Tatia caxiuanensis, Sarmento-Soares & Martins-Pinheiro, 2008

Sarmento-Soares, Luisa Maria & Martins-Pinheiro, Ronaldo Fernando, 2008, A systematic revision of Tatia (Siluriformes: Auchenipteridae: Centromochlinae), Neotropical Ichthyology 6 (3), pp. 495-542 : 510-512

Tatia caxiuanensis , new species

Figs. 16-18

Holotype. MPEG 9859 , male (32.6 mm SL), Brazil, Pará: município de Melgaço, Estação Científica Ferreira Pena , Curuá river, Caxiuanã, 01 o 44’53”S 51 o 27’13”W, 1 Nov 1999, R. Barthem and team.

Paratypes. Brazil, Pará : MPEG 6201 (7, 1 CS, 29.3-40.7 mm SL) ; MNRJ 28821 (2, 31.3-35.3 mm SL), all collected with the holotype .

Diagnosis. Tatia caxiuanensis is distinguished from its congeners by a distinctive male modified anal fin, with elongate rays, with no denticulations on ray segments. The new species is also distinguished by the following combination of characters, as cranial fontanel wide, with a single opening; infraorbital 1 with pronounced ventral process, almost reaching the antero-ventral border of eye rim; nasal ossified as tubes, with no medial flanges of bone and not sutured to mesethmoid; five branched pectoral-fin rays; and snout deep, depth more than 46.7% HL. Additional features useful for distinguishing T. caxiuanensis include caudal fin lobes with about the same length in both adult females and males; post- Weberian vertebrae 32; and a smaller adult size, less than 50.0 mmSL.

Description. Measured specimens 29.3-40.7 mm SL; morphometric data presented in Table 5. Body slim, head slightly depressed dorso-ventrally. Head robust, outline of head in dorsal view almost rectangular, broader than long. Dorsal outline of trunk from dorsal-fin base to caudal peduncle gradually compressed laterally. Lateral profile of head from snout tip to above opercular margin slightly convex until pectoralfin insertion. Ventral profile of head and abdomen flat. Ventral profile of body gently curved behind anal fin.

Head integument thick, cranial roof difficult to visualize; well-developed adipose eye lid; eye latero-dorsally located in anterior portion of head; mouth terminal, upper lip extended postero-laterally as well-developed fleshy rictal fold; snout margin rounded; anterior nostril tubular, located on anterior border of snout, above lip; posterior nostril thin, rounded, limited by small skin flap; transverse distance between anterior nostrils proportionally the same as distance between posterior ones. Maxillary barbel of moderate size, extending beyond posterior tip of postcleithral process, reaching vertical through origin or middle of dorsal fin; four mental barbels, tips not reaching pectoral-fin base, arranged in arc along ventral surface of jaw; inner mental barbel about 70.0-78.0% length of outer mentals. Postcleithral process well developed, almost reaching vertical through origin of dorsal fin. Caudal peduncle moderately deep, its depth about 11.0-13.0% SL.

Rostral border of cranium broad with mesethmoid broader than longer, premaxilla underneath with synchondral articulation; cranial fontanel elliptical, with single large opening, bounded by mesethmoid and frontal; nasal ossified, tubular, with no medial flanges ( Fig. 17 ). Autopalatine tubular, oriented obliquely to longitudinal axis of body; maxilla about same size of autopalatine; prevomer expanded with a well developed arrow-shaped lateral processes; jaws of equal size; premaxilla and dentary with three rows of conical teeth. First nuchal plate short, pentagonal; second nuchal plate laterally concave; third nuchal plate projected laterally, with pronounced narrow tip. Epioccipital process small.

Suspensorium, hyoid arch, branchial skeleton and opercular bones as in generic description. Suprapreopercle present as long canal bone. Six branchiostegal rays articulated with hyoid arch: four with anterior ceratohyal and two with posterior ceratohyal. Basibranchial 2 forming osseous rod with broad cartilaginous anterior tip, separated from shorter basibranchial 3.

Four infraorbital bones in incomplete series. Infraorbital 1 thin, with short ventro-lateral process around anterior border of eye; remaining infraorbitals thin, reduced to canalicular portions. Infraorbital 2 smallest, close to infraorbital 1, followed by non-ossified portion of canal below eye and by two posterior canal bones much close to sphenotic, forming rear of orbit. Lateral line on body with ossified canal bones only near head.

Dorsal fin I,5; dorsal-fin spine with 15-17 antrorse serrations along entire anterior margin, posterior margin smooth. Pectoral fin I,5; pectoral-fin spine with 17-20 antrorse serrations along anterior margin; 14-15 retrorse serrations along posterior margin; serrations along both margins progressively larger towards spine tip. Pelvic-fin i,5, margin rounded. Adipose fin large, origin on vertical through middle anal-fin base. Anal fin iii, 7; anal-fin pterygiophores in 8 rod-like proximal radials and seven cartilaginous distal radials. Caudal fin forked, lobes with rounded tips, 8+9 principal rays, 5-8 upper procurrent, 5-6 lower procurrent rays. Caudal fin lobes about same length in both adult females and males. Nine pleural ribs attached to consecutive vertebrae. Post-Weberian vertebrae 32 (n=1).

Color in alcohol. Dorsal mid-line and latero-dorsal parts of body dark brown, with many small dark chromatophores, less concentrated over lips and chin. Head and nuchal shield dark. Ventrolateral parts of body pale, belly whitish. Dorsal-fin spine dark pigmented, subsequent rays grayish with dark base. Pectoral, pelvic, anal and adipose fins hyaline. Caudal fin dark brown, with dark chromatophores on fin rays.

Sexual dimorphism. Based on observation of gonads, all examined T. caxiuanensis are adults. In females a genital papilla is not evident. The genital papilla of mature males is visible, with a skin tube around deferent duct. The anal fin of mature male is strongly modified with the second and third unbranched plus first branched rays elongated and thickened, ending in a rounded curved tip ( Fig. 18 , uiii, b1). No tegumentary keel precedes the first unbranched anal-fin ray. The second unbranched ray is elongated, with an intermediate size between the neighboring first and third rays. The third unbranched and first branched rays are the longest ( Fig. 18 , uiii, b1). The distal most segments of the third unbranched ray are antrorsely curved ( Fig. 18 , ac). The second branched ray has a narrow tip. Posterior branched rays are progressively shorter and not reduced.

Distribution. Known only from the type locality in Curuá river, lower Amazon basin, about 330 km southwest from the city of Belém, Pará, Brazil ( Fig. 6 ).

Etymology. The specific name, caxiuanensis , is in reference to the Floresta Nacional de Caxiuanã, a preservation area where the catfishes were caught.

Remarks. Tatia caxiuanensis is one of the smallest Tatia , reaching maturity at 29.3 mm SL. Only T. gyrina reaches maturity at a smaller size (28 mm SL).

Figures

Fig. 16. Tatia caxiuanensis. (a) holotype, MPEG 9859, male, 32.6 mm SL. (b) paratype, MPEG 6201, female, 40.7 mm SL, Caxiuanã, Pará State, Brazil.

Fig. 17. Neurocranium of Tatia caxiuanensis, new species, MPEG 6201, 29.3 mm SL. Dorsal view. Abbreviations: ep, epioccipital; fo, single cranial fontanel, fr, frontal; le, lateral ethmoid; me, mesethmoid; na, nasal; n1, first nuchal plate, n2; second nuchal plate; n3, third nuchal plate; pe, posterior epioccipital process; ps, posttemporal-supracleithrum; pt, pterotic; so, supraoccipital; sp, sphenotic. Scale bar = 1 mm.

Fig. 18. Male modified anal fin of Tatia caxiuanensis, new species, MPEG 6201, 29.3 mm SL. Left side lateral view.Abbreviations: as, antrorsely curved segment; b1, branched first ray; b7, branched seventh ray; dd, deferent duct; ui, unbranched first ray; uii, unbranched second ray; uiii, unbranched third ray. Scale bar =1.0 mm.

Fig. 6. Drainage map of northern South America illustrating the geographic distribution of the species of Tatia. Symbols may represent more than one locality. Base map by Marilyn Weitzman.