ABSTRACT
Brasergasilus jaraquensis gen. et sp. nov. and B. anodus sp. nov. (Copepoda: Cyclopidea: Ergasilidae), gill parasites of Semaprochiiodus insignis (Schomburgk) and Anodus elongatus Spix, are described from the Amazon River. The new genus has only three pairs of swimming legs and in this respect is similar only to one species from New Zealand, Abergasilus amplexus Hewitt, 1978. The two genera also have in common a three-segmented prehensile antenna. Abergasilus, however, has the base of the second antennal segment developed into a massive spine which abutts against the claw-like third segment. The new genus completely lacks this fundamental structure. Aditionally, Abergasilus has six free thoracic segments while the new genus only has five. Abergasilinae Subfam. nov. is proposed for these two genera and their three species. Ergasilinae nom. nov. is provisionally defined and proposed to include the other 11 genera of the family. The type species of Brasergasilus gen. nov. is B. jaraquensis sp. nov. and it can be distinguished from B. anodus sp. nov. by the following characteristics: 1) The type species is larger and of a greenish coloration while B. anodus has fewer pigment granules that are of a bluish tint. 2) B. jaraquensis has a more slender second antenna and the most abrupt bend of the claw occurs distally; the second antenna of B. anodus is thicker and the abrupt bend Is found proximally. 3) The uropod of the type species has two setae and two small spines, while that of the other species has three setae and lacks spines. 4) The first leg of B. jaraquensis is laterally serrate while that of B. anodus is pectinate. The two species parasitize two different genera of host fish and are probably host specific.