Jenynsia luxata, Aguilera & Mirande & Calviño & Lobo, 2013

Aguilera, Gastón, Mirande, Juan Marcos, Calviño, Pablo A. & Lobo, Luis Fernando, 2013, Jenynsia luxata, a new species from Northwestern Argentina, with additional observations of J. maculata Regan and phylogeny of the genus (Cyprinodontiformes: Anablepidae), Neotropical Ichthyology 11 (3), pp. 565-572 : 567-569

Jenynsia luxata new species

Fig. 1

Holotype. CI-FML 5464, 24.6 mm SL, male, Argentina, Tucumán, Burruyacu city, a small unnamed stream, río Tajamar basin, 26º30’13.47”S 64º44’8.75”W, Apr 2002. L. Lobo.

Paratypes. AI 234, 4, 28.0- 30.7 mm SL; CI-FML 5465, 6 (2 C&S), 20.9-29.1 mm SL; and MACN-Ict 9769, 5, 25.1-35.9 mm SL, same data as for holotype. CI-FML 5466, 12 (3 C&S), 17.3-44.3 mm SL, Argentina, Santiago del Estero, Pellegrini, small flooded pools at Ruta Provincial 4, not connected to but near to río Urueña basin, Mar 2010, P. Calviño .

Diagnosis. Jenynsia luxata is diagnosable from all other members of the genus by the medial processes of left and right pelvic bones relatively reduced, not overlapping each other at ventral midline ( Fig. 2 ). The separation between the medial processes is detectable in fresh and alcohol-preserved specimens by the independent movement of these bones when this region is gently pressed by a needle.

Among the species of the subgenus Jenynsia , the coloration pattern distinguishes J. luxata (four to six regular rows of small circular spots of dark brown chromatophores on body side, been more apparent along caudal peduncle) from J. alternimaculata (two or, occasionally, three rows of dorsoventrally elongate markings on lateral body surface), J. lineata (five to seven rows of elongate, horizontal dash-shaped markings on side), J. maculata (three or four irregular series of more or less oblong blackish spots), J. multidentata (five to seven rows and also lines formed by round or short, horizontal dash-shaped markings, more than four scales in length on ventral caudal peduncle), J. onca (distinct ovoid to circular dark spots confined to ventral half of flank posterior to pelvic fin; spots gradually more circular towards midventral line), and J.tucumana (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). Jenynsia luxata is also distinguishable from J. multidentata and J. lineata by the absence of a swelling between the urogenital opening and the anterior base of the anal fin in females; from J. obscura by the lower number of predorsal scales (12-16 vs. 19- 25); 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 and the smaller eye diameter of females (26.1- 33.1% HL vs. 33.5-40.0% HL); and from J. lineata and J. sanctaecatarinae by the absence of a distinct rounded spot on dorsal pectoral-fin base.

Description. Body stout and laterally compressed posteriorly; greatest body depth slightly anterior to pelvic-fin origin. Head blunt; head squamation in Fig. 3 . Mouth terminal to slightly oblique. Dorsal profile of body straight from snout tip to supraoccipital process, straight to concave to dorsal-fin origin, and slightly convex backwards to caudal-fin origin. Ventral profile of body slightly concave from snout tip to isthmus, more pronounced to pelvic-fin origin, oblique backward along anal-fin base, and almost straight to caudal-fin origin.Anal-fin insertion located slightly posterior to vertical line through dorsal-fin origin. Sexual dimorphism present, males smaller than females and with intromittent organ formed by first eight anal-fin rays. Dorsal-fin insertion in females at halfway between pelvic and anal fins, in males closer to anal-fin origin. Pelvic fin reaching anus in females and reaching base of gonopodium in males. Absence of swelling between urogenital opening and anal-fin base of females.

Pores of cephalic sensory system associated with lateral sensory system anterior branch of supraorbital 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, Z, W, and pores Ya and Yb separated or included, in small specimens, in open groove; tricuspid teeth in both premaxilla and dentary.

Morphometric data in Table 1. Dorsal-fin rays 8 (1) or 9 (24*). Anal-fin rays in females 10 (17). Principal caudal-fin rays 14 (5), 15 (9*), or 16 (11). Pectoral-fin rays 14 (3), 15 (12), or 16 (10*). Pelvic-fin rays 6 (25*). Lateral line 30 (4), 31 (11*), 32 (8), or 33 (2). Predorsal scales 12 (2), 13 (8*), 14 (11), 15 (3), or 16 (1). Circumpeduncular scales 16 (25*). Vertebrae 28 (1), 29 (2), or 30 (2). Epipleural ribs 9 (2), 10 (2), or 11(1). Pleural ribs 11 (1), 12 (1), or 13 (3). Gill rakers 13 (2), or 14 (1).

Coloration in alcohol. Body background yellowish, grading from brown or pale brown dorsally to cream ventrally. Head dorsum from snout tip to vertical line through anterior eye margin dark brown but paler than area between eyes to supraoccipital process, having very distinct concentration of dark brown chromatophores. Cheek and area posteriorly surrounding eye pale brown or cream. Concentration of dark brown chromatophores on upper margin of opercle. Scales on body, from dorsum to second row behind lateral line with concentration of dark brown chromatophores bordering scales on their posterior field, forming reticulated pattern. Body side with circular spots or short dash-shaped markings of dark brown chromatophores in center of each scale, which coalesce in some specimens forming continuous lines and arranged into 4 to 6 regular rows along caudal peduncle. Rows of chromatophores less evident on anterior portion of body. Midlateral row more evident than remaining ones. Belly unpigmented, only peritoneal coloration visible at midventral line through body wall. Absence of diffuse dark chromatophores on dorsal pectoral-fin base. All fins hyaline, but having scattered chromatophores following rays on dorsal, caudal, and pectoral fins. Scattered chromatophores on gonopodium from its base to tip.

Distribution. The new species is currently known to inhabit the endorheic río Tajamar or río Cajón basin near to Ruta Provincial 304, at Burruyacu, northeastern Tucumán, and also in small flooded pools not connected but near to río Urueña basin, in northwestern Santiago del Estero ( Fig. 4 ). Despite several collecting expeditions to the area and extensive sampling by the authors, no additional specimens were found.

Etymology. The specific name “ luxata ” derives from the Latin, meaning dislocate, in allusion to the diagnostic character of the species herein described, the separate pelvic bones.

Phylogenetic relationships. The morphological data matrix is presented in Table 2. The assignments of character states exhibited by specimens of Jenynsia maculata showed some differences with that by Ghedotti (1998): the fifth anal-fin ray of adult males is approximately as long as the third (46-0), the gonopodium lacks a protuberance on its tip formed by anal-fin ray eight (51-1), the hypurals are fused in adults, forming two symmetrical dorsal and ventral hypural elements (59-1), the pore W of the mandibular canal can be both present or absent (60-[01]), there is a series of three or more narrow lines composed of short, dash shaped marking (64-2), and the swelling between urogenital opening and anterior anal-fin base is absent (69-0).

Under equal weights, 12 equally most parsimonious trees of 154 steps were found (CI = 0.58; RI = 0.78). The topology of the consensus tree ( Fig. 5A ) is the same as the proposed by Lucinda et al. (2006) for the subgenus Plesiojenynsia , with J. unitaenia as the sister species of a polytomy including J. diphyes , J. weitzmani , and a clade composed of J. eigenmanni and J. eirmostigma . The subgenus Jenynsia is more resolved than in previous phylogenies, with a trichotomy at the base including J. maculata , J. sanctaecatarinae , and a clade composed of the remaining species of the subgenus. The latter clade also forms a trichotomy, composed of J. luxata and J. onca and two nodes including J. lineata and J. multidentata , and a trichotomy between J. alternimaculata , J. obscura , and J. tucumana , respectively.

Under implied weighting, two equally most parsimonious trees of 154 steps (CI = 0.58; RI = 0.78) were obtained with each concavity (K), in the range from 4 to 20. The strict consensus between these equally most parsimonious trees is completely resolved for the subgenera Plesiojenynsia and partially resolved for Jenynsia ( Fig. 5B ). Within Plesiojenynsia , J. diphyes , J. unitaenia , and J. weitzmani are successive sister species of a clade composed of J. eigenmanni and J. eirmostigma . In the subgenus Jenynsia , J. maculata , J. sanctaecatarinae , J. onca , and J. luxata are successive sister groups of a clade composed of J. tucumana , J. alternimaculata , and J. obscura as the sister group of a clade composed of J. lineata and J. multidentata .

Figures

Fig. 1. Jenynsia luxata.Above: holotype CI-FML:5464, male, 24.4 mm SL, Tucumán, Burruyacu city, a small unnamed stream, río Tajamar basin,Argentina; below: paratype CI-FML 5466, female, 34.8 mm SL, Santiago del Estero, Pellegrini, small flooded pools at Ruta Provincial 4, not connected to but near to río Urueña basin, Argentina.

Fig. 2. Pelvic girdle of Jenynsia luxata, paratype, male, CI-FML 5465, 27.8 mm SL.

Fig. 3. Diagrammatic representation of head squamation of Jenynsia luxata.

Fig. 4. Hydrographic map of South America showing the currently known distribution of Jenynsia luxata. The area delimited by the rectangle is enlarged at right, where the type locality is indicated by an open dot and an additional locality is indicated by a black dot. The small black dot indicates the capital of Tucumán.

Fig. 5. Topologies from most equally parsimonious trees and relative Bremer support/GC values under (a) equal weights (strict consensus of 12 trees), and (b) implied weighting (strict consensus of two trees), with concavities K = 4 to 20 (with supports measured under K = 8). Unsupported nodes are shown as collapsed. The relationships of genera of the family are consistent with those proposed in previous studies, therefore species of Anableps and Oxyzygonectes are not shown.