Ergasilussalmini sp. nov. (Copepoda: Ergasilidae) a branchial parasite of "dourado", Salminus franciscanus from the upper São Francisco River, Brazil

Abstract

Ergasilus salmini sp. nov. a branchial parasite of the "dourado", Salminus franciscanus Lima & Britski, 2007, from the upper São Francisco river, Minas Gerais State, Brazil, is described based on female specimens. The new species has a serrate, curved seta on the first exopod as do most of the known South American species of the genus. Other than that, it does not closely resemble any known species of this genus. Many of the known ergasilids have head, and first two thoracic segments completely fused to form a cephalothorax. In the new species, the head is incompletely fused, the first thoracic segment is fused, but thoracic segment two is free. Ergasilus hydrolycus Thatcher, Boeger & Robertson, 1984, also has a free second thoracic segment but in that species the head is completely fused and the third abdominal segment is the longest. In the new species, the third segment is the shortest of the three. Also, the new species is smaller averaging 691 x 207 µ m compared to 784 x 278 µ m for E. hydrolycus. The latter species has a two-segmented fourth endopod whereas in the new species this structure is three-segmented. In addition, the new species is from a different host and a separate river system.