No abstract

Ammoglanis obliquussp. nov., a minute catfish species reaching a maximum adult size of 15.5 mm, is described from the Rio Preto da Eva drainage in the central Brazilian Amazon. It is distinguished from all of its congeners in possessing an exclusive combination of character states, including the presence and number of premaxillary and dentary teeth, number of interopercular and opercular odontodes, presence of cranial fontanel, number of dorsal-fin rays, number of anal-fin rays, number of caudal-fin rays, number of pelvic-fin rays, number of pectoral-fin rays, absence of pelvic splint, antorbital morphology, and absence of supraorbital and autopalatine morphology. It is considered to be a member of a clade also including A. pulex and A. amapaensis due to the unique oral, antorbital, and autopalatine morphology. Ammoglanis obliquus is regarded as more closely related to A. pulex than to any other congener, as both species exhibit a similar colour pattern, an absence of the metapterygoid, and the presence of two finger-like projections on the chin region.

A new species of Gymnotus Linnaeus is described from Riacho Cambiriba a clear water stream, tributary of the Rio de Contas basin, Bahia, northeastern Brazil. The new species is a member of the G. carapo species-group, which is characterized by the presence of a transparent patch near the posterior end of the anal fin and two (vs. one) laterosensory pores in the dorso-posterior region of the preopercle bone. Gymnotus interruptus may be diagnosed by a unique combination of morphometric and meristic characters: wider interorbital distance (44.6 – 45.9% of STO); 9 scales above lateral line at midbody; 23 – 28 ventrally oriented lateral line rami; 37 – 40 pored lateral line scales to first ventral ramus of lateral line; shorter snout (29.6 – 30.5% of STO). Gymnotus interruptus, the first record of a gymnotiform fish from the rio de Contas basin, may be easily distinguished from G. carapo or G. bahianus, two congeners also occurring in northeastern Brazil, by its colour pattern, in which the pale interbands, anterior to vertical through first ventral lateral line ramus, are ventrally and/or dorsally fragmented, allowing union of adjacent dark bands

A new species of Gymnotus, from the G. pantherinus species-group, is herein described from the rio Jucuruçu basin, a coastal river drainage located in the southern part of Bahia state, northeastern Brazil. Gymnotus capitimaculatus sp. n. differs from all congeners by having an pair of round blotches anteriorly positioned or under vertical passing through eye, on ventral portion of the head. Furthermore, Gymnotus capitimaculatus also differs from all members of the G. pantherinus species-group by having the following unique combination of characters states: tail with an unique series of bands or round spots; precaudal portion of trunk without bands but either with rounded and/or vermiculated spots; forty-five precaudal vertebrae; nine scales above lateral line at mid-body; anal-fin base length 75.2 – 78.6 % of TL; anus-anal fin length 101.4 – 122.8 % of HL; and branchial opening 38.5 – 45.0 % of HL.