Leptopanchax sanguineus, Costa, Wilson J. E. M., 2019

Costa, Wilson J. E. M., 2019, Description of a new species of cynopoeciline killifish (Cyprinodontiformes, Aplocheilidae), possibly extinct, from the Atlantic Forest of south-eastern Brazil, ZooKeys 867, pp. 73-85 : 73

Leptopanchax sanguineus sp. nov. Figs 1 , 2A , Table 1

Holotype.

MNRJ 51331, male, 20.9 mm SL; Brazil: Rio de Janeiro State: Magé Municipality: temporary swamp within dense moist forest in a private reserve (Reserva Particular do Patrimônio Natural Campo Escoteiro Geraldo Hugo Nunes), Magé River Basin, near the village of Citrolândia, 22°34'57"S, 43°02'08"W, altitude about 30 m above sea level (a.s.l.); M. T. C. Lacerda and K. Tanizaki, August 1987.

Paratypes.

MNRJ 11413, 2 males, 20.6-20.8 mm SL; MZUSP 38443, 1 male, about 20 mm SL, 1 female, about 15 mm SL (C&S); collected with holotype.

Diagnosis.

Leptopanchax sanguineus differs from other cynopoecilines, except L. splendens , by the presence of red bars on the whole flank in males (vs. absence); uniquely in L. sanguineus , the bars are broad, wider than the interspace width (vs. narrow, half interspace width or less) and have sinuous margins (vs. straight). Leptopanchax sanguineus is further distinguished from L. splendens by having 15 dorsal-fin rays (vs. 12-14), 6 pelvic-fin rays (vs. 5), 27 scales on the longitudinal series and 9 on the transverse series (vs. 24-25 and 7, respectively), 29 vertebrae (vs. 26-27), pelvic fin tip posteriorly reaching the anal fin in males (vs. reaching urogenital papilla), pelvic-fin bases medially separated, in close proximity (vs. medially united), absence of filamentous rays on the caudal fin (vs. short filamentous rays on the posterior margin of the caudal fin in males), presence of a golden stripe on the distal margin of the dorsal fin in males (vs. white stripe), absence of contact organs on the male pectoral fin (vs. presence) and absence of the dermosphenotic bone (vs. presence). Leptopanchax sanguineus also differs from L. splendens and all other cynopoecilines by the presence of a small red spot on the posterior portion of the iris (vs. spot absent).

Description.

Morphometric data appear in Table 1. Body slender, sub-cylindrical. Greatest body depth at vertical just anterior to pelvic-fin base. Dorsal and ventral profiles of head and trunk slightly convex, approximately straight on caudal peduncle. Head narrow, subtriangular in lateral view. Jaws short, teeth numerous, conical, irregularly arranged; outer teeth hypertrophied, inner teeth small and numerous. Vomerine teeth absent. Urogenital papilla cylindrical and short in males, slightly projecting body-wall outside, and pocket-shaped in females.

Dorsal fin subtriangular, pointed and terminating in short filamentous ray in males, its tip posteriorly reaching vertical through caudal-fin base; dorsal fin slightly pointed to rounded in females. Anal fin sub-rectangular, pointed and longer posteriorly in males, rounded in females. Caudal fin elliptical to sub-lanceolate in males, slightly longer than deep, often posteriorly terminating in minute tip; caudal fin elliptical in females. Pectoral fin elliptical, posterior margin reaching between base of pelvic-fin base and anus. Pelvic fin small, tip reaching anal-fin origin; pelvic-fin bases separated, medially in close proximity. Dorsal-fin origin at vertical between base of 4th and 5th anal-fin rays. Dorsal-fin rays 15; anal-fin rays 18; caudal-fin rays 28; pectoral-fin rays 15; pelvic-fin rays 6. No contact organs on fins. Four neuromasts on caudal-fin base. Total vertebrae 29.

Scales small, cycloid. Body and head entirely scaled, except anterior ventral surface of head. Body squamation extending over anterior 20 % of caudal-fin base; no scales on dorsal, anal and pectoral-fin bases. Frontal squamation E-patterned; E-scales not overlapping medially; supraorbital scales absent. Longitudinal series of scales 27; transverse series of scales 9; scale rows around caudal peduncle 12. Three, or four, minute contact organ per scale of ventral portion of flank in males. Cephalic neuromasts: supraorbital 1 + 10; parietal 1; anterior rostral 1, posterior rostral 1; infraorbital 1 + 15; preorbital 3; otic 1, post-otic 2; supratemporal 1; median opercular 1, ventral opercular 1; pre-opercular 11, mandibular 7; lateral mandibular 4, paramandibular 1.

Colouration in life.

Males. Flank light metallic blue with 12 or 13 red bars, wider than interspace, margins sinuous producing overall zigzag shape. Dorsum pale yellowish brown, venter pale blue with red bars. Head light blue to greenish blue on opercle, with red reticulation; red stripe between orbit and middle opercle. Jaws red. Ventral surface of head pale blue, scale margin red. Iris bright blue, with dark reddish-brown bar through orbit centre, and small red spot on its posterior margin. Unpaired fins red with metallic blue to greenish-blue vertical vermiculate marks; broad golden stripe on distal margin of dorsal fin. Pelvic fin red with bright blue margin. Pectoral fin hyaline.

Females. Flank pale brownish grey. Dorsum pale brown, venter white. Head side grey, with pale golden iridescence on opercle. Iris yellow, with dark brownish grey bar through orbit centre, and small red spot on its posterior margin. Fins hyaline.

Colouration in alcohol.

In both sexes, specimens with head and flank pale brown; fins hyaline in females, hyaline with pale brown pigmentation in males.

Distribution and habitat.

Leptopanchax sanguineus is known from specimens collected between 1985 and 1987, from a single locality ( Fig. 3 ). The collection site was situated in a dense moist forest, consisting of a well-preserved fragment of about 200,000 m2, of the original forest that formerly occupied the plains surrounding the coastal mountain range. This forest is a campsite used by a group of Boy Scouts (Campo Escoteiro Geraldo Hugo Nunes). It is drained by small streams belonging to the Magé River Basin (also known as Roncador River Basin). Leptopanchax sanguineus was found in temporary swamp channels situated in small depressions but not directly in contact with surrounding streams. These channels were shallow, about 20 cm deep, with clear, slightly yellow water, and no aquatic vegetation ( Fig. 4 ) (see also Costa 1995: figs 128, 129). The water was acid, pH usually 4.8 to 6.0 after rains ( Tanizaki et al. 1991), and the bottom composed of dense litter.

In 1988, some killifish breeders tried to breed L. sanguineus in aquaria, but offspring contained only male specimens (J. C. Ghisolfi pers. comm. 1990). Between 1989 and 2000, annual attempts were made to collect the species again. Using GPS, the exact point of the original collection was recorded and new sites were sampled, but no specimen was found. In 2001, monthly collections were made but again no specimen of L. sanguineus was found. The shallow temporary swamp channels disappeared, probably as a result of the lowering of the water table caused by the diversion of waters from the streams to supply an ornamental fish farm in the vicinity of the forest ( Costa 2009). Sporadic attempts to find this species in other localities of the Magé River Basin, including its upper and lower courses were also unsuccessful. These attempts were directed for all areas with suitable environmental conditions for seasonal killifishes inhabiting moist forests (i.e., flooded forested plains). Since 2009, the Campo Escoteiro Geraldo Hugo Nunes became officially protected by the Brazilian Government when it was recognised as a private natural heritage reserve. However, L. sanguineus has not been found since 1987 and it is possibly extinct in the area.

Etymology.

The name sanguineus , from the Latin, meaning blood-coloured, is an allusion to the predominantly red colouration in males, unique among Neotropical killifishes.

Figures

Figure 1. Leptopanchax sanguineus sp. nov., MNRJ 51331, holotype, male, 20.9 mm SL. Scale bar: 5 mm.

Figure 2. Male fin morphology and life colour patterns in Leptopanchax. A coloured pencil drawing illustrating L. sanguineus sp. nov. in life, about 20 mm SL B L. splendens, UFRJ 6902, 22.7 mm SL C L. aureoguttatus, UFRJ 6331, 22.3 mm SL D L. itanhaensis, UFRJ 6453, 20.7 mm SL E L. citrinipinnis, UFRJ 8899, 20.6 mm SL F L. opalescens, UFRJ 8986, 20.2 mm SL.

Figure 3. Geographical distribution of L. sanguineus sp. nov. (white triangle) and L. splendens (black symbols: star, type locality; dot, 2018 collection site).

Figure 4. Habitat of L. sanguineus sp. nov. in 1988.