Hisonotus laevior Cope, 1894

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 : 12-16

Hisonotus laevior Cope, 1894

Figs. 13, 14, 4b, 7b, and 8b

Hisonotus laevior Cope, 1894: 95 [original description, type locality: Rio Jacuhy, Rio Grande do Sul, Brazil]. - Regan, 1904: 268-269 [junior synonym of Otocinclus nigricauda ]. - Gosline, 1945: 101 [listed as synonym of Microlepidogaster nigricauda ]. -Fowler, 1959: 167 [listed as junior synonym of Microlepidogaster nigricauda ]. - Schaefer, 2003: 322 [listed]. -Reis & Carvalho, 2007: 83 [listed]. - Ferraris, 2007: 248 [listed].

Otocinclus laevior . - Isbrücker, 1980: 83 [listed].

Microlepidogaster laevior . - Malabarba, 1989: 150 [listed]. Schaefer, 1997: 8 [listed].

Hisonotus leptochilus Cope, 1894: 96 new junior synonym [original description, type locality: Rio Jacuhy, Rio Grande do Sul, Brazil]. Regan, 1904: 268-269 [junior synonym of Otocinclus nigricauda ]. - Gosline, 1945: 101 [listed as junior synonym of Microlepidogaster nigricauda ]. - Fowler, 1954: 167 [listed as junior synonym of Microlepidogaster nigricauda ]. - Schaefer, 2003: 322- 323 [listed]. -Reis & Carvalho, 2007: 83 [listed]. - Ferraris, 2007: 248 [listed].

Otocinclus leptochilus . - Isbrücker, 1980: 83 [listed].

Microlepidogaster leptochilus . - Malabarba, 1989: 150 [listed]. - Schaefer, 1997: 8 [listed].

Hisonotus nigricauda , non ( Boulenger, 1891). - Ribeiro et al., 2007: 60 [misidentification, listed and illustrated].

Diagnosis. Hisonotus laevior differs from its congeners, except from H. notopagos and H. taimensis by the higher number of median plate series 25-27 ( Table 2), vs. 20-25, by the number of predorsal plates 3-4 (modally 4; Fig. 7b), vs. 2- 3 predorsal plates, and by the vertebral count 30-31, vs. 25-29. Hisonotus laevior is distinguished from H. notopagos by the presence of a posterior notch articulation in the rostral plate, vs. notch articulation in the rostral plate absent; by the possession of a rounded caudal peduncle in cross section, vs. a slight square caudal peduncle in cross section; and by having the area anterior to nares unplated, vs. area anterior nares covered by plates. Hisonotus laevior can be distinguished from H. taimensis by the wider cleithral width 20.6-24.6%SL, mean 22.9%, vs. 18.5-21.3% SL, mean 20.0% ( Fig. 15), and by the higher body depth at dorsal-fin origin 16.2-20.8 % SL, mean 18.1%, vs. 13.3-16.3%, mean 15.1% ( Fig. 16).

Description. Morphometrics and meristics in Table 3. Adult size medium to large for members of this genus (larger specimen with 47.2 mm in SL). Body robust, somewhat elongated, without conspicuous keels. Caudal peduncle round in cross section. Dorsal profile straight to concave from tip of snout to nares, slightly convex from that point to dorsal-fin origin. Straight and posteroventrally sloped at dorsal-fin base and almost straight from that point 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 concave. Head and snout broad, snout rounded to slightly square in dorsal view, body progressively narrowing posterior of pectoral-fin insertion. Snout region anterior of nares concave, 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; its tip extending to middle of pelvic fin when depressed.Posterior margin of pectoral-fin spine smooth. Half portion of spine length serrate in smaller individuals (about or less than 30 mm in SL). 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. Dorsalfin spinelet present, laterally extended.Anal fin I,5. First analfin pterygiophore exposed anterior to anal fin or covered by ventral plate series.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 with posterior notch articulation for mesethmoid. Rostral plate thickened, with an odontodes-free band between dorsad and ventrad series of odontodes. Snout plates anterior to nares reduced, large paired unplated region between rostrum and nostril. Three or four rows of predorsal plates (modally four; Fig. 7b), smaller specimens sometimes presenting three rows. Lateral line incomplete, with small gap without pores along middle length of body, posterior portion of lateral line present. Median plate series extending to posterior end of caudal peduncle, not truncated. ( Fig. 4b). Median abdominal plate series small, irregularly arranged, sometimes presenting a naked area between median and lateral abdominal plate series. Lateral abdominal plates larger, forming a regular series, variable in number ( Fig. 8b). Coracoid and cleithrum exposed and covered by odontodes, except for median region of cleithrum between arrector fossae openings and medial region of coracoids.

Head, fin-spines, and body plates covered with odontodes, these 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 and dorsal margin of rostrum. Anterior margin of rostrum presenting an odontode-free area. Odontodes on posterior parieto-supraoccipital tip not enlarged. Anteroventral margin of compound pterotic with median-to-large size perforations. Infraorbital canal entering infraorbital series via sphenotic. Lips roundish and papillose.

Premaxillary and dentary teeth slender proximally and flattened distally; bifid, major (medial) cusp large and rounded, minor (lateral) cusp pointed. 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 or with slight median notch on the posterior margin of caudal-fin skeleton, Total vertebrae 30- 31 (5 c&s).

Color in alcohol. Ground color of dorsal and lateral surfaces of body light to dark brown. Dorsal and dorsolateral surface lighter than lateral surface.Ventral surface of body almost unpigmented except for scattered chromatophores. Dorsolateral surface of head and body with light longitudinal stripes. Stripes narrow, beginning at tip of snout anterior to nares, passing above orbit and reaching posterior end of parieto-supraoccipital, bifurcated and inconspicuous at this point and completely disappearing at vertical above dorsal-fin origin. Paired, dorsal and anal fins mostly hyaline, except for several transverse dark bands with chromatophores forming narrow transverse dark bands; bands most conspicuous on unbranched rays. Caudal fin completely dark brown, except for hyaline posterior portion of uppermost rays. That hyaline portion, and unbranched rays of caudal fin with striped pattern of transverse dark bands. In some specimens caudal fin with inconspicuous light transverse band, formed by rounded clear spots.

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 slightly wider basally and progressively narrowing distally. Adult males presenting a fleshy flap in 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 unbranched thickened ray that extends beyond the anal-fin origin, with the ray never reaching that point in females.

Distribution and habitat. Hisonotus laevior is widely distributed in the laguna dos Patos system from southernmost tributaries of the laguna Mirim and canal São Gonçalo drainage to the tributaries of the northern rio Jacuí basin ( Fig. 17). The species is absent in the headwaters of the rio Jacuí basin. This species inhabits slow to median flowing watercourses, with clear to brown waters running over a sandy bottom, and is found in marginal or submerged aquatic vegetation. Hisonotus laevior is sympatric along its distribution with several species of the genus. Hisonotus laevior occurs in sympatry with H. armatus along almost all its distribution. Hisonotus laevior is collected together with H. nigricauda in some localities of the laguna dos Patos system, mainly in the lower portions of the streams, and occurs in sympatry with H. notopagos in the rio Camaquã drainage. Hisonotus laevior occurs in the banhado do Taim together with Hisonotus taimensis and in coastal plain of the Rio Grande do Sul with H. leucofrenatus .

Remarks. Hisonotus laevior is herein designated as a new senior synonym of Hisonotus leptochilus ( Fig. 18). Both species were published in the same paper by Cope (1894). Herbert H. Smith collected these species in 1882, together with a collection of fishes sent to Academy of Natural Sciences of Philadelphia (ANSP). Edward D. Cope studied this material and described several new species including the two species of Hisonotus , collected at Rio Jacuhy (rio Jacuí). According to Papavero (1973) and Malabarba (1989), Herbert H. Smith’s itinerary in the State of Rio Grande do Sul included several cities in the laguna dos Patos system and the localities of Caí (São Sebastião do Caí), São João do Montenegro ( Montenegro), and Porto Alegre. The later localities mentioned are situated in the lower portion of rio Jacuí and rio Caí drainages, where the species H. laevior is the most abundant taxa of the genus. The descriptions of H. laevior and H. leptochilus were both based on a single specimen each. The differences between these taxa according to Cope (1894: 96) are: “The important characters which distinguish this species [ H. leptochilus ] from the H. laevior , are the thin and truncate lower lip with feeble tuberculation; the numerous ventral plates; the narrower orbital space, and the greater hispidity, especially of the head”. No substantial differences were found in the lower lip tuberculation between all Hisonotus species examinated including the holotypes of H. laevior and H. leptochilus . The holotype of H. leptochilus presents more plates in the abdominal median series than H. laevior (see Cope, 1894 fig. 11b and fig. 12b, respectively). However, this is a polymorphic feature observed within some species of the genus and cannot be used to differentiate H. laevior from H. leptochilus .Another diagnostic feature used by Cope (1894) to differ H. leptochilus from H. laevior was the narrower interorbital space. Although the holotype of H. leptochilus has a narrow interorbital width (39.5% of HL, vs. 41.6% of HL in the holotype of H. laevior ), this measurement is within the range of H. laevior (36.9-46.2% of HL; Fig. 19). Finally, no difference in the hispidity of odontodes, in any portion of the body, was found that could suggest the separation of these two species or any Hisonotus in the laguna dos Patos system. For these reasons H. laevior Cope, 1894: 95 is considered senior synonym of H. leptochilus Cope, 1894: 96 . Hisonotus leptochilus is here, for the first time, suggested as junior synonym of H. laevior , although, both species had already been erroneously considered as junior synonyms of H. nigricauda before (see synonym list).

Material examined. All from laguna dos Patos system, Rio Grande do Sul, Brazil. Rio Jacuí drainage: ANSP 21253 , holotype of Hisonotus laevior , 39.2 mm SL, rio Jacuí . ANSP 21564 , holotype of Hisonotus leptochilus , 40.9 mm SL, rio Jacuí . MCN 5823 , 5 , 14.8-30.7 mm SL, São Jerônimo, arroio da Porteira at fazenda Capão . MCP 9302 , 2 , 28.7-30.2 mm SL, Pantano Grande, arroio Dom Marcos, 30º13’32”S 52º37’09”W . MCP 9533 , 3 , 23.2-27.6 mm SL, Rio Pardo , arroio Francisquinho on highway BR-290 between Butiá and Rio Pardo, 30º09’S 52º08’W . MCP 19835, 12 , 25.6-40.2 mm SL, Amarópolis, creek tributary of rio Jacuí in the sylviculture Santo Amaro , 29º55’S 51º55’W . MCP 27329, 2 , 26.0- 30.2 mm SL, Butiá, arroio Martins upstream of mine Recreio , 30º09’S 51º59’W . MCP 17359, 11 , 18.9- 31.4 mm SL, Arroio dos Ratos , arroio da Porteira, 29º24’S 51º57’W . UFRGS 2577 , 2 , 29.7-39.9 mm SL, Triunfo, arroio Gil on road between Barreto and Montenegro, 29º48’S 51º37’W . UFRGS 9153 , 4 , 33.8- 43.2 mm SL, Candelária, riceculture canal near sanga das Oveiras, 29º48’00”S 52º36’58”W . Rio Vacacaí drainage : MCP 23131, 1 , 33.5 mm SL, São Sepé, rio São Sepé at bridge lateral to highway BR-153, about 3 km south from São Sepé , 30º11’08”S 53º33’35”W . Rio Caí drainage : MAPA 1741 , 17 , 17.8-35.9 mm SL, São Sebastião do Caí , creek in Vila Conceição . MAPA 1744 , 2 , 26.8 - 36.0 mm SL, São Sebastião do Caí , arroio Três Mares . MAPA 1755 , 24 + 3 c&s, 19.7-43.4 mm SL, São Sebastião do Caí, creek in rio Branco , 29º35’S 51º22’W . MCP 23005, 2 , 14.6-39.6 mm SL, Triunfo, arroio Bom Jardim, III Polo Petroquímico near SITEL, 29º50’19”S 51º23’25”W . MCP 26053, 1 , 40.3 mm SL, Lindolfo Collor, arroio Feitoria tributary of rio Cadeia , 29º34’54”S 51º14’03”W . UFRGS 8661 , 23 , 31.6 -43.0 mm SL, Butiá , creek on property Cerro Vermelho, 30º08’S 51º59’W . UFRGS 8720 , 38 , 30.4-46.1 mm SL, Rio Pardo , creek at fazenda Limoeiro, 29º59’S 52º22’W . UFRGS 8771 , 8 , 35.5-43.8 mm SL, Pantano Grande, creek on the border of fazenda Sanga Funda, 30º08’S 52º23’W . UFRGS 8777 , 2 , 36.4-48.1 mm SL, Rio Pardo , creek tributary of arroio Iruí at fazenda Limoeiro, 30º02’S 52º22’W . UFRGS 8786 , 16 , 28.8-43.6 mm SL, Pantano Grande, creek on the border of fazendas Tarumã I and Tarumã II, 30º08’S 52º23’W . Rio dos Sinos dranaige: MCN 18633, 1, 47.2 mm SL, Sapucaia do Sul, pesqueiro at Parque Zoológico of Sapucaia do Sul. Rio Gravataí drainage: MCN 6003, 1, 29.8 mm SL, Santo Antônio da Patrulha , arroio Chicoloma . MAPA 2626 , 4 , 32.9 -38.0 mm SL, Gravataí, arroio Passo dos Ferreiros, 29º56’S 50º58’W . MAPA 2354 , 1 , 33.4 mm SL, Santo Antônio da Patrulha, arroio Ramos between Santo Antônio da Patrulha and highway BR-290 . MAPA 2628 , 2 , 35.5-36.5 mm SL, Canoas, canal at south of rio Gravataí . MCN 6062 , 1 , 39.7 mm SL, Gravataí, Banhado Grande at fazenda Quatro Irmãos . MCP 14652, 5 , 33.7-41.3 mm SL, Morungava, rio Morungava , 29º50’S 50º54’W . MCP 41574, 2 , 36.2-40.8 mm SL, Gravataí , marsh at highway RS-118, BR-290, 29º58’S 50º56’W . Lago Guaíba drainage : MAPA 1734 , 2 , 28.5 - 27.5 mm SL, Guaíba , creek at fazenda Juncal km 39 of BR-290 . MAPA 1848 , 5 , 32.5-43.8 mm SL, Porto Alegre, arroio Dilúvio between PUCRS and UFRGS câmpus. MCN 14795, 1 , 39.1 mm SL, Mariana Pimentel, arroio Ribeiro Pequeno on road RS-711, 29º23’53”S 50º44’37”W . MCN 17567, 2 , 32.3-33.8 mm SL, Porto Alegre, arroio Lami on road of Quirinas . MCP 16034, 12 , 20.6-31.4 mm SL, Viamão, lago Guaíba at praia de Itapuã near to mouth of riacho Itapuã , 30º15’00”S 51º02’20”W . MCP 23466, 1 , 40.9 mm SL, Viamão, arroio at praia da Pedreira, Parque Estadual de Itapuã , 30º21’30”S 51º02’48”W . MCP 28116 27.1-42.8 mm SL, Viamão,arroio Sandu , 30º14’S 51º00’W . MNRJ 25597 , 1 , 31.5 mm SL, Barra do Ribeiro, creek on road between Barra do Ribeiro and Guaíba about 8 km from Barra do Ribeiro . UFRGS 1239 , 1 , 38.1 mm SL, Viamão, arroio Alexandrina . UFRGS 2346 , 7 , 19.2-37.8 mm SL, Eldorado do Sul, lago Guaíba at Vila Sans Soucy. Laguna dos Patos drainage : MAPA 1753 , 7 , 24.1-42.3 mm SL, Tapes , arroio Teixeira on BR-116 . MAPA 1757 , 2 , 28.5-33.3 mm SL, Palmares do Sul, canal 16 km north of sanga Pangaré on road between Capivari and Mostardas. MCN 2622 , 1 , 44.4 mm SL, Rio Grande , arroio Vieira, 32º06’S 52º09’W . MCN 12682, 7 , 32.0- 46.7 mm SL, São Lourenço do Sul, arroio Inhuquipá (Turuçu) near Formosa, 31º28’S 52º05’W . MCN 17632, 3 , 18.5 -40.0 mm SL, Palmares do Sul, channel of lagoa dos Gateados at fazenda São Sebastião do Fundo , 30º27’S 50º39’W . MCN 17549, 1 , 38.7 mm SL, Palmares do Sul, channel of lagoa dos Gateados at fazenda São Sebastião do Fundo , 30º27’S 50º39’W . MCN 18138, 2 , 32.5-32.6 mm SL, Palmares do Sul, south margin of lagoa do Casamento , 30º29’S 50º36’W . MCP 16016, 6 , 14.7-34.8 mm SL, Viamão, creek on Varzinha at Itapuã , 30º19’S 50º56’W . MCP 19068, 1 , 34.2 mm SL, Rio Grande, arroio Bolacha , 32º09’S 52º11’W . MCP 21375, 6 , 25.6-40.5 mm SL, São José do Norte, laguna dos Patos at Barra Falsa upstream dam, 31º34’19”S 51º27’35”W . MCP 23856, 10 , 31.6-43.8 mm SL, Sentinela do Sul, arroio Faxinal tributary of arroio Velhaco on road from Cerro Grande do Sul to Camaquã , 30º43’48”S 51º45’24”W . MCP 23859, 2 , 27.1-41.8 mm SL, Sentinela do Sul, arroio Capivaras on road between Sentinela do Sul and VilaAurora. 30º39’27”S 51º36’12”W . MCP 23860, 23 , 27.6-46.2 mm SL, Tapes, arroio Texeira on highway BR-116, 30º37’26”S 51º32’45”W . MCP 31157, 4 , 31.7-33.2 mm SL, Rio Grande, Saco da Mangueira , 32º05’S 52º09’W . MCP 41575, 23 , 25.1-42.7 mm SL, Sentinela do Sul, arroio do Tigre tributary of arroio Velhaco on road from Cerro Grande do Sul to Camaquã , 30º44’30”S 51º46’26”W . MCP 41576, 2 , 31.4-31.9 mm SL, Sentinela do Sul, arroio Velhaco on road from Cerro Grande do Sul to Camaquã , 30º41’22”S 51º41’51”W . UFRGS 4220 , 3 , 22.2-35.9 mm SL, Tapes , arroio Velhaco between Tapes and Camaquã, about 24 km from mouth in laguna dos Patos, 30º45’S 51º38’W . UFRGS 6698 , 10 , 13.8-38.3 mm SL, Viamão, lagoa Negra, 30º21’35”S 50º58’34”W . Rio Camaquã drainage : MCP 23854, 12 , 34.8-44.7 mm SL, Cristal, creek tributary to arroio Santa Isabel on highway BR-116, about 17 km south from Cristal , 30º08’55”S 52º01’50”W . MCP 23857, 21 , 27.8-38.9 mm SL, Camaquã, arroio Duro on road between Vila Aurora and Dom Feliciano, 30º45’34”S 51º51’57”W . MCP 25754, 4 , 25.0- 37.2 mm SL, Camaquã, arroio Maria Ulghim on road between Camaquã and Vila Aurora, 30º49’S 50º49’W . MCP 26042, 1 , 42.3 mm SL, Caçapava do Sul, arroio do Banhado highway BR-153 about 8 km northwest from Minas do Camaquã , 30º51’48”S 53º29’50”W . MCP 41607, 1 , 36.7 mm SL, Caçapava do Sul, small creek tributary to arroio Hilário on road between Caçapava do Sul and Lavras do Sul, 30º44’24”S 53º44’51”W . UFRGS 8239 , 4 , 32.5-41.3 mm SL, Canguçu, creek tributary to rio Camaquã on highway RS-471, 31º23’S 52º40’W . UFRGS 8758 , 13 , 23.9-40.5 mm SL, Amaral Ferrador, creek at fazenda Ferraria, 30º52’S 52º15’W . MCP 44501, 2 , 26.0-32.1, Pinheiro Machado, creek tributary to arroio Boici at fazenda Chimarrão , 31º13’44”S 53º22’18”W . Rio São Gonçalo drainage : MCP 20821, 6 , 37.8-39.4 mm SL, Pedro Osório, arroio Reduzino , 31º54’S 52º55’W . MCP 21424, 13 , 33.4-48.9 mm SL, Herval , small creek tributary to arroioArambaré, between Pedro Osório and Airosa Galvão, 31º58’19”S 53º05’39”W . MCP 21144, 4 , 31.5-37.3 mm SL, Piratini, arroio Piratinizinho on vicinal road to highway BR-293, 31º43’02”S 52º59’34”W . MCP 25153, 19 , 33.1-46.3 mm SL, Pedro Osório, arroio Arambaré on road between Pedro Osório and Basílio, tributary of rio Piratini , 31º54’35”S 53º01’40”W . MCP 34778, 1 , 37.6 mm SL, Herval, arroio Arambaré on road between Pedro Osório and Herval, 31º58’37”S 53º06’15”W . MCP 34779, 8 , 33.3-48.8 mm SL, Pedro Osório, arroio Mata Olho on road between Pedro Osório and Basílio, 31º54’56”S 53º00’16”W . MCP 37683, 4 , 31.7-41.7 mm SL, Pedro Osório, creek tributary to arroio Arambaré near Carvalho de Freitas , about 35 km from Pedro Osório on the railroad bridge, 31º57’52”S 53º06’17”W . Laguna Mirim drainage. MCP 26074, 2 , 38.9-41.22 mm SL, Rio Grande, canal do arroio Taim, Estação Ecológica do Taim , 32º37’S 52º34’W .