Scleronema teiniagua, 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 : 61-66

Scleronema teiniagua , new species urn:lsid:zoobank.org:act:C32F77D3-67BA-40F5-8AAE-C00C0DF6A6A8

( Figs. 13B , 26–27 ; Tabs. 3, 10)

Scleronema sp. n. 3 —Bertaco et al., 2016: 421 (listed). —Ferrer, 2016: 106–110; figs.

47–50 (phylogenetic relationships, taxonomy).

Holotype. ZVC-P 14522 , 45.2 mm SL, Uruguay, Artigas, arroyo Tres Cruces, río Cuareím basin, lower río Uruguay, 30°35’31”S 56°37’34”W, 8 Sep 2005, F. Canteira, J. Ferrer, L. R. Malabarba & V. A. Bertaco.

Paratypes. 40 specimens. Brazil, Rio Grande do Sul State, rio Quaraí basin, lower rio Uruguay: LIRP 16776 , 1 , 29.3 mm SL, Quaraí , arroio Salsal , tributary of arroio Areal , 30°25’24”S 56°15’58”W, B. Menezes, C. Hartmann & T. Guimarães , 14 May 2014 . MCP 10963 *, 2, 30.7–35.0 mm SL, Santana do Livramento, arroio Cati , 30°33’21”S 56°06’24”W, 23 Jul 1986 , L. A. Bergmann, P. V. Azevedo & R. E. Reis. MCP 16179 *, 4, 15.5–18.2 mm SL, Santana do Livramento, rio Sarandi III, 30°34’23”S 56°04’02”W, 10 Dec 1992 , J. P. F. Silva, P. H. Wimberger, R. E. Reis. UFRGS 20737 , 2 , 18.9–32.6 mm SL Quaraí, arroio Areal, 30°25’56”S 56°18’44”W, B. Menezes, C. Hartmann & T. Guimarães , 14 May 2014 . Uruguay, Artigas, río Cuareím basin, lower río Uruguay: UFRGS 7755 *, 1, 38.5 mm SL, arroyo Cuaró Grande , 30°47’03”S 56°46’53”W, 8 Sep 2005 , F. Cantera, J. Ferrer, L. R. Malabarba & V. A. Bertaco. UFRGS 7811 *, 10, 26.9– 37.6 mm SL (2 c&s) , collected with holotype. UFRGS 14636 , 2 , 36.0– 37.3 mm SL , collected with holotype. ZVC-P 2497 , 2 , 35.6–41.3 mm SL, arroyo los Molles , 3 Feb 1970 , 30°12’24”S 56°44’31”W, staff of Facultad de Humanidades Y Ciencias. ZVC-P 7669 , 1 , 22.3 mm SL, arroyo Catalán Chico , 30°42’28”S 56°19’21”W, 25 Jan 1958 , J. Soriano. ZVC-P 9910 *, 1, 37.4 mm SL, Cañada Mataojo , 30°47’47”S 56°56’52”W, Aug 2006 , F. Quintans, F. Teixeira, I. González, M. Loureiro. ZVC-P 10122 , 1 , 38.9 mm SL, Cañada Honda , 30°29’07”S 56°50’16”W, Aug 2006 , F. Quintans, F. Teixeira, I. González, M. Loureiro. ZVC-P 10160 , 1 , 41.8 mm SL, Cañada de Brum , 30°35’40”S 56°25’23”W, Aug 2006 , F. Quintans, F. Teixeira, I. González, M. Loureiro. ZVC-P 10231 *, 1, 41.8 mm SL, Cañada de la Cruz , 30°42’04”S 57°02’26”W, Aug 2006 , F. Quintans, F. Teixeira, I. González, M. Loureiro. ZVC-P 10589 , 6 , 22.8–37.5 mm SL, Artigas, unspecific locality in río Cuareím basin, Feb 2006 . ZVC-P 10617 , 1 , 35.2 mm SL, arroyo Tres Cruzes Grande, 30°26’20”S 56°48’13”W, Feb 2006 , F. Quintans, F. Teixeira, I. González, M. Loureiro. ZVC-P 10618 , 4 , 27.7–35.1 mm SL, Artigas, unspecific locality in río Cuareím basin, Feb 2006 .

Diagnosis. Scleronema teiniagua is distinguished from all congeners by a remarkable reduction in the laterosensory system lacking the pores s1, s2, s3 e s 6 in the supraorbital line and pore i 10 in the infraorbital line (vs. presence of, at least, the pore i10) and in the lower number of pterygiophores of dorsal fin (8 vs. 9–14).

Description. Based on specimens ranging from 15.5 to 45.2 mm SL; 2 c&s (one dissected). Morphometric data for 20 types in Tab. 10.

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 and ventral profiles of trunk 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, 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 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, 6/7(n = 2), or 7(n = 21; 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 visible. Pelvic fin with distal margin convex when expanded, 4/5(n = 1) or 5(n = 22; 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 = 5), 9(n = 30; including holotype), or 10(n = 2) rays; usually first two rays unbranched. Dorsal fin with 2(n = 1) or 3(n = 1) procurrent rays. Dorsal-fin origin located at half-length of pelvic fin. Anal fin with distal margin slightly convex when expanded, 6(n = 23; including holotype) rays; usually first two rays unbranched. Anal fin with 2(n = 2) procurrent rays. Anal-fin origin located at vertical through last third of dorsal-fin base. Caudal fin with distal margin straight and corners slightly convex, 11(n = 2) or 12(n = 21; 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 12(n = 1) or 13(n = 1) procurrent rays dorsally and 9(n = 1) or 10(n = 1) procurrent rays ventrally. Procurrent rays of dorsal, anal, and caudal fins rarely visible.

Osteology. Premaxilla with 25–26(n = 1) teeth arranged in three rows. Dentary with 40(n = 1) teeth. Opercle with 14–15(n = 2) odontodes and interopercle with 17–21(n = 2) odontodes. Hyoid arch with 6(n = 2) branchiostegal rays. Free vertebrae 34(n = 1) or 35(n = 1); abdominal vertebrae 3(n = 1) or 4(n = 1). Ribs 10(n = 1) or 12(n = 1). First complete haemal arch in 4 th (n = 1) or 5 th (n = 1) free vertebra, first haemal spine in 11 th (n = 1) or 12 th (n = 1) free vertebra. Dorsal fin with 8(n = 2) pterygiophores; first one inserted anteriorly to neural spine of 14 th (n = 1) or 16 th (n = 1) vertebra. Anal fin with 6(n = 2) pterygiophores; first one inserted anteriorly to haemal spine of 18 th (n = 1) or 20 th (n = 1) vertebra.

Laterosensory system. Data for 40 specimens summarized in Tab. 3. Canals of laterosensory system with simple (non-dendritic) tubes and external pores. Supraorbital line with nasal and frontal canals invariably absent. Infraorbital line with antorbital segment and pore i10 of sphenotic canal invariably absent; pore i11 of sphenotic canal usually present. Posterior segment of frontal, sphenotic and otic canals fused 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 with two pores.

Coloration in alcohol. Lateral surface of body with midlateral line of 5–9 rounded brown blotches larger than opercle over light yellow background; blotches of some individuals becoming fade or absent towards caudal peduncle ( Figs. 13B , 26 ). Dorsal surface of body with 4–6 rectangular brown blotches extending ventrally to laterodorsal surface of body; smaller specimens with these blotches smaller, dorsally discontinuous (MCP 16179). Ventral surface of body light yellow with few brown blotches in caudal peduncle. Dorsal and laterodorsal surfaces 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- fin rays weakly brown. Dorsal and caudal fins with vertical light brown stripe basally, rays weakly brown, and distal margins hyaline ( Figs. 13B , 26 ).

Coloration in life. Coloration in life similar to that specimens preserved in ethyl alcohol, but more intense with blochtes better defined ( Fig. 27 ).

Geographical distribution. Scleronema teiniagua is endemic to the drainage of the río Cuareím ( Uruguay), also named rio Quaraí ( Brazil), a tributary to the left bank of lower rio Uruguay ( Fig. 4 ).

Only two lots identified on the basis of external characters as S. teiniagua were supposedly sampled outside of the río Cuareím basin: ZVC-P 3462 from arroyo Milano,

Santa Lucía basin (collection date 1958) and ZVC-P 5592 (collection date 1971) from río Queguay basin. The ichthyofauna of the río Santa Lucía has been densely inventoried and none trichomycterid was recorded until now (Zarucki et al., 2011; Marcelo Loureiro, 2014, pers. comm.). The unique specimen of the lot ZVC-P 5592 is originated from the type locality of S. angustirostre , Cañada de las Piedras, and all material analyzed from this locality and the río Queguay basin belong to S. minutum (senior synonym of S. angustirostre ). The occurrence of S. teiniagua in the río Santa Lucía or río Queguay basins should be considered with caution and need to be confirmed by new samples.

Ecological notes. Scleronema teiniagua inhabits rivers and streams and has not been collected with its congeners. The stomachs of two specimens were analyzed and had immature aquatic Diptera ( Chironomidae and Simuliidae ) and Ephemeroptera.

Etymology. The species epithet “teiniagua ” is given in reference to the character of a fictional tale entitled “Salamanca do Jarau” popularized in the Rio Grande do Sul State by the writer Simões Lopes Neto (Lopes-Neto, 1913). In this story, Teiniaguá was a princess transformed to a witch that lives in a cave at the hill “Cerro do Jarau”, which is inserted in the area of distribution of the new species. A noun in apposition.

Conservation status. Scleronema teiniagua has an Extent of Occurrence (EOO) less than 20,000 km 2, but no threats were detected to the species. Thus, the species can be classified as Least Concern (LC) according to IUCN criteria (IUCN, 2019).

Remarks. Specimens of Scleronema minutum analyzed by Vaz-Ferreira, Soriano

(1959) from Artigas probably belong to S. teiniagua . However, these authors did not provide the voucher numbers to confirm their identification.

Additional material examined. 30 specimens from Uruguay. ZVC-P 3462 , 17 ,

23.6–41.7 mm SL, uncertain locality. ZVC-P 5592, 1, not measured, uncertain locality.

Artigas, río Cuareím basin, lower río Uruguay: ZVC-P 412 , 3 , 18.0– 22.3 mm SL ,

río Cuareím near mouth of arroyo Yacaré. ZVC-P 10588, 8, 20.1–38.4 mm SL, río

Cuareím. ZVC-P 10590, 1, 31.9 mm SL, arroyo Catalán Grande. ZVCP 13763, 1, not measured, arroyo Catalán Grande at Paso Santiño.

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 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).

FIGURE 26 | Scleronema teiniagua, holotype (ZVC-P 14522; 45.2 mm SL) Uruguay, Artigas, arroyo Tres Cruzes, río Cuareím basin, lower río Uruguay.

FIGURE 27 | Specimen in life out of the water of Scleronema teiniagua (ZVCP 13763), Uruguay, Artigas, arroyo Catalán Grande at Paso Santiño, río Cuareim basin lower río Uruguay. Photograph taken by Sebastián Serra.