Hisonotus montanus, Carvalho, Tiago P. & Reis, Roberto E., 2009

Carvalho, Tiago P. & Reis, Roberto E., 2009, Four new species of Hisonotus (Siluriformes: Loricariidae) from the upper rio Uruguay, southeastern South America, with a review of the genus in the rio Uruguay basin, Zootaxa 2113 (1), pp. 1-40 : 22-26

Hisonotus montanus , new species

Figure 13 , Table 5

Holotype. MCP 42578, 43.0 mm SL, female, Brazil, Santa Catarina, Rio Rufino, rio Rufino on highway SC- 427 by the city of Rio Rufino , 27°51’36”S 049°46’55”W, 1 May 2007, T. P. Carvalho, A. R. Cardoso & C. A. Cramer.

Paratypes. All from Brazil, Santa Catarina, rio Uruguai basin, rio Canoas drainage , ANSP 187475 , 4 , 26.8 – 40.7 mm SL ; MCP 41459, 16 + 3 c&s, 16.0–45.1 mm SL, collected with the holotype . MCP 22369, 1 , 33.5 mm SL, Bom Retiro, creek tributary to rio João Paulo on road of Fazenda Jair Philippe , 27°45’36”S 049°36’19”W, 21 Dec 1998 , R. E. Reis, A . R. Cardoso, P. A. Buckup & F. Melo . UFRGS 9597 , 3 , 31.8 – 37.3 mm SL, Curitibanos, rio Marombas , 27°11’50”S 50°38’02”W , F. R. Carvalho & A. Hirschmann .

Diagnosis. Hisonotus montanus can be distinguished from other congeners, except Hisonotus aky and Hisonotus iota by having an infraorbital canal entering the infraorbital series via the compound pterotic vs. infraorbital canal entering the infraorbital series via the sphenotic. It is distinguished from Hisonotus aky and Hisonotus iota by having wider light stripes on the dorsal surface of head extending from snout tip to posterior end of compound pterotic, and by the presence of white marks on dorsal surface of head vs. narrow light stripes on dorsal surface of head extending from snout tip to posterior end of compound pterotic, and absence of white marks on dorsal surface of head.

Description. Morphometrics and meristics in Table 5. Adult size moderate to large for members of this genus (larger specimen surpassing 45 mm in SL). Body robust anteriorly, somewhat slender posteriorly, without conspicuous keels. Caudal peduncle round in cross section. Dorsal body profile almost straight from tip of snout to parieto-supraoccipital, except for convex bump above nares in nasal and frontal contact, straight to slightly convex from that point to dorsal-fin origin. Dorsal-fin base straight and posteroventrally sloped, slightly convex from posterior end of dorsal-fin base to caudal-fin origin. Ventral profile almost straight from snout tip to anal-fin origin. Concave at anal-fin base and straight from that point to caudal-fin origin. Greatest body depth at dorsal-fin origin. Least body depth just posterior to middle of caudal peduncle. Posterior profile of caudal-fin margin concave. Head and snout broad, snout rounded, somewhat square in dorsal view. Body progressively narrowing posterior of pectoral-fin insertion. Snout region anterior of nares slightly depressed; interorbital region straight to slightly convex. Upper margin of orbit not elevated. Eye dorsolaterally positioned. Iris operculum present.

Pectoral fin I,6. Posterior margin somewhat convex, when depressed tip extending beyond middle of pelvic fin. Posterior margin of pectoral-fin spine smooth in adults, juveniles with half of spine length serrate. Pectoral-fin axillary slit present, located below ventral margin of cleithral process. Pelvic fin i,5. Tip of depressed fin not reaching anal-fin origin in females, but extending beyond that point in males. Dorsal fin II,7, its origin located posterior to vertical through pelvic-fin origin. Dorsal-fin spinelet not laterally extended, somewhat rounded. Anal fin i,5. First anal-fin pterygiophore exposed anterior to anal fin. Adipose fin absent. Caudal fin i,14,i.

Body almost entirely covered by plates except for region overlying opening of swim bladder capsule, area between pectoral girdle and lower lip, region around anus, and bases of paired fins. Rostral plate with posterior notch articulation with mesethmoid. Rostral plate thickened, with narrow odontode-free band between dorsal and ventral series of odontodes. Area devoid of odontodes narrower at medial portion, wider laterally ( Fig. 14 ). Prenasal plates present and not reduced, without unplated area anterior to nares. Three rows of predorsal plates. Median series formed by 22–23 plates ( Tab. 2). Lateral line incomplete, with gap on line pores along midlength of body. Median plate series truncated, not reaching posterior end of caudal peduncle ( Fig. 5D ). Arrangement of abdominal plates variable. Lateral abdominal plates slightly larger and forming regular series of about two or three plates. Median abdominal plates formed by single series ( Fig. 6D ), or abdominal region plated only by enlarged lateral abdominal plates which contact each others at belly midline. Sometimes, lateral abdominal plates relative larger, forming regular series of two to three plates contacting each other at midline and median abdominal series composed by one plate, triangular in shape, located posteriorly. Pre-anal shield region formed by large size plates. Coracoid and cleithrum exposed, covered by odontodes, except for medial region of cleithrum between arrector fossae opening and symphysis.

Head without conspicuous crests. Odontodes on parieto-supraoccipital tip slightly larger than those of surrounding areas, mostly in smaller specimens. Head, fin rays, and body plates covered with odontodes, these larger on anterior surface of all fin spines, and on ventral margin of rostrum. Anterior and ventral margins of compound pterotic with median-to-large size perforations. Infraorbital canal enters infraorbital series via compound pterotic. Lips roundish and papillose, posterior margin of lower lip fimbriate. Maxillary barbel present.

Premaxillary and dentary teeth bifid, slender proximally and flattened distally; major (medial) cusp round; minor (lateral) cusp minute pointed. Accessory patch of teeth absent on dentary and premaxilla.

Hypurals 1–2 and 3–5 completely fused. Total vertebrae 28 (2 c&s).

Color. Ground color of dorsal and lateral surfaces light to dark gray. Dorsal and lateral portions of head darker than body. Light rounded spots over dorsal surface of head between nares and orbits. Pair of longitudinal light stripes starting at snout tip, passing through nares, and bifurcating posterior to orbit. One branch reaching posterior end of parieto-supraoccipital and another branch, not continuous, reaching Vshaped mark at parieto-supraoccipital tip. Stripes width about pupil diameter. Ventrolateral region of head yellowish, covered with scattered dark spots. Dorsolateral surface of body with two light longitudinal stripes, from posterior end of compound pterotic to vertical through dorsal-fin base. Dorsum, between posterior end of dorsal fin and caudal fin, with three to four light saddles. Ventral surface of body pale yellow, with scattered chromatophores, these gathered on base of pectoral fin, forming dark blotch. Unbranched rays of pectoral, pelvic, dorsal, anal, and caudal fins mostly unpigmented, except for dark transverse bands, forming barred pattern. Branched rays of these fins mostly hyaline except for dark transverse bars. Caudal fin mostly unpigmented, except for transverse dark bars, some individuals with square-lined pattern or presenting triangular hyaline areas in middle of ventral lobe of caudal fin. In life, ground color of dorsum and flanks shiny light green.

Sexual dimorphism. Characterized by the urogenital papilla, positioned just behind the anal opening in males. Adult males also possess a developed fleshy flap along the dorsal margin of first thickened pelvic-fin ray, which is absent in females. The flap is slightly wider basally and progressively narrows distally. A fleshy flap is present on the medial portion of first and second branched rays of pelvic fin. In juvenile males, flaps are smaller or absent. Males have a longer pelvic fin that surpasses anal-fin origin, with pelvic fin falling short of anal-fin origin in females.

Distribution and habitat. Hisonotus montanus is known only from the rio Canoas drainage, a tributary to the upper rio Uruguay basin ( Fig. 8 ). This species inhabits median flow watercourses, with clear waters of sandy and rocky bottom and is found associated with marginal vegetation composed mainly of grass. Hisonotus montanus is found at high altitudes, about 850 m above the sea level, and represents the species of Hisonotus occurring in the most elevated portions of the rio Uruguai basin.

Etymology. The species epithet montanus is from the Latin, meaning of mountains, referring to the high altitudes where this species is found. An adjective.

Figures

FIGURE 5. Trunk plates of Hisonotus species in lateral view of left side. A—H. iota, MCP 40029, 23.3 mm SL. B—H. leucophrys, MCP 41354, 40.8 mm SL. C—H. megaloplax, MCP 31779, 41.3 mm SL. D—H. montanus, MCP 41459, 37.9 mm SL. Scale bar is 4 mm.

FIGURE 6. Arrangement of abdominal plates of Hisonotus species. Anterior portion toward top. A—H. iota, MCP 40029, 28.0 mm SL. B—H. leucophrys, MCP 41354, 40.8 mm SL. C—H. megaloplax, MCP 31779, 37.8 mm SL. D—H. montanus, MCP 41459, 37.9 mm SL. Scale bar is 2 mm.

FIGURE 8. Drainage map showing distribution of Hisonotus species in the upper rio Uruguai basin. Some symbols represent more than one collecting locality. Open symbols represent type locality. Hisonotus iota (square); Hisonotus leucophrys (star); Hisonotus megaloplax (triangles); Hisonotus montanus (asterisk); and Hisonotus aky (circles).

FIGURE 13. Holotype of Hisonotus montanus, MCP 42578, female, 43.0 mm SL. Rio Rufino on highway SC-427 at city of Rio Rufino, Santa Catarina, Brazil.

FIGURE 14. Scanning electron micrograph of snout anterior rostral margin of Hisonotus montanus, MCP 41459, 41.4 mm SL. A—anterior view of rostrum; B—magnification of medial portion.