Hisonotus notopagos, Carvalho & Reis, 2011

Carvalho, Tiago Pinto & Reis, Roberto E., 2011, Taxonomic review of Hisonotus Eigenmann & Eigenmann (Siluriformes: Loricariidae: Hypoptopomatinae) from the laguna dos Patos system, southern Brazil, Neotropical Ichthyology 9 (1), pp. 1-48 : 24-27

Hisonotus notopagos , new species

Figs. 4c, 6c, 8c, 25, 26, and 27c

Hisonotus sp. 6 . -Reis & Carvalho, 2007: 84 [listed].

Holotype. MCP 44517, 45.0 mm SL, female, Brazil, Rio Grande do Sul, Lavras do Sul, small creek tributary of arroio das Lavras on road from Lavras do Sul to Bagé , rio Camaquã drainage, 30º50’18”S 53º55’43”W, 31 Jul 2006, T. P. Carvalho, A. R. Cardoso & J. M. Wingert.

Paratypes. All from laguna dos Patos system, Rio Grande do Sul, Brazil. Rio Camaquã drainage: MCP 40757, 4 , 35.4-41.6 mm SL, collected with the holotype. ANSP 188701 , 3 , 39.0- 44.7 mm SL, Pinheiro Machado , creek tributary to arroio Boici , at fazenda Chimarrão, 31º13’54”S 53º21’45”W, 25 Jan 2006. L. E. Lanés, M. V. Volcan, A. C. Gonçalves & M. Burns. MCP 25803, 5 , 31.8-34.9 mm SL, Bagé, arroio do Tigre, on secondary road between Bagé and Lavras do Sul, 27 Apr 2000, C. A. S. Lucena, J. F. P. Silva & V. A. Bertaco, 31º04’47”S 53º54’03”W. MCP 25924, 1 + 2 c&s, 34.8-44.4 mm SL, Lavras do Sul, arroio da Mantiqueira on secondary road between Bagé and Lavras do Sul, 30º54’24”S 53º58’06”W, 26Apr 2000, C.A. S. Lucena, J. F. P. Silva & V. A. Bertaco. MCP 40762, 3 , 31.6-41.8 mm SL, Lavras do Sul, arroio da Mantiqueira on secondary road between Bagé and Lavras do Sul, 30º54’24”S 53º58’06”W, 31 Jul 2006, T. P. Carvalho, A. R. Cardoso & J. M. Wingert. MCP 40749, 2 , 35.5 -39.0 mm SL, Bagé, arroio das Traíras on highway BR-153, 31º05’29”S 53º43’33”W, 1 Aug 2006, T. P. Carvalho, A. R. Cardoso & J. M. Wingert. MCP 40763, 1 , 51.7 mm SL, Lavras do Sul, small creek tributary to arroio das Lavras, about 2 km from Lavras on road to Bagé, 30º50’02”S 53º53’52”W, 31 Jul 2006, T. P. Carvalho, A. R. Cardoso & J. M. Wingert. MCP 44504, 9 , 24.9-39.7 mm SL, Encruzilhada do Sul, arroio Maria Santa, 30º40’36”S 52º32’57”W, 16 Jun 2007, L. E. Lanés & A. C. Gonçalves. MCP 44507, 7 , 37.2-45.3 mm SL, Pinheiro Machado, creek tributary to arroio Boici, at fazenda Chimarrão, 31º14’09”S 53º21’39”W. MZUSP 104943 , 4 , 34.6-36.9 mm SL, Pinheiro Machado, creek tributary to arroio Boici, at fazenda Chimarrão, 31º13’44”S 53º22’18”W, 25 Jan 2006. L. E. Lanés, M. V. Volcan,A. C. Gonçalves & M. Burns. UFRGS 8966 , 43 + 3 c&s 17.4- 39.2 mm SL, Brazil, Rio Grande do Sul, Encruzilhada do Sul, small creek in Encruzilhada do Sul tributary to rio Camaquã drainage, 30º35’17”S 52º33’54”W, 14 Dec 2006, J. Anza & R. Hirano .

Diagnosis. Hisonotus notopagos differs from its congeners by the absence of a rostral plate posterior notch articulation for the mesethmoid, rostral plate reduced and thin, with an unplated area, medially between the dorsad and ventrad series of odontodes, vs. presence of a rostral plate with the posterior notch articulation with the mesethmoid, rostral plates thick. The new species is also distinguished from other species of Hisonotus , except H. laevior and H. taimensis , by its great number of median plate series 25-27 ( Table 2), vs. low number of median plate series 20-25; by having four predorsal plates, vs. three predorsal plates, and by having 30-31 vertebrae, vs. 25-29. Hisonotus notopagos further differs from H. laevior and H. taimensis by having caudal peduncle slightly square in cross section, vs. round peduncle in cross section, and by having the area anterior to the nostrils covered by prenasal plates ( Fig. 6c), vs. area anterior to nostrils naked ( Fig. 6b).

Description. Morphometrics and meristics in Table 7. Adult size large for members of this genus (a female reaching 51.7 mm SL). Body elongate, without conspicuous keels. Caudal peduncle slightly square in cross section. Dorsal profile convex from snout to parieto-supraoccipital tip, slightly convex from that point to dorsal-fin origin; straight and posteroventrally sloped from dorsal-fin origin to caudal-fin origin. Greatest body depth at dorsal-fin origin. Least body depth at posterior end of caudal peduncle. Posterior profile of caudal-fin margin concave. Head and snout broad, snout rounded anteriorly in dorsal view, body progressively narrowing posterior to pelvicfin insertion. Snout region anterior to nares not depressed, interorbital region convex. Upper margin of orbit slightly elevated. Eye dorsolaterally positioned. Iris operculum present.

Pectoral fin I,6. Pectoral-fin posterior margin almost straight; when depressed tip extending beyond middle of pelvic fin (tip of pectoral-fin reaching just anterior third of pelvic fin in some specimens). Posterior margin of pectoral-fin spine serrate. In juveniles entire length of spine serrate, reduced to distal portion of spine in adults. Pectoral-fin axillary slit present, located below posterior bony 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. Dorsal-fin origin located slightly posterior of vertical through pelvic-fin origin. Dorsal-fin spinelet present, laterally extended. 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 area around base of paired fins. Rostral plate without posterior notch articulation for mesethmoid, rostral plate reduced and thinned, rostral area between dorsad and ventrad series of odontodes unplated medially. Prenasal plates anterior to nares present, not reduced ( Fig. 6c). Four rows of predorsal plates. Lateral line incomplete, with small gap without pores along middle length of body. Median plate series reaching the postrior end of caudal peduncle, not truncated ( Fig. 4c). Median abdominal plates small, irregularly arranged, often leaving naked area between median and lateral abdominal plate series. Lateral abdominal plates larger, forming a regular series of about five to seven plate in each side ( Fig. 8c). Coracoid and cleithrum exposed and covered by odontodes, except for median region of cleithrum between arrector fossae opening.

Odontodes on posterior parieto-supraoccipital tip not enlarged in adults, slightly enlarged odontodes in juvenile specimens. Head, fin spines, and body plates covered with odontodes, larger on anterior surface of all fin spines, medially directed on pelvic fin. Odontodes on head and trunk of uniform size and distribution, except for enlarged odontodes on ventral margin of rostrum, ventrad series of odontodes sometimes absent in medial portion of rostral plate. Rostrum anterior margin with wide free-odontode band ( Fig. 26). Compound pterotic with median-to-large size perforations from middle portion to ventral margin. Infraorbital canal entering infraorbital series via sphenotic. Lips roundish and papillose. Maxillary barbel present.

Premaxillary and dentary teeth slender proximally and flattened distally; bifid, major (medial) cusp large and rounded, minor (lateral) cusp pointed ( Fig. 27c). Accessory patch of teeth absent on dentary and premaxilla.

Compound ventral hypural plate (hypurals 1-2) and compound dorsal hypural plate (hypurals 3-5) completely fused to each other, but not completely fused in juveniles. Total vertebrae 31 (3 c&s).

Color in alcohol. Ground color of dorsal and lateral surfaces of body light to dark gray, brownish in some specimens. Dorsal and ventrolateral regions slightly lighter, lateral surface darker forming longitudinal band. Ventral surface of body less pigmented than lateral and dorsal portions, belly region with small scattered chromatophores. Dorsolateral surface of head and body with light longitudinal stripes. Stripes beginning on rostrum anterior to nares, passing above orbits and reaching the posterior end of parietosupraoccipital, bifurcating at this point and disappearing laterally bellow dorsal-fin base. Light longitudinal stripe on trunk located above lateral line. Tip of parieto-supraoccipital and corners of squared caudal peduncle lighter than surrounding areas. Paired, dorsal and anal fins mostly hyaline, except for chromatophores forming transverse dark bands (inconspicuous in pelvic fin); bands most conspicuous on unbranched rays. Caudal fin dark pigmented ventrally, unbranched rays with striped pattern. Upper branched rays of caudal fin almost hyaline except for transversal dark bands. Middle portion of caudal fin with hyaline transverse band formed by round light spots. Larger specimens with second hyaline band located posteriorly, on lower caudal lobe.

Sexual dimorphism. Urogenital papilla positioned just behind the anal opening in males. Adult males possess a fleshy flap along the dorsal margin of first thickened pelvic-fin ray, that is absent in females. Flap wide basally and progressively narrowing distally. Adult males with first branched ray of pelvic fin presenting a feeble fleshy flap in medial portion. In juvenile males, flaps are smaller or absent. Males have a longer pelvic-fin thickened unbranched ray that extends up to the anal-fin origin, never reaching that point in females.

Distribution and habitat. Hisonotus notopagos is known from the headwaters of rio Camaquã drainage in the laguna dos Patos system, southern Brazil ( Fig. 22). This species inhabits slow to median flow, clear waters running over a sandy bottom, and is found in marginal or aquatic submersed vegetation ( Fig. 10d). Hisonotus notopagos was collected together with H. armatus in some localities close to Lavras do Sul, and together with H. nigricauda and H. laevior close to Pinheiro Machado. Geographic variation. Populations in the northern tributaries (Encruzilhada do Sul) and southern tributaries (Pinheiro Machado and Lavras do Sul) of rio Camaquã drainage differ to a degree in morphometrics and pigmentation. Specimens from the southern tributaries possess a longer pectoral-fin spine (19.2-25.7% SL, mean 23.5%, vs. 17.7-20.7% SL, mean 19.5% in the northern population). Also, the southwestern population is relatively darker and possesses a more conspicuous light transversal band on the middle portion of the caudal fin comparing to the population near Encruzilhada do Sul. In the absence of clear and discrete diagnostic features, we considered both populations as conspecific.

Etymology. The specific epithet, notopagos , from the Greek notos meaning South; and pagos meaning hills. In allusion to the hilly terrains on the southernmost portions of the Brazilian shield, from where this species is endemic.