Jenynsia tucumana, Gastón Aguilera & Juan Marcos Mirande, 2005

Gastón Aguilera & Juan Marcos Mirande, 2005, A new species of Jenynsia (Cyprinodontiformes: Anablepidae) from northwestern Argentina and its phylogenetic relationships., Zootaxa 1096, pp. 29-39 : 33-38

Jenynsia tucumana , new species

(Fig. 2)

Holotype. CI-FML 3828, Male, 30.7 mm SL, Argentina, Tucumán, Dpto. Trancas, río Vípos (26°28’S; 65°20’W), 5 km from Ruta Nacional 9, G. Aguilera and M. Mirande, April 24, 2003.

Paratypes. CI-FML 3829, 4, 26.2-32.8 mm SL ; AI 163, 6, 26.3-40.4 mm SL ; ANSP 180781, 6, 20.4-33.0 mm SL ; CI-FML 3840, 2 C&S, 28.3-36.0, collected with holotype.

Diagnosis. Jenynsia tucumana n. sp. is distinguished from other members of the genus by the possession of a row of dark markings ranging from dots to small vertical stripes, on the lateral surface, from the tip of the adpressed pectoral fin to the margin of hypural (Fig.2).

Among the remaining species of the genus only Jenynsia alternimaculata has vertical stripes, but its pattern is different from that of the new species (two occasionally three rows of dorsoventrally elongate markings on the lateral surface of body vs. one row of short vertical stripes or dots in the new species). These differences are further elaborated below under “ Results and Discussion”. Jenynsia tucumana may also be distinguished from J. alternimaculata by the possession of a mandibular canal pore W, a wide prootic bridge, and a symmetric fifth anal-fin ray of the tubular gonopodium; from J. pygogramma by the number of predorsal scales (15-16 vs. 19-25); from J. multidentata , J. maculata and J. lineata (Jenyns) by the absence of a swelling between the urogenital opening and the anterior base of the anal fin in females; from J. sanctaecatarinae by the absence of a rounded spot on dorsal pectoral-fin base; and from J. onca by the absence of a large dorsal convex expansion at subdistal segments of right half of sixth anal-fin ray of adult males. Jenynsia tucumana can be distinguished from J. eirmostigma Ghedotti and Weitzman , J. weitzmani , J. eigenmanni , and J. unitaenia Ghedotti and Weitzman by the absence of a long posterodorsal process of the lachrymal and a shorter fourth anal-fin ray in the gonopodium.

Description. Body elongate, slightly compressed laterally; greatest body depth at vertical between pectoral and pelvic fins; mouth terminal, slightly oblique; tricuspid teeth in premaxilla and dentary. Dorsal-fin origin at vertical through or just behind first anal-fin ray insertion. Sexual dimorphism present, males much smaller than females, with tubular intromittent organ formed by 8 first anal-fin rays; length of gonopodium 1.3-1.5 in caudal peduncle; posterior two anal-fin rays not forming part of tubular intromittent organ and extending approximately two-thirds of gonopodium length. Females without swelling between urogenital opening and anterior base of anal fin. Head squamation pattern as in figure 3; anterior branch of supra-orbital sensory canal formed by pores 1 and 2a; middle part by 2b, 3, 4a, and posterior branch by 4b, 5, 6, 7; preopercular canal continuous, with 7 pores; infraorbital canal formed by 4 pores; mandibular canal with pores X, Ya, Yb, Z and W.

Morphometric measurements expressed as percents of standard length in table 1. Counts of 47 specimens, including the holotype: lateral scale series 31[11], 32[17], 33*[15], 34[4]; predorsal scales 14[5], 15[20], 16*[21]; circumpeduncular scales 16*[47]; dorsal-fin rays 7*[11], 8[36]; anal-fin rays in females 10[19], 11[1]; pectoral-fin rays 15[8], 16[26], 17*[13]; pelvic-fin rays 6*[47]; caudal-fin rays 16[10], 17[15], 18*[22]. Counts in C&S specimens: gill rakers 10[5], 11[4], 12[1]; vertebrae 31[3], 32[5]; gonopodium 10[5].

Coloration in alcohol: Body background color grading from brown dorsally to cream ventrally. Dark chromatophores in center of scales, present on dorsal part of body to fifth row of scales. Mid-dorsal stripe of dark chromatophores from posterior part of head to first dorsal-fin ray insertion; base of dorsal fin light brown; mid-dorsal stripe continued on upper portion of peduncle to anterior procurrent caudal-fin rays. Concentration of chromatophores present on two scales anterior to dorsal-fin origin. Mid-lateral row of dark markings ranging from dots to small vertical stripes, from adpressed tip of pectoral fin to posterior margin of hypural. Anterior part of this row with dark dashes irregularly distributed. Two rows of rounded dark dashes posteriorly directed in dorsal view, from vertical through pectoral-fin insertion, turning to dorso-lateral at vertical through pelvicfin insertion, and reaching 4/5 of peduncle length. Some specimens with third row of dark dashes under mid-lateral row, reaching 4/5 of peduncle length. Isthmus unpigmented. All fins with scattered chromatophores in membranes, surrounding some rays. Diffuse subdermal stripe ventrally, from posterior anal-fin insertion to half caudal peduncle length. Dark chromatophores scattered over entire surface of gonopodium.

Head brown dorsally, cream ventrally; a dark brown blotch on postero-dorsal surface of the head, extending anteriorly between the eyes. Dark brown dashes between anterior branch of supra-orbital sensory canal and posterior nares. Dark chromatophores scattered over premaxilla, lower jaw and pre-orbital canal area. Upper part of opercle with a horizontal strip. Branchiostegal membranes unpigmented.

Distribution. Jenynsia tucumana n. sp. is known from Río Vípos, Río Calera, and Río Grande; all of which are in the upper Río Salí basin (Fig. 4).

Etymology. The specific epithet tucumana means “from Tucumân ” province in Argentina, where the type locality is situated.

Remarks. This species mainly inhabits moderate to slow flowing streams with rocky bottom and algae on the substrate, where it is sympatric with Jenynsia multidentata .

Results and Discussion. Jenynsia tucumana shares two uniquely derived characters with the members of the subgenus Jenynsia (Ghedotti 1998): the lack of segmentation on the proximal and distal quarters of sixth anal-fin ray in adult males and the vertically inclined proximal radials associated with the first six anal-fin rays in the gonopodium.

The unique coloration pattern distinguishes the new species from the remaining species of the genus. Although the pattern in J. tucumana resembles that of Jenynsia alternimaculata (i.e. vertical stripes on lateral surface of body), the former species has only one row of markings vs. two or three in the latter (see Fig. 4 in Ghedotti & Weitzman, 1996). In addition J. alternimaculata has the left and right halves of anal-fin ray five asymmetric; this apomorphy, shared with J. sanctaecatarinae , is absent in J. tucumana in which both halves are similar in size. Jenynsia alternimaculata also has, as an autoapomorphic condition, a narrow prootic bridge, which is an additional character to distinguish this species from J. tucumana and from the remaining species of the genus.

A single, most parsimonious tree of 147 steps was obtained with concavity constants (K) ranging from 0.0001 to 6 (Fig. 5b), and in concavities from 7 to 100, the most parsimonious tree, with 146 steps, is one of the four most parsimonious trees under equal weights (Fig. 5a,c). Low concavity constants and equal weighting (or high concavity constants) represent opposite extreme cases in which the homoplastic characters are almost ignored, or are considered as reliable as the perfectly hierarchic ones respectively. Since the results produced by either extreme are very similar, those results clearly do not depend entirely on decisions of whether (or how strongly) to weight characters.

Regardless of weighting strength, Jenynsia tucumana belongs to the subgenus Jenynsia . The relationships of the new species vary slightly between the analyses performed due to differing relationships of J. sanctaecatarinae , as in the analysis of Lucinda et al. (2002). The latter species is the sister group of J. alternimaculata under concavities 0.0001 to 6, and the sister group of J. onca under concavities 7 to 100; under equal weights, J. sanctaecatarinae collapses basally to J. tucumana . Thus, position of the new species is basal to the remaining species of the subgenus Jenynsia , except J. onca and, for concavities below 7, also J. sanctaecatarinae .

Five species of Jenynsia are present in Argentina: the widely distributed J. multidentata and the exclusively northwesterly distributed J. alternimaculata , J. maculata , J. pygogramma and J. tucumana . Jenynsia multidentata was considered to occur in lowlands (Ghedotti & Weitzman, 1996 and Ghedotti, 1998), but we have found it together with J. tucumana in highland streams at 1200 meters above sea level. The distribution of the genus in northwestern Argentina coincides with the proposed extension of the Paranean Sea, in the Middle-Upper Miocene ( Aceñolaza & Sprechmann, 2002); this sea would have extended westward on the Brazilian/Uruguayan platform, flooding a big area of central-northern Argentina and central Paraguay, and may have acted as a barrier between southeastern Brazilian-Uruguayan and northwestern Argentine populations/ species (compare fig. 1 of Aceñolaza & Sprechmann, 2002 with fig. 29 of Ghedotti, 1998). Also, the northwestern Argentina species (or its ancestor/ancestors) probably was/were coastal species before the recession of the Paranean Sea and now are restricted to highlands. Nevertheless, this is only a hypothesis that could be corroborated or refuted only with additional information on the systematics and evolutionary history of the genus.