Simpsonichthys costai

Wilson J. E. M. Costa, 2007, Taxonomic revision of the seasonal South American killifish genus Simpsonichthys (Teleostei: Cyprinodontiformes: Aplocheiloidei: Rivulidae)., Zootaxa 1669, pp. 1-134 : 46-48

Simpsonichthys costai (Lazara, 1991)

(Figs. 28-29)

Cynolebias costai Lazara, 1991: 144 ( type locality: temporary pool in Aruana, Goias [ Aruana , Estado de Goias ] , Brazil [14°57’0.5”S 51°1’23.7”W, altitude 243 m]; holotype: MZUSP 38790 ).

Material examined

Brazil: Estado de Goiás, rio Amazonas basin, rio Araguaia drainage: UFRJ 6422 , 4; swamp close to the road GO-173, Aruana , 14°49’10.0”S 50°58’36.4”W, altitude 255 m; W. J. E. M. Costa, C. P. Bove, J. Paz & A. Oliveira, 13 Apr. 2006. Estado de Mato Grosso: UFRJ 163 , 4; UFRJ 162 , 2 (c&s); UFRJ 1157 , 4; temporary lagoon close to rio das Mortes, road to Cocalinhos ; G. C. Brasil, M. T. C. Lacerda, P. Araujo & G. Coelho, Jan. 1988. UFRJ 3549 , 31; UFRJ 3350 , 4 (c&s); MNHN 1997-0045 , 8; USNM 343822 , 6; temporary lagoon 9 km E from rio das Mortes, road to Cocalinho ; W. J. E. M. Costa, G. C. Brasil, M. I. Landim & C. R. Moreira, 16 Feb. 1996. Estado do Tocantins: UFRJ 5050 , 5; ilha do Bananal ; G. Brasil, R. D’Arrigo & D. Almeida, Apr. 1999. UFRJ 3560 , 8; UFRJ 3561 , 3 (c&s); temporary pool near Barreira do Piqui ; 15 Feb. 1996. UFRJ 3794 , 4; Formoso do Araguaia ; D. T. B. Nielsen, A. Carletto & A. de Luca, 6 Apr. 1996. UFRJ 6408 , 2; UFRJ 6439 , 4; idem , 11°47’31.6”S 49°45’54.7”W; W. J. E. M. Costa, C. P. Bove, J. Paz & A. Oliveira, 15 Apr. 2006. Rio Tocantins drainage: Estado do Tocantins: UFRJ 3798 , 10; Brejinho de Nazare ; D. T. B. Nielsen, A. Carletto & A. de Luca, 5 Apr. 1996; UFRJ 6440 , 2; UFRJ 6441 , 7; UFRJ 6442 , 4 (c&s); temporary lagoon in rio Canabrava floodplains, road TO-373 , 12°29’46.3”S 49°0’50.7”W, altitude 292 m; W. J. E. M. Costa, C. P. Bove, J. Paz & A. Oliveira, 16 Apr. 2006.

Diagnosis

Distinguished from all other congeners by possessing a unique color pattern in males, consisting of black flanks and black dorsal and anal fins, contrasting with a hyaline caudal fin. Distinguished from all congeners except S. reticulatus and S. semiocellatus in having two or three vertical rows with two neuromasts each on caudal-fin base (vs. only two neuromasts on caudal-fin base).

Description

Morphometric data appear in Table 3. Largest specimen examined 19.6 mm SL. Dorsal profile convex from snout to end of dorsal-fin base nearly straight on caudal peduncle. Ventral profile gently convex from lower jaw to end of anal-fin base, nearly straight on caudal peduncle. Body moderately deep, compressed, greatest body depth at level of pelvic-fin base. Eye positioned on dorsal portion of side of head. Snout blunt. Urogenital papilla cylindrical and short in males, pocket-shaped in females.

Dorsal and anal fins rounded in both sexes; fin fan-shaped in males; filamentous rays absent. Dorsal-fin rays unbranched. Caudal fin rounded. Pectoral fins elliptical. Posterior margin of pectoral fins reaching vertical through base of 6th or 7th anal-fin ray in males, and through base of 3rd anal-fin ray in females. Tip of each pelvic fin reaching base of 3rd or 4th anal-fin ray in males, and between urogenital papilla and anal-fin origin in females. Pelvic-fin bases in close proximity. Dorsal-fin origin on vertical between base of 4th and 6 th anal-fin rays, between neural spines of vertebrae 7 and 9 in males, and vertebrae 9 and 10 in females. Anal-fin origin between pleural ribs of vertebrae 5 and 7 in males, and vertebrae 7 and 8 in females. Dorsalfin rays 21-23 in males, 15-19 in females; anal-fin rays 23-26 in males, 19-23 in females; caudal-fin rays 21-23; pectoral-fin rays 12-13; pelvic-fin rays 6.

Frontal squamation E-patterned; E-scales overlapping medially; no scale anterior to G-scale; supraorbital scales absent. Longitudinal series of scales 22-24; transverse series of scales 9; scale rows around caudal peduncle 12. Contact organs of flank absent. Minute contact organs on two uppermost pectoral-fin rays in males.

Cephalic neuromasts: supraorbital 10-12, parietal 3-4, anterior rostral 1, posterior rostral 1, infraorbital 1 + 17-20, preorbital 2-3, otic 2, post-otic 2-3, supratemporal 1, median opercular 1, ventral opercular 1, preopercular11-14, mandibular 7-8, lateral mandibular 3-5, paramandibular 1. One neuromast on center of each scale of lateral line. Two or three vertical rows of two neuromasts on caudal-fin base.

Basihyal subtriangular, width about 40% of length; basihyal cartilage about 25% of total length of basihyal. Six branchiostegal rays. Second pharyngobranchial teeth absent. Gill-rakers on first branchial arch 2 + 8. Vomerine teeth absent. Dermosphenotic absent. Ventral process of posttemporal absent. Total vertebrae 25-26.

Coloration

Males. Sides of body dark brown to black, with blue dots on dorsal portion. Head dark brown, with two black bars on suborbital region and adjacent to posterior edge of eye, respectively, and five vertical rows of blue dots, two below eye and three on opercular region. Iris dark brown, with two narrow blue bars. Dorsal and anal fins dark brown to black, with row of blue dots on basal region and narrow subdistal blue stripe; melanophores distinctively more concentrated on posterior portion of fins. Caudal fin hyaline, with narrow light blue posterior margin, and sometimes with faint blue dots on middle. Pectoral fins hyaline. Pelvic fins black with blue dot.

Females. Sides of body light brown, with brown chromatophores irregularly arranged, forming nine or ten ill-defined bars. Head pale brown, opercular region greenish blue, with two black bars, one on suborbital region and another adjacent to posterior edge of eye. Iris yellow, with dark gray bar through center of eye. Fins hyaline; small dark brown spots on dorsal and anal fins.

Distribution

Araguaia and Tocantins river basins, Estados de Goiás, Tocantins and Mato Grosso, central Brazil (Fig. 4).

Habitat

Temporary pools in the Mata Ciliar, transitionary vegetation between the Cerrado and the Amazonian forest.