Tatia boemia Koch & Reis, 1996

Sarmento-Soares, Luisa Maria & Martins-Pinheiro, Ronaldo Fernando, 2008, A systematic revision of Tatia (Siluriformes: Auchenipteridae: Centromochlinae), Neotropical Ichthyology 6 (3), pp. 495-542 : 504-507

Tatia boemia Koch & Reis, 1996

Fig. 1 , 10-12

Tatia boemia Koch & Reis, 1996: 86 , fig. 2 [type locality: Brazil, Rio Grande do Sul, Esmeralda, Pelotas river, road Anita Garibaldi to Pinhal da Serra]. Burgess & Finley, 1996:166 [reference]. Soares-Porto, 1998: 333 [citation]. Ferraris, 2003:476 [checklist]. Ministério do Meio Ambiente, 2004: 140 [endangered species]. Ferraris, 2007: 77 [checklist].

Diagnosis. Tatia boemia is distinguished from other species of Tatia by its unique color pattern of dorsum and dorsolateral sides greyish-brown with small dark chromatophores. Chromatophores become sparse and faint towards the ventral portion of the body (cf. Koch & Reis, 1996). The species is also distinguished by the following combination of characters: nasal ossified with wide medial flanges partially sutured to lateral border of mesethmoid; pectoral fin with four branched rays; ribs attached to consecutive post-Weberian vertebrae; with two vertebrae alternatingly unribbed and ribbed ( Fig. 1 ). Additional features useful for distinguishing species include: first nuchal plate somewhat elliptical to rounded; eye 17.4- 22.8% HL; caudal-fin lobes of equal length in mature females, upper lobe slightly elongated in mature males; number of vertebrae 34.

Description. Measured adult specimens 52.4-64.5 mm SL; morphometric data presented in Table 3. 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, 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 moderate in size, extending beyond posterior tip of postcleithral process, reaching vertical through 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 50.0-61.0% length of outer mentals. Postcleithral process well developed, almost reaching vertical through middle of dorsal fin. Caudal peduncle deep, its depth about 13.6-14.2% SL.

Rostral border of cranium broad with large mesethmoid; premaxilla underneath with synchondral articulation; cranial fontanel narrow, elliptical, bounded by mesethmoid and frontal ( Fig. 11 ); nasal ossified, with medial flanges partially sutured to lateral margin of mesethmoid; autopalatine tubular, oriented obliquely to longitudinal axis of body; maxilla small, shorter than autopalatine; prevomer expanded with well developed arrow-shaped lateral processes; jaws of equal size; premaxilla and dentary with three to four rows of conical teeth; first nuchal plate somewhat elliptical; second nuchal plate laterally concave, partially in contact or not with supraoccipital; third nuchal plate relatively straight, projected laterally. Epioccipital process 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. Branchial skeleton as for genus. Basibranchial 2 forming osseous rod with broad cartilaginous anterior tip, separated from shorter basibranchial 3.

Six infraorbital bones in complete series. Infraorbital 1 broad, with moderately developed ventro-lateral process, around anterior border of eye; remaining infraorbitals thin, reduced to canalicular portions. Infraorbital 2 smallest, close to infraorbital 1, followed by three elongate canal bones, forming bottom orbital rim; infraorbital 5 small, forming posterior orbit. Lateral line on body with ossified canal bones until vertical through pelvic fin.

Dorsal fin I,5 (n=8); dorsal-fin spine with 13-16 antrorse serrations along entire anterior margin; posterior margin smooth. Pectoral fin I,4 (n=8); pectoral-fin spine with 19-22 antrorse serrations along anterior margin, small serrations close to spine base; 14-15 retrorse serrations along posterior margin; serrations along both margins progressively larger towards spine tip. Pelvic-fin i,5 (n=8), margin rounded. Adipose fin large, origin on vertical through middle anal-fin base. Anal fin iii,7 (n=8); anal-fin pterygiophores in eight rod-like proximal radials and seven cartilaginous distal radials ( Fig. 1 ). Caudal fin forked, lobes with rounded tips, 8+9 principal rays, 19-21 upper procurrent, 19-20 lower procurrent rays (n=8). First nine post-Weberian vertebrae ribbed. Tenth vertebrae correspond to a gap, with no ribs attached, plus one rib attached to 11 th vertebrae ( Fig. 1 ). Post-Weberian vertebrae 34 (n=3).

Color in alcohol. Color pattern diagnostic within Tatia , as stated in the original description by Koch & Reis (1996): Dorsal surface of head, back and upper sides, greyish-brown with many chromatophores surrounding small lighter (depigmented) areas; sides becoming paler ventrally as chromatophores become progressively more widely spaced; lower sides and ventral surfaces yellowish. Dorsal-fin spine dark. Lips, anterior nostril and chin whitish. Barbels, posterior part of nuchal shield, pectoral, pelvic, anal, and adipose fins unpigmented. Caudal fin largely pale with small dark spots.

Sexual dimorphism. Based on examination of gonads, T. boemia attains sexual maturity above 52.4 mm SL. In mature females a genital papilla is not evident. In mature males a genital papilla is visible, thick, with a short deferent duct. The anal fin of the mature males ( Fig. 12 ) is strongly modified with the three unbranched and first branched rays enlarged and thickened. The first unbranched ray is non-segmented and shortest, about half-the length of second unbranched ray ( Fig. 12 ). First unbranched anal-fin ray is immediately preceded by a tegumentary keel ( Fig. 12 , tk). The second unbranched ray has an intermediate size between the neighboring first and third rays. Third unbranched and first branched are the longest rays forming a fin tip ( Fig. 12 , uiii). Third unbranched with the three distal segments smaller, antrorsely curved ( Fig. 12 , ac). First branched ray with four distal segments retrorsely curved ( Fig. 12 , rc). The posterior branched rays are progressively shorter.

The hemal spines 15-17 are associated with anal-fin pterygiophores in males and become thick during maturity. Female hemal spines 15-18 are associated with pterygiophores and undifferentiated ( Fig. 1 ).

There is a discrete sexual dimorphism regarding the caudal-fin margin in mature males of T. boemia . The upper caudal-fin lobe is slightly elongate, about 10.0% longer than the lower lobe, whereas mature females have equal lobes.

Distribution. Tatia boemia is endemic to upper reaches of the Uruguay river drainage ( Fig. 6 ). It is the most southernly distributed species of Tatia . Together with T. neivai both are the only species inhabiting the La Plata basin (Koch & Reis, 1996).

Remarks. Tatia boemia is the only auchenipterid catfish listed in Brazil as an endangered species (Ministério do Meio Ambiente, 2004). As it is a typically nocturnal catfish, the local people call T. boemia under the common name “boa noite”, meaning good night (Walter R. Koch, pers. comm.).

In T. boemia the first (anterior) nuchal plate is variable in size. First nuchal plate is sometimes assymmetrical, permiting contact between supraoccipital and second nuchal plate (as in Fig. 11 ), or symmetrical, bordered by supraoccipital and second (middle) nuchal plate. We observed variation in first nuchal plate size in other auchenipterid species, such as Centromochlus perugiae and Glanidium leopardus . Anterior (first) nuchal plate either fully developed or reduced is reported in a few doradid species as Oxydoras niger and Doras fimbriatus ( Birindelli et al., 2007: 680) , and the species are considered polymorphic regarding this character. Polymorphism seems to be also the case in the above mentioned auchenipterids including T. boemia .

Tatia boemia is presumed to be sister to T. neivai , both sharing the presence of a single vertebrae without ribs preceding the last ribbed vertebrae (character 17, fig. 14 of Soares- Porto, 1998). This ribless vertebra (number 9 in T. neivai , 10 in T. boemia ) has each transverse process with a reduced costal facet. The last rib pair is small and attached to the hemal arch of vertebra 10 ( T. neivai ) or 11 ( T. boemia ). In all other Tatia species the ribs are attached to consecutive post-Weberian vertebrae.

Material examined. 8 specimens (33.1-64.1 mm SL). Paratypes. Brazil: Rio Grande do Sul: MCP 12949, 6 , 1 CS, (33.1-61.1 mm SL) and MZUSP 47921 , 2 (52.4-64.5 mm SL) ( R), Esmeralda, Pelotas river, road Anita Garibaldi to Pinhal da Serra (paratypes of Tatia boemia ) .

Figures

Fig. 1. Schematic representation of partialaxial skeleton of Tatia boemia MCP 12949, 59.9 mm SL.Left sidelateral view.Abbreviations:af,anal fin; dr, distalradials; hs15- hs18, hemal spines 15 and 18; pf, pelvic fin; pr, proximal radials; r8- r11, ribs 8 to 11; v8- v18, vertebral centra 8 to 18. Scale bar = 1.0 mm.

Fig. 10. Tatia boemia, (a) MZUSP 47921, paratype, male, 64.5 mm SL. (b) MZUSP 47921, paratype, female, 52.4 mm SL, rio Pelotas, Rio Grande do Sul State, Brazil.

Fig. 11. Neurocranium of Tatia boemia, MCP 12949, paratype, 59.9 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; ps, posttemporal-supracleithrum; pt, pterotic; so, supraoccipital; sp, sphenotic. Scale bar = 1.0 mm.

Fig. 12. Male modified anal fin of Tatia boemia, MCP 12949, paratype, 59.9 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. 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.