Relationships of a new fossorial Microcambevinae catfish species from southern Brazil supporting multiple dorsal-fin losses in Listrura (Siluriformes, Trichomycteridae)

Extreme reduction or loss of fins is a common evolutionary feature in fossorial and semifossorial trichomycterids. Here, we analyse the possible occurrence of independent evolutionary events of dorsal fin loss in Listrura, a genus of fossorial species endemic to the Atlantic Forest of eastern Brazil, in a molecular phylogenetic context involving all species of the genus, including three nominal species lacking a dorsal fin and another one that is described here.

Ancestral state reconstruction analysis indicated the occurrence of three independent events of dorsal fin loss: one in the subgenus Listrura (L. menezesi) and two in the subgenus Prolistrura, in L. depinnai and in the clade comprising L. boticario and the new species. Osteological comparisons indicate that there are no intermediate stages in the genus; species either possess a well-developed dorsal fin or completely lack both the fin and its internal skeletal support.

It was not possible to identify distinct environmental characteristics or ecological preferences between species with and without a dorsal fin. The new species is distinguished from L. boticario, its hypothesised sister species, by a different colour pattern, a different number of caudal-fin procurrent rays and interopercular odontodes, and a larger eye.