Hisonotus leucophrys, 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 : 12-18

Hisonotus leucophrys , new species

Fig. 9 , Table 3

Hisonotus sp. 8 .- Reis & Carvalho (2007: 84) [listed].

Holotype. MCP 42576, 42.2 mm SL, female, Brazil, Santa Catarina, Xavantina, rio Ariranhas on bridge of highway SC-466, rio Uruguai basin 27°04’17”S 052°20’34”W, 30 Apr 2007, T. P. Carvalho, A. R. Cardoso & C. A. Cramer.

Paratypes. All from Brazil, Santa Catarina, rio Uruguai basin : ANSP 187473 , 2 , 27.6 – 30.3 mm SL ; MCP 41354, 3 + 2 c&s 18.3–40.8 mm SL, collected with the holotype. MCN 12741, 2, 37.4–37.6 mm SL, same type locality, 8 Jul 1996 , W. R. Koch, M. Rosenau & K. M. Grosser . MCP 41351, 1 , 19.8 mm SL, Xavantina, rio Ariranhas about 800 meters northeast from urban area of Xavantina , 27°03’55”S 052°20’10”W, 30 Apr 2007 , T. P. Carvalho, A . R. Cardoso & C. A. Cramer. MCN 12024, 1, 40.2 mm SL, Concórdia, rio Rancho Grande on the highway SC-461, 27°20’22”S 051°57’50”W, 27 Jul 1995 , R. C. Vieira , R. R. Estevão & K. M. Grosser. MCN 12553, 1, 37.4 mm SL, Concórdia, rio Rancho Grande on highway SC-461, 27°20’22”S 051°57’50”W, 25 Apr 1996 , W. R. Koch, M. Rosenau & K. M. Grosser .

Diagnosis. Hisonotus leucophrys differs from its congeners, except Hisonotus montanus , by having comparatively broader light stripes on dorsolateral surface of head, from snout tip to posterior end of compound pterotic (wider than pupil diameter) vs. narrow light stripes on dorsal surface of head extended from snout tip to posterior end of compound pterotic, or no longitudinal stripes in that region. Hisonotus leucophrys differs from Hisonotus montanus by having the snout covered with odontodes, without an odontode-free band ( Fig.10 ) vs. anterior portion of snout with an odontode-free band; and by having an infraorbital canal entering the infraorbital series via the sphenotic vs. infraorbital canal entering the infraorbital series via the compound pterotic.

Description. Morphometrics and meristics in Table 3. Adult size moderate for members of this genus (large adult reaching 42 mm in SL). Body somewhat robust, moderately elongate, without conspicuous keels. Caudal peduncle round in cross section. Dorsal body profile convex from snout tip to nuchal plate, straight and posterodorsally inclined over nuchal plate to dorsal-fin origin. Straight and posteroventrally sloped at dorsal-fin base, straight from that point to caudal fin. Ventral profile of body almost straight from snout tip to anal-fin origin, except for somewhat concave margin from snout to posterior border of opercle. Straight and posterodorsally inclined at anal-fin base, straight from that point to caudal-fin origin. Greatest body depth at dorsal-fin origin. Least body depth at posterior end of caudal peduncle. Profile of posterior caudal-fin margin pronounced concave. Head and snout somewhat broad, snout rounded to slightly pointed in dorsal view, body progressively narrowing caudally from pectoral-fin insertions. Snout region anterior to nares depressed, interorbital region convex. Upper margin of orbit somewhat elevate. Eye dorsolaterally positioned. Iris operculum present.

Pectoral fin I,6. Posterior margin almost straight, when depressed, its tip reaching middle of pelvic fin. Posterior margin of pectoral-fin spine smooth in adults, juveniles with posterior half of spine serrate. Pectoralfin 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 II,7, its origin located posterior to vertical through pelvic-fin origin. Dorsal-fin spinelet somewhat rounded in shape. 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 base of paired fins. Rostral plate with posterior notch articulation with mesethmoid. Rostral plate thickened, anterior margin covered by odontodes, without odontode-free band, small area devoid of odontodes medially ( Fig. 10 ). Prenasal plates reduced, small unplated area positioned laterally between infraorbitals and prenasal plates. Three rows of predorsal plates. Lateral plate series formed by 23–24 plates ( Tab. 2). Lateral line incomplete, with gap on line of pores along midlength of body. Median series not truncated, reaching posterior end of caudal peduncle ( Fig. 5B ). Abdominal plates composed by three rows, lateral abdominal plates slightly larger, forming regular series of about four to five plates in each side. Median abdominal series formed by one plate series. Pre-anal shield region formed by plates of small size, irregularly arranged ( Fig. 6B ). Coracoid and cleithrum exposed and 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, forming slightly pronounced crest. Head, fin rays, and body plates covered with odontodes, these larger on anterior surface of all fin spines, and on ventral and dorsal margin of rostrum. Anteroventral margin of compound pterotic with mediun-to-large size perforations. Infraorbital canal entering infraorbital series via sphenotic. 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 not completely fused, slight median notch on posterior portion of caudal skeleton. Total vertebrae 29 (1 c&s).

Color. Ground color of dorsal and lateral surfaces dark gray to light brown. 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 and bifurcating posterior to orbit. One branch reaching posterior tip of parieto-supraoccipital and another branch, not continuous, reaching posterior parieto-supraoccipital tip. Stripes wider than pupil diameter. Ventrolateral region of head mostly yellowish, except for scattered dark marks, variable in shape. Dorsolateral surface of body with three paired light longitudinal stripes. One pair more dorsally, beginning at predorsal plate just after parieto-supraoccipital tip and reaching posterior end of caudal peduncle. Two paired stripes more laterally located. Stripes beginning at posterior end of compound pterotic, joining below dorsal-fin region and from that point, continuous as single stripe, reaching posterior end of caudal peduncle. Sometimes presenting longitudinal stripe at ventrolateral region, from opercle to vertical through end of anal-fin base. Ventral surface of body pale yellow with scaterred chromatophores. Gathered chromatophores forming dark blotches on cheeks, on bases of pectoral fin, and on caudal peduncle. Unbranched rays of pectoral, pelvic, dorsal, anal, and caudal fins mostly unpigmented, except for dark transverse bars. Branched rays of pectoral, pelvic, dorsal, and anal fins mostly hyaline except for transverse dark bars. Caudal-fin branched rays mostly dark pigmented, except for hyaline posterior portion of upper rays, and for transversal hyaline bar, composed by rounded light spots crossing middle portion of caudal fin. Ground color in life yellowish.

Sexual dimorphism. Characterized by the presence of an urogenital papilla, positioned just behind the anal opening in males. Adult males also possess a fleshy flap along the dorsal margin of the first thickened pelvic-fin ray. The flap is absent in juvenile males and females. Males have a longer pelvic-fin that surpasses anal-fin origin, falling short of anal-fin origin in females.

Distribution and habitat. Hisonotus leucophrys is only known from two tributaries of the right margin of the upper rio Uruguay, the rio Ariranhas and the rio Rancho Grande ( Fig. 8 ). This species inhabits median to fast flowing watercourses of clear water, with stones and sand on the bottom, and are found in aquatic, partially submersed, vegetation islands composed by grass. Recent collection efforts in rio Rancho Grande failed to capture additional individuals of this species. After the flooding of the reservoir of the Itá dam (a power plant downstream the mouth of rio Rancho Grande into the rio Uruguay) in the year of 2000, a large portion of the rio Rancho Grande was flooded. The changes in the environment from a rapid running river to a lentic habitat apparently are the cause of the disappearance of this species.

Etymology. The species epithet leucophrys , from the Greek leucos, white and ophrys, eyebrow, referring to the white longitudinal stripe above eye orbit in the species. A noun in apposition.

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 9. Holotype of Hisonotus leucophrys, MCP 42576, female, 42.2 mm SL. Rio Ariranhas on bridge of highway SC-466, Xavantina, Santa Catarina, Brazil.

FIGURE 10. Scanning electron micrograph of snout anterior rostral margin of Hisonotus leucophrys, MCN 12553, 37.4 mm SL. A—anterior view of rostrum; B—magnification of medial portion.