Tatia galaxias Mees, 1974

Sarmento-Soares, Luisa Maria & Martins-Pinheiro, Ronaldo Fernando, 2008, A systematic revision of Tatia (Siluriformes: Auchenipteridae: Centromochlinae), Neotropical Ichthyology 6 (3), pp. 495-542 : 516-519

Tatia galaxias Mees, 1974

Figs. 22-24

Centromochlus aulopygius . Pellegrin, 1899: 188 [Apuré, Venezuela]. Schultz, 1944: 240 [ Venezuela]. Puyo, 1949: 97 [streams on region of Approuage].

Tatia aulopygia . Gosline, 1945: 10 [in part, Apuré]. Mago- Leccia, 1967: 225 [ Venezuela]. Burgess, 1989: 242, pl. 113, 114 [northeastern South America].

Tatia galaxias Mees, 1974: 86-88 , fig. 23. [type locality: Quiribana rivulet, Orinoco Basin, Venezuela]. Sands, 1984: 36-37 [ Venezuela]; Mees, 1988: 411-412 [Guarapiche river, Venezuela]; Burgess, 1989: 242 [Apure, Venezuela]; Franke, 1990: 20-34 [notes on reproduction]. Soares-Porto, 1998: 331-350 [citation]. Ferraris, 2003: 476 [checklist]. Lasso et al., 2004: 139 [Cataniapo, Bita, Meta, Suapure, Apure, Caura, Morichal Largo, Delta, Orinoco]. Ferraris, 2007: 77 [checklist].

Tatia intermedia . Soares-Porto, 1998: 333 [citation]. Ferraris, 2003:477 [checklist]. Lasso et al., 2004: 139 [Bita, Apure, Caroní, Orinoco].

Diagnosis. Tatia galaxias is uniquely distinguished from congeners by its well developed postcleithral process, reaching almost to a vertical through the dorsal-fin origin; a large eye, 37.0-42.9% HL (vs. 17.4-31.6% in other Tatia ); and by a short snout 23.1-28.9% HL (vs. 31.2-43.6% in other Tatia ). The species is also distinguished by the following combination of characteristics: narrow elliptical cranial fontanel; ribs 7 (vs. 8-11 in most other Tatia , except T. strigata with 7 ribs and T. gyrina with 5-6 ribs). Additional features useful for distinguishing T. galaxias include: nasal ossified with wide medial flanges partially sutured to lateral margin of mesethmoid; coloration variable, sides of body usually dark with light, rounded spots or dots, or sometimes uniformly pale brown; toothed prevomer in examined large adult specimens.

Description. Measured adult specimens 54.2-125.6 mm SL; morphometric data presented in Table 7. Body slim, head slightly depressed dorso-ventrally. Head large, robust, outline of head in dorsal view elliptic, broader than long. Dorsal outline of trunk from dorsal-fin base to caudal peduncle gradually compressed posteriorly. Lateral profile of head from snout tip to above opercular margin slightly convex to pectoral-fin insertion. Ventral profile of head and abdomen flat. Ventral profile of body concave posterior to anal fin.

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 well-developed fleshy rictal fold; snout margin rounded; 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 reaching vertical through end of dorsal-fin; mental barbel short, tips not reaching pectoral-fin base, arranged in arc along ventral surface of jaw; inner mental barbel about 50.0-67.0% length of outer mentals. Postcleithral process short, reaching vertical through origin of dorsal fin. Caudal peduncle deep, its depth about 14.2-18.3% SL.

Rostral border of cranium with mesethmoid as long as broad; premaxilla underneath with synchondral articulation; cranial fontanel elliptical, bounded by mesethmoid and frontal ( Fig. 23 ); nasal ossified, with medial flanges sutured to lateral margin of mesethmoid; autopalatine tubular, oriented obliquely to longitudinal axis of body; maxilla small, shorter than autopalatine. Prevomer expanded anteriorly, with well developed arrow-shaped lateral processes, bearing small teeth attached to process in a large specimen with 85 mm SL (MCNG 25983). Jaws of equal size; premaxilla and dentary with two to three rows of conical teeth. First nuchal plate pentagonal; second nuchal plate broad, laterally concave; third nuchal plate projected laterally, with curved distal tip. Epioccipital process very small.

Suspensorium, hyoid arch, branchial skeleton and opercular bones as in generic description. Suprapreopercle large. Six branchiostegal rays articulated with hyoid arch: four with anterior ceratohyal and two with posterior ceratohyal; last one largest and expanded.

Seven to eight infraorbital bones in usually complete series. Rarely incompletely ossified with 5 canal bones. Infraorbital 1 thin, with short ventro-lateral process limited to anterior border of eye; remaining infraorbitals thin, reduced to canalicular portions. Infraorbital 2-4 small, close to infraorbital 1. Infraorbitals 5-6 long ossified canals, bordering eye below and posteriorly. Last infraorbital much small, forming posterior orbital rim, in contact to sphenotic. Lateral line on body with ossified canal bones posteriorly to vertical through pelvic origin.

Dorsal fin I,5 (n=42), dorsal-fin spine with 15-18 antrorse serrations along entire anterior margin; posterior margin smooth. Pectoral fin I,5 (n=42), pectoral-fin spine with 19-25 antrorse serrations along anterior margin; 13-17 retrorse serrations along posterior margin; serrations along both margins progressively larger towards spine tip. Pelvic-fin i,5 (n=42), margin rounded. Adipose fin moderate in size, origin on vertical through analfin base origin.Anal fin iii, 6-7 (n=42); anal-fin pterygiophores in eight rod-like proximal radials and seven cartilaginous distal radials. Caudal fin forked, lobes with rounded tips, 8+9 principal rays, 18-20 upper procurrent, 18-20 lower procurrent rays (n=42). Seven pleural ribs attached to consecutive vertebrae. Post-Weberian vertebrae 32-33 (n=4), rarely 30.

Color in alcohol. Body usually dark brown with evenly spaced small white dots; chin with scattered pigment; underparts from chin to anus and ventrals unpigmented; pectoral fin pigmented lightly ( Mees, 1974: 86). Dorsal fin with dark base and irregular spots; caudal fin usually with whitish spots irregularly distributed over lobes ( Fig. 22 ).

Color variation. Although the body usually is dark brown with whitish spots, T. galaxias may be polymorphic for color pattern, as a large array of variation regarding color is observed. Some specimens have a light brown body. Some have small roundish spots over the body and caudal fin, a common pattern in very young specimens <40 mm SL. Some have caudal fin with dark tips. All distinct patterns may be found together in the same locality.

Sexual dimorphism. Based on examination of gonads, T. galaxias attains sexual maturity above 54.2 mm SL. In mature females a genital papilla is not evident. A genital papilla is visible in mature male, with a long slender emergent deferent duct ( Fig. 24 , dd). The male anal fin is strongly modified, with the anterior rays enlarged and thickened. The first unbranched anal-fin ray have segments fused and is preceded by a tegumentary keel ( Fig. 24 , tk). The second unbranched ray is elongated, with an intermediate size between the neighboring first and third rays. Third unbranched plus the first branched are the longest rays, forming a pointing tip. The third unbranched ray has the distal segments antrorsely curved ( Fig. 24 , ac). First and second branched rays have retrorsely curved distal segments ( Fig. 24 , rc). The remaining branched rays are progressively shorter, with the last ray not reduced ( Fig. 24 , b 7 ).

Hemal spines 15-18 interdigitate with the anal-fin pterygiophores, being the hemal spines 15-17 thickened in mature males, but undifferentiated in females. The caudal-fin lobes have the same length in mature females, whereas in males the upper lobe is slightly elongated.

Distribution. Endemic to the Orinoco basin in Venezuela, including Meta drainage, in Colombia ( Fig. 6 ).

Remarks. Mees (1974) described T. galaxias on the basis of its diagnostic color pattern of small white spots evenly spaced over a dark body (pattern exemplified in Fig. 22 ). Mees, (1974: 88) considered its coloration reminiscent of that of T. intermedia , except in T. galaxias the body is darker, the spots smaller, and the tail dark with white spots (vs. pale with dark spots and cross-bars in T. intermedia ). We observed the dark body to be geographically variable in both T. galaxias and T. intermedia . In acidic black water rivers specimens of T. galaxias tend to have a darker body, when compared to those from clear water rivers. Together with the pattern of small white spots, other patterns of coloration were recognized among Orinoco specimens, such as uniformly dark and dark with white ellipsoid spots, the latter being rarest. In T. galaxias the spots are usually round, whereas in T. intermedia the spots are typically more ellipsoidal. Tatia galaxias also has a larger eye 37.0-42.9% HL (vs. 21.4-26.3% in T. intermedia ) and fewer ribs, 7, and fewer vertebrae 32-33 (vs. 10 ribs and 35-36 vertebrae in T. intermedia ).

Tatia galaxias and T. intermedia are the only species of the genus bearing a toothed prevomer. Within the Auchenipteridae prevomerian teeth appear in Asterophysus batrachus , in both adults and young specimens. Ferraris (1988) considered the presence of prevomerian teeth in Tatia an aberration. In our examination of T. galaxias only a single specimen exhibited teeth. In T. intermedia , however, prevomerian teeth were found in all large specimens> 74 mm SL (n= 4). In all other large size (> 100 mm SL) centromochlin species, such as Glanidium albescens , G. ribeiroi , G. melanopterum , G. leopardus , Centromochlus schultzi , C. heckelii and C. existimatus , the prevomer is edentulous.

Material examined. 57 specimens (27.0- 125.6 mm SL). Paratypes. CAS 6568 , 4 (49.0- 56.6 mm SL) and RMNH 26493 , 2 (48.5-55.6 mm SL) ( R), Quiribana rivulet, near Caicara, Orinoco basin (paratypes of Tatia galaxias ) . Non-type specimens. AMNH 58320 , 2 plus 1 CS, no locality, probably Venezuela. Colombia : ANSP 138104 , 1 (43.4 mm SL) ; ANSP 138106 , 1 (38.0 mm SL), Humacita farm, small stream, probably belonging to the complex of lake Mozambique, Meta river drainage ; ANSP 138105 , 2 (54.2-64.6 mm SL), El Viento rivulet, Finca El Viento south of Matazul. Venezuela. Amazonas : AMNH 91381 , 1 (125.6 mm SL), Mavaca river ; ANSP 160648 , 1 (44.0 mm SL), Sipapo river above Pendare ; CAS 158873 , 1 (40.8 mm SL), bifurcation on Orinoco river in Tamatama beach . FMNH 103487 , 2 (30.0- 36.4 mm SL), Atabapo river close to Sapo island, above San Fernando de Atabapo . MCNG 25983 , 1 (85.6 mm SL), Siapa river . MCNG 27966 , 1 (39.3 mm SL), Orinoco river in El Tigre island . Apure : FMNH 69928 , 2 (27.0- 39.6 mm SL), Cinaruco river south of San Fernando deApure ; FMNH 103487 , 2 (31.5-37.5 mm SL), Atabapo river upstream from San Fernando de Atabapo . INHS 60322 , 2 ( R), Guaritico rivulet, south of Bruzual , Apure river drainage . MCNG 7080 , 1 (32.9 mm SL) ; MCNG 15891 , 1 (43.1 mm SL), Maporal Rivulet. Bolivar : ANSP 149691 , 1 (39.2 mm SL), Urbani river on road Maripas-Las Trincheras . ANSP 149973 , 17 (28.8-44.4 mm SL), Quiribana rivulet near Caicara, Orinoco basin . ANSP 160571 , 2 (34.1-35.5 mm SL), Los Pavones rivulet, tributary of Sipao river, near Farm Fundo Malama . CAS 158860 , 2 (28.7-32.0 mm SL) ; CAS 158865 , 3 (43.7-58.4 mm SL) ; CAS 158879 , 1 (54.8 mm SL), Quiribana rivulet, near Caicara, Orinoco basin . MCNG 1028 , 2 (33.1-34.0 mm SL), Tierra Blanca rivulet, Km 82 on road Santa Elena . MCNG 16632 , 2 (43.3-64.0 mm SL), Las Claritas river Km 85 on road Santa Elena . MCNG 15595 , 1 (57.0 mm SL), Sacuima river, via Caicara-Pijiguaos . MCNG 15970 , 1 (39.0 mm SL), Chaviripa river . MCNG 23254 , 1 (44.8 mm SL), Quebrada, close to C. Serapia del Nichare river ; MZUSP 44072 , 2 (68.5-72.3 mm SL), Cocniza rivulet, tributary of Orinoco river, near Caicara del Orinoco. Guarico : INHS 61870 , 5 (20.5-29.5 mm SL) Guariquito river nearAguas Muertes, ParqueAguaro-Guariquito . INHS 61940 , 3 (24.4-25.0 mm SL) San Bartolo river . INHS 69420 , 4 (22.8-30.0 mm SL) San Bartolo river west from La Esperanza . MCNG 1914 , 3 (31.4-32.5 mm SL) Aguaro river in Hato San Jose . MCNG 15001 , 3 plus 1 CS (25.3-29.4 mm SL) San Bartolo river, Parque Aguaro . MCNG 17137 , 1 (28.3 mm SL) rivulet in Hato Batolena . MCNG 17138 , 2 (25.1-32.2 mm SL) San Bartolo river, Parque Aguaro. Monagas : RMNH 30502 , 1 (31.0 mm SL) Guarapiche river . USNM 265661 , 1 (30.0 mm SL) Guarguapo rivulet, about 500 meters upstream from its mouth in Orinoco river, upstream from Barrancas .

Figures

Fig. 22. Tatia galaxias. (a)ANSP 138105, male, 64.6 mm SL. (b)ANSP 138105, female, 54.2 mm SL, El Viento rivulet, Colombia.

Fig. 23. Neurocranium of Tatia galaxias, RMNH 26493, paratype, 55.6 mm SL. Dorsal view. Abbreviations: ep, epioccipital; fo, single cranial fontanel, fr, frontal; le, lateral ethmoid; me, mesethmoid; na, nasal; n2, second nuchal plate; n3, third nuchal plate; pe, posterior epioccipital process; ps, posttemporal-supracleithrum; pt, pterotic; so, supraoccipital; sp, sphenotic. Scale bar = 1.0 mm.

Fig. 24. Male modified anal fin of Tatia galaxias, MCNG 25983, 85.6 mm SL. Left side lateral view.Abbreviations: ac, antrorsely curved denticulation; b1, branched first ray; b7, branched seventh ray; dd, deferent duct; rc, retrorsely curved denticulation; tk, tegumentary keel; ui, unbranched first ray; uii, unbranched second ray; uiii, unbranched third ray. Scale bar = 1.0 mm.

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.