Simpsonichthys reticulatus

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 : 42-46

Simpsonichthys reticulatus Costa & Nielsen, 2003

(Figs. 26-27)

Simpsonichthys reticulatus Costa & Nielsen, 2003: 120 ( type locality: Altamira [temporary pool in island, rio Xingu, in front of Altamira] , Estado do Pará, Brazil, about 3°15’S 52°20’W [3°13’34.6”S 52°12’26.1”W, altitude 39m]; holotype: MCP 34090 ).

Material examined

Brazil: Estado do Pará: Municipio de Altamira, rio Xingu drainage, rio Amazonas basin : MCP 34090 , holotype, male, 20.1 mm SL; UFRJ 5871 , 2 paratypes; UFRJ 5872 , 2 paratypes (c&s); near the city of Altamira, about 3º15’S 52º20’W; J. L. Diniz, 5 May 2003.

Diagnosis

Distinguished from all other congeners by possessing two unique color patterns in males: sides of body greenish blue, with dark red crimson pigmentation concentrated on exposed margin of each scale, producing a reticulate color pattern, and a black and bluish white spot on anterior portion of dorsal fin.

Description

Morphometric data appear in Table 3. Largest specimen examined 20.1 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 on vertical just anterior to dorsal-fin origin. Eye positioned on dorsal portion of head. Snout blunt. Urogenital papilla cylindrical and short in males, pocket-shaped in females.

Tip of dorsal fin rounded in both sexes, posterior portion fan-shaped in males; short filamentous rays on dorsal-fin tip in males; tip of anal fin gently pointed in males, rounded in females. Dorsal-fin rays unbranched. Caudal fin rounded. Pectoral fins elliptical. Posterior margin of each pectoral fin reaching vertical through base of 8th anal-fin ray in males and vertical through anal-fin origin in females. Tip of each pelvic fin reaching base of 4th anal-fin ray in males, and base of 2nd anal-fin ray in females. Pelvic-fin bases in close proximity. Dorsal-fin origin on vertical anterior to anal-fin origin in males, anal-fin origin on vertical between base of 3rd and 6th dorsal-fin rays; dorsal-fin origin on vertical through base of 2nd anal-fin ray in females; dorsal-fin origin between neural spines of 4th and 5th vertebrae in males, and between neural spines of 8th and 9th vertebrae in females. Dorsal-fin origin on vertical through base of 2nd anal-fin ray in females. Anal-fin origin between pleural ribs of 6th and 7th vertebrae in males, and 7th and 8th vertebrae in females. Dorsal-fin rays 23-25 in males, 13-15 in females; anal-fin rays 21-22 in males, 18 in females; caudal-fin rays 22; pectoral-fin rays 14; pelvic-fin rays 5.

Frontal squamation E-patterned; E-scales overlapping medially; no scale anterior to G-scale; supraorbital scales absent. Longitudinal series of scales 23; transverse series of scales 8; scale rows around caudal peduncle12. Contact organs absent from flanks. Papillate contact organs on inner surface of two dorsalmost pectoral fin rays in males.

Cephalic neuromasts: supraorbital 14, parietal 3, anterior rostral 1, posterior rostral 1, infraorbital 1 + 19, preorbital 2, otic 2, post-otic 3, supratemporal 1, median opercular 1, ventral opercular 1, preopercular 12, mandibular 8, lateral mandibular 3-5, paramandibular 1. One neuromast on center of each scale of lateral line. Four neuromasts on caudal-fin base.

Basihyal subtriangular, width about 55% of length; basihyal cartilage about 35% of total length of basihyal. Six branchiostegal rays. Second pharyngobranchial teeth 1-2. Gill-rakers on first branchial arch 2 + 10. Vomerine teeth absent. Dermosphenotic absent. Ventral process of posttemporal absent. Total vertebrae 25.

Coloration

Males. Sides of body iridescent light greenish blue, dark red crimson on scale margins. Sides of head iridescent light greenish blue, with two black bars on suborbital region and adjacent to posterior edge of eye, respectively. Iris greenish blue, with black bar. Unpaired fins and pelvic fins brownish red, with small round blue spots; anterior edge of dorsal fin with marginal elongate black spot and submarginal bluish white spot; posterior margin of caudal fin light blue. Pectoral fins hyaline, ventral margin light blue.

Females. Sides of body pale yellowish brown, with 9 faint gray bars. Sides of head pale yellowish brown, with pale green iridescence on opercular region, and two black bars, one on suborbital region and another adjacent to posterior edge of eye. Iris yellow, with black bar. Unpaired fins hyaline, with dark grey spots. Pectoral and pelvic fins hyaline.

Distribution

Lower rio Xingu floodplains, Estado do Pará, northern Brazil (Fig. 4).

Habitat

Temporary pools in the Amazonian forest.