Troglomorphic sculpins of the Cottus Carolinae species group in Perry County, Missouri: Distribution, external morphology, and conservation status

The existence of cavernicolous sculpin (here allocated to Cottus carolinae, banded sculpin, and referred to as grotto sculpin), in the karst regions o f Perry County, Missouri, first came to our attention in 1991. Examination of 35 caves in Missouri, 96 in Illinois, 17 in Tennessee, two in Indiana, a nd 11 in Arkansas revealed that banded sculpin are common in cave habitats; however, grotto sculpin are limited to two karst areas of Perry County, Mi ssouri, where they are known from only six cave systems. These caves and th eir streams are extensive and apparently provide a unique habitat compared to other karst systems; this may be a critical factor in the present restri cted distribution of the grotto sculpin. Grotto sculpin occupy pools and ri ffles of cave streams, and occur over a variety of substrates, from sedimen t to breakdown. Density estimates in Mystery and Running Bull caves were 0. 29 and 0.63 individuals m(-2), respectively. Grotto sculpin have small eyes (1-6% SL vs. 6-10% SL in epigean samples), significantly reduced pigmentat ion (including nearly complete loss of dorsal saddles), a reduction in pelv ic fin ray number (from 4+4 elements to often 4+3 , or 3+3), and enlarged c ephalic lateralis pores (e.g., mandibular pores of cavernicolous samples ar e 2-3 times those of epigean stream samples). Multivariate analyses of body shape revealed statistically significant separation of epigean and hypogea n samples, with eye size highly variable, but smallest in the Running Bull Cave population. We interpret these results as representative of losses ass ociated with long-term cave habitation. Caves of Perry County provide ample habitat for grotto sculpin, but because the caves are located downgradient of the city of Perryville and an intensively farmed landscape, point and n on-point source pollution threaten their continued existence. Escape of far m-pond fishes through the extensive sinkhole network in Perry County has in creased potential predation pressure on grotto sculpin by channel catfish, Ictalurus punctatus, and other species normally excluded from cave environm ents.