Ituglanis paraguassuensis, Rafael M. Campos-Paiva & Wilson J. E. M. Costa, 2007

Rafael M. Campos-Paiva & Wilson J. E. M. Costa, 2007, Ituglanis paraguassuensis sp. n. (Teleostei: Siluriformes: Trichomycteridae): a new catfish from the rio Paraguacu, northeastern Brazil., Zootaxa 1471, pp. 53-59 : 55-58

Ituglanis paraguassuensis new species

(Fig. 1)

Holotype. LIRP 5780 , 41.2 mm SL; Brazil: Estado da Bahia, rio Paraguacu near Iassu, side channel far from main river channel, forming pool with current (12º 45’ S, 40º 12’ W); S. L. Jewett and R. M. C. Castro, 25 July 1988.

Paratypes. LIRP 5834 , 5 ex., 34.8-41.3 mm SL; UFRJ 7209 , 1 ex., 36.5 mm SL; UFRJ 7282 , 1 ex., 39.6 mm SL (c&s); USNM 301016 , 5 ex., 33.7-41.6 mm SL (2 c&s), 30.3-37.8 mm SL, all collected with the holotype.

Diagnosis: Distinguished from all other species of the genus by the following combination of characteristics: color pale yellow on lateral and dorsal regions of head and body, whiter on ventral. Skin covered by several irregular pale brown blotches aligned along the body (vs. distinct color patterns in all other Ituglanis ); pectoral fin-rays i,6 (vs. i,4 in I. macuniama , I. cahyensis and I. parahybae ; i,5 in I. amazonicus , I. eichorniarium , I. metae and I. nebulosus ; i,7 in I. bambui , I. passensis , I. epikarsticus ; i,8 in I. ramiroi except in I. parkoi , I. proops and I. laticeps ); pelvic-fin-rays i,4 (vs. i,3 in I. eichorniarium and I. cahyensis or pelvic-fin absent in I. parahybae ; i,5 in I. amazonicus , I. passensis except in I. gracilior , I. nebulosus , I. macunaima , I. bambui , I. ramiroi , I. epikasticus , I. parkoi , and I. guayaberensis ); parietal fontanel extending to posterior edge of medial parietal border (Fig. 2) (vs. parietal fontanel reduced or vestigial, restricted to middle of medial parietal border in all other Ituglanis except in some I. amazonicus and I. proops ); the unusual reduced number of vertebrae 34-36, where vertebral counts normally range 39 or more (in I. amazonicus , I. cahyensis , I. eichorniarium , I. parahybae , I. proops , I. gracilior , I. herberti , I. metae , Ituglanis sp. A ).

Description: Morphometric data for holotype and paratypes are given in Table 1. Body elongated, subcylindrical, compressed in caudal peduncle. Dorsal profile straight on head, convex between nape and dorsal-fin origin, approximately straight on caudal peduncle. Ventral profile straight to slightly convex between lower jaw and end of anal-fin base. Lips and barbels covered by minute papillae.

Dorsal-fin origin on vertical between centrum of 19th and 21st vertebrae. Anal-fin origin on vertical through base of 6th and 8th segmented dorsal-fin rays and through the centrum of 22nd and 24th vertebrae. First pectoral-fin ray filamentous and 20 to 30 % longer than other pectoral-fin rays. Tip of pelvic-fin reaching vertical between base of 4th and 6th segmented dorsal-fin rays. Caudal-fin subtruncate. Dorsal-fin rays 12-13 (5,vii or 5,viii); anal-fin rays 9-10 (4,v or 5,v); pectoral-fin rays 7 (i,6); pelvic-fin rays 5 (i,3,i); caudal-fin principal rays 13, dorsal procurrent rays 14-15, ventral procurrent rays 11-12. Total vertebrae 34-36; epipleural ribs 6; upper hypural plate united.

Head trapezoidal in dorsal view. Eye located on anterior half of head. Mouth subventral. Maxilla longer than premaxilla. Premaxilla trapezoidal with about 20 conical teeth, arranged in two irregular rows. Dentary slender, with about 25 conical teeth, arranged in two or three irregular rows. Tip of nasal barbel reaching posterior edge of opercular patch of odontodes; tip of maxillary barbel reaching pectoral-fin base; tip of rictal barbel reaching anterior edge of opercular patch of odontodes. Branchiostegal rays 8. Hypobranchials ossified; two anterior basibranchials ossified, third basibranchial consisting of rounded cartilage. Interopercular odontodes15; interopercular patch of odontodes about equal to preopercle in length; opercular odontodes 14-17. Odontodes conical. Cephalic laterosensory canal with simple tubes ending in simple pores, continuous and connected to each other on pterotic, sphenotic and lateral border of parietal (Fig. 2). All cephalic pores paired: supraorbital 4; s1 and s2 connected by single canal; s1 between palatine and mesethmoid, s2 on vomer. s3 on vomer, s6 on parietal; connected to one another. Infraorbital 4; i1 and i3 connected by single canal; both situated next to antorbital; i10 and i11 connected, on sphenotic. Preopercular 1; on pterotic. Lateral line 3, all connected; ll1 on postemporo- supracleithrum, ll2 and ll3 on lateral side of body near opercle. Parietal fontanel extending to posterior border of parietal; postparieto-supraoccipital fontanel restricted to middle region; sphenotic narrow, anterior tip anteriorly directed (Fig. 2). Mesethmoid somewhat widened, about equal in width to anterior portion of palatine; autopalatine with deep concavity along medial border; posterior process of palatine moderate, length about 50% of length of autopalatine without such process. Supraorbital tendon bone elongate and robust, becoming slender and curved outwards, approximately equal to autopalatine in length (Fig. 2); no process on supraorbital tendon bone (Fig. 2). Metapterygoid moderate, longest length about 60% of horizontal length of quadrate; dorsal portion of quadrate anteriorly expanded (Fig. 3). Urohyal lateral wing somewhat elongate, about equal to anterior ceratohyal in length. Two pectoral radials, first cartilaginous, second ossified, length of latter about twice first. Neural prezygapophyses conspicuous in all vertebrae.

Coloration in alcohol: Lateral and dorsal regions of head and body pale yellow, with pale brown rounded blotches. Dark brown pigmentation concentrated on head, in front of eyes, and in front of opercular and interopercular odontodes patches. Nasal and maxillary barbels whitish with dark brown marginal pigment. Rictal barbel whitish. Dorsal and caudal fins hyaline with small concentrations of dark brown chromatophores scattered on fin rays. Pectoral, pelvic and anal fins whitish. The blotches may vanish in alcohol.

Distribution: Known only from the type locality, rio Paraguaçu near Iassu, Estado da Bahia, northeastern Brazil.

Etymology: The name paraguassuensis refers to the type locality, rio Paraguaçu.

Discussion

Ituglanis has been defined by three synapomorphies: autopalatine with a deep concavity on its medial margin, anterior extremity of sphenotic directed anteriorly, and postparieto-supraoccipital fontanel represented by an orifice posteriorly situated (Costa & Bockmann, 1993). Ituglanis paraguassuensis is recognized as a member of Ituglanis because it possesses these synapomorphies. However, I. paraguassuensis has some conditions commonly found in trichomycterids other than Ituglanis : a parietal fontanel extending from the anterior half of the bone to its posterior edge, 34 to 36 vertebrae, anal-fin origin inserted on a vertical at 22nd or 24th vertebra, origin of dorsal-fin on a vertical at 19th or 20th vertebra. These features are similar to those in most species of Trichomycterus Valenciennes and in the trichomycterid basal genus Trichogenes Britski & Ortega .

Although the size of cranial fontanels show intraspecific variation in I. paraguassuensis , as they do in I. amazonicus , I. proops and juveniles of other species, the large parietal fontanel of I. paraguassuensis is unusual for the genus. A closed parietal fontanel is shared by all others Ituglanis species. All three cleared and stained exemplars of I. paraguassuensis possessed a large parietal fontanel that may be regarded as plesiomorphic within the genus. On the other hand, the reduced postparieto-supraoccipital fontanel restricted to the median region of the bone is shared by several members of the TSVSG clade, except Stegophilinae, Vandelliinae and Glanapteryginae in which the cranial roof lacks a fontanel, a condition independently acquired in different advanced groups of the Trichomycteridae (de Pinna, 1989). Only I. macunaima and some I. epikarsticus seem to have achieved a more derived condition in Ituglanis where the postparieto-supraoccipital fontanel is completely closed. According to the most accepted trichomycterid phylogeny (de Pinna, 1998), these occurrences are parsimoniously interpreted as homoplastic (Datovo & Landim, 2005).