Diapoma pyrrhopteryx, Menezes & Weitzman, 2011

Menezes, Naércio A. & Weitzman, Stanley H., 2011, A Systematic Review Of Diapoma (Teleostei: Characiformes: Characidae: Stevardiinae: Diapomini) With Descriptions Of Two New Species From Southern Brazil, Papéis Avulsos de Zoologia 51 (5), pp. 59-82 : 76-80

Diapoma pyrrhopteryx , new species

Figs. 33-39 , Table 4

Specimens examined: All specimens from Brazil.

Holotype: MCP 44104 , male, SL 51 mm, rio do Peixe , tributary of rio Uruguai, Concórdia, Santa Catarina, 27°28’S, 51°53’W.

Paratypes: MCP 12982 , 8 (SL 38-49 mm), collected with holotype ; MCP 13368 , 8 (SL 25-56 mm), rio Pelotas , tributary of rio Uruguai, Anita Garibaldi, Rio Grande do Sul, 27°47’51”S, 51°16’42”W ; MCP 44141 , 22 (SL 29-56 mm) , MZUSP 104323 , 2 (C&S), rio Canoas , tributary of rio Uruguai, road between Tupitinga and Celso Ramos, Santa Catarina, 27°35’11”S, 51°22’48”W .

Diagnosis: Diapoma pyrrhopteryx is morphologically most similar to D. speculiferum , both species sharing the posterior elongation of opercle and subopercle. This feature distinguishes it from D. terofali and D. thauma . Diapoma pyrrhopteryx differs from D. speculiferum in the presence of red fins in live males (versus fins pale to yellowish in live males of D. speculiferum ), the longer snout, 21.3-24.5% of head length, Fig. 27 (versus, 17-21.4% of head length, in D. speculiferum ) and the maxillary teeth pentacuspid, Fig. 37 (versus maxillary teeth tricuspid in D. speculiferum , Fig. 29 ).

Description: Morphometrics presented in Table 4.

Body comparatively large (SL 29-56 mm), larger than that of D. speculiferum . General body and head shapes, dorsal and ventral body profiles, mouth shape, position of fin origins and extension of maxilla as in D. speculiferum .

Dorsal fin ii, 8 in all specimens, n = 41. Posteriormost ray unbranched in all specimens, n = 41. Adipose fin present. Unbranched anal-fin rays iv or v, usually iv, branched rays 24-30 (29), 36.4, n = 41. Well-developed anal-fin lobe including anterior unbranched rays and 9-10 branched rays. Anal fin of males with bilateral hooks on last unbranched ray and anterior 10 branched rays, distributed as in Fig. 38 . Pectoral-fin rays i, 9-11 (11), 10 (unbranched pectoral-fin ray i, in all specimens), n = 41. Posterior tip of longest pectoral-fin rays extending slightly beyond pelvic-fin origin in all specimens. Pelvic-fin rays i, 6, n = 41, last pelvic-fin rays unbranched but counted as branched. Sexually mature males with hooks on pelvic

78 MENEZES, N.A. & WEITZMAN, S.H.: REVIEW OF DIAPOMA AND DESCRIPTIONS OF NEW SPECIES FROM SOUTHERN BRAZIL

fin, distributed as in fig. 39. A mature male ( MZUSP 104323, SL 52 mm) has 7 hooks on fifth, 3 on sixth and no hooks on remaining branched or unbranched rays. Distal tip of longest pelvic-fin rays falling slightly short or just extending to origin of anal fin.

Scales cycloid, with few radii (5-10) on exposed field on body and more numerous (20-30) on enlarged scale bordering pouch opening. Lateral line incomplete, with 10-22 (11), 13.4, n = 35 perforated scales on anterior segment, followed by 1-20 (18), 11.8, n = 41 non-perforated scales and a posterior segment with 6-26 (6), 13.5, n = 35 perforated scales in most specimens. Lateral series scales 36-42 (37), 38.45, n = 36. Predorsal scales 13-15 (13), 13.7, n = 41. Horizontal scale rows from dorsal-fin origin to anal-fin origin 9-11(10), 10, n = 41. Horizontal scale rows around caudal peduncle 13-14(14), 13.9, n = 35.

Premaxillay teeth in two rows ( Fig. 37 ), outer row with 2-5(4), n = 35, n = 41 tricuspid teeth, inner row with 4-5(4), 4.3, n = 41 pentacuspid teeth. Maxillary ( Fig. 37 ) with 3-6(5), 4, n = 41 anterior quadricuspid to pentacuspid teeth. Dentary ( Fig. 37 ) with 4-5(5), 4.3, n = 41 anterior quadricuspid to pentacuspid teeth and 4-10 (7), n = 41 tricuspid teeth, posteriormost teeth with vestigial cusps. Total number of gill rakers on first gill arch 12-14 (14), 13.4, n = 40. Branchiostegal rays in two cleared and stained specimens 4, 3 originating from anterior ceratohyal and 1 rays from posterior ceratohyal.

Color in alcohol: Identical to that of D. speculiferum as described above. Lateral body stripe mostly obscured by guanine with black line along its length inconspicuous.

Color in life: A male specimen ( Fig. 34 ) preserved soon after capture ( MCP 44377) had body silvery with upper part of dorsal-fin red mixed with yellow and separated from its basal dark portion by a whitish longitudinal stripe. Uppermost and lowermost caudal-fin rays red. Marginal posterior portion of caudal fin pale to yellowish and remaining area of fin with scattered dark chromatophores. Adipose fin red. Anteroventral portion of anal fin red, and contrasting with remaining portion of anterior whitish area of lobe. Remaining portion of anal-fin area yellow and marginal posterior area of fin dark. Posterior two thirds of pelvic fin red mixed with yellow, anterior third whitish. Posterior portion of pectoral fin yellowish, with upper posterior marginal portion of fin with red chromatophores. Very conspicuous dark humeral blotch present along with dark blotch on caudal peduncle, extending posteriorly to anterior portion of median caudal-fin rays. Female from the same lot ( Fig. 34 ) had body pale with yellowish areas especially distributed over dorsal part of body. All fins yellowish especially adipose, upper part of dorsal, dorsal and ventral rays of caudal and posterior part of anal fins. Humeral dark blotch, dark blotch on caudal peduncle and lateral body stripe inconspicuous.

Sexual dimorphism, reproductive mode and gonad anatomy: Pelvic- and anal-fin hooks are present only in males of D. pyrrhopteryx , but their number and arrangement on both fins are different from those in D. speculiferum (compare Figs. 31 and 32 with Figs. 38 and 39 ). Several morphometric characters in table 4 show significant statistical differences between males and females (values of p in bold), but when submitted to regression analysis none of them revealed significant differences between sexes. As in D. speculiferum no significant statistical differences was detected in opercular extensions of males and females. Histological sections could not be done through the ovary of mature females of this species.

Distribution: This species has been collected to date in the rio Canoas basin or tributaries flowing into this basin that belongs to the rio Uruguay basin in Rio Grande do Sul, Brazil ( Fig. 16 ).

Etymology: The species name, pyrrhopteryx , from the Greek words “pyrrho” meaning red and “pteryx” meaning fin is in reference to the red fin colors of the fish when alive.

Remarks: Specimens ( MCP 44377, 2, 65.4 mm, and 72.5 mm SL) from rio Passo Fundo, tributary of rio Uruguai, Rio Grande do Sul, (approximately 27°48’S, 52°35’W) used to get color pictures have all the morphological features of the type specimens.

Figures

FIGURE 16: Map of southern South America showing collecting sites and type localities (black symbols) of the species of Diapoma. Squares, Diapoma pyrrhopteryx; triangles, D. speculiferum; diamonds, D. terofali; circles, D. thauma. Some symbols may represent more than one locality.

FIGURE 27: Snout length as a function of head length for Diapoma speculiferum and D. pyrrhopteryx.

FIGURE 29: Diapoma speculiferum, MZUSP 28247, C&S, sexually active male, SL 33.5 mm; jaws and dentition, lateral view, left side, anterior at left.

FIGURE 32: Diapoma speculiferum, MZUSP 28247, C&S, sexually active male, SL 33.5 mm; pelvic-fin rays, ventral view, left side, showing pelvic-fin hooks.

FIGURE 33: Diapoma pyrrhopteryx, MCP 44104, adult male above, SL 51.0 mm, and MCP 13368, adult female below, SL 44.0 mm.

FIGURE 34: Diapoma pyrrhopteryx, MCP 44377. Color pictures of adult male, above, SL 72.5 mm and adult female below, SL 65.4 mm.

FIGURE 35: Diapoma pyrrhopteryx, MZUSP 104323, C&S, sexually active male, SL 52.0 mm; opercular bones, lateral view, left side. OP, opercle; POP, preopercle; IOP, interopercle; SOP, subopercle.

FIGURE 37: Diapoma pyrrhopteryx, MZUSP 104323, C&S, sexually active male, SL 52.0 mm jaws and dentition, lateral view, left side, anterior at left.

FIGURE 38: Diapoma pyrrhopteryx, MZUSP 104323, C&S, sexually active male, SL 52.0 mm; anterior portion of anal fin, lateral view, left side, showing anal-fin hooks.

FIGURE 39: Diapoma pyrrhopteryx, MZUSP 104323, C&S, sexually active male, SL 52.0 mm; pelvic-fin rays, ventral view, left side, showing pelvic-fin hooks.