Notes on the Reproductive Biology of the Alabama Red Hills Salamander (Phaeognathus hubrichti )

Abstract

Living Amphibia exhibit two major life history modes, possession of an aquatic larval stage or direct development, with the latter assumed to be the derived evolutionary condition (Duellman and Trueb 1986, Wake 1989). A small group (n = 20 species) of plethodontid salamanders, the subfamily Desmognathinae, is of great interest because its members display both developmental modes (Marks 1995). For decades the prevailing phylogenetic hypothesis for the group, based upon morphology and habitat, was a monophyletic sequence from the larger, more aquatic species that possessed the longest larval lives to two dwarf terrestrial species with direct development Dunn (1926). This “aquatic to terrestrial” hypothesis remained unchallenged even with the discovery of a new, giant, fossorial species, the Alabama Red Hills Salamander (Phaeognathus hubrichti), that was thought to be a third species with direct development (Highton 1961).
Recently, analysis of mtDNA sequences revealed that the terrestrial desmognathines form the three deepest branches in desmognathine phylogeny, compelling the authors to advance an alternative phylogenetic hypothesis that absence of an aquatic larval stage may be ancestral for desmognathines (Titus and Larsen 1996). Their hypothesis rested, however, on details of the developing embryo and hatchlings in the three species with direct development, but critical data on the eggs, hatchlings, and whether larvae exist in P. hubrichti are unavailable.
Aspects of the reproductive biology of the rare and secretive Phaeognathus hubrichti are difficult to observe in the field because the species is a burrower. One clutch laid by a female kept in captivity for six years apparently was unfertilized because the eggs failed to develop (Brandon and Moruska 1982). The large size and small number of ripe ovarian oocytes observed in preserved specimens, coupled with the unusual terrestrial burrowing behavior of the species, suggest the absence of an aquatic larval stage (Brandon 1965).
On several visits to one ravine in Butler Co., Alabama (31°32’N, 86°45’W) during the spring and summer of 2002, I repeatedly observed a 105 mm SVL gravid female, discovered her eggs, kept them in captivity until they hatched, then returned the female and her clutch alive back into the field. Here I describe the field observations, eggs, embryos, and hatchlings.