Trichomycterus vitalbrazili, Vilardo & Katz & Costa, 2020

Vilardo, Paulo J., Katz, Axel M. & Costa, Wilson J. E. M., 2020, Capoeta saadii, Zoological Studies 59 (53), pp. 1-12 : 3-10

Family Trichomycteridae Bleeker, 1858 Genus Trichomycterus Valenciennes, 1832

Trichomycterus vitalbrazili sp. nov. Vilardo, Katz and Costa ( Figs. 2–4 , 6 ; Table 1) urn:lsid:zoobank.org:act:95141315-8577-463C-9622-64D49BE5F1CF

Holotype: UFRJ 12151, male, 88.0 mm SL; Brazil: Rio de Janeiro State: Nova Friburgo Municipality: mountain stream tributary to the Rio Grande drainage, Rio Paraíba do Sul basin, Serra dos Órgãos, inside the advanced campus of the Instituto Vital Brazil, São Lourenço road, 22°20'51"S 42°37'18"W, about 1130 m asl; A. Katz and F. Pereira, 24 Feb. 2016.

Paratypes: All from Brazil: Rio de Janeiro State: Nova Friburgo Municipality: Rio Grande drainage, Rio Paraíba do Sul basin, Serra dos Órgãos. UFRJ 10924, 2, 75.0– 75.1 mm SL; UFRJ 10923, 1, 75.4 mm SL; UFRJ 12128, 1, 55.4 mm SL (C&S); collected with holotype. UFRJ 12125, 3, 24.1–29.1 mm SL (DNA); same locality as holotype; A. Katz and P. Vilardo, 20 Jan. 2019. UFRJ 5979, 8, 32.1–50.9 mm SL; UFRJ 12150, 2, 34.4–36.2 mm SL (C&S); stream tributary of Rio Bengala, near km 66 of road RJ-116, 22°21'36"S 42°31'43"W, 1010 m asl; L. Villa Verde, 24 Aug. 2003. UFRJ 7210, 10, 25.0– 48.8 mm SL; CICCAA 04083, 3, 31.5–35.2 mm SL; same locality as UFRJ 5979; L. Villa Verde, 11 Sep. 2005.

Diagnosis: Trichomycterus vitalbrazili is distinguished from all other congeners except T. albinotatus by the presence of a vertical row of dark brown to black spots on the caudal peduncle end, often coalesced to form a precaudal bar in live and preserved specimens ( Fig. 2A–B ; vs. never a similar colour pattern); two horizontal rows of white spots on the flank in live juveniles ( Fig. 3A–C ; vs. never a similar colour pattern); and medial margin of the autopalatine nearly straight to slightly convex ( Fig. 4A ; vs. concave). Trichomycterus vitalbrazili is distinguished from T. albinotatus ( Fig. 5A–B ) by possessing diffuse irregularly shaped dark brown blotches on the flank in adult specimens ( Fig. 2A–B ; vs. well-delimited dark grey to black, sometimes coalesced in larger specimens); fins with dark brown spots in adults specimens ( Fig. 2A–B ; vs. without spots); and eight branchiostegal rays (vs. seven).

Description: Morphometric data appear in table 1. Body moderately slender, subcylindrical and slightly depressed anteriorly, compressed posteriorly. Greatest body depth at vertical immediately in front pelvic-fin base. Dorsal profile slightly convex between snout and end of dorsal-fin base, straight on caudal peduncle; ventral profile straight to slightly convex between lower jaw and end of anal-fin base, slightly concave on caudal peduncle. Anus and urogenital papilla in vertical through middle of dorsal-fin base, nearer tip of pelvic fin than anal-fin origin. Skin papillae minute. Head trapezoidal in dorsal view. Anterior profile of snout nearly straight to slightly convex in dorsal view. Eye moderate, dorsally positioned in head. Posterior nostril located nearer anterior nostril than anterior orbital rim. Tip of maxillary barbel reaching anterior third of pectoral fin. Tip of rictal barbel reaching behind opercular patch of odontodes. Tip of nasal barbel reaching orbit. Mouth subterminal. Jaw teeth pointed, arranged in irregular rows, three in premaxilla, four in dentary; premaxillary anterior-most row with 12–13 teeth, dentary external row with 14–17. Branchial membrane attached to isthmus only at its anterior point. Branchiostegal rays 7.

Dorsal and anal fins subtriangular, distal border slightly convex; total dorsal-fin rays 11 or 12 (ii–iii + II + 7), total anal-fin rays 10 (iii + II + 5); anal-fin origin in vertical just posterior to dorsal-fin base. Dorsal-fin origin in vertical through centrum of 18th vertebra; anal-fin origin in vertical between centrum of 21st or 22nd vertebrae. Pectoral fin subtriangular in dorsal view, first pectoral-fin ray terminating in short filament reaching about 25–40% of pectoral-fin length without filament; total pectoral-fin rays 8 (I + 7). Pelvic fin sub-truncate, posterior margin slightly convex; posterior extremity of pelvic fin posteriorly just surpassing urogenital papilla; pelvic-fin bases medially separated by minute interspace; total pelvic-fin rays 5 (I + 4). Caudal fin truncate; total principal caudal-fin rays 13 (I + 6 + 5 + I), total dorsal procurrent rays 13–15 (xiii–xv), total ventral procurrent rays 12–13 (xi–xii + I). Vertebrae 35 or 36. Ribs 13.

Laterosensory system: Supraorbital sensory canal continuous, connected to infraorbital sensory canals posteriorly. Supraorbital sensory canal with 3 pores: s1, adjacent to medial margin of anterior nostril; s3, adjacent to medial margin of posterior nostril; and s6, on middle part of dorsal surface of head, in transverse line through posterior portion of orbit; pores s6 medially in close proximity. Infraorbital sensory canal arranged in 2 segments, each with two pores; anterior segment with pore i1, in transverse line through anterior nostril, and pore i3, in transverse line just anterior to posterior nostril; posterior segment with pore i10, adjacent to ventral margin of orbit, and pore i11, posterior to orbit. Postorbital canal with 2 pores: po1, in vertical line above posterior portion of interopercular patch of odontodes, and po2, in vertical line above posterior portion of opercular patch of odontodes. Lateral line of body short, with 2 pores, posterior-most pore in vertical just posterior to pectoral-fin base.

Mesethmoidal region and adjacent structures ( Fig. 4A ): Anterior margin of mesethmoid nearly straight, mesethmoid cornu slender, tip rounded to slightly pointed. Antorbital thin, elliptical in dorsal view. Sesamoid supraorbital elongate and narrow, its length about 2.5 times antorbital length. Premaxilla subrectangular in dorsal view, without distinctive processes, sometimes its lateral extremity slightly narrowed. Maxilla boomerang-shaped, slightly shorter than premaxilla. Autopalatine subrectangular in dorsal view when excluding posterolateral process, broad, its width about three fifths of autopalatine length, lateral margin about straight, medial margin straight to slightly convex; latero-posterior process of autopalatine triangular, short, its length about half autopalatine length without process.

Suspensorium and opercular apparatus ( Fig. 4B ): Metapterygoid subtriangular, deeper than wide. Quadrate robust, dorsoposterior flap continuous to hyomandibula anterior outgrowth. Hyomandibula broad, with well-developed anterior outgrowth flap; middle portion of dorsal margin of hyomandibular anterior outgrowth with shallow concavity; postero-dorsal process of hyomandibula well-developed, pointed. Opercle moderately robust, its smallest depth about one fourth of its horizontal length measured between point just below articular facet to hyomandibula and posterior limit of odontode patch; dorsal process of opercle short, tip rounded; ventral process of opercle short, its length about two fifths of the opercle horizontal length. Interopercle long, its largest length about three fourths of hyomandibula largest length; dorsal interopercular process with deep anterior concavity. Odontodes conical, numerous, 13–19 on opercle, about 56–70 on interopercle. Preopercle compact, with pronounced ventral flap.

Branchial arches ( Fig. 4C ): Basibranchial 2 subcylindrical, gradually widening anteriorly, wider and slightly longer than basibranchial 3, basibranchial 3 cylindrical; basibranchial 4 cartilage sub-pentagonal, longer than wide. Hypobranchial 1 subcylindrical, without expansions; hypobranchials 2 and 3 triangular, osseous portion longer than cartilaginous portion. Ceratobranchial 1 slender, proximal portion slightly wider than distal one; ceratobranchial 2 slightly widened in its middle portion, with shallow concavity on posterior margin of proximal portion; ceratobranchial 3 similar to ceratobranchial 2, except by deep concavity on posterior margin of proximal portion; ceratobranchial 4 sub-rectangular, slightly widening distally; ceratobranchial 5 sub-rectangular, slightly curved, moderately wide, its width nearly equal to width of proximal portion of ceratobranchial 4; posteroproximal portion of ceratobranchial 5 bearing patch of small, slightly curved, conical teeth; cartilaginous accessory element of ceratobranchial 4 minute. Epibranchial 1 slender, with well-developed sharp anterior uncinate process and minute posterior process; epibranchial 2 slender, with rudimentary anterior and posterior uncinate processes; epibranchial 3 slender, with well developed, curved posterior uncinate process; epibranchial 4 broad, sub-retangular, proximal portion broader than distal portion. Pharyngobranchial 3 short, subcylindrical; pharyngobranchial 4 long, bearing broad dentigerous plate with curved conical teeth.

Colouration in life: In adult specimens (approximately above 35 mm SL), flank brownish yellow with diffuse irregularly shaped dark brown blotches, more concentrated on dorsal half of flank, often forming interrupted diffuse stripe along lateral midline between pectoral and caudal-fin bases. Posterior end of caudal peduncle with vertical row of coalesced dark brown spots, forming precaudal bar. Dorsum between head and dorsal-fin origin dark brown, with some depigmented small spots; venter brownish yellow, with diffuse pale brown spots. Side and dorsal surface of head dark brown, opercular and interopercular patches of odontodes pale brownish yellow. Barbels dark brown to black. Iris brown, with narrow yellow line around pupil bluish silver iridescence. Fins hyaline with irregular transverse rows of dark brown spots; spots larger and darker in vertical row on caudal-fin base; intense concentration of dark brown pigmentation on dorsal-fin base. In juveniles, flank light yellowish brown, with two horizontal rows of white spots, upper row on dorsal part of flank, lower row on flank midline, upper row with 8–10 small rounded white spots, alternated with brown spots, lower row with 6 horizontally elongated white spots, often inconspicuous, alternated with similar dark brown to black spots. Vertical black bar on posterior end of caudal peduncle. Head side pale yellowish brown, with two postorbital dark brown spots. Nasal region and barbel black. Maxillary and rictal barbels hyaline, with grey pigmentation on basal portion. Iris bluish silver, with melanophores on ventral margin. Dark brown blotches on centre of dorsal surface of head. Fins hyaline with transverse rows of small faint grey spots; unpaired fins with yellowish pigmentation concentrated on basal portion of rays; bright white pigmentation over basal portion of pectoral fin. The ontogenetic variation of colour pattern is presented in figure 6.

Colouration in alcohol: Similar to colouration in life, but paler, disappearing white marks in preserved juveniles.

Etymology: The name vitalbrazili was given in honour of Vital Brazil Mineiro da Campanha (1865– 1950), an important Brazilian biomedical scientist who first discovered the polyvalent anti-ophidic serum, successfully used to treat venomous snake bites, and founded the Vital Brazil Institute, where the new species was found.

Distribution, habitat and conservation: Trichomycterus vitalbrazili is only known from the upper section of the Rio Grande drainage, Rio Paraíba do Sul basin, south-eastern Brazil ( Fig. 7 ). The type locality is a clearwater mountain stream, about 30–100 cm deep. In this locality, adult specimens (above about 35 mm SL), including the holotype, were only collected using traps at night, in a part of the stream about 1 m wide, within dense forest, bottom comprising rocks and gravel ( Fig. 8 ). Juveniles were collected in gravel and sand on the stream bottom during daytime with small dip nets, just below the other site, where margins were deforested and the stream width was about 2.5 m. In this site speciemens of Neoplecostomus variipictus Bizerril, 1995 , Rhamdioglanis transfaciatus Miranda-Ribeiro (1908) , Characidium interruptum Pelegrin, 1909 and Phalloceros harpagos Lucinda, 2008 were co-occuring with the new species. Both juveniles and small adults about 35 mm SL were collected in 1983 and 1984 in the Parque Municipal Juarez Frotté, upper Rio Bengala subdrainage, by one of us ( WJEMC), but are not currently preserved. In this site, the river was about 5 m wide and about 1.5 m deep in the deepest areas. The bottom was mainly composed of gravel and small rocks. Some juvenile specimens were found during daylight over or buried in the gravel substrate.

The region includes well preserved areas, indicating that the species is not threatened with extinction.

Figures

Fig. 2. Trichomycterus vitalbrazili. Brazil: Rio de Janeiro State: Nova Friburgo Municipality: Rio Paraíba do Sul basin. (a) UFRJ 12151, 88.0 mm SL (preserved holotype), left lateral view; (b) UFRJ 12151, 88.0 mm SL (live holotype), left lateral view. Caudal-fin margin of holotype is damaged, see figure 6 for correct information of caudal morphology.

Fig. 3. Trichomycterus vitalbrazili. Brazil: Rio de Janeiro State: Nova Friburgo Municipality: Rio Paraíba do Sul basin. (a), UFRJ 12125, 24.1 mm SL (live juvenile paratype), left lateral view; (b) UFRJ 12125, 29.1 mm SL (live juvenile paratype), left lateral view; and (c) UFRJ 12125, 29.1 mm SL (live juvenile paratype), dorsal view. Arrow indicates the midline row with white spots, which is not visible in left lateral view of figure 3b due to the light angle.

Fig. 4. Osteological features of Trichomycterus vitalbrazili. (a), UFRJ 12128, 55.4 mm SL, mesenthmoidal region and adjacent structures, middle and left portion, dorsal view; (b), UFRJ 12150, 36.2 mm SL, left suspensorium and opercular apparatus, lateral view; (c), UFRJ 12128, 55.4 mm SL, middle and left portion of branchial arches, ventral view of dorsal elements on left, dorsal view of ventral elements on right. Larger stippling represents cartilages. Abbreviations: ae4, accessory element of ceratobranchial 4; b2–3, basibranchials 2–3; bc4, cartilaginous basibranchial 4; c1–5, ceratobranchials 1–5; e1–4, epibranchials 1–4; h1–3, hypobranchials 1–3; p3, pharyngobranchial 3; pt4, pharyngobranchial 4 tooth-plate. Scale bar = 1 mm.

Fig. 6. Ontogenetic variation in Trichomycterus vitalbrazili. (a), UFRJ 10924, 75.0 mm SL (preserved paratype), left lateral view; (b), UFRJ 5979, 49.5 mm SL (preserved paratype), left lateral view; (c), UFRJ 5979, 38.2 mm SL (preserved paratype), left lateral view; (d), UFRJ 5979, 32.7 mm SL (preserved paratype), left lateral view; (e), UFRJ 7210, 25.0 mm SL (preserved paratype), left lateral view.

Fig. 5. Trichomycterus albinotatus. Brazil: Rio de Janeiro State: Itatiaia Municipality: Rio Paraíba do Sul basin. (a) UFRJ 11668, 42.8 mm SL (live adult specimen), left lateral view; and (b) UFRJ 11658, 29.0 mm SL (live juvenile specimen), left lateral view. Table 1. Morphometric data of Trichomycterus vitalbrazili sp. nov.

Fig. 7. Geographical distribution of Trichomycterus vitalbrazili and T. albinotatus. Black circle with a white cross inside indicates type locality.

Fig. 8. Stream tributary to the Grande river drainage, Rio Paraiba do Sul basin, inside the advanced campus of Instituto Vital Brazil in São Lourenço road, the type locality of Trichomycterus vitalbrazili.