Plesiolebias canabravensis Costa & Nielsen

Costa, Wilson J. E. M., 2007, Taxonomy of the plesiolebiasine killifish genera Pituna, Plesiolebias and Maratecoara (Teleostei: Cyprinodontiformes: Rivulidae), with descriptions of nine new species, Zootaxa 1410, pp. 1-41 : 29-31

Plesiolebias canabravensis Costa & Nielsen , new species

( Figs. 20–21 )

Plesiolebias aruana non P. aruana (Lazara) ; Costa, 1998a: 325 (misidentification).

Material examined. Holotype. UFRJ 6424 (male, 17.6 mm SL); Brazil: Estado do Tocantins: temporary lagoon in left rio Canabrava floodplains, rio Santa Tereza drainage, rio Tocantins basin, road TO-373, between Alvorada and Peixe, 12º29’46.3”S, 49º0’50.7”W, altitude 292 m; W. J. E. M. Costa, C. P. Bove, J. Paz & A. Oliveira, 16 April 2006.

Paratypes. Brazil: Estado do Tocantins: rio Tocantins basin: UFRJ 6425 (10 males, 15.5–19.5 mm SL, 10 females, 15.9–18.3 mm SL); MCP 40500 (3 males, 16.0– 17.2 mm SL, 3 females, 16.1–17.4 mm SL); collected with holotype. UFRJ 3801 (24 males, 13.2–15.2 mm SL, 31 females, 11.6–16.0 mm SL); UFRJ 4006 (4 males, 14.7–16.7 mm SL, 2 females, 13.5–15.2 mm SL [c&s]); same locality; D. T. B. Nielsen, A. Carletto & A. de Luca, 4 April 1996.

Diagnosis. Distinguished from all its congeners by the combined set of the following morphological features: no filamentous ray on each pelvic fin in males (vs. filamentous ray present); pelvic-fin rays 7 (vs. 8–9); eye bright green in males (vs. yellow); flank without oblique black bars in males (vs. black bars present); red stripe on anterior portion of flanks anteriorly reaching orbit in males (vs. red stripe not reaching orbit or absent); basal portion of dorsal fin with transverse rows of dark red and white spots in males (vs. red); no distinctive black spot on posterior portion of anal fin in males (vs. black spot present); dorsal-fin origin at vertical through base of 7th or 8th anal-fin rays (vs. in vertical between base of 5th or 6th anal-fin ray); oblique rows of dark brown dots restricted to the median portion of flanks, sometimes absent (vs. dark brown dots and elongated spots on whole flanks); anal-fin base with white elongate spots in males (vs. long curved bars, ventral tips anteriorly directed, often converging to a point on anterior margin of fin); 1 + 27–31 + 1 infra-orbital neuromasts (vs. 1 + 16–22 + 1).

Description. Morphometric data appear in Table 4. Largest male examined 19.5 mm SL, largest female examined 18.3 mm SL. Dorsal profile gently convex from snout to end of dorsal-fin base, approximately straight on caudal peduncle. Ventral profile weakly convex from lower jaw to end of anal-fin base, nearly straight on caudal peduncle. Body slender, compressed. Greatest body depth at level of pelvic-fin base. Jaws short, snout blunt.

Tip of dorsal and anal fins rounded, without filaments. Caudal fin rounded. Pectoral fins elliptical, posterior margin reaching vertical between urogenital papilla and base of 2nd anal-fin ray in males, between anus and base 3rd anal-fin ray in females. Pelvic fins slightly pointed, without filaments; tip of each pelvic fin reaching base of 4th anal-fin ray in males, reaching anal-fin origin in females. Pelvic-fin bases in close proximity medially. Dorsal-fin origin on vertical between base of 7th and 8th anal-fin rays, and between neural spines of 13th and 14th vertebrae. Anal-fin origin between pleural ribs of 9th and 10th vertebrae. Dorsal-fin rays 9–10; anal-fin rays 14–16; caudal-fin rays 22–24; pectoral-fin rays 11–12; pelvic-fin rays 7.

Scales large, cycloid. Body and head entirely scaled, except anterior ventral surface of head. Body squamation extending over anterior 25 % of caudal fin; no scales on dorsal and anal-fin bases. Frontal squamation G-patterned; E-scales overlapping medially; scales arranged in regular transverse pattern. Two supraorbital scales. Longitudinal series of scales 23–24; transverse series of scales 7; scale rows around caudal peduncle 12. Three minute contact organs on posterior margin of each scale of ventral portion of flank in males.

Cephalic neuromasts: supraorbital 6 + 7, parietal 1, anterior rostral 1, posterior rostral 1, infraorbital 1 + 27–31 + 1, preorbital 4, otic 1, post-otic 2, supratemporal 1, median opercular 1, ventral opercular 1, preopercular 2 + 10, mandibular 5 + 2, lateral mandibular 3. One neuromast on center of each scale of lateral line of trunk. Two neuromasts on caudal-fin base.

Basihyal narrow, longest width about 25 % of length; basihyal cartilage about 20 % of basihyal length. Five branchiostegal rays. Six or seven teeth on second pharyngobranchial. Gill-rakers of first branchial arch 1 + 7. Vomerine teeth absent. Ventral process of posttemporal absent. Total vertebrae 24–25.

Coloration. Males: Sides of body gray, with narrow, oblique orangish red bars, alternating with oblique series of small greenish blue spots. Broad orangish red stripe between dorsoposterior margin of orbit and point in vertical through pelvic-fin base. Dorsum gray. Venter white. Sides of head and jaws gray, opercular region metallic green. Iris bright green, with dark gray bar through center of eye. Dorsal fin hyaline, with alternating transverse rows of dark red and light blue spots on basal two thirds of fin. Anal fin dark gray, with blue iridescence, with 5 white elongate spots on basal region, separated by dark reddish gray interspace. Caudal fin gray, with transverse rows of small dark red spots on basal half of fin. Pectoral fins hyaline. Pelvic fins gray, with dark red spot and small white spot on basal portion of fin.

Females: Sides of body light brownish gray, with oblique rows of dark brown dots on ventral portion of middle flank, sometimes inconspicuous. Dorsum light brownish gray. Venter white. Sides of head and jaws gray, pale greenish yellow on opercle. Iris pale yellow, with gray bar through center of eye. Fins hyaline.

Etymology. The name canabravensis refers to the occurrence of P. canabravensis in the rio Canabrava floodplains.

Distribution and habitat. Plesiolebias canabravensis is known only from a seasonal lagoon near rio Canabrava, rio Tocantins basin ( Fig. 13 ), in a savannah region.

Figures

FIGURE 13. Geographic distribution of genus Plesiolebias. Triangle = P. aruana; inverted triangle = P. altamira; star = P. filamentosus; dots = P. aruana and P. fragilis; square = P. canabravensis; six-tip asterisk = P. lacerdai; eight-tip asterisk = P. glaucopterus; lozenge = P. xavantei. One symbol may represent more than one collecting site.

FIGURE 20. Plesiolebias canabravensis, male holotype, 17.6 mm SL, UFRJ 6424 (some hours after collection); Brazil: Tocantins: rio Canabrava floodplains. Photo by W. J. E. M. Costa.

FIGURE 21. Plesiolebias canabravensis, female paratype, 16.7 mm SL, UFRJ 6425 (some hours after collection); Brazil: Tocantins: rio Canabrava floodplains. Photo by W. J. E. M. Costa.