Scleronema guapa, 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 : 11-17

Scleronema guapa , new species urn:lsid:zoobank.org:act:78F28718-7E96-401E-A8C5-AC73A4555E3E

( Figs. 6–7 ; Tabs. 2–3)

Scleronema sp. n. 4 —Bertaco et al., 2016: 421 (listed). —Ferrer, 2016: 85–89; figs.

47–50 (phylogenetic relationships, taxonomy).

Holotype. UFRGS 23500 , 36.4 mm SL, Brazil, Rio Grande do Sul State, Rosário do Sul, sanga Santo Antônio, tributary of rio Ibicuí da Armada , rio Ibicuí basin, lower rio Uruguay, 30°17’41”S 54°59’17”W, 8 Sep 2013, A. Duarte, J. Ferrer, L. R. Malabarba, M. Loureiro & M. Volcan.

Paratypes. 63 especimens from Brazil, Rio Grande do Sul State, rio Ibicuí basin, lower rio Uruguay: LIRP 16770 , 5 , 28.4–32.6 mm SL, collected with holotype. LIRP 16769 , 5 , 33.0– 35.3 mm SL, Alegrete, arroio Jacaquá , 29°51’39”S 55°20’56”W, 1 May 2007, B. Klotzel, L. E. Lanés & M. Volcan. MCN 20231, 5, 29.7–36.9 mm SL, Alegrete , arroio Jacaquá , 29°51’39”S 55°20’56”W, 1 May 2007, B. Klotzel, L. E. Lanés & M. Volcan. MCP 25224 *, 3, 26.7–31.7 mm SL, São Francisco de Assis , arroio Taquari , 29°23’46”S 55°08’52”W, 27 Set 1999, J. F. P. Silva, R. E. Reis & V. A. Bertaco. UFRGS 14034 *, 4, 29.5–37.6 mm SL, São Gabriel, sanga do Areal, tributary of rio Santa Maria , 8 Oct 2007, 30°09’50”S 54°43’58”W, J. F. P. Silva. UFRGS 18087 *, 27 (1 c&s), 16.2–33.6 mm SL, collected with holotype. UFRGS 19307 *, 1, 29.2 mm SL, Alegrete, unnamed stream tributary of arroio São João, 29°46’07”S 55°23’53”W, 28 Oct 2013, C. Hartmann, L. Poldigaiski, M. Dalmolin, R. B. Dala-Corte & T. Guimarães. UFRGS 19649 , 2 , 31.6 –40.0 mm SL, Santana do Livramento , arroio Capivara, tributary of sanga da Divisa, 30°59’42”S 55°24’12”W, 14 May 2014, C. Hartmann, M. Dalmolin, R. B. Dala-Corte & T. Guimarães. UFRGS 19655 *, 10 (1 c&s), 29.8–42.3 mm SL, Alegrete, arroio Jacaquá, 29°51’39”S 55°20’56”W, 1 May 2007, B. Klotzel, L. E. Lanés & M. Volcan .

Diagnosis. Scleronema guapa is distinguished from all congeners by the lateral surface of body with diffuse, scattered brown spots, sometimes grouped forming irregular and small marks at midlateral line (vs. lateral surface of body with a midlateral line of black or brown rounded blotches). Scleronema guapa is further distinguished from S. macanuda and S. operculatum by the maxillary barbel longer than half-length of the head (vs. smaller than half-length of the head); the tips of pectoral-fin rays not extending beyond the interadial membrane (vs. extending beyond the interadial membrane), the skin flap in the posterior margin of the opercle rounded and short (vs. skin flap pointed and long); the fleshy flap at the base of the maxillary barbel located posteriorly, thin, restricted to the maxilla and 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). Scleronema guapa is further distinguished from S. ibirapuita , S. milonga , and S. teiniagua by having the pore s3 of the supraorbital line of the laterosensory system (vs. pore s3 absent).

Description. Based on specimens ranging from 16.2 to 42.3 mm SL; 2 c&s (one dissected). Morphometric data for 20 type specimens in Tab. 2.

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 to slightly convex. Dorsal and ventral profiles of caudal peduncle straight. Dorsal margin of caudal peduncle with thin membrane, resembling adipose fin. Head depressed and wide, usually 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 (holotype with anterior snout profile straight; Fig. 6 ). 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 between anterior and posterior margins of eye. Maxillary barbel long; emerging from edge of upper lip and extending between anterior and posterior margins of interopercle. 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 posteriorly oriented. Upper lip wider than lower lip. Lower lip with round fleshy lobes in corners. Ventral surface of lower 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 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, 6(n = 5), 6/7(n = 9) or 7(n = 48; including holotype) rays; first ray unbranched and not prolonged as filament; fourth and fifth longest. Pectoral-fin insertion posterior to branchial aperture usually 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, 4(n = 1), 4/5(n = 2) or 5(n = 59; including holotype) rays; first ray 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, 7(n = 2), 8(n = 5), 9(n = 46; including holotype), or 10(n = 9) rays; usually first two rays unbranched. Dorsal-fin origin located at vertical through half-length of pelvic fin. Anal fin with distal margin slightly convex when fin expanded, 5(n = 2) or 6(n = 60; including holotype); usually first two rays unbranched. Anal-fin origin located at vertical through last third of dorsal-fin base. Caudal fin with distal margin straight and corners slightly rounded, 11(n = 5), 12(n = 57; 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 9(n = 1) procurrent rays dorsally and 8(n = 1) procurrent rays ventrally. Procurrent rays of dorsal, anal, and caudal fins rarely visible.

Osteology. Premaxilla with 14–19(n = 2) teeth arranged in two rows. Dentary with 28–32(n = 1) teeth arranged in one to three rows. Opercle with 9–14(n = 2) odontodes and interopercle with 10–14(n = 2) odontodes. Hyoid arch with 6(n = 1) or 6/7(n = 1) branchiostegal rays. Free vertebrae 35(n = 1) or 36(n = 1); abdominal vertebrae 3(n = 1). Ribs 11(n = 2). First complete haemal arch in 4 th (n = 1) free vertebra, first haemal spine in 12 th (n = 1) free vertebra. Dorsal fin with 9(n = 2) pterygiophores; first one inserted anteriorly to neural spine of 16 th (n = 2) vertebra. Anal fin with 6(n = 2) pterygiophores; first one inserted anteriorly to haemal spine of 20 th (n = 2) vertebra.

Laterosensory system. Data for 61 specimens summarized in Tab. 3. Canals of laterosensory system with simple (non-dendritic) tubes and external pores. Supraorbital line with nasal canal usually absent and 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 and usually with one pore each (po1 and po2, respectively). Trunk canal short usually with two pores.

Coloration in alcohol. Lateral surface of body with brown spots over light yellow background ( Fig. 6 ). Occasionally, smaller specimens with spots grouped forming small blotches in midlateral line of trunk ( Fig. 7 ). Dorsal surface of body usually with brown spots irregularly distributed or with vermicular brown marks extending ventrally to dorsolateral surface of trunk over light yellow background. Ventral surface of body light yellow with few brown blotches in caudal peduncle. Dorsal and laterodorsal surfaces of head with small brown spots over light yellow background. Anterior portion of opercle black. Ventral surface of body light yellow. Barbels uniformly yellow or intercalated with brown areas. Pectoral and dorsal fins hyaline or with rays of anterior portion faintly brown. Pelvic and anal fins hyaline. Caudal fin with rays faintly brown and distal margin hyaline. Caudal fin with vertical light brown stripe basally ( Figs. 6–7 ).

Coloration in life. Coloration in life similar to that of specimens preserved in ethyl alcohol, but more intense ( Figs. 6–7 ).

Geographical distribution. Scleronema guapa is endemic to the rio Ibicuí basin, a tributary to the left bank of rio Uruguay, State of Rio Grande do Sul, southern Brazil

( Fig. 4 ).

Ecological notes. Scleronema guapa inhabits rivers and streams, with fine sandbottoms. The species is usually collected syntopically with S. operculatum .

Etymology. The species epithet “ guapa ” is a regional adjective used to describe a beautiful person, an allusion to the beauty of the new species.

Conservation status. Scleronema guapa has an Extent of Occurrence (EOO) less than

5,000 km 2, but no specific threats were detected and the species can be classified as LC

according to IUCN criteria (IUCN, 2019).

Additional material examined. 55 specimens from Brazil, rio Ibicuí basin, lower rio Uruguay: MCP 17436 , 6 , 24.6–29.5 mm SL, São Francisco de Assis, rio Jaguari .

MCP 48738, 1 (c&s), not measured (specimen with axial skeleton and fins damaged),

São Francisco de Assis, rio Jaguari. MCP 26866, 1, 38.8 mm SL, Rosário do Sul, arroio do Salso, tributary of rio Ibicuí da Armada. MCP 25192, 14, 20.0– 21.7 mm SL, São

Francisco de Assis, rio Inhacunda. MCP 27505, 1, 23.2 mm SL, São Francisco de Assis,

arroio Taquari, tributary of rio Miracatu. MCP 54170, 19, 17.6–27.0 mm SL, São Francisco de Assis, unnamed stream tributary of rio Inhacundá. MCP 54169, 13, 17,3– 26, 3 mm SL, Jaguari, arroio do Tigre, tributary of rio Jaguari.

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 6 | Scleronema guapa just after the fixation in formalin, holotype (UFRGS 23500; 36.4 mm SL), Brazil, Rio Grande do Sul State, Rosário do Sul, sanga Santo Antônio, tributary to rio Ibicuí da Armada, lower rio Uruguay.

FIGURE 7 | Scleronema guapa just after the fixation in formalin, paratype (UFRGS 18087, 32.0 mm SL), Brazil, Rio Grande do Sul, Rosário do Sul, sanga Santo Antônio, tributary to rio Ibicuí da Armada, lower rio Uruguay.