Sunday, November 28, 2010
Cryptobranchus bishopi - In our waters and live more than 30 years
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The Ozark hellbender is a large, strictly aquatic salamander endemic to streams of the Ozark plateau in southern Missouri and northern Arkansas. Its dorso-ventrally flattened body form enables movements in the fast-flowing streams it inhabits (Nickerson and Mays 1973a, p. 1). Ozark hellbenders have a large, keeled tail and tiny eyes. An adult may attain a total length of 11.4 to 22.4 inches (in) (29 to 57 centimeters (cm)) (Dundee and Dundee 1965, pp. 369-370; Johnson 2000, p. 41). Numerous fleshy folds along the sides of the body provide surface area for respiration (Nickerson and Mays 1973a, pp. 26-28) and obscure their poorly developed costal grooves (grooves in the inner border of the ribs; Dundee 1971, p. 101.1). Ozark hellbenders are distinguishable from eastern hellbenders (Cryptobranchus alleganiensis alleganiensis) by their smaller body size, dorsal blotches, increased skin mottling, heavily pigmented lower lip, smooth surfaced lateral line system, and reduced spiracular openings (openings where water is expelled out of the body) (Grobman 1943, p. 6; Dundee 1971, p. 101.3; Peterson et al. 1983, pp. 227-231; LaClaire 1993, pp. 1-2). Despite these distinguishing characteristics, the two subspecies are not easily or readily distinguishable absent the presence of both subspecies or when encountered outside of their subspecies’ range.
The Ozark hellbender was originally described as Cryptobranchus bishopi by Grobman (1943, pp. 6-9) from a specimen collected from the Current River in Carter County, Missouri.
Adult Ozark hellbenders are frequently found beneath large rocks in moderate to deep (less than 3 feet (ft) to 9.8 ft (less than 1 meter (m) to 3 m)), rocky, fastflowing streams in the Ozark plateau. In spring-fed streams, Ozark hellbenders will often concentrate downstream of the spring, where there is little water temperature change throughout the year. Adults are nocturnal, remaining beneath cover during the day and emerging to forage at night, primarily on crayfish. Ozark hellbenders are territorial and will defend occupied cover from other hellbenders. This species migrates little throughout its life. For example, one tagging study revealed that 70 percent of marked individuals moved less than 100 ft (30 m) from the site of original capture. Home ranges average 91.9 square (sq) ft (28 sq m) for females and 265.7 sq ft (81 sq m) for males
Hellbenders are habitat specialists that depend on consistent levels of dissolved oxygen, temperature, and flow. The lower dissolved-oxygen levels found in warm or standing water do not provide for the hellbender’s respiratory needs. In fact, hellbenders have been observed rocking or swaying in still, warm water to increase their exposure to oxygen.
Typically, Ozark hellbender populations are dominated by older, large adults. Hellbenders are long-lived, capable of living 25 to 30 years in the wild. Hellbenders may live up to 29 years in captivity.
Breeding generally occurs between mid-September and early October. Males prepare nests beneath large flat rocks or submerged logs. Ozark hellbenders mate via external fertilization, and males will guard the fertilized eggs from predation by other hellbenders. Clutch sizes vary from 138 to 450 eggs per nest, and eggs hatch after approximately 80 days. Hatchlings and larvae are rarely collected during surveys due to low detectability. Larvae and small individuals hide beneath small stones in gravel beds.
Ozark hellbenders are endemic to the White River drainage in northern Arkansas and southern Missouri historically occurring in portions of the Spring, White, Black, Eleven Point, and Current Rivers and their tributaries (North Fork White River, Bryant Creek, and Jacks Fork) (LaClaire 1993, p. 3). Currently, hellbenders are considered extirpated in the mainstem White, Black, and Spring Rivers and Jacks Fork, and their range has been considerably reduced in the remaining rivers and tributaries.
Hellbenders are state endangered and federally protected. Hellbender expert Jeff Briggler states research has been conducted that proves “Between 1971 and 1973,researchers observed more than 1,000 hellbenders in the Niangua River. By the 1990s, however, the population had declined by 80 percent. Hellbender numbers in the Big Piney, Gasconade, Eleven Point and North Fork rivers showed similar decreases.