Rhinolekos capetinga, Roxo, Fabio F., Ochoa, Luz E., Silva, Gabriel S. C. & Oliveira, Claudio, 2015

Roxo, Fabio F., Ochoa, Luz E., Silva, Gabriel S. C. & Oliveira, Claudio, 2015, Rhinolekoscapetinga: a new cascudinho species (Loricariidae, Otothyrinae) from the rio Tocantins basin and comments on its ancestral dispersal route, ZooKeys 481, pp. 109-130 : 113-118

Taxon classification Animalia Siluriformes Loricariidae

Rhinolekos capetinga sp. n. Figs 1, 3; Table 1

Rhinolekos sp. 1 - Roxo et al. 2014a: 9(8) e105564 (phylogenetic relationships).

Holotype.

MZUSP 116102, (male, 37.5 mm SL), Brazil, Goiás State, municipality of Água Fria de Goiás, córrego da Branca, drainage of the rio Tocantizinho, rio Tocantins basin, 14°53'47.2"S, 47°34'58.4"W, 30 June 2014, FF Roxo, GSC Silva, LE Ochoa.

Paratypes.

Brazil, Goiás State, rio Tocantins basin (56 specimens). LBP 17089 (1 male, 39.1 mm SL), municipality of Agua Fria de Goiás, córrego da Branca, drainage of the rio Tocantizinho, 14°57'01.6"S, 47°35'57.0"W, 21 November 2012, R Devidé, BF Melo, JMH Martinez, GSC Silva; LBP 18996, (1 female, 24.1 mm SL), municipality of São João D’Aliança, córrego Roncador, drainage of the rio Tocantizinho, 14°43'51.3"S, 47°32'34.0"W, 30 June 2014, FF Roxo, GSC Silva, LE Ochoa; LBP 19001 (15 females, 26.8-36.2 mm SL, 20 males, 39.5-30.2 mm SL, 3 c&s, 37.2-32.6 mm SL, 9 unsexed juveniles not measured), collected with holotype. LBP 19466 (2 females, 36.5-37.1 mm SL) municipality of Água Fria de Goiás, córrego da Branca, drainage of the rio Tocantizinho, 14°53'47.2"S, 47°34'58.4"W, 09 November 2014, FF Roxo, LH Roxo, GSC Silva, LE Ochoa; MZUSP 113920 (2 females, 29.3-37.3 mm SL, 3 males, 30.4-39.0 mm SL), municipality of Água Fria de Goiás, córrego da Branca, drainage of the rio Tocantizinho, 14°53'47.2"S, 47°34'58.4"W, 27 November 2012, OT Oyakawa, AM Zanata, P Camelier, M Melo.

Diagnosis.

Rhinolekos capetinga differs from Rhinolekos garavelloi and Rhinolekos schaeferi in that it has a lower number of vertebrae, 31 (vs. 32) and the anterior portion of the compound supraneural-first dorsal-fin proximal radial contacts the neural spine at the 9th vertebra (vs. 10th, Fig. 2a). The new species can be distinguished from Rhinolekos britskii by the absence of transverse dark bands in the pectoral, pelvic and anal-fin rays (vs. present), lower number of plates in the dorsal series 24-28 (vs. 30-35), lack of odontodes on the ventral tip of the snout (vs. tip of snout completely covered by odontodes), and by having a greater prenasal length, 41-60% of HL (vs. 32-40% of HL). Moreover, the new species differs from Rhinolekos schaeferi by the absence of accessory teeth (vs. present) and from all congeners by the smaller head length, 20-27% of SL (vs. 28-32% of SL in Rhinolekos britskii ; 29-35% of SL in Rhinolekos garavelloi ; 29-32% of SL in Rhinolekos schaeferi ), and by the greater snout length, 61-85% of HL (vs. 52-57% of SL in Rhinolekos britskii ; 49-60% of SL in Rhinolekos garavelloi ; 53-59% of SL in Rhinolekos schaeferi ). It differs from Rhinolekos britskii and Rhinolekos garavelloi by the smaller caudal-peduncle depth, 6-9% of SL (vs. 9-11% of SL in Rhinolekos britskii and 10-13% of SL in Rhinolekos garavelloi ); it differs from Rhinolekos garavelloi by the smaller thoracic length 10-15% of SL (vs. 18-21% of SL), and by the smaller folded dorsal-fin length, 14-21% of SL (vs. 22-26% of SL).

Description.

Morphometric and meristic data presented in Table 1. Maximum body length 39.1 mm SL; dorsal profile of head in lateral view convex to straight from upper part of rostrum to anterior margin of eyes, slightly curved from eyes to posterior margin of parieto supraoccipital, almost straight to dorsal-fin origin; dorsal profile of trunk almost straight, descending from base of dorsal-fin origin to caudal peduncle; ventral profile slightly concave from snout tip to pelvic-fin origin, slightly convex to caudal peduncle; greatest body depth at dorsal-fin origin; greatest body width at cleithral region, gradually decreasing towards snout and caudal-fin. Cross-section of caudal peduncle almost ellipsoid; rounded laterally and almost flat dorsally and ventrally.

Head rounded in dorsal view. Snout slightly pointed, its tip rounded, elongated (61-85% of HL) and depressed in front of each nostril on dorsal surface. Anterior margin of snout covered with odontodes, except ventral tip of snout; odontodes of margin of snout similar in size to remaining ones found on head. Odontodes on head and trunk well defined and not forming longitudinal rows; eye small (12-23% of HL), dorsolaterally positioned; iris operculum not present; lips roundish and papillose; papillae uniformly distributed on base of dentary and premaxillary and slightly decreasing distally. Lower lip larger than upper lip; its border fringed; maxillary barbel present; Teeth slender and bicuspid; mesial cusp larger than lateral cusp; premaxillary teeth 15-34. Dentary teeth 14-30.

Dorsal fin ii,6-7; dorsal-fin spinelet short, roughly triangular shaped, locking mechanism non-functional; dorsal-fin origin slightly posterior of vertical through pelvic-fin origin. Anterior portion of compound supraneural-first dorsal-fin proximal radial contacting neural spine of 9th vertebrae (Fig. 2a). Tip of adpressed dorsal-fin rays slightly surpassing end of anal-fin base. Pectoral fin i,5-6; tip of longest pectoral-fin ray almost reaching to middle of adpressed pelvic-fin, when depressed. Pectoral axillary slit not present even in juveniles. Pectoral spine supporting odontodes anteroventrally; pelvic fin i,5; its tip not exceeding anal-fin origin when depressed in both sexes. Pelvic-fin unbranched ray with dermal flap along its dorsal surface in males; anal fin i,5; its tip reaching 7th and 8th plate from its origin; Caudal fin i,14,i; distal margin forked; Adipose-fin absent. Total vertebrae 31 (3 c&s).

Body covered with bony plates except on ventral part of head, around pectoral and pelvic-fin origin and on dorsal-fin base. Cleithrum and coracoid totally exposed; Arrector fossae partially enclosed by ventral lamina of coracoids. Abdomen entirely covered by plates in adults (about 25.0 mm SL); lateral plate series with elongate and large plates, formed by two lateral plate series, similar in size; median plates formed by four to five irregular plate series reaching anal shield. Lateral side of body entirely covered by plates; mid-dorsal and mid-ventral plates well developed, reaching typical adipose-fin region.

Parts of head osteology presented in Fig. 2b. Tip of snout formed by two square rostral plates. Nasal almost rectangular forming anterior medial nostril margin in contact posteriorly with frontals, and anterior and lateral margins contacting pre-nasals. Lateral surface of head formed by three posterior rostrum plates, second one large and triangular shaped. Complete infraorbital plate series, present mesial to posterior rostrum series, composed of five plates; fourth infraorbital expanded ventrally, all associated with latero-sensory canal system; first and second infraorbitals largest and fifth smallest. Large lateronasal plate mesial to second infraorbital, forming anterior distal nostril margin in contact anteriorly with prenasals and posteriorly with prefrontal. Preopercle present just ventral to fifth infraorbital; an elongated bone covered by latero-sensory canal. Subocular cheek plates present ventral to preopercle plate. Top of head composed of compound pterotic-supracleithrum, supraoccipital, prefrontal, frontal, and sphenotic; parieto-supraoccipital bearing fenestrae irregularly distributed and of different sizes and shapes.

Color in life.

Pale yellowish ground color. Dorsal surface of head dark brown, except for pale yellowish areas on snout tip. Four dark-brown saddles crossing dorsum, reaching longitudinal dark strip on side of trunk: first at dorsal-fin origin, second below dorsal-fin base, third typically at adipose-fin region, and fourth at end of caudal peduncle. Caudal-fin black, with small hyaline circular area on each lobe, tip of lobes hyaline; some specimens with caudal-fin lobe entirely dark (Fig. 3).

Color in alcohol.

Similar pattern described for living specimens, but with ground color dark brown (Fig. 1).

Sexual dimorphism.

Adult males are distinguished by having a papilla at the urogenital opening (vs. papilla absent in females), and by an unbranched pectoral- and pelvic-fin ray supporting a dermal flap on their proximal dorsal surface in males.

Etymology.

The specific name capetinga from the Tupi-guarani dialect is in reference to the old and unused name of São João D´Aliança municipality. The name «capetinga» means white, or clear water. A noun in apposition.

Distribution.

Rhinolekos capetinga is known from two localities at the córrego da Branca and one locality at the córrego Roncador, all drainages of the rio Tocantizinho, rio Tocantins basin (Fig. 4a).

Habitat.

Rhinolekos capetinga was collected on flat areas of the córrego da Branca and córrego Roncador, rio Tocantins basin, in places of shallow clear waters, about 1 m depth and median to fast current flow. The fishes captured were associated with the vegetation that covers the bottom and the border of the headwaters (Fig. 4b).

Phylogenetic and time calibrated tree

Partial sequences of the three mitochondrial genes (16S rRNA, COI, Cytb) and one nuclear gene (F-reticulon 4) were obtained from GenBank (Suppl. material 3 - Table S1) (same data available in Roxo et al. 2014a). The combined sequence data resulted in a matrix of 4,500 base pairs. This matrix was used to perform all phylogenetic and biogeographic analyses. Bayesian and ML phylogenetic analyses resulted in very similar topologies (Suppl. material 1 - Fig. S1). Our results illustrate the same phylogenetic relationship of Roxo et al. (2014) that the clades Hypoptopomatinae, Neoplecostominae and Otothyrinae are monophyletic with strong statistical support (BS = 96, P = 0.99 for Hypoptopomatinae; BS = 99, P = 1.00 for Neoplecostominae; BS = 96, P = 0.99 with BI for Otothyrinae). The new species Rhinolekos capetinga formed sister group to the species Rhinolekos garavelloi , and both species formed sister group to the species Rhinolekos britskii .

Our time calibrated phylogeny and the ancestral area reconstruction (Suppl. material 2 - Fig. S2; Fig. 5) suggested that the genus Rhinolekos originated in the upper rio Paraná basin about 17.5 Mya (9.6-27.9 Mya 95% HPD) and the new species Rhinolekos capetinga reached the area D (Amazon and Orinoco basins) from drainages of the rio Paranaíba about 6.3 Mya (4.1-13.9 Mya 95% HPD) at the end of Miocene.