Isbrueckerichthys epakmos Pereira & Oyakawa 2003, new species

Isbrueckerichthys epakmos, new species Fig. 2

Holotype. MZUSP 79804, male, 103.1 mm SL; Brazil: São Paulo: Tapiraí: rio Ribeira de Iguape drainage, rio Verde at Piúva, on road to Rio Verde, 23º58’22"S 47º34’23"W, 27 Jun 2002, O. T. Oyakawa, F. C. T. Lima, J. C. Nolasco & V. Moreira.

Paratypes. Brazil: São Paulo: MZUSP 79498, 4 (1) 33.2-66.7 mm SL; collected with the holotype. MZUSP 78444, 6 (4) 28.1- 78.2 mm SL; Ibiúna: creek tributary of rio Juquiá at Cachoeira da Fumaça, 24º2’18"S 47º14’53"W, 20 Oct 2001, A. Akama, J. C. Nolasco, O. T. Oyakawa, M. Ghazzi & R. T. Nakasumi. MCP 28276, 63 (20) 39.5-83.3 mm SL; Tapiraí: rio Coruja, tributary to rio Juquiá, on road from Tapiraí to Juquiá near Cachoeira do Chá, 24°1’47”S 47°34’29”W, 29 Jan 2001, C. A. S Lucena, J. F. P. da Silva, E. H. L. Pereira & A. R. Cardoso.

Diagnosis. Two putative autapomorphies were found for Isbrueckerichthys epakmos. The new species can be distinguished from its congeners by having a soft and rugose fleshy area well developed on anterior portion of snout of mature males (versus mature males with thin soft fleshy area on lateral margins of head or absent); and by the presence of a clump of hypertrophied odontodes located only on anterior portion of snout usually short and thick, directed forward or slightly upward (versus hypertrophied odontodes in mature males situated along lateral margin of head or absent).

Description. Standard length of measured specimens 56.4 to 103.2 mm. Counts and proportional measurements presented in Table 1. Dorsal surface of body covered by plates except for naked area around dorsal fin. Body moderately depressed. Progressively narrowing from cleithrum to end of caudal peduncle. Dorsal profile of body slightly convex, rising from snout tip to origin of dorsal fin and then descending to end of caudal peduncle. Trunk and caudal peduncle mostly ovoid in cross-section, slightly flattened ventrally and more compressed caudally. Greatest body depth at dorsal-fin origin. Ventral surface of head, region from pelvic-fin insertion to anal fin origin and around the anal-fin totally naked. Abdomen covered by minute platelets, scattered between posterior margin of lower lip and insertion of pelvic fin; sometimes concentrated in central area of abdomen.

Head broad and moderately square; without crests. Lateral margin covered with minute hypertrophied odontodes. Snout in lateral profile sloping abruptly towards its tip and slightly straight anteriorly. Mature males with well developed soft fleshy area on anterior portion of snout. Snout slightly concave anteriorly to nostrils. Soft fleshy area ornamented with short and thick hypertrophied odontodes (Figs. 2-3). Females with soft fleshy area but hypertrophied odontodes very short. Eye moderately small (10.6 to 13.5% of head length), dorsolaterally placed. Iris with minute dorsal flap covering pupil, sometimes absent. Lips roundish and well developed, occupying most of ventral surface of head. Lower lip almost reaching pectoral girdle and covered with minute papillae, which decrease in size towards its edge. Papillate surface of lower lip projecting between dentary and premaxillary rami. Maxillary barbell long, coalesced with lower lip and ornamented with small papillae. Teeth small and bicuspid, inner cusp slightly curved inwards. Lateral cusp small, usually not reaching half-length of inner cusp.

Dorsal fin originating on vertical line passing through pelvic-fin origin; nuchal plate present but spinelet absent and locking mechanism non-functional. Dorsal-fin spine moderately flexible, followed by 7 branched rays. Adipose fin present, preceded by 0-1 median, unpaired pre-adipose azygous plates. Pectoral fin moderate in size; with long, curved spine, covered with short hypertrophied odontodes on lateral margin; dorsal surface with discrete dermal flap along its entire length; 6 branched rays. First branched ray as long as spine. Subsequent branched rays reducing gradually in size. Last ray about half-length of first one. Posterior margin of pectoral fin straight; overlapping approximately half-length of pelvic fin when adpressed in mature males. Pelvic-fin moderate in size, with one spine and 5 branched rays, not reaching insertion of anal fin when adpressed. Pelvic-fin spine depressed, covered with minute odontodes ventrally and laterally; dermal flap on its dorsal surface, very large and extending to tip of spine in mature males. Anal fin with one unbranched and 5 branched rays. Caudal fin border concave; lower lobe slightly longer than upper, 14 branched rays.

Color in alcohol. Dorsal surface of body and head grayish or dark-brown, pale yellow ventrally. Dorsum covered by lighter brown blotches. Usually these blotches forming four saddles on dorsum: on origin of dorsal fin; on posterior portion of dorsal-fin base; between end of dorsal fin and adipose fin, and between adipose and caudal fins. Ventral margin of head, outer portion of upper lip, and ventral portion of caudal peduncle dusky. Spines of dorsal, pectoral, pelvic and anal fins grayish or with 3-4 wide dark stripes. Branched rays homogeneously grayish or with small, dark-brown blotches along entire length, sometimes forming 3 or 4 narrow bands. Caudal fin with 2-3 narrow bands, more visible when fin widely open. Fin membranes hyaline. Ventral surface unpigmented between anal-fin origin and head.

Distribution. Isbrueckerichthys epakmos inhabits in the headwaters of the rio Juquiá, rio Ribeira de Iguape basin in São Paulo State, Brazil (Fig. 1).

Etymology. The species name is from the Greek adjective (= epakmos) meaning in the bloom of age, alluding to the highly developed odontodes on the snout tip in mature males. Gen- der masculine.

Ecological notes. The rio Verde, a small stream with clear water

and moderate to strong current, with loose stones and, in some places, sand on the bottom, is located inside the largest remnant of the Atlantic Forest of southeastern Brazil at 700 m above sea level. It is about 5.0 m wide and 0.3-0.5 m depth. The following species occur syntopically with Isbrueckerichthys epakmos: Characidium sp., Rhamdia cf. quelen, Neoplecostomus ribeirensis, ‘ Cichlasoma’ cf. facetum, Geophagus brasiliensis, Phalloceros caudimaculatus.

Key to the species of Isbrueckerichthys

1 Teeth of dentary and premaxilla with small lateral cusp; pectoral-fin spine short (16.4-21.4% SL)............................... 2

1’ Teeth of dentary and premaxilla simple, without lateral cusp; pectoral-fin spine long (27.4-32.0% SL)............... I. alipionis

2 Mature males with large and rugose soft fleshy area on anterior portion of snout; more developed, hypertrophied odontodes inserted on anterior portion of snout (odontodes directed upward; short and usually strong)........ I. epakmos

2’ Mature males with thin soft fleshy area on lateral margins of head; more developed, hypertrophied odontodes inserted on cheeks (odontodes directed outward and usually weak).............................................................. I. duseni