Scleronema macanuda, Ferrer & Malabarba, 2020

Ferrer, Juliano & Malabarba, Luiz R., 2020, Systematic revision of the Neotropical catfish genus Scleronema (Siluriformes: Trichomycteridae), with descriptions of six new species from Pampa grasslands, Neotropical Ichthyology (e 190081) 18 (2), pp. 1-81 : 21-28

Scleronema macanuda , new species urn:lsid:zoobank.org:act:6931E764-6A53-4014-848A-C794FAB57E00

( Figs. 1A , 9 , 10A , 11 ; Tabs. 3, 5)

Scleronema operculatum [non Eigenmann, 1917] —Vaz-Ferreira, Soriano, 1960: 6–11 (brief description), figs. 1, 3, 4, 5 (drawings of a specimen from lateral view and detail of head).

Scleronema minutum [non Boulenger, 1891] —Carvalho et al., 2012: 32 (listed), 45; fig. 17M (photo in lateral view), 46 (diagnosis in key).

Scleronema sp. —Ferrer, Malabarba, 2011: 66 (material examined). —DoNascimiento, 2012: 329 (material examined; phylogenetic relationships).

Scleronema sp. n. 5 —Bertaco et al., 2016: 421 (listed). —Ferrer, 2016: 77–84; figs. 47–50 (phylogenetic relationships, taxonomy).

Scleronema aff. operculatum —Carvalho, 2017: 21 (diet, ecomorphology and reproduction).

Holotype. MCN 20230, 71.8 mm SL, Brazil, Rio Grande do Sul State, Sentinela do Sul, irrigation water channel draining to arroio Velhaco , laguna dos Patos system, 30º43’13”S 51º39’28”W, 15 Jul 2010, M. A. Azevedo & T. V. Aguzzoli.

Paratypes. 229 specimens. Brazil, Rio Grande do Sul State, laguna dos Patos system: LIRP 16771 , 2 , 68.8–79.9 mm SL, Jaguarão, arroio Telha Chico, 32°13’52”W 53°26’13”W, L. Poldigaiski, M. Camana, R. B. Dala-Corte, T. Guimarães & V. Bastazini , 11 Jan 2014. MCN 12660*, 7 (1 c&s), 15.8–52.3 mm SL, São Lourenço do Sul , arroio Evaristo, 31°11’22”S 52°11’39”W, 14 Jun 1996, K. M. Grosser, M. R. da Costa & S. C. Freitas. MCN 12670, 13, 31.0– 41.8 mm SL, São Lourenço do Sul , arroio Evaristo, 31°09’42”S 52°10’05”W, 14 Jun 1996, K. M. Grosser, M. R. da Costa & S. C. Freitas. MCN 14811*, 1, 47.1 mm SL, Mariana Pimentel, arroio Ribeiro Pequeno, 31 Jul 1997, L. F. Guterrez, P. Guterrez & W. R. Koch. MCP 17257 *, 3 (1 c&s), 31.0– 41.8 mm SL, São Sepé, rio São Sepé , rio Vacacaí basin, 30º11’06”S 53º33’35”W, A. R. Cardoso, A. Ramires & J. F. Pezzi, 24 Jun 1994. MCP 23034 , 1 , 46.2 mm SL, São Sepé, rio São Sepé , rio Vacacaí basin, 30º11’06”S 53º33’35”W, A. R. Cardoso, A. Ramires & J. F. Pezzi, 24 Jun 1994. MCP 54168 *, 8 (1 c&s), 25.1–67.2 mm SL, Viamão, stream at Praia da Pedreira , Parque Estadual de Itapuã Conservation Unit , 30°21’30”S 51°02’48”W, 23 Jun 1999, C. A. Lucena, C. Porto, J. P. Silva & V. A. Bertaco. MCP 54167 *, 29 (2 c&s), 24.6–84.0 mm SL, Pedro Osório, arroio Mata Olho, rio Piratini basin, 31º54’56”S 53º00’17”W, 20 Nov 1999, C. A. Lucena, E. Pereira, V. Bertaco & Z. M. Lucena. UFRGS 3955 *, 5, 39.7–49.9 mm SL, Barra do Ribeiro , arroio Ribeirinho, 30°21’15”S 51°25’43”W, 22 Set 1986, Malabarba et al. UFRGS 7615 *, 7, 23.3–43.5 mm SL, Encruzilhada do Sul , unnamed stream tributarty of rio Camaquã , 30°53’60”S 52°32’19”W, 15 Jul 2005, A. Schaan, G. Neves, J. Anza, J. Ferrer & J. Giora. UFRGS 7616 *, 1, 41.2 mm SL, Canguçu, rio Camaquã , 16 Jul 2005, 30°56’24”S 52°38’45”W, A. Schaan, G. Neves, J. Anza, J. Ferrer & J. Giora. UFRGS 7618 *, 6 (1 c&s), 25.4–44.5 mm SL, Canguçu, unnamed stream tributary of rio Camaquã , 30°57’49”S 52°39’26”W, 16 Jul 2005, A. Schaan, G. Neves, J. Anza, J. Ferrer & J. Giora. UFRGS 8770 *, 10 (1 c&s), 29.2–49.6 mm SL, Rio Pardo , unnamed stream, rio Pardo basin, 12 Jul 2006, J. Anza. UFRGS 8972 *, 4, 25.6–48.7 mm SL, Encruzilhada do Sul , arroio Abranjo, rio Camaquã basin, 30°53’60”S 52°32’19”W, 1 Dez 2006, J. Anza & R. Hirano. UFRGS 12484 , 5 , 31.0– 41.8 mm SL, Camaquã, arroio Velhaco, 30°45’02”S 51°38’09”W, 26 Mar 2010, J. Ferrer & J. Wingert. UFRGS 12580 *, 4 (2 c&s), 30.4–41.7 mm SL, Camaquã, arroio Velhaco, 30°45’02”S 51°38’09”W, 26 Mar 2010, J. Ferrer & J. Wingert. UFRGS 13099 *, 5 (1 c&s), 41.7–53.3 mm SL, Eldorado do Sul , arroio Calombos, rio Jacuí basin, 30°06’02”S 51°41’41”W, 30 Abr 2010, J. Giora & J. Ferrer. UFRGS 14966 , 4 , 39.3 –64.0 mm SL, Eldorado do Sul , arroio Calombos, rio Jacuí basin, 30°06’02”S 51°41’41”W, 6 May 2011, C. K. Fukakusa. UFRGS 17417 , 8 , 25.6–45.5 mm SL, Eldorado do Sul , arroio Calombos, rio Jacuí basin, 30°06’02”S 51°41’41”W, 17 Mar 2013, J. Ferrer. UFRGS 19304 , 8 , 37.3–81.9 mm SL, Santana da Boa Vista , arroio das Neves, 30°51’17”S 53°13’38”W, 13 Dez 2013, C. Hartmann, L. Poldigaiski, M. Dalmolin, R. B. Dala-Corte & T. Guimarães. UFRGS 19322 14, 39.8–77.9 mm SL, Jaguarão, unnamed stream tributary of arroio Telha Chico, 32º14’28”S 53º27’17”W, L. Poldigaiski, M. Camana, R. B. Dala-Corte, T. Guimarães & V. Bastazini, 12 Jan 2014. UFRGS 19387 , 4 , 41.5–75.6 mm SL, Jaguarão, unnamed stream tributary of arroio Quilombo, 32°15’09”S 53°23’44”W, L. Poldigaiski, M. Camana, R. B. Dala-Corte, T. Guimarães & V. Bastazini, 13 Jan 2014. Rio Negro basin, lower rio Uruguay: LIRP 16772 , 10 , 36.6 –59.0 mm SL, Bagé, rio Piraí , 31º28’31”S 54º24’34”W, 17 Mar 2016, J. Chuctaya, J. Ferrer, L. R. Malabarba & M. C. Malabarba. MPEG 34068 , 5 , 32.0– 71.5 mm SL, Bagé, rio Piraí , 31º28’31”S 54º24’34”W, 17 Mar 2016, J. Chuctaya, J. Ferrer, L. R. Malabarba & M. C. Malabarba. UFRGS 20739 , 2 , 38.5–38.7 mm SL, Bagé, arroio do Acampamento, tributary of rio Piraí , 31°15’03”S 54°21’08”W, 13 Mar 2015, B. Collares, B. Meneses, L. de Fries & T. Guimarães. UFRGS 21635 , 40 (10 c&s), 22.2–75.6 mm SL, Bagé, rio Piraí , 31º28’31”S 54º24’34”W, 17 Mar 2016, J. Chuctaya, J. Ferrer, L. R. Malabarba & M. C. Malabarba. Uruguay, laguna Merín basin, laguna de los Patos system: ZVC-P 14526 *, 2, 47.1– 76.8 mm SL, Treinta y Tres, río Tacuarí at Paso del Dragón , 32°45’51”S 53°43’10”W, 24 Fev 2001, F. Scasso, F. Teixeira, M. Loureiro & N. Marchand. ZVC-P 14525 *, 6, 23.4–70.7 mm SL, Treinta y Tres, río Olimar , 33°15’27”S 54°23’06”W, 21 Fev 2001, F. Scasso, F. Teixeira, M. Loureiro & N. Marchand. ZVC-P 14524 *, 1, 73.2 mm SL, Lavalleja, río Cebollatí at Paso del Rey , 33°44’19”S 54°53’03”W, 2 Fev 2001, F. Scasso, F. Teixeira, M. Loureiro & N. Marchand. ZVC-P 8951 *, 2, 51.4–93.6 mm SL, Treinta y Tres, río Tacuarí at Paso del Dragón , 32°45’51”S 53°43’10”W, 21 Fev 2001, F. Scasso, F. Teixeira, M. Loureiro & N. Marchand. ZVC-P 13639 , 1 , 50.9 mm SL, Treinta y Tres, río Tacuarí at Paso del Dragón , 32°45’51”S 53°43’10”W, 6 Dez 2013, A. Duarte, D. Hernández, E. Burress, M. Loureiro & S. Serra. Río Negro basin, lower río Uruguay: UFRGS 21923 *, 1, 49.5 mm SL, Rivera, arroyo Batovi, 31°06’58”S 55°24’56”W, 27 May 2005, F. Cantera, L. R. Malabarba, P. Lehmann & V. Bertaco. ZVC-P 7531 *, 5, 37.5–55.1 mm SL, Flores, arroyo Grande , 33°14’56”S 57°15’44”W, 20 Nov 2006, A. D’Anatro, F. Teixeira de Mello , I. González, M. Loureiro & S. Oviedo. ZVC-P 9374 *, 1, 74.5 mm SL, Durazno, río Yi at Paso San Borja , 33°23’50”S 56°24’12”W, 23 Ago 2005, I. González –Bergonzoni. ZVC-P 14523 *, 5, 50.8–70.3 mm SL, Durazno, río Yi at Paso San Borja , 33°23’50”S 56°24’12”W, 23 Nov 2005, A. D’Anatro, F. Teixeira de Mello , I. González, M. Loureiro & S. Oviedo .

Diagnosis. Scleronema macanuda is distinguished from all congeners with the exception of S. operculatum by the following external characters: maxillary barbel smaller than half-length of the head (vs. larger than half-length of the head); tips of the pectoral-fin rays extending beyond the interadial membrane (vs. not extending beyond the interadial membrane), skin flap in the posterior margin of the opercle pointed and long (vs. skin flap round an short); fleshy flap at the base of the maxillary barbel located anteriorly, thick, prolonged up to the snout and with distal margin straight (vs. fleshy flap located posteriorly, thin, restricted to the maxilla and with distal margin rounded); and the caudal fin with a transversal black bar distally (vs. caudal fin with black bar absent). Scleronema macanuda differs from S. operculatum by having a midlateral line of 6–9 rounded black blotches larger than opercle (vs. midlateral line of 10–14 rounded black blotches as large as or smaller than opercle); tip of nasal barbel usually extending beyond anterior margin of eye (vs. tip of nasal barbel never reaching anterior margin of eye), tip of maxillary barbel extending between anterior and posterior margins of interopercle (vs. tip of maxillary barbel never surpassing anterior margin of interopercle).

Description. Based on types ranging from 15.8 to 93.6 mm SL; 11 c&s (3 dissected). Morphometric data for types and non-types in Tab. 5.

External morphology. Greatest height of body in trunk and greatest width of body in anterior portion of trunk. Body elongate and compressed. Dorsal and ventral profiles of trunk straight to slightly convex. Dorsal and ventral profiles of caudal peduncle straight to slightly convex up to anteriormost procurrent ray insertion. Dorsal margin of caudal peduncle with thin membrane, resembling adipose fin ( Fig. 1A ). Head depressed and wide, trapezoidal from dorsal view, wider posteriorly. Dorsal and ventral profiles of head straight. Anterior snout profile rounded from dorsal view. Nostrils of equivalent size, smaller than eye diameter. Anterior nostril surrounded by fleshy flap of integument, posterolaterally continuous with nasal barbel. Posterior nostril surrounded anterolaterally by thin flap of integument. Eyes rounded, dorsally oriented but also visible from lateral view; located behind posterior nostrils; orbital rim not free; eyes covered by thin and transparent skin.

Barbels with large bases and tapering gradually towards tips. Nasal barbel short; emerging from posterolateral edge of anterior nostril and usually extending between anterior and posterior margins of eye (few specimens with nasal barbel surpassing posterior nostril and not reaching anterior margin of eye). Maxillary barbel short; emerging from edge of upper lip and extending between anterior and posterior margins of interopercle. Basal portion of maxillary barbel wide and with thick flashy flap dorsally with distal margin straight. Maxillary barbel with thinner portion smaller in length than wider one. Rictal barbel emerging from lateral lobe of lower lip and slightly shorter than maxillary barbel. Mouth subterminal with edges posteriorly oriented. Upper lip wider than lower lip. Lower lip with round fleshy lobes in corners. Lower lip and corners of upper lip with small papillae. Gill openings not constricted united with isthmus anteriorly forming free fold. Opercular patch of odontodes rounded, inserted in posterior region of head and visible from dorsal and lateral views. Posterior margin of opercle with distinct skin flap, thin and pointed; some specimens with groove in skin flap. Interopercular patch of odontodes elongate inserted on posteroventral region of head visible from lateral and ventral views. Odontodes of opercle and interopercle barely visible, completely involved by flesh.

Pectoral fin with distal margin convex when expanded, 7 rays(n = 41; including holotype); first one always unbranched and not prolonged as filament; fourth and fifth longest. Pectoral-fin insertion posterior to branchial aperture usually covered by branchial membrane anteriorly. Rays of pectoral fin extending slightly beyond interadial membrane. Some specimens with wilted skin above anterior portion of pectoral fin or with intumescence, axillary pore not visible. Pelvic fin with distal margin convex when expanded, 5(n = 40) or rarely 6(n = 1) rays; first one always unbranched. Pelvic-fin origin located at half-length of SL extending between urogenital papilla and anal-fin anterior insertion; tangentially inserted with inner margins separated by large interspace. Urogenital papilla located between last third of pelvic fins.

Dorsal fin with distal margin straight when expanded, 10(n = 9), 11(n = 9), 12(n = 15; including holotype), 13(n = 5) or 14(n = 3) rays; first two rays unbranched. Dorsal fin with two(n = 4) or three(n = 7) procurrent rays. Dorsal-fin origin located at vertical through first half of pelvic fin. Anal fin with distal margin slightly convex when expanded, 6(n = 36; including holotype) or 7(n = 6) rays; first two rays unbranched. Anal fin with one(n = 1) or two(n = 10) procurrent rays. Anal-fin origin located at vertical through last third of dorsal-fin base. Caudal fin with distal margin straight and corners slightly rounded, 12(n = 41; including holotype) rays; most external rays of dorsal and ventral plates of caudal fin always unbranched and smaller than branched rays. Branched rays of caudal fin splitting up to twice. Caudal fin with 11(n = 2), 12(n = 7), 13(n = 1) or 14(n = 1) procurrent rays dorsally and 9(n = 9), 10(n = 1) or 13(n = 1) procurrent rays ventrally. Procurrent rays of dorsal, anal and caudal fins rarely visible.

Osteology. Premaxilla with 19–29(n = 3) teeth arranged in three rows. Dentary with 34–38(n = 1) teeth inserted in one to three rows. Opercle with 9–13(n = 3) odontodes and interopercle with 14–19(n = 3) odontodes. Hyoid arch with 6(n = 11) branchiostegal rays. Free vertebrae 34(n = 2), 35(n = 2), 36(n = 4), 37(n = 2) or 38(n = 1); abdominal vertebrae 3(n = 5). Ribs 8(n = 5), 9(n = 4) or 10(n = 2). First complete haemal arch in 4 th (n = 5) free vertebra, first haemal spine in 7 th (n = 1), 8 th (n = 3) or 9 th (n = 2) free vertebra. Dorsal fin with 10(n = 1), 11(n = 5) or 12(n = 4) or 14(n = 1) pterygiophores; first one inserted anteriorly to neural spine of 13 th (n = 2), 14 th (n = 2), 15 th (n = 3), 16 th (n = 3) or 17 th (n = 1) vertebra. Anal fin 5(n = 2) or 6(n = 9) pterygiophores; first one inserted anteriorly to haemal spine of 19 th (n = 1), 20 th (n = 4), 21 st (n = 4) or 22 nd (2) vertebra.

Laterosensory system. Data for 107 specimens summarized in Tab. 3. Canals of laterosensory system with simple (non-dendritic) tubes and external pores. Supraorbital line usually with two paired nasal canals (right and left; Fig. 10A ); however, one or both canals can be absent. Nasal canal, when present, interrupted (not connecting with frontal canal) with pores s1 and s2. Frontal canal usually with pores s3 and s6. Infraorbital line with antorbital segment invariably absent and sphenotic canal usually with pores i10 and i11. Posterior segment of frontal, sphenotic and otic canals fused to each other. Otic, posotic and scapular canals present with preoperculo-mandibular and pterotic branches short with one pore each (po1 and po2, respectively). Trunk canal short usually with two pores.

Coloration in alcohol. Lateral surface of body with two longitudinal lines (midlateral and laterodorsal) of 6–9 black rounded blotches (distinctly larger than opercle) over light yellow background ( Figs. 9 , 11 ). Occasionally, smaller individuals with blotches becoming fade or absent towards to caudal peduncle and larger individuals with scattered small blotches among larger ones ( Fig. 11 ). Longitudinal line of laterodorsal blotches visible from dorsal view. Anterior portion of dorsal surface of body with numerous black rounded blotches. Ventral surface of body uniformly light yellow. Dorsal and lateral surfaces of head and nape area with numerous black rounded blotches or uniformly black. Ventral surface of head light yellow. Dorsal surface of maxillary and rictal barbels weakly black and ventral surface light yellow. Nasal barbel weakly black. Opercle with anterior and dorsal margins black; posterior fold light yellow. Pectoral, pelvic, dorsal and anal fins hyaline. Dorsal fin of some larger individuals with black stripe basally.

Caudal fin hyaline with vertical stripe basally and vertical black bar in distal margin,

which could extend up to mid-length of fin in larger individuals ( Figs. 9 , 11 ).

Coloration in life. Coloration in life similar to that of specimens preserved in ethyl alcohol, but more intense ( Fig. 11 ).

Geographical distribution. Scleronema macanuda is widely distributed in rivers and streams that drain to laguna dos Patos ( Brazil) and lagoa Mirim ( Brazil and Uruguay);

and in small Atlantic coastal drainages of Uruguay ( Fig. 4 ). In the lower rio Uruguay basin, the species occurs in the rio Negro and tributaries ( Brazil and Uruguay) and in arroyo Higueritas ( Uruguay). The specimen figured by Vaz-Ferreira, Soriano (1960: fig. 1; ZVCP 170) from the mouth of río Queguay in the rio Uruguay ( Uruguay) was not analyzed, but can be identified as S. macanuda .

Ecological notes. Scleronema macanuda inhabits rivers and streams usually with sand- bottoms. The species is collected syntopically with S. minutum in some localities.

The stomachs of 11 specimens were analyzed and six had immature aquatic Diptera

( Chironomidae ), Oligochaeta, unidentified plant fragments and sand. Invididuals of

S. macanuda larger than 35.0 mm SL are capable to spawn and considered adults by

Carvalho (2017). The diet of immatures of S. macanuda is composed of Chironomidae and Ephemeroptera according to Carvalho (2017).

Etymology. The species epithet “macanuda ” is a regional adjective to describe a “large and strong” person, an allusion to being the largest species of the genus.

Conservation status. Scleronema macanuda is frequent and abundant in the rio Negro basin and Laguna dos Patos system. In addition, no specific threats were detected and the species can be classified as Least Concern (LC) according to IUCN criteria (IUCN,

2019).

Additional material examined. 75 specimens. Brazil: FMNH 125684 , 1 , 13.1 mm

SL, Santa Maria, rio Vacacaí-Mirim. MCN 12681, 3, 22.6–54.3 mm SL, São Lourenço do Sul, arroio Inhuquipá. MCN 12701, 2, 48.9–50.3 mm SL, Arambaré, arroio Velhaco.

MCN 20232, 1, 34.1 mm SL, São Jerônimo, arroio dos Cachorros. MCP 54172, 1,

53.2 mm SL, Barra do Ribeiro, arroio do Ribeiro. MCP 19454, 17, 17.2–39.9 mm SL, Barra do Ribeiro, arroio Petim. MCP 34753, 16, 23.3–54.0 mm SL, Herval, arroio Arambaré. MCP 54166, 3, 42.0– 68.5 mm SL, Pedro Osório, unnamed stream tributary of rio Piratini. UFRGS 3954, 1, 27.1 mm SL, Tapes, arroio Velhaco. UFRGS 3957, 1, 34.8 mm SL, Tapes, arroio Velhaco. UFRGS 21296, 6, 14.5–21.2 mm SL, Tapes, arroio Velhaco. UFRGS 8466, 2, 20.1–26.4 mm SL, Eldorado do Sul, arroio Calombos. UFRGS 14967, 1, 52.8 mm SL, Eldorado do Sul, arroio Calombos. UFRGS 18022, 4, 25.9–44.3 mm SL, Eldorado do Sul, arroio Calombos. UFRGS 18023, 3, 30.4–32.8 mm SL, Eldorado do Sul, arroio Calombos. UFRGS 19305, 2, 34.9–40.7 mm SL, Santana da Boa Vista, arroio das Neves UNICTIO 1024, 2, 44.0–49.0 mm SL, Morungava, arroio Demétrio. UNICTIO 1045, 1, 26.8 mm SL, Morungava, arroio Demétrio. Uruguay: FMNH 71372, 2, 35.5–39.1 mm SL, Lavalleja, arroyo Polanco, río Cebollatí, basin. ZVC-P 3522, 1, 67.0 mm SL, Colonia, Nueva Palmira, arroyo Higueritas. ZVC-P 5008, 1, 118.7 mm SL, Cerro Largo, arroyo de las Cañas at Paso de las Cañas. ZVC-P 7179, 3, 28,5–55,6 mm SL, Maldonado, arroyo José Ignacio at Paso Correa.

Figures

FIGURE 1 | Lateral view of A. Scleronema macanuda, new species, paratype (ZVC-P 9374; 74.5 mm SL) and B. S. milonga, new species, holotype (MCP 54165; 37.8 mm SL) showing the thick fleshy flap in the base of the maxillary barbel (red arrows), the skin flap in the posterior margin of the opercle (black arrows), the dorsal membrane in the caudal peduncle (white arrows), and the vertical black bar in the caudal fin (blue arrow).

FIGURE 4 | Geographical distribution of the genus Scleronema. Circles and squares indicate species of the S. minutum group and S. operculatum group, respectively. Some symbols represent more than one collection locality. AR = Argentina; BR = Brazil; PY = Paraguay; UY = Uruguay.

FIGURE 9 | Scleronema macanuda, new species, holotype (MCN 20230; 71.8 mm SL), Brazil, Rio Grande do Sul Sentinela do Sul, irrigation water channel draining to arroio Velhaco, laguna dos Patos system.

FIGURE 10 | Dorsal view of the head of A. Scleronema macanuda, new species, paratype (UFRGS 21635; 75.6 mm SL) and B. S. operculatum (UFRGS 19646; 56.1 mm SL) showing the pores of the laterosensory system.

FIGURE 11 | Specimens in life of Scleronema macanuda, new species, paratypes, (UFRGS 21635; A. 75.6 mm SL, B. 65.7 mm SL), Brazil, Rio Grande do Sul, Bagé, rio Piraí, tributary of rio Negro, lower rio Uruguay.