Tatia nigra, 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 : 532-534

Tatia nigra , new species

Fig. 36-39

Holotype. INPA 12291 (116.8 mm SL), Brazil, Amazonas : Uatumã river, approximate coordenates 02 o 14’35”S 58 o 49’58”W, Oct 1983, Ichthyology INPA team.

Paratypes. Brazil, Amazonas : INPA 25501 , 1 (107.3 mm SL), collected with the holotype ; INPA 11073 , 1 (93.7 mm SL) ; INPA 11075 , 1 (113.5 mm SL) ; INPA 11081 , 6 (86.6-107.8 mm SL) ; MNRJ 32024 , 1 plus1 CS (97.0- 98.2 mm SL), Uatumã river , Samaúma lake, Presidente Figueiredo ; INPA 12296 , 1 (72.0 mm SL) Uatumã river , igarapé Miriti. Pará : MNRJ 12358 , 3 (70.0- 82.3 mm SL) Trombetas river , Porto Trombetas .

Diagnosis. Tatia nigra is uniquely distinguished from congeners by having dark brown body color ( Fig. 36 ) and short postcleithral process about 60.0% HL (vs. more than 80.0% HL in other Tatia ). Additional features useful for distinguishing T. nigra include: postcleithral spine not reaching vertical through origin of dorsal fin; nasal with well developed medial flanges; 32 vertebrae.

Description. Measured specimens 70.0- 116.8 mm SL; morphometric data presented in Table 12. Body deep, head depressed dorso-ventrally. Outline of head in dorsal view almost rectangular, slightly broader than long. Trunk from dorsal-fin base to caudal peduncle becoming gradually compressed laterally. Lateral profile of head from snout tip to opercular margin convex until pectoral-fin insertion. Ventral profile of head and abdomen slightly convex. Ventral profile of body concave behind anal-fin origin.

Head integument thin, cranial roof visible; well-developed adipose eye lid; eye latero-dorsally located in anterior portion of head; mouth terminal, upper lip extended posterolaterally as a well-developed fleshy rictal fold; anterior nostril tubular, located on anterior border of snout; posterior nostril large, rounded, limited by small skin flap; transverse distance between anterior nostrils larger than distance between posterior ones. Maxillary barbel of moderate size, extending well beyond posterior tip of postcleithral process, reaching vertical line tangent to origin of dorsal fin; mental barbel short, tips not reaching pectoral-fin base, arranged in arc along ventral surface of jaw; inner mental barbel about 54.0-65.0% length of outer mentals. Postcleithral process short, almost reaching vertical through middle nuchal plates. Caudal peduncle deep, depth about 14.4-17.0% SL.

Cranium with mesethmoid as long as broad; premaxilla underneath with synchondral articulation; elliptical narrow concavity for cranial fontanel, opening bounded by mesethmoid and frontal ( Fig. 37 ); nasal ossified, with wide medial flanges partially sutured to lateral margin of mesethmoid; autopalatine tubular, oriented obliquely to longitudinal axis of body; maxilla about same size of autopalatine; prevomer expanded anteriorly with well developed arrowshaped lateral processes; jaws of equal size; premaxilla and dentary with three to four rows of conical teeth. First nuchal plate somewhat pentagonal; second nuchal plate concave along lateral margins; third nuchal plate curved, projected laterally, with small tip. Epioccipital process very small.

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

Five infraorbital bones in incomplete series. Infraorbital 1 broad, with short ventro-lateral process; remaining infraorbitals thin, reduced to canalicular portions. Infraorbital 2 smallest, close to infraorbital 1; infraorbital 3 elongate, followed by short non-ossified portion of canal. Posterior three canal bones forming posterior orbital rim. Lateral line on body with ossified canal bones only close to head.

Dorsal fin I,5 (n=12); dorsal-fin spine with 19-22 antrorse serrations along entire anterior margin; posterior margin smooth. Pectoral fin I,5 (n=12); pectoral-fin spine with 28-31 antrorse serrations along anterior margin; 19-21 retrorse serrations along posterior margin; serrations along both margins progressively larger towards spine tip. Pelvic-fin i,5 (n=12), margin rounded. Adipose fin small, origin on vertical through end of anal-fin base. Anal fin iii,7 (n=12); anal-fin pterygiophores in eight rod-like proximal radials and seven cartilaginous distal radials. Caudal fin forked, lobes with rounded tips, upper lobe slightly elongated in comparison to lower lobe, 8+9 principal rays, 17-19 upper procurrent, 17-20 lower procurrent rays (n=12). Pleural ribs 10 attached to consecutive vertebrae. Post-Weberian vertebrae 32 (n=1).

Color in alcohol. Tatia nigra dark colored in large adult specimens. Dorsal mid-line and dorsolateral parts of body dark brown, as well as dorsal surface of head, nuchal shield, dorsal fin and adipose fin ( Fig. 36 ). Body progressively paler towards ventral parts. Ventral portion of head around chin, lips and anterior nostrils light brown. Belly whitish to origin of pelvic fin. Pectoral, pelvic and anal fins light brown. Caudal fin dark brown.

Sexual dimorphism. Tatia nigra attains sexual maturity above 80.0 mm SL. The mature females have a small intumescent genital papilla. Male genital papilla is formed by a thick skin flap around a slender emergent deferent duct. Male modified anal fin ( Fig. 38 ) has three unbranched and first branched rays enlarged and thickened. The first unbranched anal-fin ray is immediately preceded by a tegumentary keel ( Fig. 38 , tk). The second unbranched ray has an intermediate size between the neighboring first and third rays. Third unbranched is the longest ray, slightly curved towards fin tip; bearing smaller antrorsely curved distal segments ( Fig. 38 , ac). First branched ray is slightly curved towards the fin tip. First and second branched rays have retrorsely curved distal segments ( Fig. 38 , rc). Posterior branched rays are progressively shorter; with the last ray not reduced ( Fig. 38 , b 7 ). Caudal-fin lobes of both analyzed mature females and males have the upper lobe elongated.

Six mature males of T. nigra with a modified anal fin were examined. In two of these males the modified anal fin is laterally curved and spoon shaped ( Fig. 39 ), suggesting reproductive modification for internal inseminating.

Distribution. Known from the centralAmazon, in the Uatumã and Trombetas river drainages, northern tributaries of the Amazon river ( Fig. 6 ).

Etymology. The specific name nigra , is a Latin reference to the dark color pattern of this species.

Remarks. Tatia nigra has well-developed lateral ornamented medial flanges of bone on the nasal, but not as large as the flanges observed in T. aulopygia . The expanded nasal with medial flanges partially sutured to mesethmoid was recognized as a derived feature for the genus ( Soares-Porto, 1998), and was also observed in T. aulopygia , T. boemia , T. dunni , T. neivai , T. strigata , and adult specimens of T. intermedia .

Female genital papilla in T. nigra is not a common condition within the genus. The only other Tatia with female genital papilla is T. gyrina . The intumescent female genital papilla may represent a transitory condition in species of Tatia , and perhaps is observed in specimens only close to reproductive phase. The elongated upper caudal-fin lobe in both mature females and males is rare within the genus and may be also associated to the reproductive phase.

Tatia nigra occurs in sympatry with T. brunnea in the Trombetas river, at lago do Batata, but not syntopically. The specimens of T. nigra were captured in the lake, while the T. brunnea was recorded from the igarapé Saracazinho, a tributary of the Batata lake.

Figures

Fig.36. Tatia nigra.(a) holotype, INPA 12291, male, 116.8 mm SL.(b) paratype, INPA25501, female, 107.3 mm SL, Uatumã river, Amazonas State, Brazil.

Fig. 37. Neurocranium of Tatia nigra, MNRJ 32024, 97.0 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. 38. Male modified anal fin of Tatia nigra, MNRJ 32024, 97.0 mm SL.Left side lateral view.Abbreviations:al, antrorsely curved distal segment; b7, branched seventh ray; dd, deferent duct; rl, retrorsely curved distal segment; ui, unbranched first ray; uii, unbranched second ray; uiii, unbranched third ray.Scale bar= 1.0 mm.

Fig. 39. Detail of male modified anal fin in Tatia nigra. (a) INPA 11081, male, 107.8 mm SL, anal fin parallel to body. (b) INPA 11081, male, 105.2 mm SL, anal fin spoon shaped and laterally curved.

Fig. 7. Tatia aulopygia, (a) INPA 11080, male, 104.6 mm SL, Guaporé river, Amazonas State, Brazil. (b) ZMA 114.280, young female, 46.3 mm SL, Humaitá,Amazonas State, Brazil.

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.