Cynolebias gorutuba, 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 : 334-338

Cynolebias gorutuba sp. n. Figs 3, 4, Table 2

Holotype.

UFRJ 6789, male, 88.8 mm SL; Brazil: Minas Gerais state: Janaúba municipality: temporary pool near road MG-401, floodplains of Gorutuba River, Verde Grande River drainage, São Francisco River basin, 15°47 ’57” S, 43°19 ’18” W, altitude about 525 m asl; W. J. E. M. Costa et al., 29 January 2010.

Paratypes.

UFRJ 9447, 1 female, 50.1 mm SL; UFRJ 9448, 2 males, 50.7-83.9 mm SL, 1 female, 42.0 mm SL (C&S); same area as holotype, 15o48 ’06” S, 43o19 ’14” W, altitude about 525 m asl; W. J. E. M. Costa, C. P. Bove & B. B. Costa, 16 January 2016.

Diagnosis.

Cynolebias gorutuba is similar to other species of CZC ( C. altus Costa, 2001, C. attenuatus Costa, 2001, C. gibbus Costa, 2001, C. leptocephalus Costa & Brasil, 1993, C. parietalis Costa, 2014, C. perforatus Costa & Brasil, 1991, C. oticus Costa, 2014), and distinguished from all other congeners, by the following character states: contact organs distributed on the inner surface of entire pectoral fin of males (vs. restricted to the dorsal portion of the fin), trunk scales extending over dorsal-fin base (vs. not extending), scales extending over one third or more of caudal-fin base (vs. about one fourth), and gill-rakers of first branchial arch bowed and with numerous denticles on its surface (vs. straight to slightly curved, usually without denticles, or one or two when present). Cynolebias gorutuba is distinguished from all other species of CZC by the presence of small round dark grey spots on dorsolateral portion of the trunk in females (vs. absence) and by the second proximal radial of dorsal fin between neural spines of 16th and 18th vertebrae in males (vs. between neural spines of 14th and 16th vertebrae); it is also distinguished from all other species of the Cynolebias zeta-clade, except C. oticus , by having more preopercular neuromasts (75-87 vs. 53-72). Cynolebias gorutuba also differs from C. oticus by having the anterior lateral profile of the body convex (vs. without a concavity on the head), otic and post-otic neuromast series separated (vs. united), more vertebrae (37-38 vs. 35-36), and absence of bars on the flank in males above 75 mm SL (vs. presence), and from C. parietalis and C. perforatus by fewer caudal-fin rays (30-31 vs. 33-35).

Description.

Morphometric data appear in Table 2. Body relatively deep, sub-cylindrical anteriorly, slightly deeper than wide, compressed posteriorly. Greatest body depth at vertical through pectoral-fin base. Dorsal and ventral profiles of head and trunk slightly convex, nearly straight on caudal peduncle. Head moderately wide, sub-triangular in lateral view. Jaws moderately long, teeth numerous, conical, irregularly arranged; outer teeth hypertrophied, inner teeth small and numerous, tip slightly curved inside mouth. Vomerine teeth absent. Gill-rakers on first branchial arch 3 + 9, gill-rakers gently bowed, with numerous denticles on distal region.

Dorsal and anal fins short, pointed, and with short filamentous rays in males, rounded and without filaments in females. Caudal fin rounded. Pectoral fin rounded, posterior margin reaching vertical urogenital papilla in males, through anus in females. Pelvic fin small, tip reaching base of 1st anal-fin ray; pelvic-fin bases medially separated by short interspace. Dorsal-fin origin at vertical through base of 6th anal-fin ray. Dorsal-fin rays 18-19 in males, 16-17 in females; anal-fin rays 21 in males, 20 in females; caudal-fin rays 30-31; pectoral-fin rays 14-15; pelvic-fin rays 6. In males, papillate contact organs on whole inner surface of pectoral fin. Second proximal radial of dorsal fin between neural spines of 16th and 18th vertebrae, first proximal radial of anal fin between pleural ribs of 14th and 15th vertebrae; total vertebrae 37-38.

Scales small, cycloid. Body and head entirely scaled, except anterior ventral surface of head. Body squamation extending over anterior third of caudal-fin base; few scales extending over middle portion of dorsal and anal fins; pectoral-fin fin base scaled. Scales irregularly arranged on frontal region and trunk. Longitudinal series of scales 38-41; transverse series of scales 16; scale rows around caudal peduncle 24. No contact organs on scales. Cephalic neuromasts: supraorbital 42-48; parietal 5-7; anterior rostral 3, posterior rostral 4; infraorbital 6 + 40-48; preorbital 3; otic 11-12, post-otic 9-12; supratemporal 3-5; median opercular 2, ventral opercular 4; preopercular plus mandibular 75-87; lateral mandibular 12-21, paramandibular 1.

Colouration.

Males. Flank and dorsum pale silver, scale margins pale yellow in larger fish, flank pale brown in smaller; three or four pale grey humeral spots. Venter white. Dorsal portion of head pale yellow to pale brown, with reddish brown dots on otic, post-otic and supra-temporal neuromasts; infraorbital and opercular regions pale silver with pale blue and pale golden iridescence. Jaws white. Iris yellow, with dark reddish brown bar through orbit centre. Dorsal and caudal fins light grey, basal portion pale yellow; white dots on whole dorsal fin and dorsal part or most caudal fin. Anal fin light grey, basal por tion pale yellow with white dots, filaments black. Pelvic fin pale yellow. Pectoral fin hyaline.

Females. Flank pale brown, with 11 or 12 pale almost inconspicuous grey bars; 2-4 dark brownish grey spots on humeral region and 4-6 dark grey round spots on dorsolateral portion of trunk. Dorsum pale brown, venter white. Head pale 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 fins of males and golden iridescence on opercular region of both sexes inconspicuous.

Distribution and conservation.

Cynolebias gorutuba is only known from pools in the floodplains of the Gorutuba River, within the town of Janaúba, Minas Gerais, Brazil. This area was first sampled in January 2002, in a vast undisturbed temporary pool with dense aquatic vegetation (15o48 ’06” S, 43o19 ’14” W, altitude about 525 m asl), when the single species found was Hypsolebias janaubensis (Costa, 2006). In January 2005, the area was visited again, but the whole original pool sampled three years before had been destroyed after expansion of an adjacent road. In a few remnant, small pools with very turbid water and no aquatic vegetation, 15 exemplars of H. janaubensis and four of C. gorutuba were found. In the third visit, January 2010, pools and typical vegetation had been completely extirped from the area studied before. Searching around this area, some shallow temporary pools were found about 300 m from the former pool (15 º47’57” S, 43 º19’18” W, altitude about 525 m a.s.l.). This new area, not visible in previous trips by being covered by dense high vegetation, was then open, with scarce grass, and restricted to shallow turbid water pools. A few specimens of H. janaubensis and one of C. gorutuba (the holotype) were found. More recently, the area was visited twice, in January and April 2017. No vestige of pools was found in areas previously studied, but within a dense Caatinga forest not distant from the first collecting site, a large temporary pool was found, with about 100 m2 and about 1 m deep. Hypsolebias janaubensis was common in all parts of the pool, a few exemplars of H. magnificus (Costa & Brasil, 1991) were found in shaded zones, but no specimen of Cynolebias gorutuba was collected. These field studies suggest that C. gorutuba is a rare species, possibly highly threatened with extinction.

Etymology.

The name gorutuba refers to the Gorutuba River floodplains, the type locality of C. gorutuba . The origin and original meaning of the name is uncertain; local people associate this name to a frog popular name, which needs confirmation.