Leptolebias itanhaensis, Costa, 2008

Costa, Wilson J. E. M., 2008, Monophyly and taxonomy of the Neotropical seasonal killifish genus Leptolebias (Teleostei: Aplocheiloidei: Rivulidae), with the description of a new genus, Zoological Journal of the Linnean Society 153 (1), pp. 147-160 : 153-154

LEPTOLEBIAS ITANHAENSIS sp. nov. ( FIGS 8–10 )

Holotype: UFRJ 6453, male, 20.7-mm SL; Brazil, Estado de São Paulo, temporary channels within forest, 2.8 km from the road BR-101, Itanhaém , 24°13′8.9′S, 46°55′24.7′W, 14 m a.s.l.; W. J. E. M. Costa, C. P. Bove & B. B. Costa, 11 December 2005 . Paratypes: UFRJ 6323, two males, 19.0–19.1-mm SL, and two females, 16.2–16.9-mm SL; UFRJ 6324, four males, 17.9–21.7-mm SL; collected with holotype. UFRJ 5219, eight males, 14.3–20.4-mm SL (c&s) ; same locality and collectors, 5 November 2000 .

Diagnosis: Distinguished from all congeners except L. aureoguttatus by having four caudal neuromasts (vs. two), and horizontal golden lines on caudal fin in males (vs. no similar colour pattern). It is distinguished from L. aureoguttatus in having two dark-red stripes on dorsal and ventral submarginal portion of caudal restricted to anterior portion of fin in males (vs. along all fin extension), male caudal-fin stripes parallel to fin rays, not branching posteriorly (vs. branching posteriorly), basal portion of dorsal fin with dark-orange small spots in males (vs. dark-red to dark-brown short transverse bars), and five or six lateral mandibular neuromasts (vs. three or four). It may also be distinguished from all congeners in having more caudal-fin rays (27–31 vs. 25–28).

Description: Morphometric data appear in Table 1. Largest specimen: 21.7-mm SL. Dorsal profile: approximately straight to gently convex from snout to end of dorsal-fin base, approximately straight along caudal peduncle. Ventral profile: slightly convex from lower jaw to end of anal-fin base, roughly straight along caudal peduncle. Body: slender, deeper than wide, subcylindrical anteriorly to compressed posteriorly. Greatest body depth found at vertical through pelvic-fin base. Jaws short, snout blunt.

Dorsal and anal fins distally pointed in males. Dorsal fin slightly pointed and anal fin rounded in females. Caudal fin: elliptical. Pectoral fin: elliptical, posterior margin reaching vertical through anus in males, and vertical between pelvic-fin base and anus in females. Tip of pelvic fin reaching vertical between urogenital papilla and base of first anal-fin ray in males, between anus and urogenital papilla in females. Pelvic-fin bases medially in contact. Dorsalfin origin: on vertical between base of fifth and sixth anal-fin rays. Urogenital papilla: free of anal fin. Dorsal-fin rays, 13–16; anal-fin rays, 16–19; caudalfin rays, 27–31; pectoral-fin rays, 15; pelvic-fin rays, six.

Scales: small, cycloid. Body and head entirely scaled, except anteroventral surface of head. Body scales extending over anterior 25% of caudal-fin base; scales absent on dorsal and anal-fin bases. Frontal squamation E-patterned; E-scales not overlapped; A-scale with posterior margin exposed. Longitudinal series of scales, 25–27; transverse series of scales, eight; scale rows around caudal peduncle, 12–14. Minute contact organs on posterior margin of scales of flank in males.

Cephalic neuromasts: supraorbital, 1 + 8–10; parietal, 1; anterior rostral, 1; posterior rostral, 1; infraorbital, 2 + 16–18; preorbital, 3–4; otic, 1–2; postotic, 2; supratemporal, 1; median opercular, 1; ventral opercular, 3–5; preopercular, 2 + 9–11; mandibular, 5–6 + 2; lateral mandibular, 5–6. One or two neuromasts on the centre of each scale of lateral line; four neuromasts on caudal-fin base.

Coloration: Males: sides of body dark orange, with longitudinal rows of small golden spots, more concentrated on anterior half of flank. Dorsum: lightorangish brown. Venter: pale orange. Head: lightorangish brown, opercle greenish golden with two red stripes with transverse extensions to form reticulated pattern. Lower jaw: reddish orange. Iris: greenish golden with oblique reddish brown bar. Dorsal fin: yellow with dark-orange small spots on basal and posterior portions of fin. Basal portion of anal fin: yellow with dark-red spots. Distal portion of anal fin: dark-orangish brown. Caudal fin with pale blue horizontal lines on middle, light golden on dorsal and ventral portions of fin; two short dark-orangish red stripes through anterior portion dorsal and ventral submarginal parts of fin; dark-orangish red narrow stripes parallel to fin rays between caudal-fin base and posterior margin of fin. Pectoral fins: hyaline. Pelvic fins: dark orange.

Females: trunk and head, light-orangish brown; fins, hyaline; iris, yellow.

Distribution: Known to occur only from the type locality: seasonal pools in the Itanhaém river basin, São Paulo state, south-eastern Brazil ( Fig. 4 ).

Habitat and conservation: Leptolebias itanhaensis sp. nov. is found in shallow (about 10–40-cm deep), temporary channels within dense rainforest, in teacoloured and acidic (pH 3.5–4.0) water that contains litter at the bottom. No other fishes were found at this habitat, but some temporary channels may be in contact with small creeks containing the rivulid Rivulus santensis Köhler, 1906 , the characids Mimagoniates lateralis (Nichols, 1913) , Rachoviscus crassiceps Myers, 1926 , and Hollandichthys multifasciatus (Eigenmann & Norris, 1900) , and the callichthyid Scleromystax macropterus (Regan, 1913) . The area is undergoing slight urbanization, making L. itanhaensis sp. nov. an endangered species.

Etymology: The name itanhaensis denotes the occurrence of the new species in the Itanhaém river basin, an isolated small coastal drainage of south-eastern Brazil.

Figures

Figure 4. Geographical distribution of Leptolebias in São Paulo and Paraná states, southern Brazil: L. aureoguttatus (•) and L. itanhaensis (Ɨ).

Figure 8. Leptolebias itanhaensis, UFRJ 6453, male, holotype, 20.7-mm standard length (some hours after collection); Brazil, Estado de São Paulo, Itanhaém (photo by W. J. E. M. Costa).