Simpsonichthys nigromaculatus

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 : 31-33

Simpsonichthys nigromaculatus Costa, 2007

(Figs. 17-18)

Simpsonichthys nigromaculatus Costa, 2007: 200 (original description; type locality: temporary swamp, floodplains of rio da Prata, rio Apore drainage, upper rio Parana basin, near the road GO-050, Chapadao do Ceu , 18º33’2.0”S 52º37’43.1”W, altitude 778 m, Estado de Goiás, Brazil; holotype: UFRJ 6467 ).

Material examined

Brazil: Estado de Goiás, rio Paranaíba drainage, rio Paraná basin: UFRJ 6467 , holotype, male, 24.0 mm SL; UFRJ 6468 , 5 paratypes; UFRJ 6469 , 3 paratypes (c&s); UFRJ 6473 , 2 paratypes; temporary swamp, floodplains of rio da Prata, rio Apore drainage, upper rio Parana basin, near the road GO-050, Chapadao do Ceu , 18º33’2.0”S 52º37’43.1”W, altitude 778 m; W. J. E. M. Costa, C. P. Bove & B. B. Costa, 14 January 2007.

Diagnosis

Distinguished from all congeners in having 2-4 black spots on posterobasal portion of dorsal fin in males. It is also distinguished from all other species of Simpsonichthys by the unique combination of the following features: pelvic fin and pelvic girdle absent (vs. present), 24-25 vertebrae (vs. 26-31), second pharyngobranchial teeth absent (vs. present), ventral process of posttemporal absent (vs. long), 17-20 anal-fin rays in females (vs. 20-22), body depth 33.5-36.0 % SL in males (vs. 28.8-32.5 % SL), maximum adult size 25.6 mm SL (vs. about 40.0 mm SL), bright blue bars on flank in males much narrower than interspace (vs. approximately as wide as red bars), five alternating bright blue and pink to red bars on head side in males (vs. never a similar color pattern), short postorbital pink stripe connecting pink bars 2 and 3 (vs. stripe absent), anterior and posterior margins of iris bright blue (vs. yellow), dark gray band bordered by a bright blue line on distal margin of dorsal and anal fins, and posterior margin of caudal fin in males (vs. never a similar color pattern), ground color of dorsal and anal fins orange in males (vs. other colors, such as dark red, dark gray, or black), bars on unpaired fins absent in males (vs. bars present), and yellow dots on the caudal fin in males (vs. dots absent).

Description

Morphometric data appear in Table 2. Largest specimen examined 25.6 mm SL. Dorsal profile convex from snout to end of dorsal-fin base, approximately 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 in vertical just anterior to anal-fin origin. Eye positioned on dorsal portion of of each side of head. Snout blunt. Urogenital papilla cylindrical and short in males, pocket-shaped in females.

Tip of dorsal and anal fins gently pointed in males, rounded in females; filamentous rays absent. Dorsalfin rays unbranched. Caudal fin round. Pectoral fins elliptical. Posterior margin of each pectoral fin reaching vertical between base of 3rd and 5th anal-fin rays in males, and between anus and urogenital papilla in females.

Pelvic fins and pelvic girdle absent. Dorsal-fin origin on vertical between base of 2nd and 5th anal-fin ray in males, between base of 2nd and 3rd anal-fin ray in females; dorsal-fin origin between neural spines of vertebrae 9 and 10 in males, and vertebrae 9 and 11 in females. Anal-fin origin between pleural ribs of vertebrae 7 and 8 in males, and vertebrae 8 and 10 in females. Dorsal-fin rays 16-19 in males, 15-17 in females; anal-fin rays 19-22 in males, 17-19 in females; caudal-fin rays 25-26; pectoral-fin rays 12-13.

Frontal squamation E-patterned; E-scales medially overlapping; no scale anterior to G-scale. One or no supraorbital scale. Longitudinal series of scales 24-26; transverse series of scales 9; scale rows around caudal peduncle 12. Minute contact organ on each scale of anteroventral portion of lateral surface of body in males. Minute papillate contact organs on medial surface of first two pectoral-fin rays in males.

Cephalic neuromasts: supraorbital 2 + 7, parietal 1, anterior rostral 1, posterior rostral 1, infraorbital 1 + 12-14, preorbital 2, otic 1, post-otic 1, supratemporal 1, median opercular 1, ventral opercular 2, preopercular 10-14, mandibular 5-6, lateral mandibular 2, paramandibular 1. One neuromast on center of each scale of lateral line. Two neuromasts on caudal-fin base.

Basihyal subtriangular, width about 50 % of length; basihyal cartilage about 15 % 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 24-25.

Coloration

Males. Sides of body pink with 10-11 narrow light blue bars. Five narrow alternating light blue and pink bars on side of head; short postorbital pink stripe connecting pink bars 2 and 3. Iris light yellow, posterior and anterior margins metallic blue; brownish red bar through center of eye. Proximal portion of dorsal and anal fins orangish yellow, distal portion dark gray, distal and proximal portions separated by bright blue horizontal line; faint small reddish gray spots on anterior portion of dorsal-fin base and entire anal-fin base; 2-4 black spots on posterior portion of dorsal-fin base. Caudal fin orangish yellow with light yellow dots; broad dark gray margin and narrow, zigzag bright blue submarginal line. Pectoral fins grayish hyaline.

Females. Sides of head and body light yellowish brown, with 9-10 dark gray bars; one or two rounded black blotches on anterocentral portion of flank. Iris yellow, anterior and posterior borders bright blue, with dark brown bar through center of eye. Unpaired fins hyaline with rounded dark gray spots, larger and transversely elongated close to base of dorsal and anal fins. Pectoral fin grayish hyaline.

Distribution

Rio da Prata floodplains, rio Aporé drainage, upper rio Paraná basin, Estado de Goiás, central Brazil (Fig. 1).

Habitat

Temporary shallow canals in Campo Úmido, Cerrado.