Pareiorhaphis scutula, Pereira & Vieira & Reis, 2010

Pereira, Edson H. L., Vieira, Fábio & Reis, Roberto E., 2010, Pareiorhaphis scutula, a new species of neoplecostomine catfish (Siluriformes: Loricariidae) from the upper rio Doce basin, Southeastern Brazil, Neotropical Ichthyology 8 (1), pp. 33-38 : 34-37

Pareiorhaphis scutula , new species

Fig. 1

Holotype. MCP 44046, 84.7 mm SL, Brazil, Minas Gerais, Nova Era, rio Doce drainage, córrego Prainha , tributary to rio Piracicaba , 19°38’54”S 42°57’37”W, 17 Aug 2007, F. Vieira & I. A. Figueiredo.

Paratypes. Brazil: Minas Gerais: rio Doce drainage : MCP 44045, 15 , 21.3-67.6 mm SL (10, 51.1-67.6 mm SL) ; UFRGS 10820 , 2 , 53.0- 53.7 mm SL ; MNRJ 33986 , 2 , 47.2-53.2 mm SL ; AMNH 249486 , 2 , 45.3-55.9 mm SL ; ANSP 189490 , 2 , 47.9-59.5 mm SL, all collected with the holotype . MCP 37182, 27 + 2 c&s, 28.2-84.7 mm SL (6, 58.1-84.7 mm SL), Nova Era, córrego Prainha on Road to Cachoeira da Fumaça , 19°38’53”S 42°57’37”W, 9 Oct 2004, E. H. L. Pereira , R. E. Reis & P. Lehmann . MCP 28683, 10 + 1 c&s, 25.3- 90.5 mm SL (7, 54.9-90.5 mm SL), Nova Era, córrego Prainha, tributary to rio Piracicaba , 19°45’S 43°03’W, Jun 2001, F. Vieira & P. S. Pompeu . MCP 38811, 3 , 69.9-87.7 mm SL (3), Nova Era, córrego Prainha, tributary to rio Piracicaba , at limit between Antônio Dias and Nova Era , Aug 1998, F. Vieira & P. S. Pompeu . MCP 38810, 6 + 1 c&s, 42.5-77.1 mm SL (2, 64.3-77.1 mm SL), Nova Era, córrego Prainha, tributary to rio Piracicaba , 19°39’12”S 42°57’20”W, 28 Jul 2004, F. Vieira & I. A. Figueiredo .

Diagnosis. Pareiorhaphis scutula is uniquely diagnosed from all remaining Pareiorhaphis species by having the abdomen entirely covered with small platelets imbedded in skin and irregularly scattered from pectoral girdle to pelvic-fin insertions (vs. abdomen totally naked or with one to four small platelets on each side just posterior to gill opening in P. parmula and P. nasuta ; Fig. 2 ). The new species can be further distinguished from P. parmula by having 51-71 premaxillary teeth (vs. 31-48), 24-28 lateral plates in the median series (vs. 28-31), and longer snout length (62.1-70.0 vs. 53.8 - 63.0% HL) and from P. nasuta by having a shorter snout length (62.1- 70.0 vs. 71.1-75.6% HL) and a larger orbital diameter (11.9-14.8 vs. 8.6-11.3% HL; Fig. 3 ).

Description. Member of Neoplecostominae as diagnosed by Pereira (2009). Counts and proportional measurements in Table 1. Small to medium-sized loricariid with standard length of measured specimens 51.1-90.5 mm SL. Body elongate and moderately depressed, progressively tapering from cleithrum to end of caudal peduncle. Dorsal profile of body gently convex, rising from snout tip to origin of dorsal fin and then descending to end of caudal peduncle. Greatest body depth at dorsal-fin origin. Least body depth at shallowest part of caudal peduncle. Trunk and caudal peduncle mostly oval in cross-section, slightly flattened ventrally and more compressed caudally. Lateral-line canal in median series complete, pored tube visible from compound pterotic to caudal-fin base. Ventral profile almost straight between snout tip and pelvic girdle, slightly elevating posteriorly along analfin base, almost straight along caudal peduncle. Dorsal surface of body covered by plates except for small naked area around dorsal-fin base. Ventral surface of head, portion from pelvic-fin insertions to anal-fin origin, and portion around anal fin totally naked.Abdomen covered by small, embedded platelets, irregularly arranged from pectoral girdle to insertion of pelvic fins. Some adult males with few small platelets behind insertion of pelvic fin but never reaching to anal-fin origin.

Head broad and moderately depressed. Dorsal profile of head round in dorsal view; females and juveniles more slender. Interorbital space straight or slightly concave. Three weakly elevated ridges between orbits and snout tip. Outer ridges from middle of snout to upper margins of orbits slightly more prominent. These ridges ornamented with short hypertrophied odontodes in adult males. Snout gently convex in lateral profile; snout tip with small ovoid area of naked skin. Adult males with well-developed soft fleshy lobes extending along lateral portion of head. Soft fleshy area ornamented with short hypertrophied odontodes, approximately perpendicular to body axis. Eye small, dorsolaterally placed; orbit diameter 11.9-14.8% HL of head length. Iris operculum absent or very small. Nares ovoid, slightly longer than wide, positioned midway between snout tip and anterior orbit margin. Oral disk roughly circular. Lips well developed, occupying most of ventral surface of head. Lower lip wide and long but not reaching pectoral girdle, upper lip narrow. Lower lip densely covered by minute papillae. Papillae surrounded by small naked areas, decreasing in size towards edge. Posterior edge slightly fringed. Maxillary barbel short and united to lip by membrane basally, free distally. Both premaxillae and dentaries angled at approximately 120°, with mesial ends slightly curved inwards. Teeth slender, asymmetrically bifid, medial cusp slightly curved inwards. Lateral cusp small and pointed, almost reaching half-length of medial cusp.

Dorsal fin originating slightly anterior to vertical line passing through pelvic-fin origin. Dorsal fin short, not reaching preadipose azygous plates when adpressed. Nuchal plate exposed, not covered by skin. Dorsal-fin spinelet present but dorsal-fin locking mechanism non-functional. Dorsal-fin spinelet transversely oval-shaped, wider than base of dorsal spine. Dorsal spine moderately flexible, followed by seven branched rays. Adipose fin with well-ossified leading spine bearing odontodes. Adipose-fin membrane extended slightly beyond adipose-fin spine. Adipose fin preceded by two to four median unpaired preadipose azygous plates. Pectoral fin moderate in size, with curved and flattened unbranched ray, covered by minute odontodes in immature males and females. Adult males with pectoral-fin spine very broad; bearing straight and short hypertrophied odontodes on its entire surface. Six branched rays, first and second as long as spine. Subsequent branched rays decrease gradually in size. Posterior margin of pectoral fin slightly round, overlapping pelvic-fin origin when adpressed. Pelvic fin with one unbranched and five branched rays, not reaching anal-fin origin when adpressed. Pelvic-fin unbranched ray depressed, covered with minute odontodes ventrally and laterally; dermal flap on its dorsal surface present and well developed, extending to ray tip. Pelvic-fin flap distinctly higher near fin base. Anal fin long with one unbranched and five branched rays; passing vertical at adipose-fin origin when adpressed. Caudal fin forked or slightly concave; lower lobe slightly longer than upper; one upper unbranched, 14 branched, and one lower unbranched rays. Upper caudal-fin lobe with five and lower lobe with four or five ventral plate-like procurrent rays, posteriormost elongate. Odontodes on principal and procurrent rays small and irregularly arranged.

Color in alcohol. Ground color of dorsal surface of body and head greyish-brown, darker anteriorly; light brown to yellowish white ventrally, skin of abdomen white and lips pale yellow. Dorsum irregularly spotted with dark brown, forming three irregular and diffuse saddles located at origin of dorsal fin, behind dorsal-fin base, and at adipose fin. Skin between dermal plates darker, conferring slightly reticulate pattern, especially on ventral surface of caudal peduncle.Adult males with fleshy lobes on margin of head and pectoral-fin spines whitish-grey and yellow to orange hypertrophied odontodes. Dorsal-fin rays with 3-5 and caudal-fin rays with 4-5 dark spots forming irregular transverse bands on orange-brown background. Pectoral-, pelvic-, and anal-fin rays also spotted with dark brown on a pale yellow background, but spots not forming clear bands. Pectoral and pelvic fins whitish tan on ventral surface. Interradial membrane of all fins hyaline or pale white.

Distribution. Pareiorhaphis scutula is so far known from the córrego Prainha, a creek tributary to the rio Piracicaba in the upper reaches of the rio Doce drainage basin near Nova Era, Minas Gerais, Brazil ( Fig. 4 ).

Habitat and ecological notes. The córrego Prainha, where most specimens of Pareiorhaphis scutula were collected,

is a shallow creek (0.2-0.5 m depth and approximately 5 m wide) with rocky bottom, swift current, and clear water. Most of the creek banks are deforested and covered with grasses. Other fish species collected syntopically are Trichomycterus sp. , Geophagus brasiliensis , Neoplecostomus sp. , and Astyanax sp.

Sexual dimorphism. According to Pereira et al. (2007: 444) adult males of Pareiorhaphis can be recognized by having cheeks (postrostral and cheek plates) covered with hypertrophied odontodes. In addition, adult males of Pareiorhaphis scutula are also characterized by the following sexually dimorphic character: (1) Large soft fleshy lobes extending along the entire lateral margins of head. This soft fleshy area is ornamented with short hypertrophied odontodes, approximately perpendicular to the body axis. Odontodes also occur in females and juveniles, but are much smaller, while soft fleshy lobes are absent in females and juveniles. (2) Unbranched pectoral-fin ray very thick from the base to approximately three-fourths of its length, with distal portion soft and with somewhat short hypertrophied odontodes on outer and ventral surfaces. (3) Fully developed males have a well-developed flashy flap along the entire length of the dorsal margin of the pectoral-fin spine. (4) Unbranched pelvic-fin ray with developed dermal flap on dorsal surface, extending to ray tip and distinctly higher near fin base.

Etymology. The specific epithet scutula from the Latin, a diminutive of scuta, plate, scute, in allusion to the small plates that cover the abdominal region of Pareiorhaphis scutula . A noun in apposition.

Figures

Fig. 1. Pareiorhaphis scutula, holotype, male, MCP 44046, 84.7 mm SL, córrego Prainha, tributary to rio Piracicaba, Nova Era, rio Doce drainage, Minas Gerais, Brazil.

Fig. 2. Abdominal plates of Pareiorhaphis. (a) P. scutula, MCP 37182; (b) P. nasuta, MCP 37176; and (c) P. parmula, MCP29434.Scale bar = 5 mm.

Fig. 3. Scatter plot and regression line of orbital diameter and snout length on head length, in Pareiorhaphis scutula (dots) and P. nasuta (triangles).

Fig. 4. Map of eastern Brazil showing type-locality of Pareiorhaphis scutula. One symbol represents more than one lot and locality.