Meeting Abstract

P2-85   -   Counting chromosomes: evolution of karyotype in the genus Sphaerichthys Mobley, B*; Renn, SCP; Anderson, AP; Reed College, Portland OR; Reed College, Portland OR; Reed College, Portland OR bmobley@reed.edu

Of all the teleost fish, few are as karyotypically notable as Sphaerichthys osphromenoides, commonly called the Chocolate Gourami. S. osphromenoides has the fewest chromosomes of any known teleost fish (2n=16) and though the phylogenetic relationships of the genus are established, the evolutionary history of this extreme karyotype remains unclear. Closely related species are morphologically, ecologically, and geographically similar making change in chromosome number a candidate for a mechanism of speciation in this taxon. We investigate the origins of this reduced karyotype by identifying the chromosome numbers of congeners and closely related species. Karyotypes for the yet-unexamined species were determined by arresting regenerating caudal fin cells in metaphase, followed by the creation of metaphase spreads for banding, staining, and analysis. Our work provides insight into the evolution of an extreme karyotype among teleosts and has implications for diversification in this taxon of gourami.