Diapoma speculiferum Cope, 1894

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 : 73-76

Diapoma speculiferum Cope, 1894

Figs. 28-32 , Table 3

Diapoma speculiferum Cope, 1894a:67 [original description, type locality: Brazil, Rio Grande do Sul, rio Jacuhy (= rio Jacuí)]; 1894b:92: more complete description of holotype). – Fowler, 1906:334 (redescription of holotype of D. speculiferum ). – Eigenmann, 1910:438 (listed); 1914:38 (listed Eigenmann, 1921: plate 61, figure 4 (drawing of holotype). – Eigenmann & Myers, 1929:471 (redescription of species based on holotype). – Myers, 1942:91 (notes on specimens from río Cebollati, departments of Rocha and Minas, Uruguay; elongate opercles recorded for both males and females). – Fowler, 1951:412 (listed with synonymy. – Vaz-Ferreira, 1969:33: brief description, figure after Fowler, 1951), – Fowler, 1975:332 (listed). – Géry, 1977:359 (diagnosed in key). – Malabarba, 1983:187 (listed, specimens from arroyo dos Ratos, São Jerônimo and Santo Antônio da Patrulha, Rio Grande do Sul, Brazil. – Böhlke, 1984:54 (listed). – Weitzman & Fink, 1985:17, 96, 103, 109, 116 (additional locality records from rio Jacuí system, caudal morphology, caudal pump function, relationships, note on ecology). – Malabarba, 1989:134 (listed). – Burns et al., 1995:140-141 (shape of sperm cells). – Malabarba & Weitzman, 2000:279 (sperm cells elongated). – Weitzman, 2003:224 (maximum length; distribution; remarks and references. – Menezes, 2007:38 (listed in catalog; distribution). – Javonillo et al., 2010:500 (listed in table); 2010:509 (listed as member of Stevardiinae ).

Specimens examined: Brazil: MCP 7979 , 70 (SL 21.6-42.5), Rio Grande do Sul, Barra do Ribeiro , açude dos Garcia, km 56 on road BR 116 , approximately 30°17’S, 51°18’W ; MZUSP 14720 , 1 (SL 42.2 mm), rio Fão in Vila do Fão, município de Lajeado ; MZUSP 14715 , 4 (SL 26.2-34.2) , USNM 221151 , 9 (SL 27.5-32.7 mm), 221157, 3 (SL 21-32 mm) 221160, 13 (SL 21-32.7 mm), Marquês de Souza, município de Lajeado rio Forqueta , approximately 29°19’S, 52°06’W ; MZUSP 14717 , USNM 221154 , 17 (SL 21-33 mm), arroio Gran- de, muncípio de Arroio Grande, stream 1 km from city, where crosses under road BR 116 , between Pelotas and Jaguarão , approximately 32°06’S, 52°47’W . Uruguay: USNM 221155 , FMNH 70496 , 30 (SL 27-42 mm), Arroyo Blanco , Rivera, approximately 31°38’S, 54°47’W .

Diagnosis: D. speculiferum can be easily differentiated from its congeners, except D. pyrrhopteryx by the posterior prolongation of the operculum in both sexes consisting of a triangular extension of the posteroventral field of the opercle and a posteriorly broadened posterior region of the subopercle ( Fig. 28 and 35 ). The greatest horizontal length of the bony opercle is about three fourths of its total vertical length in adult males of about 32-38 mm SL. Diapoma pyrrhopteryx has the same opercular modifications, but its adipose fin, upper portion of the dorsal, posterior portions of the pelvic and caudal fins, and the ventral part of the anal fin are red in live or recently preserved males ( Fig. 34 ) contrasting with the pale fins of live or recently preserved male specimens of D. speculiferum ( Fig. 26 ). Additionally D. pyrrhopteryx has the maxillary teeth pentacuspid ( Fig. 37 ) and the snout longer ( Fig. 27 ) whereas in D. speculiferum the maxillary teeth are tricuspid ( Fig. 29 ) and the snout shorter ( Fig. 27 ).

Description: Morphometrics presented in Table 3.

Body comparatively small (SL 21-42.5 mm). General body shape, dorsal and ventral body profiles, mouth shape, position of fin origins and extension of maxilla identical to those of D. terofali and D. thauma described above. Posterior of head, however, very different from these two species due to bony and fleshy extension of gill cover in D. speculiferum . Dorsal region of opercle vertically oriented, its apical portion flat, narrowing to a blunt end, posteroventral opercular region prolonged, triangular shaped, subopercle posteriorly broadened ( Fig. 28 ). Opercular process extending slightly beyond to anterior base of pectoral fin.

Dorsal-fin rays ii, 8 in all specimens, n = 136. Adipose fin present. Anal-fin rays iv or v, branched rays 25-32, 28.1, n = 136. Posteriomost ray unbranched in all specimens, n = 136. Moderately developed anal-fin lobe including anterior unbranched rays and 6 or 7 branched rays. Anal fin of males with bilateral hooks on last unbranched ray and anterior 11 branched rays, distributed as in Fig. 31. Pectoral-fin rays i, 9-12 (anterior unbranched ray i, in all specimens), 10.4, n = 136. Posterior tip of longest pectoral-fin rays not reaching or just extending to pelvic-fin origin in mature males. Pelvic-fin rays i, 6, n = 136, last pelvic-fin ray unbranched, but counted as branched. Sexually mature males with hooks on pelvic-fin rays as shown in Fig. 32. A mature male ( MZUSP 28247, 33.5 mm SL) with 4 hooks on last unbranched ray, 5 on first, 7 on second, 8 on third, 7 on fourth, 5 on fifth and 12 on sixth branched rays. Distal tip of longest pelvic-fin rays extending slightly beyond anal-fin origin in males and females.

Scales cycloid, with few radii (3-7) along exposed field on body and radii more numerous (15-20) on enlarged scale bordering pouch opening. Lateral line incomplete, anterior segment with 8-13, 10, n = 113 perforated scales, followed by 14-30, 25.3, n = 113 non-perforated scales. Some specimens with additional posterior short segment represented by 3-13, 6.2, n = 34 perforated scales. Lateral series scales 36-39, 37.3, n = 113. Predorsal scales 12-16, 13.8, n = 127. Horizontal scale rows from dorsal-fin origin to anal-fin origin 9-11, 10, n = 129. Horizontal scale rows around caudal peduncle 14, n = 79.

Premaxillary teeth in two rows ( Fig. 29 ), outer row with 2-5, 3.6, n = 136 tricuspid teeth, inner row with 4-5, 4.1, n = 136 pentacuspid teeth. Maxillary ( Fig. 29 ) with 2-8, 4.2, n = 136 tricuspid teeth. Dentary ( Fig. 29 ) with 4, n = 136 anterior quadricuspid to pentacuspid teeth and 4-11, 6, n = 136 posterior tricuspid teeth, some of which with barely apparent cusps. Total number of gill rakers on first gill arch 12-16, 14.4, n = 135. Branchiostegal rays 4 in two cleared and stained specimens, 3 rays originating from anterior ceratohyal and 1 ray from posterior ceratohyal.

Color in alcohol: General body color as described above for D. terofali . Dark humeral blotch extending ventrally to fourth perforated lateral line scale, its anterior margin separated by 3 scales from upper portion of opercle. Lateral dark stripe inconspicuous but with a very conspicuous black line of chromatophores along stripe, inserted more deeply into musculature along stripe ( Fig. 25 ). Line extending from anterior margin of dark blotch to caudal-fin base. Fleshy extension of bony opercle and subopercle heavily pigmented with dark chromatophores surrounded by marginal clear area; pigmentation especially conspicuous in mature males and females. Other specimens have only scattered dark chromatophores so that opercle and subopercle are mostly silvery.

Color in life: Specimen photographed in life ( USNM 221115, SL 32.3 mm) with body silvery dark humeral blotch and lateral body stripe conspicuous. Fins pale to yellowish.

Sexual dimorphism, reproductive mode and gonad anatomy: As in other species, pelvic- and anal-fin hooks are present only in males. Several morphometric characters appeared to differ statistically between males and females when treated as proportions of standard length or head length ( Table 3, values of p in bold). However, when compared through regression analysis, the same data of males and females completely overlapped. Opercular extensions are about equally developed in both sexes and when tested through regression analysis, head length (measured from tip of snout to tip of opercle) of males and females revealed no significant statistical differences. In D. speculiferum spermatozoa were also found in the ovary of a female and ovoid sperm cells in the testes of a male, with the sperm nuclei slightly more elongate than those of D. terofali ( Burns et al., 1995, table 3).

Distribution: D. speculiferum occurs in lowland coastal streams in Rio Grande do Sul, Brazil, and Uruguay ( Fig. 16 ).

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 25: Diapoma speculiferum, USNM 221155, adult male above, SL 45.1 mm and adult female below, SL 47.5 mm.

FIGURE 26: Diapoma speculiferum, USNM 221152, male, SL 32.3 mm. Photographed in life.

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

FIGURE 28: Diapoma speculiferum, MZUSP 28247, C&S, sexually active male, SL 33.5 mm; opercular bones, lateral view, left side. OP, opercle; POP, preopercle; IOP, interopercle; SOP, subopercle.

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 30: Diapoma speculiferum, MZUSP 28247, C&S, sexually active male, SL 33.5 mm; caudal-fin squamation of ventral portion of caudal-fin lobe, lateral view, left side.

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 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.