsylvania. ANN. CARNEGIE MUS., 36:225-228, 1964.
  • Riss, W., H. D. Knapp, and F. J. Scalia. Optic pathways in Cryptobranchus alleganiensis as revealed by the Nauta technique. J. COMP. NEUROL., 121 (1): 31-43, 1963.
  • Routman, E. Mitochondrial DNA variation in Cryptobranchus alleganiensis a salamander with extremely low allozyme diversity. COPEIA, 1993(2). 407-416, 1993.
  • Routman, E., Wu, R., and Templeton, A. R. Parsimony, molecular evolution and biogeography: The case of the North American giant salamander. EVOLUTION, 48 (6), 1799-1809, 1994.
  • Salthe, S.N. The egg capsules in the Amphibia. J. MORPH., 113:161-171, 1963
  • Sanders, J. M. The development of the thyroid gland in urodeles. J. MORPHOL., 57(2): 592-615, 1935.
  • Seibert, H. C. Cryptobranchus alleganiensis (Daudin) Hellbender. Pp.65-71 in SALAMANDERS OF OHIO. R. A., Pfingsten, and F. L. Downs eds. Ohio Biol. Surv. Bull. New Series Vol. 7, No. 2, 1989.
  • Seibert, H. C., and Brandon R. A. The salamanders of southeastern Ohio. THE OHIO J. SCI., 60(5):291-303, 1960.
  • Sever, D.M. Comparative anatomy and phylogeny of the cloacae of salamanders amphibia Caudata II Cryptobranchidae Hynobiidae and Sirenidae. J. OF MORPHOL., 207 (3). 1991. 283-302, 1991.
  • Shaffer, H. B. and Breden, F. The relationship between allozyme variation and life history: non-transforming salamanders are less variable. COPEIA, 1989: 1016-1023, 1989.
  • Smith, B. G. Preliminary report on the embryology of Cryptobranchus allegheniensis. BIOL. BULL., vol. 11, no. 3, 1906.
  • Smith, B. G. Life History and Habits of Cryptobranchus allegheniensis. BIOL. BULL., 13: 5-39, 1907
  • Smith, B. G. A case of defensive self-mutilation in Cryptobranchus. BULL. WIS. NAT. HIST. SOC., 9:64-65, 1911.
  • Smith, B. G. The embryology of Cryptobranchus allegheniensis, including comparisons with some other vertebrates. I. Introduction; the history of the egg before cleavage. J. MORPH. 23(1): 61-157, 1912a.
  • Smith, B. G. The embryology of Cryptobranchus allegheniensis including comparisons with some other vertebrates. II. General embryonic and larval development, with special reference to external features. J. MORPH., 23(3): 455-579, 1912b.
  • Smith, B. G. An experimental study of concrescence in the embryo of Cryptobranchus allegheniensis. BIOL. BULL., Vol. 26, 1914.
  • Smith, B. G. Notes on the late history of the germinal vesicle in Cryptobranchus allegheniensis. 17TH REPORT OF THE MICHIGAN ACAD. OF SCI., 1915.
  • Smith, B. G. The individuality of the germ-nuclei during the cleavage of the egg of Cryptobranchus allegheniensis. J. MORPH., Vol. 36., 1919.
  • Smith, B. G. The embryology of Cryptobranchus allegheniensis III. Formation of the blastula. J. MORPH. AND PHYSIOL., 42(1): 197-252, 1926.
  • Smith, B. G. The history of the chromosomal vesicles in the segmenting egg of Cryptobranchus allegheniensis. J. MORPH. AND PHYSIOL. 47(1): 89-134, 1929.
  • Smith, H. M. HANDBOOK OF AMPHIBIANS AND REPTILES OF KANSAS. Univ. Kansas Mus. Nat. Hist. Misc. Publ. No. 2, 1950.
  • Smith, P. W. THE AMPHIBIANS AND REPTILES OF ILLINOIS. Bull. Illinois Nat. Hist. Survey 28(1), 1961.
  • Smith, P. W. and Minton, Jr., S. A. A distributional summary of the herpetofauna of Indiana and Illinois. AMER. MIDLAND NAT., 58(2): 341-351, 1957.
  • Smith, W. H. Report on the reptiles and amphibians of Ohio. OHIO GEOL. SUR.,4: 713-734, 1882.
  • Snider, A. T., and J. K. Bowler. LONGEVITY OF REPTILE AND AMPHIBIANS IN NORTH AMERICAN COLLECTIONS. 2ND ed., SSAR, Herpetological Circular No. 21, 1992.
  • Soule, N and Lindberg, A. L. The Use of Leverage to Facilitate the Search for the Hellbender. HERP. REV., Vol. 25 No. 1 pp. 16: 1994
  • Stein, H. A., and Smith, P. W. The hellbender, Cryptobranchus, in Illinois. COPEIA, 1959(2): 178-179, 1959.
  • Steven, D. M. The dermal light sense. BIOL. REV., 38:204-240, 1963.
  • Stone, J. W. THE EFFECTS OF HYPERTONIC MEDIA ON VARIOUS SERUM AND URINE CONSTITUENTS OF THE HELLBENDER, Cryptobranchus alleganiensis. M.S. Thesis S. W. Missouri State College, Springfield, Mo., 1971
  • Surface, H. A. First report on the economic features of the amphibians of Pennsylvania. ZOOL. BULL., DIV. ZOOL. PENN. DEPT. AGRICULT., 3:68-152, 1913.
  • Swanson, P. L. Notes on the Amphibians of Venango County, Pennsylvania. AMER MIDLAND NAT., 40: 362-371, 1948.
  • Taber, C. A., Wilkinson R. F. Jr., and Topping, M. S. Age and Growth of Hellbenders in the Niangua River, Missouri. COPEIA, 1975(4): 633-638, 1975.
  • Taketa, F., and Nickerson, M. A. Hemoglobin of the aquatic salamander Cryptobranchus. COMP. BIOCHEM. PHYSIOL. 46A: 583-591, 1973.
  • Taketa, F., and Nickerson, M. A. Comparative studies on the hemoglobins of representative salamanders of the families Cryptobranchidae, Proteidae, and Hynobiidae. J. COMP. BIOCHEM. PHYSIOL., 45(3B):549-556, 1973.
  • Tilley, S. G., and Huheey, J. E. REPTILES AND AMPHIBIANS OF THE SMOKIES. Great Smoky Mountians Natural History Association, Gatlinburg, Tenn., 2001
  • Topping, M. S. Secondary production in the hellbender, Cryptobranchus alleganiensis alleganiensis. TRANS. MISSOURI ACAD. SCI., 15:246-247, 1981.
  • Topping, M. S., and Ingersol, C. A. C. A. Fecundity in the Hellbender, Cryptobranchus alleganiensis. COPEIA, 873-876, 1981.
  • Townsend C. H. Habits of the Menopoma. AMER. NAT., 16: 139-140, 1882.
  • Trauth, S. E., Wilhide, J. D., and Daniel P. Status of the Ozark hellbender, Cryptobranchus bishopi (Urodela: Cryptobranchidae), in the Spring River, Fulton County, Arkansas. PROC. ARKANSAS ACAD. SCI., 46:83-86, 1992. .
  • Troost, G. List of reptiles inhabiting the state of Tennessee. GEOLOGICAL REPORT OF THE STAE OF TENN., 7:39-42, 1844.
  • Ultsch, G. R. and Duke, J. T. Gas exchange and habitat selection in the aquatic salamanders Necturus maculosus and Cryptobranchus alleganiensis. OECOLOGIA (HEIDELBERG), 83 (2), 250-258, 1990.
  • Vondersaar, M. E., and Stiffler, D. F. Renal Function in amphibians a comparison of strictly aquatic and amphibious species with observations on the effects of anesthesia. COMP. BIOCHEM. AND PHYSIOL., 94 (2). 243-248, 1989.
  • Walton, A. C. Studies on some nematodes of North American amphibia. II. Cryptobranchidae. J. PARASITOL., 17(1):20-24, 1930.
  • Walton, A. C. The nematoda as parasites of amphibia. J. PARASITOL., 20(1): 1-32, 1933.
  • Walton, A. C. The nematoda as parasites of amphibia. II. J. PARASITOL., 21:27-50, 1935.
  • Walton, A. C. A new species of Zanchlophorus from Cryptobranchus alleganiensis. TRANS. ILLINOIS STATE ACAD. SCI., 28:267-268, 1936.
  • Walton, A. C. The parasites of the Cryptobranchidae. J. PARASITOL 28(6): 29, 1942.
  • Welter, W. A., and Carr, K. Amphibians and reptiles of northeastern Kentucky. COPEIA 1939(3): 128-130, 1939.
  • Wikramanayake, E. D., and Dryden, G. L. Body length of male Cryptobranchus alleganiensis at sexual maturity. BULL. MARYLAND HERP. SOC., 21:76-79, 1985.
  • Wiggs, J. N. FOOD HABITS, STARVATION, AND GROWTH IN THE HELLBENDER, Cryptobranchus alleganiensis. Master’s Thesis. Springfield, Missouri: Southwest Missouri State Univ., 1976.
  • Wiggs,R.L. MOVEMENT AND HOMING IN THE HELLBENDER, Cryptobranchus alleganiensis, IN THE NIANGUA RIVER, MISSOURI. Master’s thesis. Springfield, Missouri: Southwest Missouri State Univ., 1977.
  • Wilcox, E. V. Notes on the batrachians of Ohio. OTTERBEIN AEGIS, 1:133-135, 1891.
  • Wilder, B.G. Habits of Cryptobranchus AMER. NAT.,16, 1882.
  • Willey, A. Remarks on the respiratory movements of Necturus and Cryptobranchus. PROC. ZOOL. SOC., 1920(43): 649-651, 1920.
  • Williams, R. D., Gates, J. E., and Hocutt, C. H. An Evaluation of Known and Potential Sampling Techniques for the Hellbender, Cryptobranchus alleganiensis J. HERP., 15(1): 23-27, 1981.
  • Williams, R. D., Gates, J. E., and Hocutt, C. H., and Taylor, G. J. The hellbender: a nongame species in need of management. WILDL. SOC. BULL., 9:94-100, 1981.
  • Wonderly, D. E. A comparative study of the gross anatomy of the digestive system of some North American salamanders. J. OHIO HERP. SOC., 4(1-2): 31-48, 1963.
  • Wortham Jr., J. W. Ed A DISC ELECTROPHORETIC STUDY OF SERUM PROTEINS OF Cryptobranchus FROM THE OZARK PLATEAU. M. S. Thesis, Arkansas State Univ., Jonesboro, Arkansas, 1970.
  • Wortham, E., and Nickerson, M. A. A serum protein study of Ozark Cryptobranchus. HERP. REV., 3:14, 1971.