Rhamdia gabrielae, Angrizani & Malabarba, 2018

Angrizani, Rafael C. & Malabarba, Luiz R., 2018, Morphology and molecular data reveal the presence of two new species under Rhamdia quelen (Quoy & Gaimard, 1824) (Siluriformes: Heptapteridae) species complex, Zootaxa 4388 (1), pp. 41-60 : 49-51

Rhamdia gabrielae sp. nov.

urn:lsid:zoobank.org:act: 1040F05A-64AC-4640-B608-20034625A535 ( Fig. 8 ; Table 4)

Rhamdia sP. MAlAbArbA et al., 2013:74 [diAgnosis; PhoTo; disTribuTion reCords in The rio TrAmAndAí drAinAge].

Holotype. UFRGS 22010 , 194 mm SL, Brazil, state of Rio Grande do Sul, municipality of Maquiné, arroio Pinheiro, tributary of rio Maquiné , 29o39’43”S, 50o15’55”W; F. G. Becker, 19 Jun 1999.

Paratypes (total = 65). All from Brazil: UFRGS 18033 , 10 (1 c&s), 139.63–194.16 mm SL, state of Rio Grande do Sul, municipality of Maquiné, rio Maquiné , 29o38’52”S, 50o13’03”W ; J. M. Santos, 30 Mai 13. UFRGS 19094, 8, 118.88– 139.74 mm SL, state of Rio Grande do Sul, municipality of Maquiné, rio Maquiné , 29o35’16”S, 50o16’13”W; L . R. Malabarba, C. Hartmann, R. C. Angrizani, 7 Jul 2013. MCP 27312, 1 (c&s), 136 mm SL, state of Rio Grande do Sul, municipality of Maquiné Lajeado, arroio Lajeado tributary of rio Maquiné , 29°34'16"S, 50°16'51"W ; F. Becker, F. Vilella, 23 Mar 2001. MCP 28113, 1 (c&s), 125 mm SL, state of Rio Grande do Sul, municipality of Maquiné, arroio Forqueta tributary of rio Três Forquilhas , 29°31'59"S, 50°14'00"W ; F. Vilella, J. Anza, 13 Mar 2001. UFRGS 18008, 3, 141.53– 145.67 mm SL, state of Rio Grande do Sul, municipality of Três Forquilhas, rio Três Forquilhas , 29o32’56”S, 50o04’13”W ; J. Santos, 31 Mai 2013. UFRGS 18010, 14, 121.46– 193.37 mm SL, state of Rio Grande do Sul, municipality of Três Forquilhas, rio Três Forquilhas , 29o32’56”S, 50o04’13”W ; J. Santos, 31 Mai 2013. MZUSP 36464, 5, 108.5– 220.04 mm SL, state of Santa Catarina, municipality of Morrinhos do Sul, rio Faxinalzinho tributary to rio Mampituba , E. Pereira, R. Reis, J. Pezzi, 20 Jul 1999. UFRGS 19902, 8, 102.22– 137.05 mm SL, state of Santa Catarina, municipality of Mãe dos Homens, rio Mãe dos Homens, tributary to rio Mampituba , 29o13’02”S, 49o59’58”W, data . UFRGS 6194 , 1 , 260.50 mm SL, state of Santa Catarina, municipality of Treviso, rio Mãe Luiza tributary to rio Araranguá , 49°28’18”S, 28°27’58”W; C . Ricken, R. Vicente, 21 Oct 2002. UFRGS 19903, 14, 61.13–270.63 mm SL, state of Santa Catarina, municipality of Jordão, rio Jordão, tributary of Araranguá , 28o35’11”S, 49o31’24”W, R .C. Angrizani, L.R. Malabarba, M.C. Malabarba, 21 Feb 2015.

Diagnosis. Rhamdia gabrielae is diagnosed from sympatric populations of R. aff. quelen by the number of branched dorsal-fin rays (6 vs. 7–8); last ray of dorsal fin not reaching origin of adipose fin (vs. last ray reaching origin of adipose fin); posterior tip of anal fin not reaching vertical through posterior insertion of adipose-fin base (vs. anal fin surpassing posterior insertion of adipose fin). Rhamdia gabrielae is diagnosed from the neotype of R. quelen sensu Silfvergrip by shorter maxillary barbel (46.6–69.9% SL vs. 97% SL); longer caudal-peduncle (17.1– 21.4% SL vs. 14.62% SL); shorter pelvic fin (10.6–14.6% SL vs. 15.62% SL); shallower dorsal fin (11.2–16% SL vs. 18.41% SL), shorter dorsal spine (5–10.6% SL vs. 15.42% SL) and shorter pectoral-fin spine (8.1–10.9% SL vs. 15.42% SL). Rhamdia gabrielae is diagnosed from R. eurycephala by head width across orbital line (63.00– 73.85% HL vs. 75.18–89.58% HL). Rhamdia gabrielae is diagnosed from R. laticauda , R. foina , R. poeyi and R. itacaiunas by the upper lobe of caudal fin smaller than lower lobe (vs. lower lobe longer than the upper lobe); from R. humilis and R. nicaraguensis by having serrations on both sides of pectoral-fin spine (vs. only anterior serrations in R. humilis and only posterior serrations in R. nicaraguensis ); from R. xetequepeque and R. muelleri by smaller orbit (15–19% HL vs. 30.5–36.9 in R. xetequepeque , 21.7–37.8% in R. muelleri ); from R. xetequepeque and R. laukidi by having 40–41 post-Weberian vertebrae (vs. 31–34 in R. xetequepeque , typically 43–46 in R. laukidi ); from R. jequitinhonha by the head sensory pores simple (vs. head sensory pores multiple); from R. muelleri by shorter maxillary barbel (46.6–69.9% SL vs. 73.9–12.9% SL in R. muelleri ); from R. cinerascens , R. guatemalensis , R. saijaensis , and R. voulezi by shorter dorsal-fin base (11.4–13.1% SL vs. more than 14.3%;); from R. voulezi by the last ray of dorsal fin not reaching anterior insertion of adipose fin (vs. last ray reaching origin of adipose fin); and from R. reddelli , R. enfurnada , R. zongolicensis , R. macuspanensis and R. laluchensis by the lack of morphological adaptations to troglobitic life.

Description. Measurements in Table 1. Body elongated; cross section of trunk roughly circular at dorsal-fin origin and along dorsal-fin base, gradually compressed posteriorly to caudal peduncle. Anterodorsal profile of body convex from supraoccipital to dorsal-fin base. Dorsal-fin base nearly straight, posteroventrally slanted, and gently convex from dorsal fin to base of caudal fin. Ventral body profile nearly straight from mouth to caudal-fin base. Body widest at pectoral girdle and deepest at dorsal-fin origin. Caudal peduncle longer than deep. Number of post-Weberian vertebrae 40(2) or 41(1).

Head depressed and flat dorsally. Dorsal head profile straight and rising slightly from snout tip to supraoccipital in lateral view. Head shape somewhat triangular in dorsal view. Snout rounded anteriorly in dorsal view, longer than deep. Transverse distance between posterior nares slightly smaller than that between anterior nares. Mouth wide, subterminal, transverse gape larger than interorbital distance; snout projecting slightly beyond lower jaw. Large, fleshy rictal fold at corners of mouth. Both upper and lower lips with several longitudinal plicae.

Barbels flattened in cross section, wide at their base and tapering towards distal tip. Maxillary barbel longest; length variable, maximally exceeding origin of adipose fin; inserted above upper lip and posterolateral to anterior nares. Two pairs of mental barbels with bases aligned. Outer mental barbels surpassing origin of pectoral fin. Inner mental barbels shorter than outer mental barbels, maximally reaching origin of pectoral fin. Gular fold distinct and V -shaped. Branchiostegal rays 5(3). Gill rakers thick and moderately long, with 8(1), 9(1) and 10 (1) rakers on first ceratobranchial, and 2(3), on first epibranchial. Eye large, slightly elliptical (longitudinally elongated); rim circumscribed by deep, continuous invagination that is distinctly more pronounced along lateral border. Eye positioned dorsolaterally, approximately at midpoint between tip of snout and corner of opercular membrane; interorbital space wide. Pupil rounded. Sensory channels of head simple.

Dorsal fin with two unbranched rays and six branched rays, distal margin convex and base length less than or equal to fin height. First unbranched dorsal-fin ray small and not externally visible, second unbranched ray stiffened proximally, segmented distally. Dorsal-fin origin anterior to midlength between pectoral and pelvic-fin origins; insertion of last branched ray just before or at pectoral-fin origin. Tip of last branched dorsal-fin ray not reaching anterior insertion of adipose fin. Adipose fin long; with ascendant curve in in lateral profile and posterior lobe conspicuously free from body. Adipose-fin origin at vertical through middle of depressed pelvic fin and posterior insertion at final third of caudal peduncle.

Pectoral fin within one unbranched and five branched rays; when adpressed, reaching approximately origin of third branched dorsal-fin ray. Unbranched ray of pectoral fin stiffened, straight and with strong serrations along distal anterior side and delicate serrations along proximal posterior side. Pelvic fin rounded, approximately same size of pectoral fin, having one unbranched ray and five branched rays, distal tip surpassing genital papilla, never reaching anal-fin origin. Pelvic-fin origin nearly at middle of standard length, after insertion of last dorsal-fin ray. Anal fin rounded, with three unbranched rays anteriorly, followed by eight, nine or ten branched rays; when adpressed, never exceeds posterior insertion of adipose-fin. Length of anal-fin base equal to that of dorsal fin. Caudal fin deeply forked, lobes rounded; dorsal lobe smaller in depth and length; seven branched rays in dorsal lobe and nine branched rays in ventral lobe

Colour of preserved specimens. Body grayish, with or without irregular small brown spots. Head and fins grey without spots. Ventral portion of head and body white. Dorsal fin with dark band across middle length of rays. Maxillary barbels same colour as body.

Distribution and Habitat. Restricted to the upstream portions of hydrographic systems of rio Maquiné, rio Três Forquilhas, rio Mampituba and rio Araranguá, Brazil. Found in rapid waters over rocky bottoms.

Etymology. In honour of Gabriele Volkmer, the wife of the first author of this paper.

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Figures

FIGURE 8. HoloTyPe of Rhamdia gabrielae (UFRGS 20010), holoTyPe, 194 mm SL. In dorsAl, lATerAl,And venTrAl views.