Trichomycterus anhanga, Dutra¹ & Wosiacki¹ & de Pinna², 2012

Dutra ¹, Guilherme M., Wosiacki ¹, Wolmar B. & de Pinna ², Mario C. C., 2012, Trichomycterus anhanga, a new species of miniature catfish related to T. hasemani and T. johnsoni (Siluriformes: Trichomycteridae) from the Amazon basin, Brazil, Neotropical Ichthyology 10 (2), pp. 225-231 : 226-229

Trichomycterus anhanga , new species

Figs. 1 , 2a , 3 , 4

Holotype. INPA 25125 , 10.0 mm SL, Brazil, Amazonas, Novo Aripuanã, igarapé Extrema, tributary of rio Aripuanã , rio Madeira drainage, 05°07’14.0”S 60°22’46.9”W, 29 Apr 2005, L. Rapp Py- Daniel, O. M. Ribeiro, L. M. Sousa & A. Galuch.

Paratypes (all from Brazil). INPA 36117 , 3 , 9.8-10.6 mm SL, same data as holotype . MZUSP 108822 , 2 +1 c&s, 9.7-10.2 mm SL, same data as holotype . INPA 31402 , 1 , 10.5 mm SL, Amazonas, Novo Aripuanã, igarapé Palhalzinho, tributary of rio Aripuanã , rio Madeira drainage, 05°59’32.0”S 60°12’35.0”W, 06 Sep 2007, L . R. Py-Daniel, M. S. Rocha & R. R. de Oliveira . MPEG 6973 , 1 , 9.9 mm SL, Pará, Juruti, igarapé Juruti Grande , tributary of rio Amazonas, 02°34’39.0”S 56°23’59.9”W, 12 Sep 2002, W. B. Wosiacki & A. Bezerra . MPEG 14356 , 1 c&s, 13.1 mm SL, Pará, Juruti, igarapé Mutum, tributary of rio Aruã , tributary of rio Branco , rio Arapiuns basin, rio Tapajós drainage, 02°36’42.0”S 56°11’36”W, 27 Nov 2007, A. Hercos .

Diagnosis. Trichomycterus anhanga differs from all other congeners by its reduced latero-sensory canal system, which is restricted to a short section between LL1 and LL2, on the pterotic, and entirely absent on the rest of body and cranium. It also differs from all other species currently in Trichomycterus except T. hasemani and T. johnsoni by the single hypertrophied cranial fontanel, which occupies nearly the entire skull roof (vs. fontanel restricted to one or more narrow spaces along the dorsal midline of skull).

Trichomycterus anhanga differs further from T. hasemani and T. johnsoni by the presence of three (i,2) pectoral-fin rays (vs. i,3-5 rays); the absence of pelvic fins and girdle (vs. presence); the reduced oral dentition, with only two teeth each on premaxilla and dentary (vs. teeth numerous in both upper and lower jaws); the reduced pharyngeal dentition, with only a single tooth in the lower pharyngeal plate and none in the upper (vs. pharyngeal dentition well developed); the presence of five to seven odontodes in the interopercle (vs. 9-10 in T. hasemani and 9-12 in T. johnsoni ), the absence of procurrent rays anterior to dorsal and anal fins (vs. one vestigial ray anterior to the main ray series in each fin), the lack of a lateral series of dark spots (vs. presence); the presence of a small dark spot on the ventral surface of the lower lip (vs. absence); the narrow comma-shaped palatine, lacking a posterior process (vs. palatine broad, with large posterior process) ( Fig. 2 ); the lack of a parasphenoid (vs. parasphenoid present); the presence of a single pair of pleural ribs (vs. two or three), the insertion of the first dorsal-fin pterygiophore anterior to the neural spine of the 16 th vertebra (vs. 17 th or 18 th vertebra in T. johnsoni , and 18 th to 20 th in T. hasemani ). It can be further distinguished from T. hasemani by the insertion of the first anal-fin pterygiophore anterior to the hemal spine of 16 th vertebra (vs. anterior to hemal spine of 19 th- 20 th vertebra); and from T. johnsoni by the absence of irregular longitudinal dark lines on the sides of the body (vs. presence), the absence of a dark midventral line (vs. presence), and the smaller interorbital distance (17.8-23.2% SL vs. 25.5- 37.0% SL).

Description. Morphometric data given in Table 1. Body elongate, approximately cylindrical near head, progressively more compressed posteriorly to strongly compressed caudal peduncle. Dorsal profile gently convex from tip of snout to posterior margin of head and straight from this point to end of caudal peduncle. Dorsal-fin base in recess on dorsal profile of body. Ventral profile straight from snout tip to pectoral-fin origin, gently convex from that point to anus, then straight to end of caudal peduncle. Anal opening on vertical line through origin of dorsal fin.

Head depressed, its greatest width across bases of interopercular odontodes; snout round in dorsal view; lateral surface of head with well-developed muscle protruding from posterior margin of eye to opercular patch of odontodes. Eye small and circular, with well-defined margin, located on anterior half of HL, dorsally oriented.

Anterior nostril round, its diameter equal to eye lens, surrounded by short tube of integument continuous posterolaterally with nasal barbel. Posterior nostril occluded anteriorly by fleshy integument shaped like a half-shell, positioned closer to eye than to anterior nostril. Posterior nostril slightly displaced medially relative to line between anterior nostril and eye.

Mouth subterminal, with corners slightly posterolaterally oriented. Upper lip extending slightly further anteriorly than lower one, its anterior margin gently rounded in ventral view, continuous laterally with bases of maxillary and rictal barbels. Lower lip thinner than upper one, its anterior margin gently rounded in ventral view. Jaw dentition reduced, with two conical feeble teeth on each premaxilla and each dentary ( Fig. 3 ).

Barbels elongate, wider at base, narrowing gradually distally, ending in sharp filament. Origin of nasal barbel on posterolateral portion of anterior nostril, reaching posterior margin of eye or slightly beyond that. Maxillary barbel variably reaching to point between base and posterior limit of interopercular patch of odontodes. Rictal barbel variably reaching to point between base and middle of interopercular patch of odontodes; its base lacking fleshy lobe.

Interopercle with five to seven (six*) odontodes. Interopercular patch with odontodes arranged in two main series. Opercle with six to 10 (seven*) odontodes ( Fig. 4 ). Odontodes on anterior series straight and those on posterior series slightly longer and curved medially. Opercle with small odontodes anterior to first series. Gill membrane united to isthmus only at anteriormost portion. Gill opening wide. Branchiostegal rays, four* or five.

Pectoral fin i,2, with first ray prolonged as filament and branched rays approximately one third of length of first ray. Dorsal fin ii,5(5), iii,3(1), or iii,4*(2), its distal margin rounded; unbranched rays gradually increasing in size, last unbranched ray and first branched ray larger than others, branched rays gradually decreasing in size. Anal fin ii,4, its distal margin gently convex; first unbranched ray two-thirds of length of second ray; second unbranched ray and first branched ray longer than others; branched rays slightly decreasing in size, with their origin at vertical through second or third dorsal-fin ray. Caudal fin truncate, i,8,i(1), i,8,ii(1), ii,7,ii(2) or iii,7,ii*(5). Procurrent caudal-fin rays six or seven* dorsally (eight visible in c&s), and six* or seven ventrally, visible in alcoholic specimens. Pelvic fin and girdle absent.

Lateral line with two pores dorsal to pectoral-fin insertion, LL1 and LL2. Cephalic portion of latero-sensory canal system (supraorbital, infraorbital and preorbital) absent. Vertebrae 29(1), 31(3), or 32(4). One pair of pleural ribs. Dorsal fin with seven or eight pterygiophores, first one anterior to neural spine of 16 th or 17 th free vertebrae.Anal fin with six pterygiophores, first one anterior to hemal spine of 16 th vertebra.

Color in ethanol. Ground color cream. Flank, dorsum, and posteroventral region with tiny light brown spots, irregular in shape. Dorsum with series of four to eight transverse dark brown spots; when eight, first to fifth ones anterior to dorsal fin insertion, sixth over dorsal-fin origin, seventh on vertical line through posterior margin of dorsal fin and eighth on posterior portion of caudal peduncle. Series of three to five dark brown transverse spots on ventral surface of body; first one immediately anterior to anus, second at origin of anal-fin base, third immediately posterior to anal-fin base, fourth approximately in middle of caudal peduncle, and fifth near insertion of first ventral caudal-fin procurrent rays.

Ground color of head cream. Snout with spot extending from base of maxillary barbel to anterior margin of eye. Region of neurocranium with light brown spot extending lateroventrally to interopercular patch of odontodes, sometimes merging with first dorsal spot. Ventral surface of head with few light brown chromatophores concentrated between interopercular odontodes. Ventral surface of lower lip with conspicuous dark spot at symphysis. Opercular and interopercular patches of odontodes with few chromatophores more concentrated at odontode bases. Nasal, maxillary and rictal barbels with small brown spots on dorsal surface, more concentrated basally.

Pectoral fin hyaline. Bases of dorsal and anal fins with light brown spot on insertion of first three rays, individuals without spots sometimes with few brown chromatophores on dorsal and anal fins. Caudal fin with dark brown vertical bar at base, darker across central rays, gradually lighter toward dorsal and ventral ends. Middle part of fin with dark brown chromatophores, more concentrated near spot at base; edge hyaline.

Distribution. Known from igarapé da Extrema and igarapé Palhalzinho, tributaries to the rio Aripuanã, itself a tributary to the rio Madeira; igarapé Juruti Grande, tributary to the right margin of the rio Amazonas; and igarapé Mutum, a tributary of the rio Aruã, a tributary of rio Branco, itself tributary of the rio Arapiuns, tributary of the rio Tapajós basin ( Fig. 5 ).

Etymology. The specific name anhanga is a reference to the Amazonian Anhangá legend, a spirit that lives in the woods,

protector of animals. Its presence can be detected by a whistle and thereafter, the animal that was being hunted disappears. Anhangá is thus regarded as a protector of forest life. A noun in apposition.

Figures

Fig. 1. Trichomycterus anhanga, holotype, INPA 25125, 10.0 mm SL. Brazil, Amazonas, igarapé Extrema, tributary of rio Aripuanã, rio Madeira drainage. a) lateral view; b) dorsal view; c) ventral view.

Fig. 2. Palatine in Trichomycterus, dorsal view. a) T.anhanga, left side, INPA 36117, paratype; b) T. hasemani, inverted of right side, MPEG 4968. Scale bars = 0.1 mm. 1 = anterior articular facets; 2 = posterior articular facets.

Fig. 3. Jaws of Trichomycterus anhanga, MZUSP 108822. Scale bars = 0.1 mm.a) upper jaw in ventral view; b) lower jaw in ventrolateral view, left side. PMX = premaxilar, MET = mesethmoid, DEN = dentary;AAR = anguloarticular.

Fig. 4. Opercle and Interopercle of Trichomycterus anhanga, lateral view, left side, INPA 36117, paratype. OP = opercle; IO = interopercle.Scale bar = 0.1 mm.

Fig. 5. Map of northern South America showing the distribution