Cynolebias elegans, Costa, Wilson J. E. M., 2017

Costa, Wilson J. E. M., 2017, Description of two endangered new seasonal killifish species of the genus Cynolebias from the Sao Francisco River basin, Brazilian Caatinga (Cyprinodontiformes, Aplocheilidae), Zoosystematics and Evolution 93 (2), pp. 333-341 : 333-334

Cynolebias elegans sp. n. Figs 1, 2, Table 1

Holotype.

UFRJ 9431, male, 36.1 mm SL; Brazil: Bahia state: Pindaí municipality: temporary pool close to road BR-122, about 8 km S of the village of Pindaí, Mata Veado Creek floodplains, Verde Grande River drainage, São Francisco River basin, 14o33 ’39” S 42o42 ’10” W, altitude about 630 m asl; W. J. E. M. Costa and C. P. Bove, 15 January 2005.

Paratypes.

UFRJ 9350, 1 male, 37.6 mm SL, 1 female, 35.1 mm SL; UFRJ 6890, 2 males, 36.8-37.9 mm SL, 1 female, 36.9 mm SL (C&S); collected with holotype.

Diagnosis.

Cynolebias elegans is similar to other species of the C. gilbertoi group ( C. gilbertoi Costa, 1998 and C. ochraceus Costa, 2014) and distinguished from all other congeners of the subgenus Cynolebias , by the following character states: numerous vomerine teeth (9-16 vs. 1-4, when teeth are present), 7-8 gill-rakers on the ventral part of the first branchial arch (vs. 9-12), highest body depth at vertical just anterior to pelvic-fin base (vs. through pectoral-fin base), and presence of light dots on flank arranged in vertical groups (vs. light dots when present not arranged in vertical groups). Cynolebias elegans differs from C. gilbertoi and C. ochraceus by having long dorsal and anal fins in males, their extremities excluding filaments posteriorly reaching caudal-fin base (vs. reaching caudal peduncle), greater pre-pelvic length in males (52.2-53.9 % SL, vs. 48.5-49.9 % SL in C. gilbertoi and 48.9-50.5 % SL in C. ochraceus ), and first proximal radial of the anal fin between neural spines of 9th and 10th vertebrae in males, and between neural spines of 11th and 12th vertebrae in females (vs. between neural spines of 11th and 13th vertebrae in males, and between neural spines of 12th and 14th vertebrae in females). Cynolebias elegans is also distinguished from C. gilbertoi by having larger head (31.3-34.2 % SL in males, 32.1-33.4 % in females, vs. 27.9-30.3 % SL in males, 29.0-31.1 % in females) and smaller eye (25.5-29.1 % of head length in males, 27.3-29.9 % in females, vs. 30.0-31.0 % of head length in males, 31.5-34.2 % in females); and from C. ochraceus by having fewer vertebrae (31-32 vs. 33-34), more slender body (body depth 32.5-34.5 % SL, vs. 35.0-37.8 % SL), and flank light purplish brown in males (vs. light yellow ochre). The largest specimen examined was 37.9 mm SL, suggesting that C. elegans is the smallest species of the genus.

Description.

Morphometric data appear in Table 1. Body relatively deep, compressed. Greatest body depth at vertical just anterior to pelvic-fin base. Dorsal and ventral profiles of head and trunk slightly convex, approximately straight on caudal peduncle. Head moderately wide, sub-triangular in lateral view. Jaws short, teeth numerous, conical, irregularly arranged; outer teeth hypertrophied, inner teeth small and numerous. Vomerine teeth 13. Gill-rakers on first branchial arch 2 + 7, gill-rakers short, straight, without denticles.

Dorsal and anal fins relatively long and pointed in males, posteriorly reaching caudal-fin base when excluding filaments, rounded in females; in males, short filamentous rays on dorsal-fin extremity, long filamentous rays on anal-fin extremity, posteriorly reaching middle portion of caudal fin; no filamentous rays in females. Caudal fin rounded. Pectoral fin rounded, posterior margin reaching vertical between base of 5th and 6th anal-fin rays in males, reaching base of 3rd anal-fin ray in females. Pelvic fin small, tip reaching between base of 3rd and 4th anal-fin rays in males, reaching base of 2nd anal-fin ray in females; pelvic-fin bases medially separated by short interspace. Dorsal-fin origin at vertical between base of 3rd and 5th anal-fin rays in males, through base of 3rd anal-fin ray in females. Dorsal-fin rays 17-18 in males, 16-17 in females; anal-fin rays 18-20 in males, 18-19 in females; caudal-fin rays 28-29; pectoral-fin rays 12; pelvic-fin rays 6. In males, papillate contact organs on inner surface of three or four dorsal-most pectoral-fin rays. Second proximal radial of dorsal fin between neural spines of 12th and 13th vertebrae in males, between neural spines of 13th and 14th vertebrae in females; first proximal radial of anal fin between pleural ribs of 9th and 10th vertebrae in males, between pleural ribs of 11th and 12th vertebrae in females; total vertebrae 31-32.

Scales small, cycloid. Body and head entirely scaled, except anterior ventral surface of head. Body squamation extending over anterior 25 % of caudal-fin base; no scales on dorsal, anal and pectoral-fin bases. Scales irregularly arranged on frontal region and trunk. Longitudinal series of scales 34-36; transverse series of scales 13-14; scale rows around caudal peduncle 22. No contact organs on scales. Cephalic neuromasts: supraorbital 25-30; parietal 4; anterior rostral 2, posterior rostral 2; infraorbital 5 + 31-33; preorbital 3-4; otic 5, post-otic 7-8; supratemporal 2-3; median opercular 1-3, ventral opercular 5-8; pre-opercular plus mandibular 45-47; lateral mandibular 3-4 + 8-9, paramandibular 1.

Colouration in life.

Males. Flank light purplish brown, with 10 or 11 lighter pale golden brown bars and minute white dots arranged in vertical zones. Dorsum pale purplish brown, venter white. Head pale purplish brown, with dark grey dots on otic, post-otic and supra-temporal neuromasts; golden iridescence on opercular region. Iris yellow, with dark brown bar through orbit centre. Dorsal and caudal fin light grey, with white dots. Anal fin pale pink, basal portion with white dots; filaments pale pink. Pelvic fin pale pink. Pectoral fin hyaline.

Females. Flank light purplish brown, with 11 or 12 pale golden brown bars; 1-2 black spots on centre of flank. Dorsum pale purplish brown, venter white. Head pale purplish brown, with dark grey dots on otic, post-otic and supra-temporal neuromasts; pale golden iridescence on opercular region. Iris yellow, with dark brown bar through orbit centre. Fins hyaline.

Colouration in alcohol.

Similar to colouration in life, dark marks still distinct, but paler; white dots on trunk and fins and pink pigmentation on anal and pelvic fins of males, and golden iridescence on opercular region of both sexes inconspicuous.

Distribution and conservation.

Cynolebias elegans is known from a single locality, a temporary pool in the Verde Grande River drainage, Bahia, Brazil (14o33 ’39” S 42o42 ’10” W, altitude about 630 m asl). This pool was first explored in January 2002, when the only species found was Hypsolebias mediopapillatus (Costa, 2006). At that time, the pool was densely covered by aquatic vegetation and marginal spiny bushes, making it difficult to access the pool, except in its portion closer to the road. During a second visit, January 2005, cattle were introduced in the area and original vegetation was substituted by grass. Both C. oticus and H. mediopapillatus were abundant, but only six specimens of C. elegans (the type series) and one of Hypsolebias fulminantis (Costa & Brasil, 1993) were collected. In several other pools found along the road, many specimens of C. oticus , C. leptocephalus and H. mediopapillatus were found, but both C. elegans and H. fulminantis were absent. The type locality and neighbouring pools were sampled again in May 2009 and January 2010, but no specimen of C. elegans was found. New visits occurred in January and May 2017, but the type locality was now highly modified into a permanent pool containing only small not identified Characiformes . These field records indicate that C. elegans is a rare, critically endangered species, if not already extinct.

Etymology.

From the Latin elegans (elegant, fine), an allusion to the distinctive general appearance of the new species, with males combing relatively slender body with long unpaired fins.