Spectrolebias brousseaui, Nielsen, 2013

Nielsen, Dalton Tavares Bressane, 2013, Spectrolebias brousseaui (Cyprinodontiformes: Rivulidae: Cynolebiatinae), a new annual fish from the upper río Mamoré basin, Bolivia, Neotropical Ichthyology 11 (1), pp. 81-84 : 82-84

Spectrolebias brousseaui , new species

Figs. 1-2

Holotype. MNKP 10162 , male, 28.4 mm SL, Bolivia, Departamento Santa Cruz, 47.5 km north of San José dos Chiquitos, pool near of río San Pablo , tributary of río Mamoré , 17°25’31”S 60°40’44”W, 19 Apr 2008, R. D. Brousseau.

Paratypes. MZUSP 109219 , 1 male and 2 female, 25.3-28.7 mm SL, collected with the holotype. MNKP 10163 , 3 females, 26.7- 34.6 mm SL collected with the holotype .

Diagnosis. The new species differs from the remaining representatives of the genus Spectrolebias , by the unique color pattern of males, viz., anterior third of body light brown, posterior two-thirds of body dark blue, almost black in the dorsal region, with rows of bright blue spots, relatively large size, with about half the diameter of the pupil. Spectrolebias brousseaui distinguished from all congeners except S. filamentosus , by having pelvic-fin bases separated by an interspace (vs. pelvic-fin bases in contact), long filamentous rays on the tip of dorsal and anal fins in males (vs. absence of filaments, or presents only on dorsal fin in S. semiocellatus and S. inaequipinnatus , or presents only on anal fin in S. chacoensis ), and presence (vs. absence) of contact organs on scales of flank in males.

Additionally males of Simpsonichthys brousseaui differ from males of S. filamentosus by the color pattern of males, viz., anterior third of body light brown, posterior two-thirds of body dark blue, almost black in the dorsal region, with rows of bright blue spots (vs. overall color pattern in males reddish, with white spots), developed urogenital papillae in males and females (vs. poorly developed urogenital papillae in both sexes), and by the longer dorsal-fin base (33.8-36.2% SL vs. 29.0-31.1%), longer head (27.5-28.8% SL vs. 25.8-26.7%), lower head (88.6- 91.4% HL vs. 96.2-107.6%), narrower head (55.6-54.6% SL vs. 63.4-70.7%), greater number of dorsal-fin rays (21-22 vs. 16-19), and fewer scales in transverse series (8-9 vs. 11-12).

Females of Simpsonichthys brousseaui differ from females of S. filamentosus by their lower body (30.6-33.3% SL vs. 34.7- 36.8%), lower caudal peduncle (11.9-12.6% SL vs. 13.0-15.0%), shorter anal-fin base (21.9-27.8% SL vs. 28.8-31.4%), longer head (29.2-30.6% HL vs. 27.3-28.7%), lower head (78.1-91.6% HL vs. 93.4-107.2%), smallerheadwidth(53.0-59.6% HL vs. 62.7- 64.6%), smaller eye diameter (29.5-32.3% SL vs. 33.6-34.9%), fewer scales in the longitudinal series of scales (23-24 vs. 27- 29), and fewer scales in the transverse series of scales (10 vs. 12).

Description. Morphometric data in Table 1. Largest specimen examined 34.6 mm SL. Dorsal profile slightly concave on head, convex from nape to end of dorsal-fin base, approximately straight along caudal peduncle. Ventral profile slightly convex from tip of jaw to origin of caudal peduncle and slightly concave from latter point to uppermost procurrent caudal-fin rays. Body moderately deep, compressed, greatest body depth on vertical slightly ahead to anal-fin origin. Eye positioned on lateral portion of head. Snout blunt. Large number of labial papillae in males. Urogenital papilla cylindrical and long in males, pocket-shaped in females. Tip of both dorsal and anal fins pointed in males with two or three elongated rays; dorsal fin in females pointed without filaments; anal fin rounded in females. Very long filamentous rays on tip of dorsal and anal fins in males, tip reaching vertical close to distal margin of caudal fin. Dorsal-fin rays unbranched. Caudal-fin subtruncate. Pectoral fins elliptical.

Posterior margin of each pectoral fin reaching vertical between base of fifth to seventh anal-fin rays in males, and between base of first to second anal-fin rays in females. Tip of each pelvic fin reaching base of third to fifth anal-fin rays in males, and base of first to second anal-fin rays in females. Pelvic-fin bases separated by interspace about equal to width of pelvic-fin base. Dorsal-fin origin on vertical line through base of fourth to fifth anal-fin rays.

Dorsal-fin rays 21-22 in males, 15-16 in females; anal-fin rays 24-26 in males, 21-22 in females; caudal-fin rays 20-22; pectoral-fin rays 10-12; pelvic-fin rays 5-6. Frontal squamation E-patterned; E-scales overlapping medially; no scale anterior to G-scale; supraorbital scales absent. Longitudinal series of scales 23-29; transverse series of scales 8-10; scale rows around caudal peduncle 12-16. Contact organ present on flank and absent on pectoral fin in males.

Coloration. Males. Head and trunk to vertical line passing through anal fin origin light brown. Posterior two-thirds of body dark blue, almost black in dorsal region, including unpaired fins. Trunk at height of beginning of dorsal fin with row of bright blue spots, each with diameter of approximately half of pupil, aligned vertically up to caudal peduncle. Dorsal region darker than ventral region.

Tip of jaw darkened. Dorsal fin with same color pattern of body, spots of smaller size than those on body. Anal fin with same pattern of background color of body and with same iridescent blue spots, but randomly distributed. Black Filaments on dorsal and anal fins. Anterior region of caudal fin dark blue, gradually becoming translucent towards edge of caudal fin. Caudal fin with fewer iridescent blue spots than body, concentrated on its dark portion. Hyaline pectoral fin. Dark pelvic fin with iridescent blue spots on center. Black bar vertically crossing eye.

Females. Side of body light brown, with 10-11 dark gray bars; one to three black spots on mid-body. Sides of head light brown, opercular region pale greenish golden. Iris light yellow, with dark vertical brown bar across center of eye. Fins hyaline, with dorsal and anal-fin rays light brown.

Distribution. Known from the type locality in río San Pablo basin, a tributary of the río Mamoré, Departamento Santa Cruz, Bolivia.

Habitat. The type locality lies at the plateau area (316 m. a.s.l.), just southwest of Llanos de Mojos, which occupy much of the río Mamoré basin in Bolivia (see Loubens et al., 1992). Water temperature at the surface of the pool was 31ºC, while at the depth of 1 m, 22ºC. In the marginal area of the pool, at the depth of 15 cm, water temperature was 35ºC. Only small specimens of Trigonectes sp. were collected in marginal areas. Specimens of Simpsonichthys brousseaui were collected in the deepest areas, at about 1 m deep. The pool presented dark water, pH 6.8 and water hardness 80 ppm. Other fish species collected syntopically were Trigonectes sp.

Etymology. The specific name is in honor to Roger D. Brousseau, discoverer of the species.

Figures

Fig. 1. Spectrolebias brousseaui, male (above), holotype, MNKP 10162, 28.4 mm SL and female (below), paratype, MZUSP109219,25.3 mmSL.