Tatia aulopygia (Kner, 1857)

Sarmento-Soares, Luisa Maria & Martins-Pinheiro, Ronaldo Fernando, 2008, A systematic revision of Tatia (Siluriformes: Auchenipteridae: Centromochlinae), Neotropical Ichthyology 6 (3), pp. 495-542 : 500-504

Tatia aulopygia (Kner, 1857)

Figs. 7-9

Centromochlus aulopygius Kner, 1857: 432 , Pl. 8 (fig. 26) [type locality: Guaporé river]. - Steindachner, 1876: 664-665 [no locality]. Eigenmann & Eigenmann, 1890: 270 [citation]. Pearson, 1937: 110 [Mamoré river drainage].

Tatia aulopygia . Miranda Ribeiro, 1911: 361 [generic designation]. Gosline, 1945: 10 [listing]. Mees, 1974: 59-63 [notes and distribution, in part, Maciel, Guaporé river]. Sands, 1984: 38-39 [listing]. Lauzanne & Loubens, 1985: 112 [Mamoré river drainage]. Burgess, 1989:242 [listing]. Soares-Porto, 1995:204 [citation]. Soares-Porto, 1998: 331- 350 [citation]. Lasso et al., 2001:97 [citation]. Ferraris, 2003:476 [checklist]. Ferraris, 2007: 77 [checklist].

Centromochlus intermedius . Fisher, 1917: 422 [in part, Maciel, Guaporé river]. Pearson, 1937: 110 [Mamoré river drainage].

Diagnosis. Tatia aulopygia is distinguished from all other species of Tatia by having a short cranial fontanel, with the opening restricted to the frontals ( Fig. 8 ); a genital papilla with thick flap of skin around the deferent duct in males ( Fig. 9 ); and a notched anal fin in adult males ( Fig. 9 ). The species also is distinguished from congeners by a combination of characteristics: nasal bone partially sutured to lateral margin of mesethmoid; anal fin with 7-8 branched rays; 10-11 ribs; 38-39 post-Weberian vertebrae. Additional features useful for distinguishing this species include: third nuchal plate well projected laterally with curved tip; and caudal-fin lobes of mature females similar in length, but mature males with slightly elongated upper lobe.

Description. Measured adult specimens 75.2-159.0 mm SL; morphometric data presented in Table 2. Body deep, head slightly depressed dorsoventrally. Head large, robust, outline of head in dorsal view somewhat elliptical, broader than long. Dorsal outline of trunk from dorsal-fin base to caudal peduncle increasingly 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 gently curved, concave behind anal-fin origin. Head integument thin, cranial roof visible; adipose eye lid well-developed; eye dorsolaterally located in anterior portion of head; mouth terminal, upper lip extended posterolaterally as well-developed fleshy rictal fold; anterior nostril tubular, located on anterior border of snout, above lip; posterior nostril large, rounded, limited by small skin flap; transverse distance between anterior nostrils slightly shorter than distance between posterior ones. Maxillary barbel short, extending slightly beyond tip of postcleithral process, sometimes shorter; mental barbels short, tips not reaching pectoral-fin base, arranged in arc along ventral surface of jaw; inner mental barbel about 65.0-75.0% length of outer mental. Postcleithral process almost reaching vertical through origin of dorsal fin. Caudal peduncle deep, depth about 14.0- 15.8% SL.

Rostral border of cranium broad with large mesethmoid; premaxilla underneath with synchondral articulation; cranial fontanel short, ovoid, bounded by frontal ( Fig. 8 ); nasal ossified with wide medial flanges partially sutured to lateral margin of mesethmoid; autopalatine tubular, oriented obliquely to longitudinal axis of body; maxilla very small, shorter than autopalatine; prevomer expanded anteriorly with well developed arrow-shaped lateral processes; jaws of equal size; premaxilla and dentary with four to five rows of conical teeth. First nuchal plate somewhat pentagonal; second nuchal plate deeply concave along lateral margin; third nuchal plate curved, projected laterally. Epioccipital process small.

Suspensorium, hyoid arch and opercular bones as in generic description. Suprapreopercle present as short robust canal bone. Six branchiostegal rays articulated with hyoid arch: four with anterior ceratohyal and two with posterior ceratohyal.

Basibranchials 2 and 3 fused together forming osseous rod with broad cartilaginous anterior tip; basibranchial 4 large flattened and completely cartilaginous; fused basibranchial 2 plus 3 bordered laterally by cartilaginous head of hypobranchial 1, cartilaginous head of hypobranchial 2 and cartilaginous hypobranchial 3. Basibranchial 4 bordered laterally by cartilaginous head of ceratobranchial 4 and posteriorly by cartilaginous head of ceratobranchial 5. Hypobranchials, ceratobranchials, epibranchials and pharyngobranchials as described in generic description.

Four infraorbital bones in incomplete series. Infraorbital 1 broad with short ventro-lateral process on 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 two posterior canal bones, one long and one short, forming posterior orbital rim. Lateral line on body with ossified canal bones posteriorly to vertical through pelvic-fin origin.

Dorsal fin I,5 (n=7); dorsal-fin spine with 14-16 antrorse serrations along entire anterior margin; posterior margin smooth. Pectoral fin I,5 (n=7); pectoral-fin spine with 21-24 antrorse serrations along anterior margin; small serrations close to spine base; 14-16 retrorse serrations along posterior margin; serrations along both margins progressively larger toward spine tip. Pelvic fin i,5 (n=7); margin rounded. Adipose fin small, origin on vertical through end of anal-fin base. Anal fin iii,7-8 (n=7); 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, 17-20 lower procurrent rays (n=7). Pleural ribs 10-11 attached to consecutive vertebrae. Post- Weberian vertebrae 38-39 (n=4).

females a genital papilla is not evident. The genital papilla of mature males is visible, with a thick skin flap around the deferent duct. The anal fin of mature males ( Fig. 9 ) is strongly modified, with the three unbranched and first two branched rays enlarged and thickened. The first unbranched anal-fin ray is immediately preceded by a tegumentary keel. The second unbranched ray is intermediate in size between the neighboring first and third rays. The third unbranched ray is the longest, forming a minute pointed fin tip ( Fig 9 , uiii); distal segments are smaller, and antrorsely curved ( Fig. 9 , ac). The first branched ray is slightly curved towards the fin tip, bearing retrorsely curved distal segments ( Fig. 9 , rc). The fourth and fifth branched rays are shorter, forming a central notch in distal margin of the anal fin. The posterior branched rays are normally developed and not reduced.

The hemal spines interdigitating with anal-fin pterygiophores are thick in males; but those hemal spines are undifferentiated in females. Caudal-fin lobes are of comparable length in mature females, whereas upper lobe is more elongated in mature males.

Specimens of T. aulopygia historically housed in collections are mostly juveniles, with only one syntype bearing a modified anal fin. Information on male anal-fin morphology was improved by recent captures of adult specimens in the Amazon basin.

Color in alcohol. Head and body mottled with dark and light brown patches of pigmentation, sometimes forming faint blotches irregularly distributed over sides of body ( Fig. 7 ). Lips and chin dark brown. Dorsal fin dark brown, pectoral fin usually pale brown or not pigmented. Adipose fin pale brown, caudal fin usually with transverse bars but young specimens with whitish spots. Pelvic fins and belly whitish.

Color variation. Body coloration in T. aulopygia is somewhat variable, usually with large bands or blotches irregularly distributed over sides of body. In some specimens coloration is uniformly dark or pale brown, with caudal fin mottled. Some young specimens have small spots over ventrolateral parts of body and a barred caudal fin.

Mees (1974) noted the presence of longitudinal pale streaks on the body and observed irregular patches of pigmentation on specimens from the Guaporé river, but all specimens available to him are now very faded and unsuitable for accurate description of coloration. Recent expeditions to the Guaporé river provided more adult specimens of T. aulopygia , on which the above description is based.

Sexual dimorphism. Based on examination of gonads, T. aulopygia attains sexual maturity above 80 mm SL. In mature Distribution. Tatia aulopygia occurs in the Madeira river drainage of the Amazon basin. Most records are from upper reaches, in the Guaporé and Mamoré rivers ( Fig. 6 ).

Remarks. A short cranial fontanel, limited to the frontal in T. aulopygia , is unique among known Tatia species. In specimens less than 60 mm SL, however, the cranial fontanel is larger, its opening extends between the mesethmoid and frontals (exemplified by MNHN 1988-994). An ontogenetic shift may occur, as adult specimens have a much reduced opening. A reduced cranial fontanel is found in adult Centromochlus perugiae and C. romani , but in these species the opening is contained by the mesethmoid and frontal (see Soares-Porto, 1998, fig. 4 for comparison).

Tatia aulopygia is somewhat similar in color pattern to three congeners: T. neivai , T. dunni , and T. intermedia . All three species also have the caudal fin with spots or vertical bars, with T. aulopygia most closely resembling T. neivai . Diagnostic features aside, T. aulopygia is further distinguished from T. neivai by having a large first nuchal plate ( Fig. 8 , vs. reduced in T. neivai ). Tatia aulopygia is further distinguished from T. dunni by having a shallower snout, depth 41.5-45.9% HL (vs. 47.0-51.8% in T. dunni ). Tatia aulopygia is further distinguished from T. intermedia by a narrower interorbital distance, 53.2-58.9% HL (vs. 60.1-63.6% HL in T. intermedia ).

Material examined. 17 specimens (21.8-159.0 mm SL). Syntypes. Brazil : NMW 47331, 1 (50.0 mm SL) and NMW 47333, 1 (55.0 mm SL), Guaporé river (syntypes of Centromochlus aulopygius ) . Non-type specimens. Bolivia: Beni: AMNH 39818 , 2 (25.8-27.8 mm SL), Itenez river ; INHS 37034 , 1 (75.2 mm SL), Matos river, Apere river drainage, Amazon basin ; MNHN 1988-994 , 1 (56.3 mm SL) ( R), Mamoré river drainage ; UMMZ 204834 , 1 (24.6 mm SL), Baures river, about 500 m upstream from mouth of Itenez river. Brazil: Amazonas : ZMA 114.280 , 2 (39.6-46.8 mm SL) ( R), Madeira river drainage at Humaitá. Rondônia : FMNH 58015 , 3 (21.8-43.8 mm SL), Guaporé river in Maciel ; INPA 11078 , 1 (76.2 mm SL) , INPA 11079 , 1 (159.0 mm SL) and INPA 11080 , 3 , 1 CS (80.0- 104.6 mm SL) Guaporé river .

Figures

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. 8. Neurocranium of Tatia aulopygia, INPA 11080, 80.0 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 = 1.0 mm.

Fig. 9. Male modified anal fin of Tatia aulopygia, INPA 11080, 80.0 mm SL.Left side lateral view.Abbreviations:ac,antrorsely curved denticulation; b4, branched fourth ray; b8, branched eighth ray; dd, deferent duct; rc, retrorsely curved denticulation; sf, skin flap; 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.