Melanorivulus, Costa, 2006

Ota, Renata Rúbia, Deprá, Gabriel de Carvalho, Graça, Weferson Júnio da & Pavanelli, Carla Simone, 2018, Peixes da planície de inundação do alto rio Paraná e áreas adjacentes: revised, annotated and updated, Neotropical Ichthyology 16 (2), pp. 1-111 : 99

Melanorivulus sp.

Fig. 36

Body elongated; greatest depth contained 4.1 to 4.6 and caudal peduncle depth 6.3 to 7.2 times in SL; head length 3.6 to 3.9, predorsal distance 1.2 to 1.3, prepelvic distance 1.7 to 1.9; dorsal-fin base length 8.6 to 10.0, anal-fin base length 4.2 to 5.1 and head width 4.6 to 5.1 times in SL; horizontal orbital diameter 2.8 to 3.3 in HL. Mouth terminal, premaxilla and dentary with several small teeth. Longitudinal series with 29-31 scales and transverse series with 8 or 9 scale rows. Dorsal fin with 8 or 9, pectoral fin with 11 or 12, pelvic fin with 6 or 7 and anal fin with 13-15 rays. Males with ground color greyish or pale brown, with dark-brown oblique and irregular stripes, V-shaped (its vertex turned forward); dark-brown transverse stripes on opercle; dorsal, anal and caudal fins with dark-brown transverse stripes. Females with similar color pattern, besides dark-brown rounded blotch on caudal-fin base.

Maximum standard length. 25.0 mm.

Distribution. Upper rio Paraná basin.

Remarks. Melanorivulus sp. was identified as Rivulus apiamici by Graça, Pavanelli (2007). Costa (2011) included all species of the former Rivulus punctatus Boulenger, 1895 species complex in the genus Melanorivulus Costa, 2006 , one of which is M. apiamici (Costa 1989) . Recently, Nielsen (2016) restricted the distribution of M. apiamici to the right bank of the upper rio Paraná, between Bataguassu and Três Lagoas, State of Mato Grosso do Sul. According to literature, the only two species known from the upper rio Paraná floodplain are the recently described Melanorivulus amambaiensis Volcan, Severo-Neto, Lanés 2018 and M. ivinhemensis Volcan, Severo-Neto, Lanés 2018 . We analyzed preserved specimens from the rio Ivinhema (NUP 9350) and rio Amambaí (NUP 17575) basins, as well as from other localities in the upper rio Paraná floodplain (NUP 10022 and 12082). The specimens from these lots have 22-26 total caudal-fin rays, which is close to the counts recorded for M. amambaiensis in the original description, and less than the counts recorded for M. ivinhemensis . In fact, Melanorivulus specimens from other nearby localities available to us also show overlapping counts: from the rio Verde basin (NUP 6217), 24-30 rays; from the lower rio Paranapanema basin (NUP 6060, 6075, 7598), 22-28 rays. Thus, we prefer to use Melanorivulus sp. until more information, such as color pattern in life, is available.

Figures

Fig. 36. a. Melanorivulus sp., NUP 17575, córrego Querência, Amambaí, State of Mato Grosso do Sul (top, female, 24.7 mm SL; bottom, male, 28.3 mm SL). b. Pamphorichthys hollandi, NUP 16549, rio Baia, Taquarussu, State of Mato Grosso do Sul, Brazil (top, female, 22.8 mm SL; bottom, male, 17.6 mm SL). c. Phalloceros harpagos (top, female, NUP 9360, 22.7 mm SL, female, córrego de nome desconhecido, Jatei, State of Mato Grosso do Sul; bottom, male, NUP 1938, 18.0 mm SL, riacho Caracu, Porto Rico, State of Paraná). d. Phallotorynus pankalos, NUP 5839, córrego Sossego, tributary of the rio Iguatemi, Paranhos, State of Mato Grosso do Sul (top, female, 28.4 mm SL; bottom, male, 18.6 mm SL). e. Phallotorynus victoriae, NUP 1603, lagoa do Portinho, tributary of the rio Paraná, Três Lagoas, State of Mato Grosso do Sul (top, female, 14.6 mm SL; bottom, male, 18.6 mm SL). f. Poecilia reticulata, fresh specimens, uncat (top, female, 35.2 mm SL; bottom, male, 20.3 mm SL). g. Plagioscion squamosissimus, 330.0 mm SL, fresh specimen, uncat.