Simpsonichthys semiocellatus

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 : 52-54

Simpsonichthys semiocellatus (Costa & Nielsen, 1997)

(Figs. 32-33)

Spectrolebias semiocellatus Costa & Nielsen, 1997: 259 ( type locality: temporary pool close to rio Formoso, rio Araguaia basin, Formoso do Araguaia , Estado do Tocantins, Brazil [11°47’31.6”S 49°45’54.7”W]; holotype: MZUSP 50654 ).

Material examined

Brazil: Estado do Tocantins, rio Araguaia drainage, rio Amazonas basin: MZUSP 50654 , holotype, male, 20.8 mm SL; MZUSP 50655 , 3 paratypes; UFRJ 3632 , 6 paratypes; UFRJ 3633 , 5 paratypes (c&s); UFRJ 3933 , 2; temporary pool close to rio Formoso, Formoso do Araguaia ; D. T. B. Nielsen, A. Carletto & A. C. de Luca, 4 Apr. 1996. UFRJ 6404 , 2; UFRJ 6407 , 12; 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. UFRJ 5266 , 14; ilha do Bananal ; D. Almeida & R. D’Arrigo, 20 Apr. 1999.

Diagnosis

Distinguished from the remaining species of the subgenus Spectrolebias by possessing F-patterned frontal squamation (vs. E-patterned), translucent body (vs. well-pigmented), and a black oval spot on posterior portion of distal edge of anal fin, with a light blue subdistal outline in males (never a similar color pattern). Distinguished from all congeners except S. reticulatus and S. costai 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 25.8 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 slender, compressed, greatest body depth at level of pelvic-fin base. Eye positioned on dorsal portion of head side. Snout blunt. Urogenital papilla cylindrical and long in males, pocket-shaped in females.

Tip of dorsal fin pointed in males, rounded to slightly pointed in females. Tip of anal fin rounded in both sexes. Long filamentous rays on tip of dorsal fin in males, tip reaching vertical through middle of caudal fin. Dorsal-fin rays unbranched. Caudal fin subtruncate. Pectoral fins elliptical. Posterior margin of each pectoral fin reaching vertical through base of 7th or 8th anal-fin ray in males, and base of 5th or 6th anal-fin ray in females. Tip of pelvic fin reaching base of 2nd or 3rd anal-fin ray. Pelvic-fin bases in close proximity. Dorsalfin origin on vertical through base of 8th or 9th anal-fin ray, between neural spines of vertebrae 10 and 11 in males and neural spines of vertebrae 12 and 13 in females. Anal-fin origin between pleural ribs of vertebrae 6 and 7 in males, and pleural ribs of vertebrae 8 and 10 in females. Dorsal-fin rays 15-17 in males, 13-16 in females; anal-fin rays 23-25 in males, 22-23 in females; caudal-fin rays 21-23; pectoral-fin rays 12-14; pelvic-fin rays 5-6.

Frontal squamation F-patterned; E-scales overlapping medially; no scale anterior to G-scale; supraorbital scales absent. Longitudinal series of scales 29-30; transverse series of scales 8-9; scale rows around caudal peduncle 12. Contact organs absent.

Cephalic neuromasts: supraorbital 13-14, parietal 3, anterior rostral 1, posterior rostral 1, infraorbital 2 + 18-19, preorbital 2-3, otic 2-3, post-otic 2-3, supratemporal 1, median opercular 1, ventral opercular 1, preopercular12-15, mandibular 9-10, lateral mandibular 5-6, paramandibular 1. One neuromast on center of each scale of lateral line. Two or three vertical rows with two neuromasts each on caudal-fin base.

Basihyal subtriangular, width about 40% of length; basihyal cartilage about 30% of total length of basihyal. Six branchiostegal rays. Second pharyngobranchial teeth 4-6. Gill-rakers on first branchial arch 2-3 + 11-12. Vomerine teeth absent. Dermosphenotic absent. Ventral process of posttemporal absent. Total vertebrae30-31.

Coloration

Males. Side of body brownish hyaline, with small bright greenish blue spots. Sides of head pale brown, opercular region metallic green. Iris pale yellow, with two reddish brown bars, anterior bar through center of eye, posterior bar adjacent to posterior margin of iris. Suborbital oblique dark gray bar continuous with anterior eye bar; small greenish blue spot on each side of suborbital bar. Dorsal and anal fins pale reddish brown, with small bright greenish blue spots on basal region; elongate black spot anteriorly bordered by bright blue line on posterior portion of distal margin of anal fin; brilliant blue line on distal margin of anal fin, anterior to black spot. Pectoral and caudal fins hyaline. Pelvic fin reddish brown.

Females. Side of body light brownish translucent, with 7-8 dark gray bars. Sides of head pale brown, opercular region pale metallic green. Iris pale yellow, with two brown bars as described for males. Fins hyaline; gray spot on posterior portion of distal margin of anal fin.

Distribution

Rio Araguaia basin, central Brazil (Fig. 1).

Habitat

Temporary pools in the Mata Ciliar, transition area between the Cerrado and the Amazonian forest.