Microcambeva ribeirae, Wilson J. E. M. Costa, Sergio M. Q. Lima & Carlos Roberto S. F. Bizerril, 2004

Wilson J. E. M. Costa, Sergio M. Q. Lima & Carlos Roberto S. F. Bizerril, 2004, Microcambeva ribeirae sp. n. (Teleostei: Siluriformes: Trichomycteridae): a new sarcoglanidine catfish from the Rio Ribeira do Iguape basin, southeastern Brazil., Zootaxa 563, pp. 1-10 : 3-8

Microcambeva ribeirae new species

(Figs. 1-2)

Holotype. MZUSP 84301 , 47.5 mm SL; Brazil: Estado de São Paulo: Municipio de Pedro de Toledo, Rio Sao Lourencinho, no Bairro Sao Lourenco ; O. Oyakawa and party, 12 September 2001.

Paratypes. Brazil: Estado de São Paulo, Rio Ribeira do Iguape basin . MZUSP 78617 , 5 ex., 41.3-48.1 mm SL; collected with holotype. - MZUSP 68169 , 3 ex. (c&s), 37.7-41.8 mm SL; Ribeirao Poco Grande, under the bridge at the road SP-79, km 204, Municipio de Juquia ; O. Oyakawa and party, 11 March 2001. - MZUSP 74669 , 10 ex., 33.5-46.2 mm SL; Rio Fau , Municipio de Miracatu ; O. Oyakawa and party, 12 March 2001. - MZUSP 79953 ; 20 ex., 37.7-41.8 mm SL; Rio Espraiado, Estacao Ecologica Jureia-Itatins , Municipio de Iguape ; O. Oyakawa and party, 11 October 2002. - MNRJ 12314 , 1 ex., 29.4 mm SL; MNRJ 14304 , 4 ex. (1 c&s), 27.0-31.5 mm SL; MZUSP 49463 , 1 ex. (c&s), 32.5 mm SL; Miracatu, Bairro do Furadinho, Ribeirao Areado, tributary of Rio Sao Lourencinho, Rio Juquia drainage ; C. R. S. F. Bizerril, 13 May 1995. - DZSJRP 2297 , 1 ex., 42.1 mm SL; Fazenda Seara, Jacupiranga ; L. M. T. F. Camargo and J. A. S. Zuanon, 23 August 1985.

Diagnosis: Distinguished from M. barbata in having short nasal barbels which reach to just behind posterior nostril (vs. reaching posterior margin of eye); eye positioned on posterior half of head (vs. on central portion); first pectoral-fin ray shorter than posterior ones, its tip not forming a distinct filament (vs. first ray elongate, forming a prominent filament); anal fin origin posterior of vertical through base of last dorsal-fin ray (vs. at vertical through last dorsal-fin ray); posteriormost pore of each supraorbital canal united in the midline, composing a single median pore (vs. all supraorbital pores located laterally) (Fig. 3); frontal elongated anteriorly (vs. frontal not elongated) (Fig. 3); fontanel not extending anteriorly beyond posteriormost supraorbital pore (vs. fontanel extending anteriorly to a point close to anteromedial border of frontal) (Fig. 3); anterior portion of sphenotic with a prominent lateral process (vs. a short process) (Fig. 3); anterior palatine ossification absent (vs. present) (Fig. 4); posterior process of palatine elongate, about 60% of palatine bony portion without posterior process (vs. short, about 45% of that length) (Fig. 4); and supraorbital bone elongate, about three times as long as lacrimal (vs. approximately as long as lacrimal) (Fig. 4).

Description: Morphometric data given in Table 1. Body elongate, approximately cylindrical anterior to pelvic-fin insertion, where it is slightly wider than deep, becoming gradually more compressed toward caudal-fin base; head moderately flattened, wider than deep. Dorsal profile slightly convex between snout and end of dorsal fin base, straight on caudal peduncle, slightly concave anterior to dorsal procurrent caudal-fin rays; ventral profile about straight along head, slightly convex along abdomen, gently concave between pelvic-fin insertion and anal-fin origin, and between this point and caudal-fin base. Greatest body depth at vertical just posterior to pectoral-fin base.

Head depressed, longer than wide, subtriangular in dorsal view. Anterior profile of snout slightly rounded in dorsal view. Mouth subventral. Maxilla longer than premaxilla. Teeth conical, arranged in two irregular rows, on premaxilla and dentary; premaxilla with 12-15 teeth in outer row, 11-13 in inner row; dentary with 10-11 teeth in outer row, 6-10 in inner row. Eye approximately at posterior portion of head. Maxillary barbel moderate in length, tip reaching half distance between eye and opercular patch of odontodes, basal portion very broad; rictal barbel shorter than maxillary, tip reaching middle of eye; nasal barbel short, tip reaching just behind nostril. Pair of anteriorly directed barbel-like structures on ventral surface of head, just anterior to branchiostegal region, approximately on midway between mouth and branchial aperture. Branchial membranes united to isthmus, branchial opening wide. Branchiostegal rays 6. Interopercular patch of odontodes short, with 6-8 conical odontodes; opercular patch of odontodes wider, with 9-14 conical odontodes (Fig. 5).

Dorsal fin subtriangular, origin at vertical through centrum of 14th or 15th vertebra. Anal fin rounded, origin at vertical posterior to dorsal-fin base, through centrum of 20th or 21st vertebra. Caudal fin emarginate. Pectoral fin subtriangular, lateral and posterior margins slightly convex; first pectoral-fin ray shorter than posterior ones, its tip not forming distinct filament. Pelvic fin about same length as pectoral fin, not reaching anal fin nor covering urogenital pore; pelvic-fin bases separated by small interspace; pelvic-fin base at vertical anterior to dorsal-fin base. Dorsal-fin rays 9 (ii, 6, i); anal-fin rays 8 (iii, 4, i); principal caudal-fin rays 13 (i, 10-11, i), dorsal procurrent rays 6-7, ventral procurrent rays 6- 7; pectoral-fin rays 7 (i, 6); pelvic-fin rays 5 (i, 4).

Supraorbital canal with three pores; first pore in transverse line through anterior nostril, second pore in close proximity to posterior nostril, third pore fused into single pore in middle of head, in transverse line just posterior to orbit. Infraorbital canal with one pore, posterior to orbit. Preopercular canal with one pore, at vertical through anterior margin of opercular patch of odontodes. Lateral line of body short, with single pore at vertical just posterior to pectoral-fin base.

Frontal slender, portion anterior to second sensory pore elongate, longer than portion posterior to that pore; fontanel not anteriorly extending beyond posterior supraorbital pore (Fig. 3). Anterior portion of sphenotic with prominent lateral process (Fig. 3). Maxilla elongate, longer than total length of premaxilla; premaxilla with long and pointed lateral process; no anterior ossification on palatine; posterior process of palatine elongate, about 60% of palatine bony portion without posterior process; supraorbital elongate, about twice longer than lacrimal; anteromedian border on mesethmoid approximately straight (Fig. 4). Dorsal portion of quadrate narrow, without distinct posterior process; hyomandibula with narrow and pointed anterior process, anterodorsally directed (Fig. 5). Total vertebrae 34. Pleural ribs 5. Caudal skeleton consisting of two plates, triangular dorsal plate formed by fused parhypural and hypurals 3-5, and rectangular ventral plate formed by hypurals 1-2.

Coloration in alcohol: Side of body and dorsum pale yellow with longitudinal row of 9-13 dark brown spots along midline of flank, and two similar rows of spots on dorsolateral portion of body and dorsal midline, respectively. Venter white. Head pale yellow, with small dark brown spots on nape; dark chromatophores on center of dorsal surface of head just anterior to eye and base of nasal barbel. Melanophores concentrated on opercle and opercular patch of odontodes. Fins hyaline; faint gray stripe on dorsal fin and faint gray bar on caudal-fin base.

Coloration in life: Body almost translucent, with dark brown spots as described above. Golden iridescence around dark spots of lateral and dorsolateral rows of flank.

Distribution: Rio Ribeira do Iguape basin, southeastern Brazil.

Habitat notes: Collected in clear, shallow streams (about 60 cm deep), with a gray sandy bottom, in which some specimens were found entirely buried, except for snout and barbels (Bizerril, pers. obs.).

Etymology: From Ribeira, referring to the river basin (Ribeira do Iguape) in which the type locality of the new species is located.

Discussion

The geographic distribution of M. ribeirae represents the southernmost record for the Sarcoglanidinae . The previous record of Microcambeva for the Rio São João basin, Rio de Janeiro state, the present record for the Rio Ribeira do Iguape basin, São Paulo state, and two undescribed species of Microcambeva from the Rio Doce basin, Minas Gerais state, and Rio Jucuruçu basin, Bahia state, suggest that Microcambeva is widespread along coastal basins of southern, southeastern and eastern Brazil. This biogeographic pattern is similar to those patterns of some other freshwater fishes, including the characid genus Rachoviscus Myers (Weitzman and da Cruz, 1981), the rivulid annual fish genus Leptolebias Myers (Costa, 1995), and the loricariid genus Otothyris Myers (Garavello, Britski and Schaefer, 1998).

Microcambeva ribeirae is clearly more closely related to M. barbata than to any other currently described sarcoglanidine. Besides having a similar general morphology, both share an apomorphically rectangular ventral hypural plate, which was noted by Costa and Bockmann (1994) as diagnostic for the genus.

An anterior ossification on the anterior palatine cartilage occurs both in M. barbata (also present in the undescribed species of Microcambeva reported above) and in most other sarcoglanidines (de Pinna, 1989; de Pinna and Starnes, 1990; Costa and Bockmann, 1994), and is considered a synapomorphy for a clade that includes all sarcoglanidines except Ammoglanis (Costa, 1994). Therefore, the absence of that ossification in M. ribeirae may be interpreted as a reversal.

Like M. barbata , M. ribeirae possesses a pair of barbels on the ventral surface of the head, a condition otherwise only recorded for Malacoglanis gelatinosus and a single specimen of Stenolicmus sarmientoi (Myers & Weitzman, 1966; de Pinna in Costa, 1994). Unlike its only described congener, M. ribeirae has a median sensory pore on the dorsal surface of head, a condition otherwise found only in Sarcoglanis simplex and Malacoglanis gelatinosus among sarcoglanidines. The shared occurrence of both derived conditions would suggest a possible close relationship between Microcambeva and Malacoglanis , as already postulated by Costa & Bockmann (1994). However, all species of Microcambeva do not exhibit the synapomorphies of a clade including Stauroglanis , Malacoglanis and Sarcoglanis : reduced number of opercular odontodes (2-3, vs. 9-13 in Microcambeva ), reduced number of interopercular odontodes (0-4, vs. 6-8), anteromedian border on mesethmoid convex (vs. approximately straight), and widened dorsal process of quadrate (vs. attenuated) (de Pinna, 1989; Costa, 1994). However, only with basis on a detailed phylogenetic analysis involving all sarcoglanidines it would be possible to evaluate the distribution of these and other features to generate most parsimonious hypotheses, but this is beyond the scope of the present paper.