Scleronema mate, 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 : 29-34

Scleronema mate , new species urn:lsid:zoobank.org:act:7B4355E7-07B0-4B79-A82A-060C122A16C8

( Figs. 5A , 12 , 13A , Tabs. 3, 6)

Scleronema angustirostris [non Devincenzi, 1942] —Wosiacki, de Pinna, 2007: 69 (listed). Scleronema sp. —Becker et al., 2013: 85 (listed). Scleronema sp. 6 —Ferrer, 2016: 101–105; figs. 47–50 (phylogenetic relationships, taxonomy).

Holotype. MCP 54183 , 49.3 mm SL, Brazil, Rio Grande do Sul, Venâncio Aires, arroio Grande, tributary of arroio Castelhano , rio Taquari basin, laguna dos Patos system, 29º33’S 52º17’W, 14 Oct 1994, C. A. S. Lucena, J. F. P. Silva & Z. M. Lucena.

Paratypes. 91 specimens from Brazil, Rio Grande do Sul, laguna dos Patos system: LIRP 16773 , 5 , 31.4–39.4 mm SL, Rio Pardo, unnamed stream tributary of rio Pardo, 12 Jul 2006, J. Anza. LIRP 16774 , 5 , 22.9–30.5 mm SL, Cruzeiro do Sul , rio Sampaio , tributary of rio Taquari , 29°31’10”S 52°04’43”W, 27 Mar 2013, J. Ferrer & J. Wingert. MCP 9479 , 2 , 24.3–30.1 mm SL, Santa Cruz do Sul , rio Pardinho , 29º40’S 52º29’W, 15 Sep 1983, C. A. S. Lucena, L. R. Malabarba & R. E. Reis. MCP 10059 *, 1, 36.4 mm SL, Três Coroas, arroio Moreira, rio do Sinos basin, 29º31’S 50º46’W, 27 Jul 1984, C. Rangel et al. MCP 17498 *, 13 (1 c&s), 36.2–50.1 mm SL, collected with holotype. UFRGS 17616 *, 18 (2 c&s), 18.4–34.3 mm SL, Cruzeiro do Sul, rio Sampaio , tributary of rio Taquari , 29°31’10”S 52°04’43”W, 27 Mar 2013, J. Ferrer & J. Wingert. UFRGS 17418 , 2 , 34.9–38.1 mm SL, Taquara, rio da Ilha, rio do Sinos basin, 20 Dec 2012, R. Dala-Corte et al. UFRGS 21924 *, 22, 23.6–43.5 mm SL, Rio Pardo , unnamed stream tributary of rio Pardo , 12 Jul 2006, J. Anza. Following lots from Caraá, rio do Sinos, 29°46’18”S 50°19’58”W: MCN 19024, 1, 21.1 mm SL, 6 Feb 2007, B. Calegari, M .

Azevedo & T. V. Aguzzoli. MCN 19025*, 4, 27.3–39.1 mm SL, 27 Sep 2006, B. Galegari, M. A. Azevedo & R. Hirano. MCN 19026, 1, 22.8 mm SL, 28 Aug 2007, M. A. Azevedo, R. Dala-Corte & T. Aguzzoli. MCN 19027*, 1, 28.8 mm SL, 30 Oct 2006, M. A. Azevedo & R. Hirano. MCN 19028, 8, 19.4–28.2 mm SL, 23 Apr 2006, M. A. Azevedo & T. Aguzzoli. MCN 19029, 5 (1 c&s), 28.8–29.7 mm SL, 1 Oct 2007, M. A. Azevedo, R. Dala-Corte & T. Aguzzoli. MCN 19030, 3, 29.4–30.1 mm SL, 3 Nov 2007, M. A. Azevedo & T. Aguzzoli .

Diagnosis. Scleronema mate is distinguished from all congeners, with the exception of S. operculatum , by having the rounded blotches at the midlateral line as large as or smaller than opercle (vs. rounded blotches larger than opercle or absent). Scleronema mate differs from S. operculatum by the maxillary barbel longer than half-length of the head (vs. shorter than half-length of the head); tips of the pectoral-fin rays not extending beyond the interadial membrane (vs. extending beyond the interadial membrane), skin flap in the posterior margin of the opercle rounded and short (vs. skin flap pointed and long); fleshy flap at the base of the maxillary barbel, thin, restricted to the maxilla and with distal margin rounded (vs. fleshy flap located anteriorly, thick, prolonged up to the snout and with distal margin straight); and by the caudal fin uniformly brown (vs. caudal fin with a transversal black bar distally).

Description. Based on specimens ranging from 18.4 to 50.1 mm SL; 4 c&s (2 dissected). Morphometric data for 16 types in Tab. 6.

External morphology. Greatest height and width of body in half-length of trunk. Body elongate, trunk roughly cylindrical gradually compressed towards to caudal fin. Dorsal profile of trunk convex and ventral profile straight. Dorsal and ventral profiles of caudal peduncle straight. Dorsal margin of caudal peduncle with thin membrane, resembling adipose fin. Head depressed and wide, trapezoid-shaped from dorsal view, wider posteriorly; square-shaped in specimens with muscles of cheeks well developed. Dorsal and ventral profiles of head straight to slightly convex. Anterior snout profile usually 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 long; emerging from posterolateral edge of anterior nostril extending up to posterior margin of eye or briefly surpassing. Maxillary barbel long; emerging from edge of upper lip and extending up to posterior margin of interopercle or briefly surpassing. Basal portion of maxillary barbel wide with thin fleshy flap dorsally and distal margin rounded. Maxillary barbel with thinner portion longer in length than wider one. Rictal barbel emerging from lateral lobe of lower lip and slightly shorter than maxillary barbel. Mouth subterminal with edges po steriorly oriented. Upper lip wider than lower lip. Lower lip with round fleshy lobes in corners. Ventral surface of lips 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 visible from dorsal and lateral views. Posterior margin of opercle with distinct skin flap short and rounded. 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(n = 14; including holotype) rays; first one always unbranched and not prolonged as filament; fourth and fifth longest. Pectoral-fin insertion posterior to branchial aperture covered by branchial membrane anteriorly. Some specimens with intumescence above anterior portion of pectoral fin and axillary pore not visible. Pelvic fin with distal margin convex when expanded, 5(n = 14; including holotype) 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 to slightly convex when expanded, 8(n = 1), 9(n = 3), 10(n = 5; including holotype) or 11(n = 4) rays; usually first two rays unbranched. Dorsal fin with one(n = 1) or two(n = 1) procurrent rays. Dorsal-fin origin located at vertical through first third to half-length of pelvic fin. Anal fin with distal margin slightly convex when expanded, 6(n = 13; including holotype) or 7(n = 1) rays; usually first two rays unbranched. Anal fin with two(n = 2) procurrent rays. Anal-fin origin located at vertical through last third to posterior edge of dorsal-fin base. Caudal fin with distal margin straight and corners slightly rounded, 10(n = 1), 11(n = 1), 12(n = 10) or 13(n = 2; 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 13(n = 2) procurrent rays dorsally and 9(n = 2) procurrent rays ventrally. Procurrent rays of dorsal, anal and caudal fins rarely visible.

Osteology. Premaxilla with 21–22(n = 1) teeth arranged in two to three rows. Dentary with teeth inserted in one to three rows. Opercle with 9–12(n = 3) odontodes and interopercle with 9–18(n = 3) odontodes. Hyoid arch with 5/6(n = 3) branchiostegal rays. Free vertebrae 34(n = 1) or 35(n = 2); abdominal vertebrae 3(n = 3). Ribs 11(n = 1) or 12(n = 1). First complete haemal arch in 4 th (n = 3) free vertebra, first haemal spine in 12 th (n = 2) or 13 th (n = 1) free vertebra. Pelvic girdle with basipterygium with anterolateral process absent. Dorsal fin with 9(n = 4) pterygiophores; first one inserted anteriorly to neural spine of 14 th (n = 1) or 15 th (n = 2) free vertebra. Anal fin with 6(n = 4) pterygiophores; first one inserted anteriorly to haemal spine of 19 th (n = 3) free vertebra.

Laterosensory system. Data for 34 specimens summarized in Tab. 3. Canals of laterosensory system with simple (non-dendritic) tubes and external pores. Supraorbital line with nasal canal invariably absent and presence of pores s3 and s6 of frontal canal variable ( Fig. 5A ). 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 each other. Otic, posotic and scapular canals present with preoperculo-mandibular and pterotic branches short usually with one pore each (po1 and po2, respectively). Fifteen specimens of 34 with additional pores mainly in infraorbital line. Trunk canal short usually with two pores.

Coloration in alcohol. Lateral surface of body with midlateral line of 4–5 rounded brown blotches as large as or smaller than opercle over light yellow background; blotches becoming fade or absent towards caudal peduncle ( Figs. 12 , 13A ). Dorsal surface of body with 5–6 rectangular brown blotches extending ventrally to laterodorsal surface of body. Ventral surface of body light yellow with few brown blotches in caudal peduncle. Dorsal surface of head almost entirely black. Laterodorsal surface of head with numerous brown rounded blotches over light yellow background. Anterior portion of opercle black. Ventral surface of head light yellow with few small brown blotches in lower lip, sometimes forming thin stripe. Barbels uniformly yellow or intercalated with brown areas. Pectoral, pelvic and anal fins with rays weakly brown and distal margins hyaline. Dorsal and caudal fins with vertical light brown stripe basally, rays weakly brown, and distal margins hyaline ( Figs. 12 , 13A ).

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

Geographical distribution. Scleronema mate occurs in four tributaries of the rio Jacuí (rio Caí, rio Pardo, rio Taquari, and rio dos Sinos), laguna dos Patos system, Brazil ( Fig. 4 ).

Ecological notes. Scleronema mate inhabits rivers and streams with sand- and gravel-bottoms. In the rio Pardo basin, the species is collected syntopically with S. macanuda .

Etymology. The species epithet “mate ” is given in reference to the herb used as an infusion in a traditional drink (“chimarrão”) from South Brazil, Argentina, and Uruguay. Additionally, the type locality of the new species, “Venâncio Aires”, is known

Systematic revision of Scleronema as the “Terra do Chimarrão”. A noun in apposition.

Conservation status. Scleronema mate has an Extent of Occurrence (EOO) less than 5,000 km 2. The arroio Castelhano in Venâncio Aires has suffered from siltation and is strongly impacted by domestic and industrial sewage, as well as excess of fertilisers and pesticides in the surrounding crops. A similar decline in the quality of habitat due to dense urbanisation and agricultural activity can be observed in other areas of occupancy of S. mate . Therefore, the species can be classified as Near Threatened (NT), approaching EN B1b(iii) according to IUCN criteria (IUCN, 2019).

Additional material examined. 15 specimens from Brazil, Rio Grande do Sul State: MCN 6252, 1, 38.7 mm SL, Três Coroas, arroio Quilombo, rio dos Sinos basin. MCN 6888 , 3 , 24.9–31.8 mm SL, Três Coroas, arroio Quilombo, rio dos Sinos basin. MCN 10910 , 1 , 39.5 mm SL, Três Coroas, arroio Moreira, rio dos Sinos basin. MNRJ 41088 , 7 (not measured), Rolante, rio Rolantezinho, rio dos Sinos basin. MCP 11173 , 1 , 23.9 mm SL, São Sebastião do Caí, rio Caí. MCP 17504 , 1 , 42.9 mm SL, Cruzeiro do Sul , rio Sampaio , tributary of rio Taquari. MCP 19136 , 1 , 29.2 mm SL, Vera Cruz, arroio Andreas .

Figures

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 5 | Dorsal view of the head of A. Scleronema mate, new species, paratype (UFRGS 17418; 34.9 mm SL), B. S. ibirapuita, new species, paratype (UFRGS 27402; 49.4 mm SL), C. S. milonga, new species, paratype (LIRP 16775; 35.3 mm SL), and D. S. minutum (UFRGS 19651; 46.4 mm SL) showing the pores of the laterosensory system. “Ap” = additional pore.

FIGURE 12 | Scleronema mate, new species, holotype (MCP 54183; 49.3 mm SL), Brazil, Rio Grande do Sul, Venâncio Aires, arroio Grande, tributary of arroio Castelhano, rio Taquari basin, laguna dos Patos system.

FIGURE 13 | Small specimens of A. Scleronema mate, new species, paratype (UFRGS 17616; 34.3 mm SL) and B. S. teiniagua, new species, paratype (LIRP 16776; 29.3 mm SL).