Overview

Distribution

Tocantins River, Brazil.
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South America: Rio Tocantins drainage in Brazil.
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Physical Description

Diagnostic Description

(Figs. 1 and 2, Table 1)

 

Diagnosis. Jupiaba elassonaktis is distinguished from J. acanthogaster , J. atypindi , J. keithi , J. maroniensis , J. meunieri , J. minor , J. pinnata , and J. poekotero by the medial cusps of premaxillary teeth much larger than remaining cusps (vs. cusps similar in size to each other) and by dentary teeth decreasing abruptly in size from the fifth tooth backwards (vs. decreasing gradually). Jupiaba elassonaktis is distinguished from J. abramoides , J. anteroides , J. apenima , J. asymmetrica , J. pirana , J. poranga , J. yarina , and J. zonata by the lower number of scales on lateral line (33-39 vs. 40-66, respectively). Jupiaba elassonaktis is distinguished from J. ocellata by the first dorsal- and anal-fin rays not prolonged by an elongate filament (vs. prolonged by an elongate filament) and from J. mucronata by the presence of a vertically elongate humeral spot (vs. humeral spot horizontally elongate). The number of scales series above lateral line distinguishes J. elassonaktis from J. polylepis , J. potaroensis , and J. zonata (5-7 vs. 8-11, respectively). The number of pectoral-fin rays distinguishes J. elassonaktis from J. essequibensis and J. scologaster (9-11 vs. 13-16, respectively). Jupiaba elassonaktis is also distinguished from J. essequibensis and J. scologaster by the incomplete series of median predorsal scales (vs. complete in later species). Futhermore, J. elassonaktis is also distinguished from J. polylepis and J.essequibensis by the number of humeral spots. Jupiaba elassonaktis possesses two humeral spots. First humeral spot is large and vertically elongate located at fifth and sixth scales of lateral line and the second humeral spot very diffuse. Jupiaba polylepis and J. essequibensis exhibit only one humeral spot (surrounded by a light area and located on sixth to nineth lateral line scales in J. polylepis ).

 

Description. Morphometric data summarized in Table 1. Body compressed and somewhat deep; greatest body depth at base of first dorsal-fin ray. Dorsal head profile straight or slightly concave. Profile convex to nearly straight from supraocciptal tip to base of last dorsal-fin ray, and straight towards adipose-fin origin. Anterior portion of ventral profile of head oblique. Posterior portion of ventral profile of head convex. Ventral body profile convex from pectoral-fin origin to pelvic-fin origin, and straight to slightly concave towards anal-fin origin. Body profile along anal-fin base posterodorsally slanted. Caudal peduncle nearly straight to slightly concave along dorsal and ventral margins. Snout rounded from margin of upper lip to vertical through anterior nostrils. Mouth terminal. Distal tip of maxilla anterior to vertical through center of orbit. Anterodorsal border of maxilla straight and posterodorsal border slightly concave. Anteroventral border straight and posteroventral borders convex. Maxilla slightly widened posteriorly.

 

Two tooth rows on premaxilla. Outer row with three pentacuspid teeth with central cusp longer. Inner row with five teeth, gradually decreasing in length from first to third teeth; all teeth with seven cusps, except last hexacuspidate tooth. First tooth with third cusp twice or three times longer and broader than other cusps. Second, third, and fourth teeth with central cusp twice or three times longer and broader than other cusps. Fifth tooth with fourth cusp twice or three times longer and broader than other cusps. Maxilla with two, three or four teeth; first and second teeth tricuspid, tetracuspid or pentacuspid; third teeth truncate, conical or tricuspid; fourth teeth conical. Five anteriormost dentary teeth larger than remaining teeth. First tooth heptacuspid; Second to fourth teeth with six cusps, followed by one truncate medium-sized tooth, and seven tricuspid teeth; central cusp in all teeth two to three times longer and broader than other cusps. All cusp tips slightly curved posteriorly.

 

Dorsal-fin rays ii, 8[20], 9 [21], 10[5] (n = 46; mean = 8.7); first unbranched ray approximately one-half length of second ray. Dorsal-fin origin located anterior to middle of SL and in same vertical through pelvic-fin origin. Adipose-fin located approximately at vertical through insertion of base of 17th -19th anal-fin rays. Anal-fin rays iii -iv, 18[7], 19[12], 20[14], 21[11], 22[3] (n = 46; mean = 19.8). Anal-fin profile concave. Anal fin origin anterior to vertical through base of last dorsal-fin ray. Pectoral-fin rays i, 9[1], 10[20], 11[25] (n = 46; mean = 10.5). Pectoral-fin tip not reaching pelvic-fin origin. Pelvic-fin rays i, 7 (n = 46). Pelvic-fin origin located anterior to vertical through dorsal-fin origin. Pelvic bone modified into strong spine. Anterior tip of two pelvic bones diverging widely and usually exserted from body wall. Dorsal procurrent rays 11 [1]. Ventral procurrent rays 9 [1]. Scales cycloid, moderately large. Lateral line complete. Scales in longitudinal series 33[4], 34[16], 35[15], 36[4], 37[1], 39[1] (n = 41; mean = 34.7). Scale rows between dorsal-fin origin and lateral line 5[4], 6[12], 7[28] (n = 44; mean = 6.5); scale rows between lateral line and pelvic fin origin 4[4], 5[38], 6[2] (n = 44; mean = 5.0). Precaudal vertebrae 15 [1], 16 [1]; caudal vertebrae 19 [2]; total vertebrae 34 [1], 35 [1]; supraneurals 4 [1], 5[1]. Gill-rakers 7+1/8 [2].

 

Color in alcohol. Ground color pale yelow. Head dorsum light gray. Two humeral spots separated by a light area. First humeral spot dark brown large and vertically elongate, trespassing upon fifth and sixth lateralline scales and extending over eight or nine horizontal series of scales, including lateral line; center of first humeral spot forming a circular darker spot inside. Second humeral spot very diffuse, trespassing upon ninth and tenth lateral-line scales and extending over eight to ten horizontal series of scales, including lateral line. Second humeral spot not visible in some specimens. Flanks with silvery narrow stripe extending from posterior opercular border to caudal spot. Patch of black chromatophores on caudal peduncle continued by black spot extending over middle caudal-fin rays. Yellow pigmentation on base of outer edge of caudal-fin rays. Remaining fins lacking distinctive patches of pigmentation (Fig. 1).

 

Sexual dimorphism. No apparent sexual dimorphism was observed.

 

Etymology. The specific epithet elassonaktis, from the Greek elasson, meaning few, and aktis, meaning rays, is in allusion to the small number of anal-fin rays.

 

Distribution. Jupiaba elassonaktis is known from medium and upper portions of rio Tocantins drainage, Brazil (Fig. 2).

 

Discussion

 

We herein describe a new species in Jupiaba , since it conforms to the definition of Zanata (1997), who established the genus on the basis of six putative synapomorphies associated with the elongation of the pelvic spine-like bones. On the other hand, the intrageneric phylogenetic relationships of Jupiaba species are not known. However, Zanata & Lima (2005) artificially divided the genus in two distinct species-group on the basis of tooth morphology: (1) species with premaxillary and dentary teeth somewhat compressed, with cusps similar in size to each other and dentary teeth decreasing gradually in size; (2) species with more robust teeth bearing one largest median cusp and small lateral ones, and larger dentary teeth anteriorly followed by distinctly smaller teeth. Jupiaba elassonaktis belongs to the second species-group, which also contains J. mucronata , J. essequibensis , J. scologaster , J. ocellata , J. polylepis , J. anteroides , J. abramoides , J. poranga , J. potaroensis , J. zonata , J. pirana , J. yarina , J. asymmetrica , and J. apenima . Nonetheless, the lack of phylogenetic information precludes any unambiguous assertions on the possible relationships of the new species, given that it is unwarranted to assume that these similarities effectively reflect common ancestry. This condition also prevents any reasonable biogeographic inferences.

 

Two other Jupiaba species inhabit the rio Tocantins drainage, namely J. apenima Zanata and J. polylepis Günther . Jupiaba elassonaktis is distinguished [[from]] J. apenima by the lower number of scales on lateral line (33- 39 vs. 55-59, respectively). The number of scales series above lateral line distinguishes J. elassonaktis from J. polylepis (5-7 vs. 8-11, respectively). Futhermore, J. elassonaktis is also distinguished from J. polylepis by the number of humeral spots. Jupiaba elassonaktis possesses two humeral spots. First humeral spot is large and vertically elongate located at fifth and sixth scales of lateral line and the second humeral spot very diffuse. Jupiaba polylepis exhibit only one humeral spot surrounded by a light area and located on sixth to nineth lateral line scales.

 

Jupiaba elassonaktis is known from upper and medium portions of the rio Tocantins drainage and probably is an additional example of endemism in this basin. The rio Tocantins drainage is an area of endemism for several Neotropical freshwater fish groups including new recently described characid species such as Hyphessobrycon hamatus , Astyanax elachylepis , Moenkhausia pankilopteryx , and Moenkhausia hysterosticta (Bertaco & Malabarba, 2005; Bertaco & Lucinda, 2005, 2006; Lucinda et al., 2007). Especially in its upper regions, the rio Tocantins drainage appears to be a highly endemic center for the Ancistrini, as shown by the presence of three recently described species of Hemiancistrus Bleeker (Cardoso & Lucinda, 2003), and by four endemic species of Ancistrus Kner (Fisch-Muller et al., 2001, 2005).

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Thiago N. A. Pereira

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Ecology

Habitat

Environment

benthopelagic; freshwater
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Conservation

Threats

Not Evaluated
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