Gymnotocinclus canoeiro, Roxo, Fábio F., Silva, Gabriel S. C., Ochoa, Luz Eneida & Zawadzki, Cláudio H., 2017

Roxo, Fábio F., Silva, Gabriel S. C., Ochoa, Luz Eneida & Zawadzki, Cláudio H., 2017, Description of a new species of Gymnotocinclus from the rio Tocantins basin with phylogenetic analysis of the subfamily Hypoptopomatinae (Siluriformes: Loricariidae), Zootaxa 4268 (3), pp. 337-359 : 342-349

Gymnotocinclus canoeiro , new species

Figs. 4 , 5 , 6 ; Tables 1, 2

Holotype. MZUSP 121544 , male, 51.5 mm SL, Brazil, Goiás State, municipality of Cavalcante , tributary of rio das Almas, tributary of rio Paranã, rio Tocantins basin, 13°43′12.6′′ S ; 47°27′19.8′′ W; L.H. Roxo, F.F. Roxo, G.S.C. Silva & L.E. Ochoa; 0 9 November 2014.

Paratypes. All from Brazil, Goiás State, municipality of Cavalcante , tributary of rio das Almas, tributary of rio Paranã, rio Tocantins basin; 13°43′12.6′′ S ; 47°27′19.8′′ W (66 specimens in total). ANSP 203112 (3, 43.8¯ 60.7 mm SL), collected with holotype. AUM 68056 (3, 49.2¯ 58.3 mm SL), collected with holotype. LBP 19469 (46, 28.0¯ 54.3 mm SL, 5 c&s), collected with holotype. LBP 19303 (3, 43.4¯ 56.8 mm SL), C. Oliveira, M. Taylor, B.F. Melo & G.S.C. Silva, 16 August 2014. MZUSP 121545 (3, 47.3¯ 51.9 mm SL), collected with holotype. NUP 17787 (3, 45.0¯ 50.6 mm SL), collected with holotype.

Diagnosis. Gymnotocinclus canoeiro differs from G. anosteos by having (1) the presence of body dermal plates (vs. extreme reduction of body dermal plates); (2) the pectoral girdle not exposed in ventral view, Fig. 4 (vs. pectoral girdle completely or partially exposed); (3) the pelvic spine longer than pectoral spine in males, Fig. 1 (vs. the pelvic spine shorter than pectoral spine in males); (4) the pectoral fin with seven (i, 7 in 49 specimens) to eight (i, 8 in one specimen) branched rays (vs. six [i,6] branched rays); and (5) the presence of an adipose fin, Fig. 4 (vs. absence of an adipose fin).

Description. Morphometrics in Table 1 and meristics in Table 2. Large to medium-sized Otothyrini specimens, maximum size 62.3 mm SL. In lateral view, body elongated, dorsal profile slightly convex to straight from tip of snout to area between orbits; straight from this point to dorsal-fin origin, then descending straightly from dorsal-fin origin to unbranched caudal-fin insertion. Ventral profile slightly convex from snout tip to caudal-fin origin. Largest body depth at dorsal-fin origin. Largest body width at cleithrum (22.8–39.0 mm of SL), progressively narrowing to snout tip and to caudal peduncle. Cross-section of trunk and caudal peduncle rounded, dorsally and ventrally flatted.

TABLE]. Morphometric đata for Gymnotocinclus canoeiro . SD = Stanđarđ Deviation, IO = Interorbital, OD = Orbital Diameter, CP = Cauđal Peđuncle. Measurements followeđ Armbruster 2003).

G. canoeiro , n= 50 Males, n= 26 Females, n=24

…..continued on the next page TABLE]. (Continueđ)

G. canoeiro , n= 50 Males, n= 26 Females, n=24

Holotype Range Mean SD Range Mean SD Range Mean SD

Percents of HL

Head-eye length 36.5 31.0*39.0 35.0 1.97 31.7*38.8 34.7 1.84 31.0*38.4 35.2 2.15 Orbital diameter 12.9 9.0*14.4 11.8 1.06 9.0*14.4 11.4 1.11 10.9*13.2 12.3 0.71 Snout length 59.1 54.3*65.0 60.7 2.48 57.7*64.3 61.3 1.69 56.1*65.0 60.9 2.67 Internares width 15.3 12.4*17.7 14.9 1.12 12.4*17.3 14.8 1.01 12.9*17.2 14.9 1.08 Interorbital width 32.1 30.6*36.4 33.5 1.41 30.6*36.4 33.6 1.65 32.1*35.9 33.6 1.12 Head depth 62.1 56.0*68.1 60.9 2.77 56.0*65.1 60.5 2.12 56.0*68.1 61.7 3.52 Mouth length 50.1 47.3*56.9 53.0 2.58 48.7*56.9 53.1 2.57 47.3*56.9 52.9 2.87 Barbel length 8.22 3.2*9.0 6.2 1.31 3.2*8.4 5.9 1.49 4.6*9.0 6.3 1.02 Dentary tooth cup length 21.3 16.9*25.3 20.5 1.80 18.0*22.2 20.2 1.27 16.9*25.2 20.4 2.06 Premaxillary tooth cup length 22.4 17.9*23.6 21.0 1.26 17.9*23.6 20.9 1.34 18.5*23.0 21.3 1.11 G. canoeiro , n= 50 Males, n= 26 Females, n=24 Head flat to slightly convex between orbits; snout elongated (54.3–65.0 mm of HL) and round in dorsal view. Head without crests even in juveniles. Dorsal surface of head at frontal (f), parieto supraoccipital (soc), and sphenotic (sp) region without odontodes. Eye small (9.0– 14.4 mm of HL), situated dorsolaterally in midpoint of head. Perforations of compound pterotic distributed on whole bone, greater and more concentrated on its posterior distal margin. Nostril small. Iris operculum present, poorly developed. Mouth wide; oral disk oval with papillae uniformly distributed on base of dentary and premaxilla; papillae increasing to medial region and then decreasing to edge. Skin with deep transverse slit at each medial upper and lower jaw articulation. Lower lip reaching pectoral girdle and larger than upper; its border crenulated. Maxillary barbel short and adnate to the lower lip. Teeth slender, bicuspid, curved inward; crown with long lanceolate mesial cuspid and minute lateral cuspid. Premaxillary teeth 29–61 (mode 47). Dentary teeth 27–53 (mode 40).

Dorsal fin ii,7; its origin slightly posterior to pelvic-fin origin. Dorsal-fin posterior margin straight to slightly rounded, reaching end of pelvic-fin rays when adpressed. Dorsal-fin spinelet short and ovoid; locking mechanism not functional. Pectoral fin i, 7-i,8 (mode i,7); unbranched ray depressed and slightly curved; posterior margin reaching pelvic-fin insertion when adpressed; unbranched ray covered with backward-oriented odontodes, more developed on ventral portion. Pectoral-fin axillary slit absent. Pelvic-fin i, 5–i,6 (mode i,5); posterior margin nearly straight, reaching anal-fin insertion when adpressed in males and almost reaching anal-fin insertion in females. Pelvic-fin unbranched ray and first branched ray with dermal flap along its dorsal surface in males; unbranched ray ventrally covered with backward-oriented odontodes. Anal-fin i,5; posterior margin almost straight; unbranched ray ventrally covered with posteriorly-oriented odontodes. Adipose fin well developed, not preceded by azygous plate. Caudal fin i,7,7,i; emarginate; lower unbranched ray similar in length to upper unbranched ray. Total vertebrae 31 (1 c&s).

Body entirely covered by dermal plates, except in ventral portion of head, around pectoral and pelvic-fin origins and dorsal-fin base. Abdomen weakly covered by small platelets surrounded by naked areas. Cleithrum and coracoid not exposed. Arrector fossae almost totally exposed. Body lateral entirely covered by plates; dorsal plates series developed from posterior margin of head to caudal peduncle; mid-dorsal plates developed and reaching middle of adipose-fin base; median plates series continuous and complete; mid-ventral plates reaching adipose-fin origin; ventral plates series developed from posterior margin of pelvic-fin to caudal peduncle.

Head bones and plates shown in figure 3. Snout tip with large naked area without plates or odontodes. Nasal (n) almost triangular forming anterior medial nostril margin, contacting anteriorly with pre-nasals (pn) and posteriorly with frontals (f). Canal passing through nasal (n). Pre-nasals (pn) formed by several small triangular, rectangular and oval shaped plates. Dorsal surface of head also composed by parieto supraoccipital (soc), compound pterotic (cpt), frontal (f), prefrontal (pf) and sphenotic (sp). Two posterior small and triangular in shape rostral plates (pr1-pr2); Infraorbital plate series with five plates (io1-io5) present just above posterior rostrum series, with io3-io5 forming inferior orbital margin of eyes. Infraorbital plate series contains portion of laterosensory system. Preopercle (pop) elongated and rectangular, laterosensory canal passing through pop; preopercle present under io4, and upper cp1 and op. One subocular cheek plate (cp1) and operculum (op) form posterior lateral margin of head. Second subocular cheek plate (cp2) absent.

Color in life. Background color of dorsal and lateral surfaces of body brown. Saddles randomly distributed through body surface and more concentrated following lateral line from posterior margin of head to caudal fin, almost forming a well-defined dark stripe. Dorsal surface of head dark brown to almost black. Top of head at soc region completely dark. Four dark brown saddles on dorsal surface of trunk, first inconspicuous and below dorsalfin base; second below end of dorsal fin; third at adipose-fin origin; and fourth at end of caudal peduncle. Ventral surface light brown with few dark spots mainly on caudal peduncle and on lower caudal-fin unbranched ray. All fins with inconspicuous irregular and very poorly defined bands; dorsal and pectoral fins almost forming three bands; adipose and pelvic fins almost forming two bands; anal fin with one band and caudal fin almost forming four bands ( Fig. 5 ).

Color in alcohol. Same pattern described for living specimens, but with darker brown background color ( Figs. 4 and 6 ).

Sexual dimorphism. Mature males have three characters that are absent in females: (1) a conspicuous papilla just posterior urogenital opening; (2) a well-developed membrane along the dorsal portion of the unbranched pelvic-fin ray and slightly developed membranes in dorsal portion of the first four branched pelvic-fin rays; (3) the pelvic spine larger than pectoral spine. Additionally, males seem to reach larger size.

Etymology. The specific name “ canoeiro ” is from Portuguese language for those person or people who handle and/or build canoes. The name is a reference to the indigenous people Avá-Canoeiro, a once numerous and powerful indigenous people inhabiting the upper rio Tocantins valley. The Avá-Canoeiro are now restricted to some small villages due to a series of gradual and abrupt murders, diseases, and the lack of legal hunting territories ( Pequeno, 2005). Recently, the Avá-Canoeiro were known as the invisible people due to the fact that some of the few survivors used to live for more than a decade in caves to avoid contact with civilization, just leaving the caves at night to collect and chase food.

Distribution. Gymnotocinclus canoeiro is known from a single locality of a small tributary of the rio das Almas, which flows to the rio Paranã, rio Tocantins basin, Brazil (Fig. 7).

Ecological notes. The new species Gymnotocinclus canoeiro is found in a shallow and small clear water river, with rocky outcrops forming small waterfalls and substrates of rocks and sand, Fig. 8 . In several portions of the stream where the new species was found, the marginal vegetation was well preserved, and due to the large trees there is poor light penetration. The species was found at the bottom of the river associated with substrates of rocks and wood.

Figures

FIGURE 1. Maximum likelihood tree showing the relationship among species of the tribes Hypoptopomatini and Neoplecostomini. Numbers on branches of the phylogeny denote the bootstrap values higher that 50 %.

FIGURE 4. Gymnotocinclus canoeiro, MZUSP 121544, holotype, male, 51.5 mm SL, from Brazil, Goiás State, municipality of Cavalcante, unknown river, tributary of rio Paraná, rio Tocantins basin.

FIGURE 5. Live specimen of Gymnotocinclus canoeiro. Upper picture, paratype, LBP 19303, 49.3 mm SL. Photo: M. Taylor. Lower picture, holotype, MZUSP 121544, 51.5 mm SL.

FIGURE 6. Picture of a female specimen of Gymnotocinclus canoeiro, LBP 19469, paratype, 43.8 mm SL.

FIGURE 8. Type locality and habitat of Gymnotocinclus canoeiro. Specimens were collected associated with loose stones on the stream bed.