Austrolebias univentripinnis, Wilson J. E. M. Costa & Morevy M. Cheffe, 2005

Wilson J. E. M. Costa & Morevy M. Cheffe, 2005, Austrolebias univentripinnis sp. nov. (Teleostei: Cyprinodontiformes: Rivulidae): a new annual killifish from the Mirim Lagoon basin, southern Brazil., Zootaxa 1052, pp. 41-48 : 44-47

Austrolebias univentripinnis new species

(Figs. 1A-B)

Holotype. UFRJ 6081, male, 24.0 mm SL; Brazil: Estado do Rio Grande do Sul: Município de Jaguarão: Telho, temporary swamp about 200 m from Jaguarão River bank, tributary to Mirim Lagoon, Patos Lagoon system; (22H 0268740 UTM 6402377); L. E. K. Lanés, M. V. Volcan, B. Klotzel & G. M. Wallwitz, 5 September 2004.

Paratypes. All from Município de Jaguarão, Estado do Rio Grande do Sul, Brazil: CIMC 8625, 6 males, 22.6-34.6 mm SL, 27 females, 23.6-32.0 mm SL ; UFRJ 6082, 1 male, 32.6 mm SL, 3 females, 25.5-32.2 mm SL ; UFRJ 6083, 3 males, 30.0-35.6 mm SL, 3 females, 26.6-33.0 mm SL (c&s); collected with holotype . CIMC 8629, 6 males, 30.1- 38.6 mm SL, 2 females, 26.8-27.2 mm SL; 27 de Novembro Street, between the second and the third bridge, about 10 km from the road BR-116; same collectors and data as holotype . CIMC 8631, 3 males, 30.2-36.5 mm SL, 9 females, 24.2-33.4 mm SL; Telho Creek floodplains; same collectors and date . CIMC 8635, 84 males, 14.2-40.5 mm SL, 90 females, 13.8-25.6 mm SL; Telho, about 21 km from the city of Jaguarão; same collectors and date . CIMC 8642, 19 males, 26.0-39.4 mm SL, 22 females, 21.2-32.3 mm SL; same locality and collectors as holotype, 6 September 2004 . UFRJ 6086, 17 males, 20.5-35.8 mm SL, 11 females, 20.2-30.4 mm SL; same locality as CIMC 8635; L. E. K. Lanés, M. V. Volcan, B. Klotzel & A. C. Gonçalves, 24 October 2004 .

Diagnosis: Differs from all congeners, except A. bellottii (Steindachner) and A. melanoorus (Amato) , in having the entire urogenital papilla attached to the anal fin in males (vs. urogenital papilla free from the anal fin). The new species is distinguished from A. bellottii in having the dorsal-fin origin more anteriorly positioned in males (between neural spines of seventh and ninth vertebrae, vs. between neural spines of ninth and eleventh vertebrae) with a consequent shorter predorsal length (49.5-52.9% SL, vs. 54.2- 57.7% SL). It also differs from those two species in having a shorter anal-fin base (42.6- 46.4% SL in males and 26.5-30.9 % SL in females, vs. 47.1-50.8% SL and 33.8-36.1% SL, respectively), a more slender body (body depth 36.6-39.8% SL in males, 36.0-40.4% SL in females, vs. 40.1-46.1% SL and 39.4-45.5% SL, respectively) and a wider basihyal (width about 65% of length, vs. about 50%). In addition, it also differs from A. bellottii in usually having more vertical rows of bright dots on the flank in males (11-18 vs. 9-12). The new species is distinguished from A. melanoorus by its dorsal profile, which is slightly convex in females (vs. strongly convex), pelvic-fin bases united at about 75-90% of its medial margin (vs. about 10-25%), and by a combination of distinct color patterns: males with flank dark bluish gray with vertical rows of bright greenish blue dots (vs. light bluish gray bars alternating with dark gray bars), and unpaired fins with bright dots (vs. elongate light spots and bright lines parallel to fin rays); females either with one or two black spots on the center of the flank or (more often) black spots absent (vs. always with 5-15 black spots). It may also be distinguished from A. melanoorus by possessing a single anterior rostral neuromast, except in one specimen with two (vs. always two anterior rostral neuromasts).

Description: Morphometric data appear in Table 1. Male larger than female, largest male 35.6 mm SL. Dorsal profile slightly convex from snout to end of dorsal-fin base, approximately straight on caudal peduncle. Ventral profile convex from lower jaw to end of anal-fin base, nearly straight on caudal peduncle. Greatest body depth at level of pelvic-fin base. Body deep and compressed. Snout blunt, jaws short.

Tip of dorsal and anal fins rounded. Anteromedian rays of anal fin of female lengthened, anal fin shape approximately triangular. Caudal fin rounded. Pectoral fin elliptical, posterior margin on vertical between base of 3rd and 5th anal-fin rays in male, and between pelvic-fin base and urogenital papilla in female. Tip of pelvic fin reaching between base of 3rd and 4th anal-fin ray. Medial pelvic-fin membranes 75-90% coalesced (Fig. 2A). Entire urogenital papilla of male attached to anal fin (Fig. 2B). Dorsal-fin origin on vertical slightly posterior to anal-fin origin in male, between base of 2nd and 4th anal-fin ray, and between neural spines of 7th and 9th vertebrae. In female, dorsal-fin origin on vertical just anterior to anal-fin origin, anal-fin origin on vertical through base of 2nd dorsal-fin ray, to dorsal-fin origin on vertical slightly posterior to anal-fin origin, on base of 2nd anal-fin ray; dorsal-fin origin between neural spines of 10th and 12th vertebrae. Anal-fin origin between pleural ribs of 7th and 9th vertebrae in male, between pleural ribs of 9th and 11th vertebrae in female. Dorsal-fin rays 23-28 in male, 20-23 in female; anal-fin rays 26-30 in male, 22-26 in female; caudal-fin rays 23-25; pectoral-fin rays 11-12; pelvic-fin rays 5 (last three characters same for both sexes).

Scales large, cycloid. Body and head entirely scaled, except anterior ventral surface of head. Few scales on anal-fin base, no scales on dorsal-fin base. Frontal squamation G- patterned, except H-patterned in one specimen; E-scales not overlapping medially; scales arranged in transverse pattern, all scales with exposed posterior margin. Longitudinal series of scales 28-30; transverse series of scales 13-14; scale rows around caudal peduncle 16. Minute contact organs on scales of ventral portion of male flank. Row of minute contact organs on uppermost pectoral-fin ray.

Cephalic neuromasts: supraorbital 17-18, parietal 3, anterior rostral 1 except one specimen with 2, posterior rostral 1, infraorbital 2 + 22-25, preorbital 3, otic 3, postotic 3- 4, supratemporal 1, median opercular 1, ventral opercular 2, preopercular 24-26, mandibular 15, lateral mandibular 5.

Jaw teeth gently bowed. Basihyal roughly triangular, its width about 65% of length; basihyal cartilage long, about 65% of total basihyal length, with pronounced lateral projection. Six branchiostegal rays. Urohyal deep. Second pharyngobranchial teeth 6-8. Gill-rakers on first branchial arch 3-4 + 11-12. Two, one or no dermosphenotic ossifications. Ventral process of posttemporal long. Total vertebrae 29-31.

Coloration in life: Male: side of body dark greenish gray, with 11-18 vertical rows of bright greenish blue dots, often forming lines; venter yellowish white. Side of head dark greenish gray to bright blue on opercle and infraorbital region; pale gray infraorbital bar and dark gray supraorbital bar. Iris dark yellow, with dark brown bar through center of eye. Dorsal fin dark bluish green to pale pink on anterodistal portion, with light green dots and posterodistal black margin. Anal fin dark bluish green to light blue on distal portion, with subbasal row of small light green spots; preserved specimens with black distal stripe. Caudal fin dark bluish green, with greenish blue dots; posterior portion hyaline with green iridescence. Pelvic fin dark bluish green with black tip. Pectoral fin hyaline with dark greenish blue ventral margin, extending from fin base to tip of fifth or sixth ventralmost rays.

Female: side of body light yellowish brown, with vertically elongate dark gray spots, often vertically arranged, sometimes forming bars; sometimes one or two black spots on anterocentral portion of flank; venter pale yellow. Opercular region pale greenish blue.

Iris light yellow with gray bar through center of eye. Fins hyaline; dorsal and anal fins with dark gray small spots on basal region.

Distribution: Jaguarão River drainage, Mirim Lagoon basin, Patos Lagoon system, southern Brazil.

Habitat notes: The new species was collected in small shallow marshes (about 40 cm deep). The pH was 6.6-6.8 and the water was whitish.

Etymology: From the Latin uni (single, fused), ventri (ventral) and pinnis (fin), referring to the median fusion of the pelvic fins.

Discussion

Austrolebias univentripinnis is a member of the clade diagnosed, in a recent phylogenetic analysis of the genus (Costa, 2002), by the possession of a long and triangular anal fin in females (Fig. 1B). This condition is found in A. viarius , A. arachan , A. adloffi , A. charrua , A. minuano , A. nigrofasciatus , A. vandenbergi , A. bellottii , A. melanoorus and A. univentripinnis . All these species also have the medial margin of the pelvic-fin united, an uncommon condition among cynolebiatins (Costa, 2002). In A. univentripinnis , the condition is pronounced, the fins being united over 75-90 % of their medial margins (Fig. 2A), in contrast to 60% or less as in A. arachan , A. melanoorus , A. viarius , A. charrua , A. minuano , and A. nigrofasciatus .

A derived condition supports the monophyly of the assemblage including A. vandenbergi , A. bellottii , A. univentripinnis and A. melanoorus . It is the frequent possession of one or two small dermal ossifications approximately at the place of the dermosphenotic (Costa, 2002), which is absent in all other species of the clade including Cynolebias , Megalebias and Austrolebias (Costa, 1998). Although this condition is not always present in all specimens of these four species (for example, among six cleared and stained paratypes of A. univentripinnis , one specimen had two ossifications, three specimens had one, and in two specimens both ossifications were absent), this condition does not occur in any other species of Austrolebias . Relationships within the clade including A. vandenbergi , A. bellottii , A. univentripinnis and A. melanoorus are still unclear, but among them and among all species of the clade Austrolebias-Megalebias-Cynolebias, only A. bellottii , A. univentripinnis and A. melanoorus have the urogenital papilla attached to the anterior margin of the anal fin in males (Costa, 2002) (Fig. 2B).