Moenkhausia australis Eigenmann, 1908

Reia, Lais, Vicensotto, Ana Maria P. F., Oliveira, Claudio & Benine, Ricardo C., 2019, Taxonomy of Moenkhausia australis Eigenmann, 1908 (Characiformes, Characidae) with a discussion on its phylogenetic relationships, Zootaxa 4688 (2), pp. 213-231 : 218-223

Moenkhausia australis Eigenmann, 1908

( Figs. 2–3 , Table 3 )

Moenkhausia australe Eigenmann, 1908:103 (original description, type locality “Arroyos Trementina and Chagalalina”, Paraguay); Lima et al., 2003:150 (listed, as a synonym of M. sanctaefilomenae ); Benine et al., 2009:167 (comparison to M. forestii ); Litz & Koerber, 2014:16 (listed, as a synonym of M. sanctaefilomenae ); Mirande & Koerber, 2015:27 (listed, as a synonym of M. sanctaefilomenae ); Dagosta et al., 2015:424 (listed, comparative material); Koerber et al., 2017: 42 (as a synonym of M. sanctaefilomenae ); Ota et al., 2018: 4, 29–31, fig. 8d (in part: listed, Rio Paraná floodplain, Paraná, Brazil; short description, photo).

Tetragonopterus agassizii (not Steindachner).─ Boulenger, 1900: 2 (in part: listed).

Poecilurichthys agassizii (not Steindachner).─ Eigenmann, 1903b:522 (Arroyo Trementina and Arroyo Chagalalina, Para- guay).

Moenkhausia oligolepis (not Günther).─ Lima et al., 2013:318–319 (in part: specimens from Rio Guaporé).

Moenkhausia sanctaefilomenae (not Steindachner). ─ Eigenmann, 1917: 82 (in part; specimens from Paraguai basin); Britski et al., 2007: 51 (in part: short description, Rio Paraguai basin, Brazil); Bertaco et al., 2016:414 (listed, Rio Uruguai basin, Rio Grande do Sul, Brazil).

Moenkhausia aff. sanctaefilomenae . Graça & Pavanelli, 2007:67–68 (short description, photo; Rio Paraná basin, Brazil).

(not Mariguela et al., 2013; Azevedo-Santos & Benine, 2016)

Diagnosis. Moenkhausia australis is readily distinguished from all congeners, except M. cosmops Lima, Britski & Machado, M. diktyota Lima & Toledo-Piza, M. forestii , M. lineomaculata Dagosta, Marinho & Benine , M. oligolepis , M. pyrophthalma Costa , M. sanctaefilomenae and M. uirapuru Ohara & Lima by the presence of a reticulated body color pattern, formed by a dark pigmentation concentrated on the posterior portion of the scales, and a large dark blotch on the peduncle caudal preceded by a lighter area (vs. absence of a similar color pattern). Moenkhausia australis differs from M. cosmops , M. diktyota , M. pyrophthalma , M. lineomaculata , and M. uirapuru by the presence of the prepelvic region compressed laterally (vs. a prepelvic region flattened). Additionally, Moenkhausia australis can be distinguished from M. oligolepis by the number of lateral line scales (23–27 vs. 28–31). It is distinguished from M. sanctaefilomenae by the number of transversal series of scales above and below the lateral line (5/5 vs. 4/4). Moenkhausia australis is distinguished from M. lineomaculata by the absence of a longitudinal series of dark spots at body sides (vs. presence). Finally, M. australis is readily distinguished from M. forestii , M. pyrophthalma , M. cosmops , M. diktyota , and M. uirapuru by bearing a completely pored lateral line (vs. incomplete lateral line).

Description. Morphometric data in Table 3 . Largest specimen examined 62.3 mm SL. Body compressed, moderately short, greatest body depth at dorsal-fin origin. Dorsal profile of head slightly concave from snout to tip of supraoccipital spine. Dorsal profile of body slightly convex from posterior tip of supraoccipital to end of dorsal-fin base; straight, slightly inclined posteroventrally, from end of dorsal-fin to adipose-fin origin, and slightly concave along caudal peduncle. Ventral profile of body convex from anterior tip of dentary to anal-fin origin, straight along anal-fin base, and slightly concave along caudal peduncle. Prepelvic region compressed laterally.

Mouth terminal. Premaxillary teeth in two rows; outer row with 3(5), 4*(152), 5(12), tricuspid teeth; inner row with 4(1), 5*(165), 6(3) pentacuspidate teeth. Maxilla with 1(34), 2*(132), 3(3) pentacuspidate teeth. Dentary with 4*(133), 5*(33) pentacuspidate teeth, followed by a series of 7–10 small conical teeth. Central cusp in all teeth longer than lateral cusps ( Fig. 4 ).

Dorsal-fin rays ii, 8(5), 9*(163), 10(1). Anal-fin rays iv(2) or v(3), 18(1), 20(8), 21(28), 22(31), 23*(40), 24*(31), 25(21), 26(7). Pectoral-fin rays i, 10(32), 11(93), 12(40), 13(4), some specimens with last ray unbranched (i) (117); its tip reaching beyond pelvic-fin origin. Pelvic-fin rays i, 6(4), 7*(162), 8(2), its tip when adpressed reaching analfin origin. Caudal-fin rays 10+9(5). Caudal fin forked, lobes similar in size, with 8(2), 10(3) dorsal procurrent rays and 7(4), 9(1) ventral procurrent rays. First gill arch with 9*(16), 10*(119), 11(34) gill-rakers on lower limb and 6(4), 7(83) 8(79), 9(3) gill-rakers on upper limb. Total vertebrae 30(2), 31(3). Supraneurals 4(2), 5(3).

Scales cycloid with straight divergent radii. Lateral line with 23(4), 24(22), 25(64), 26*(20), 27*(18) pored scales. Scale rows between lateral line and dorsal-fin origin with 4(11) or 5*(158). Scale rows between lateral line and midventral scale series 4(7), 5*(162). Predorsal scales 6(3), 7(26), 8(95), 9(23). Scales around caudal peduncle 11(30), 12(108), 13(24), 14(6). Single row of scales overlaying basal portion of anterior rays of anal fin. Small scales covering proximal two-thirds of caudal-fin lobes.

Color in alcohol. Overall ground coloration dark silver or yellowish tan (depending on degree of retention of guanine). Dark chromatophores concentrated on distal margin of scales resulting in conspicuous reticulated pattern. Mid-dorsal region darker than flanks. Two conspicuous vertical dark humeral blotches, first more conspicuous, extending horizontally along two scales, and vertically three to four scales, including lateral line. Posterior humeral blotch inconspicuous, extending horizontally one scale, and vertically two scales, including lateral line. Some specimens lacking second dark blotch. Few dark chromatophores scattered on infraorbitals and opercle. Dark thin stripe extending along horizontal septum on posterior half of body. Caudal fin with conspicuous dark blotch extending from its anterior portion onto proximal one third of caudal-fin rays. Caudal peduncle with conspicuous light area preceding caudal-fin blotch. Adipose fin hyaline with chromatophores randomly distributed; dorsal, pectoral, pelvic and anal fins hyaline with chromatophores scattered on interradial membranes ( Fig. 3 ).

Color in life. Overall ground coloration bright silver to light plumbeous. Reticulate pattern similar to preserved specimens. Dorsal portion of head and body with a golden hue. Dorsal portion of eyes red, yellowish around iris, and bright silver ventrally. Distal portion of dorsal, pelvic and anal-fin rays light brown. Caudal fin yellowish ( Fig. 5 ).

Sexual dimorphism: Mature males bear one to two small bony hooks per segment on the posterior branches of the first to fourth anal-fin rays, and first to three pelvic-fin rays.

Distribution. Moenkhausia australis is known from the La Plata basin in the lower portion of the upper Paraná basin (Mato Grosso do Sul State), the Rio Paraguai, and Rio Uruguai basins, and in the Amazon basin, at the upper Rio Madeira basin (Rio Guaporé and Rio Mamoré) ( Fig. 6 ).

Etymology. Eigenmann (1908) used the adjective “austral” to compose the name of his new species as indicative of its distribution “South of Amazon”. This author, however, mistakenly used the neuter form “australe” as the specific epithet of the feminine name Moenkhausia . We herein correct the specific epithet to “ australis ” for proper gender concordance.

Remarks. The reexamination of the material identified as Moenkhausia australis used in the phylogenetic analysis of Mariguela et al. (2013) and in the comparative material of Azevedo-Santos & Benine (2016) showed them to be, instead, specimens of M. forestii .

Figures

FIGURE 2. Moenkhausia australis (a) CAS 70818, lectotype, undetermined sex, 38.5 mm SL, Arroyo Trementina (= Rio Aquidaban in Concepcion, Paraguay); (b) CAS 70819, paralectotype, 30.7 mm SL, Arroyo Chagalalina (= Rio Aquidaban in Concepcion, Paraguay).

FIGURE 3. Moenkhausia australis: (a) MZUSP 59317, 40.7 mm SL, Rio Taboco, Aquidauana, Mato Grosso do Sul, Brazil; (b) MCP 27464, 43.2 mm SL, Rio São Francisco, São Francisco de Assis, Rio Grande do Sul, Brazil; (c) LBP 9665, 37.5 mm SL, Córrego Azul, Ivinhema, Mato Grosso do Sul, Brazil; (d) MZUSP 115631, 36.2 mm SL, Rio Guaporé, Vila Bela da Santíssima Trindade, Mato Grosso, Brazil.

FIGURE 4. Moenkhausia australis, LBP 9714, 51.1 mm SL. (a) Left maxilla (medial view); (b) left premaxilla (medial view); (c) left dentary (medial view). Scale bar 1 mm.

FIGURE 5. Moenkhausia australis MZUSP 115631, 32.8 mm SL, Rio Guaporé, Mato Grosso, Brazil, color in life. Photo by F. Dagosta.

FIGURE 6. Partial map of South America indicating the distribution of M. australis. Red triangle indicates type-locality. Rio Paraguai basin = orange; upper Rio Paraná = violet; Rio Uruguai basin = light brown; Rio Madeira basin = blue.