Abstract
The Pennsylvania grotto sculpin is known from just two caves of the Nippenose Valley in central Pennsylvania, USA. They exhibit emergent troglobitic morphological traits and are the second northern-most cave adapted fish in the world. Two mitochondrial (16S rRNA and D-loop gene) and one nuclear (S7 ribosomal protein gene intron) gene in both cave and epigean populations were sequenced. For the three markers, a large proportion of cave specimens possess unique haplotypes not found in their local surface counterparts, suggesting a vicariance in their evolutionary history. The cave population also has haplotypes from two separate lineages of surface sculpins of the Cottus cognatus/bairdii species complex. Since morphology, nuclear, and mitochondrial markers are not correlated among cave individuals, hybridization with introgression is suggested.
Highlights
Modern biology as a science and evolutionary biology in particular have had a long history of interest in cavefishes
While the surface population has haplotypes corresponding to C. cognatus, the cave population has haplotypes shared with two sculpin lineages: C. cognatus and C. bairdi
One of these haplotypes was identical to the sequence obtained from all 15 surface fish sequenced from Antes Creek and from the seven surface C. cognatus from Willsey Brook, New York
Summary
Modern biology as a science and evolutionary biology in particular have had a long history of interest in cavefishes. In 2003, Espinasa and Jeffery described a previously unreported cave population of sculpins (Cottidae: Scorpaeniformes: Actinopterygii) inhabiting Eiswert #1 Cave (Stone, 1953) in the Nippenose Valley, Lycoming County, Pennsylvania Specimens of this cave population retain some degree of pigmentation and eye functionality. Espinasa and Jeffery (2003) showed that the cave population differ from the surface fish by wider and more abundant mandibular pores, wider head, longer pectoral fins, and reduced eyes (Fig. 2). This population is currently the second northern-most cave adapted fish in the world (Romero and Paulson 2001; BehrmannGodel 2017)
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