Some Aspects of the Life History and Ecology of the Salamander Leurognathus

Leurognathus inhabits trout streams in the southern Appalachian Mountains from southwestern Virginia to northeastern Georgia. These salamanders have a discontinuous distribution; they are strangely absent from some drainages. Specimens are best collected by diverting the flow of water so that a part of the stream bed is drained. This area is then carefully searched and the routed animals captured with the use of a funnel-shaped trap made of screen or fine-mesh hardware cloth. Some individuals attain a maximum snout-vent length of 78 mm and a weight of 13 grams. Generally males are larger than females, have a relatively wider head, less vomerine teeth, enlarged maxillary teeth, a larger and papillated cloaca, and an enlarged (but not conspictious) mental gland. Spawning occurs chiefly in June. Eggs are attached to the underside of a rock located in the main current. They average about 40 per clutch and hatch in about three months. Hatchlings average 11 mm in snoutvent length. The larval stage may be as short as 10 months or as long as 20 months. The average size at metamorphosis varies seasonally and geographically. It ranges from 25 to 38 mm; the over-all average is near 30 mm. Males reach sexual maturity when about 50 mm in snout-vent length and at least two years of age. Females mature when they are three years old and about 55 mm in size. Maximum size is probably approached at the age of five years. There is no evidence that either sex prefers a special habitat or that the sex ratio is other than one to one. Leurognathus are mainly noctural and secretive. They spend much time under rocks and feed almost exclusively on the larval or nymphal forms of aquatic insects. Much geographic and individual variation in body proportions and in coloration and markings occurs in this species. One of the most interesting types of variation involves the absence of dark pigment. These specimens are mostly whitish-yellow but may have dark blotches over both venter and dorsum. Some completely lack dark markings, but all have normal colored eyes and soles of the feet. The incidence of albinistic specimens has gradually increased from less than one per cent in 1954 to nine per cent in 1960. No albinistic larvae have been found. The smallest specimen showing such albinism measured 39 mm from snout to vent. However, some specimens as small as 45 mm were among the most albinistic ones collected. Thus a very conspicuous change in phenotype may occur in individuals and in populations within a relatively short period of time. A survey of the morphological features and adaptive trends of desmognathine salamanders supports retention of the genus Leurognathus. This content downloaded from 207.46.13.86 on Sun, 16 Oct 2016 04:35:27 UTC All use subject to http://about.jstor.org/terms 2 THE AMERICAN MIDLAND NATURALIST 67(1)