Trichogenes claviger

description

Description. Morphometric data given in Table 1. Body blunt, deeper than broad anteriorly and gradually more compressed posteriorly to caudal fin. Anterior part of body and head, from snout to dorsal-fin origin, in broad continuous convex arc. Dorsal profile of posterior region of body, from endpoint of dorsal fin to caudal-fin origin, mostly straight. Ventral profile broadly convex from snout to origin of pelvic fins, then straight along entire length of anal-fin base. Deepest part of body at middle of abdomen, then gradually less deep to base of caudal fin. Head wide and deep, its depth approximately threequarters or more of HL. Mouth terminal, positioned at middepth of head, with jaws equally long or sometimes either upper or lower jaw slightly longer. Upper and lower lips narrow. Upper lip continuous laterally with maxillary barbel. Lower lip smaller and narrower than upper lip, subdivided into welldefined elongate fleshy lobe laterally, separating lip from base of rictal barbel. Dentary teeth 19 - 23, disposed in two rows. Outer row with 7 or 8 large, distally expanded, compressed and slightly tan-colored, bilobed teeth, with round cusp edges, gradually smaller laterally. Teet

A new species of Trichogenes from the rio Itapemirim drainage, southeastern Brazil, with comments on the monophyly of the genus (Siluriformes: Trichomycteridae)

diagnosis

Diagnosis. Three autapomorphies unique among Trichomycteridae distinguish T. claviger from all other members of the family: the sexually dimorphic posterior process of the opercle, much elongated in males (Fig. 2; vs. short in both males and females); the terminal mouth (Fig. 1; vs. subterminal or inferior); and the presence of an anterodorsal claw-like process on the dorsal surface of the neural arch of each of the anterior four free vertebrae (Fig. 3 a). Further distinguished from its only congener, T. longipinnis, by several additional characteristics (some of which may also be autapomorphic, pending more detailed analysis): the shape of the interopercle, with odontodes extending onto the posterodorsal margin of the interopercle on a bony expansion; (Fig. 4; vs. odontodes mostly restricted to ventral and posterior margins of the bone); the posterior naris broader than long (vs. round); the presence of an entirely differentiated fleshy lobe laterally on the lower lip (vs. fleshy lobe mostly continuous with the lower lip); the lack of branched anal-fin rays in specimens of any size (vs. most anal-fin rays branched in specimens over 41 mm SL); the less deep caudal peduncle (9.3 - 1

A new species of Trichogenes from the rio Itapemirim drainage, southeastern Brazil, with comments on the monophyly of the genus (Siluriformes: Trichomycteridae)

discussion

Remarks. The geographical ranges of T. longipinnis and of T. claviger are separated by approximately 500 km in straight line, and by several intervening independent drainages along the Atlantic coast. The two species probably have had a long history of isolation, as judging by the large set of distinguishing characteristics in external morphology and internal anatomy, summarized in the Diagnosis above. Some of the diagnostic characters deserve comment. Vertebral number seems to be a consistent meristic difference between the two species of Trichogenes, with a well-defined gap in counts. Interestingly, very limited variation was detected in the material examined, with T. longipinnis having 38 (n = 9, holotype) or 39 (n = 5) vertebrae and all specimens of T. claviger with 35 (n = 18). The pattern of integumentary pigmentation in the two species of Trichogenes, although similar in general features, also consistently differ. Although much variation is seen among different populations of T. longipinnis (some of which is illustrated in Sazima, 2004), in no case does its pigmentation match the one in T. claviger. Part of the difference includes a dark line along the base of the anal fin o

A new species of Trichogenes from the rio Itapemirim drainage, southeastern Brazil, with comments on the monophyly of the genus (Siluriformes: Trichomycteridae)

distribution

Distribution. Trichogenes claviger is known only from the type locality, an upland tributary of the headwaters of the rio Itapemirim drainage in southeastern Brazil (Fig. 7). Ecological notes. The type series was collected in a shallow sector (ca. 30 cm) of the córrego Picada Comprida (Fig. 8), on a plateau at ca. 1150 m altitude. The water is darkly tea-stained and transparent, with slow current and negligible altitudinal gradient. The stream runs through an area of moderately impacted high-altitude rainforest mingled with sectors of exotic pine culture. The substrate is mostly exposed sand, with masses of accumulated leaf litter and other vegetable debris in many spots. Fish were concentrated on quiet shaded areas with litter, swimming in midwater, and were collected with hand seines. No other fish species seems to co-occur with T. claviger. Preliminary observation of gut contents revealed numerous disarticulated arthropod remains, indicating that the feeding habits of the species are broadly similar to those of T. longipinnis. Specimens of the species were also observed swimming in two other nearby spots in tributaries to the córrego Picada Comprida, but were not seen in four ad

A new species of Trichogenes from the rio Itapemirim drainage, southeastern Brazil, with comments on the monophyly of the genus (Siluriformes: Trichomycteridae)