Macropsobrycon uruguayanae Eigenmann, 1915

Figs. 1-7

Macropsobrycon uruguayanae Eigenmann, 1915: 48 [original description; dentition figured; type locality Uruguayana (Uruguaiana) and Cacequi, Rio Grande do Sul, Brazil, rio Uruguay drainage]. -Henn, 1928: 59 [type material listed from Carnegie Museum]. -Ibarra & Stewart, 1987: 54 [type material listed from Field Museum of Natural History]. - Ringuelet, 1967 [listed as freshwater fish from Argentina]. - Géry, 1972: 15-18 [inclusion inAphyoditeini]. - Géry, 1973: 108-109 [compared to Macropsobrycon xinguensis]. - Géry, 1977: 594 [in key to Aphyoditeina genera and species]. - Malabarba 1989: 136 [listed to laguna dos Patos drainage]. - Burns et al., 1997: 434 [listed as inseminating species]. - Malabarba, 1998: 218 [phylogenetic diagnosis of the genus and placement in Compsurini]. - Burns et al., 1998: 242 [short description of sperm ultrastructure]. - Malabarba & Weitzman, 1999: 416, 427 [comparison with Acinocheirodon melanogramma]. - Malabarba & Weitzman, 2000: 270, 279-280 [comparison with Kolpotocheirodon theloura]. -López et al., 2003: 31 [listed from Argentina]. - Malabarba et al., 2003: 217 [listed in Cheirodontinae]. - Quagio-Grassiotto et al., 2003: 41 [sperm morphology compared to other characiforms]. -Menni, 2004: 78 [listed from Argentina]. - Malabarba et al., 2004: 324-325 [comparison with Kolpotocheirodon figueiredoi]. - Malabarba, 2007: 37 [listed in Cheirodontinae]. - Pecio et al., 2007: 458 [sperm morphology compared along with other inseminating characids]. - Oliveira et al., 2008: 691- 697 [description of sperm ultrastructure and comparison to inseminating characids]. - Bührnheim et al., 2008: 671 [referred as bearing conical teeth]. - Miquelarena et al., 2008: 78 [listed from Argentina]. - Javonillo et al., 2010: 505-507 [relationships within Characidae]. - Azevedo et al., 2010: 87-96 [reproductive biology and gill gland development].

Diagnosis. Same as the genus.

Description. Morphometrics given in Table 1. Body slightly elongate and compressed, deepest at dorsal-fin origin. Dorsal profile convex from snout tip to dorsal-fin origin, straight or slightly convex from that point to adipose-fin origin. Ventral profile convex from snout tip to pelvic-fin insertion, straight or somewhat concave up to anal-fin origin, straight to convex on anal-fin base. Caudal-peduncle profile slightly concave dorsally and ventrally. Snout short, mouth superior above horizontal line projected through pupil dorsal border and below horizontal line projected through orbit dorsal edge.

Premaxilla slender with 3(1), 4(1), 5(11), 6(14) or 7(4) conical teeth, aligned and similar in size; ascending process wide and square shaped. Maxilla toothless, wide, arched, with distal tip reaching or surpassing vertical line projected through orbit anterior edge. Dentary with 4(2), 5(8), 6(13), 7(4), 8(2) or 10(2) aligned teeth; teeth conical, rarely bicuspid; four medial teeth larger with similar size, following teeth smaller decreasing in size laterally (Fig. 2).

Dorsal-fin origin slightly posterior to vertical through middle of standard length. Dorsal-fin rays ii,8-10 (mean = 9.0, n = 120). Adipose-fin origin at vertical line through last analfin ray insertion.Anal-fin origin slightly anterior to last dorsal-fin ray insertion; anterior rays longer than posterior ones; distal profile more convex on females than on males. Anal-fin rays iii-v,17-22 (mean = 23.8, n = 121); last unbranched up to nineth anal-fin branched ray of mature or maturing males bearing small retrorse hooks (Fig. 3). Hooks placed from middle length to near the distal tip of anal-fin rays, attached at posterior margin and usually posterior branch in branched portion, bent over lateral surface, and directed anteriorly to anal-fin frontal margin. One or two hooks per anal-fin ray segment. Pectoral-fin rays i,10-12 (mean = 10.6, n = 121); longest rays surpassing pelvic-fin insertion. Pelvic-fin insertion anterior to vertical line through dorsal-fin origin. Pelvic-fin rays i,7; all of them bearing 1-2 unilateral ventromedial antrorse hooks per segment on mature males. Caudal fin with 18-20 (mean = 19.0, n = 121) principal rays. Principal caudalfin rays 12 th and 13 th bearing recurved strong hooks anteriorly directed on branched portions, usually dorsally; principal caudal-fin rays 14 th to 18 th bearing posteriorly directed feeble spinelets along proximal portion, and anteriorly directed bony hooks along mid- and distal portions of fin rays on mature males (Fig. 4).

Lateral line incomplete, with 3-8 (mean = 6.1, n = 91) perforated scales. Total scales at lateral line series 30-37 (mean = 33.6, n = 120) scales. Scale rows between dorsal-fin insertion and lateral line 5; scale rows between lateral line and pelvicfin insertion 2-4 (mean = 3.2, n = 121). Predorsal scales 10-16 (mean = 12.9, n = 119); postdorsal scales 7-10 (mean = 8.2, n = 121); scales rows around caudal peduncle 12-14 (mean = 13.8, n = 121). Last scales of lateral scale rows with higher radii number on adult males than other body scales. Last scale of scale row below lateral line larger and posteriorly hypertrophied on mature males, with distal margin reaching or slightly overlapping most proximal caudal-fin ray spinelets (Figs. 5-6).

Mature males with gill gland on first branchial arch (Fig. 7). Gill rakers of first branchial arch 1.5 times longer than rakers from remaining branchial arches, not bearing denticles, 3(2), 4(2) on hypobranchial, 13(3), 14(1) on ceratobranchial, 7(4) on epibranchial. Supraneurals 4(1), 5(15), 6(74), 7(115), 8(28), 9(2). Total vertebrae 29(1), 30(35), 31(179), 32(35). Precaudal vertebrae 12(4), 13(227), 14(20).

Pseudotympanum as large muscular hiatus between first and second pleural ribs, limited dorsally by the lateralis superficialis muscle, posteriorly by naked anterior face of second pleural rib, posteroventrally by obliquus inferioris muscle, anteroventrally by obliquus superioris muscle.

Color in alcohol. Overall body color varying from light yellow in fresh preserved specimens to pale brownish on old preserved specimens (Fig. 1a,c). Head black to dark brown dorsally. Region of infraorbitals 3-5 and opercular apparatus silver on freshly preserved specimens and yellow on older ones. Dark melanophores surround nares, lips, and anterior margin of orbit. Mental region dark due to high concentration of melanophores. Humeral spot absent. Dorsal and dorsolateral portion of body with melanophores distributed at posterior margin of the scales. Thin dark line extending laterally on body, from posterior region of pseudotympanum to caudal spot. Posterior portion of this line sometimes silver. Caudal region with few melanophores distributed in oblique lines along myoseptum of epaxialis and hypaxialis muscles. Ventral region with higher concentration of melanophores around pelvic-fin insertion in mature males. All fins hyaline with scattered melanophores, except dorsal fin with a small elongated spot between distal tip of first unbranched ray and midpoint of second unbranched ray.Anal fin with an elongated small spot at base of unbranched anal-fin rays. Males with higher concentration of melanophores at distal margin of anal fin than females. Caudal spot round, not reaching dorsal and ventral margins of caudal peduncle, and not extending over middle caudal-fin rays; not conspicuous on some specimens.

Color in life. Overall body and head color pattern silver to white (Fig. 1b). Lateral body band silver.All the fins are hyaline with few scattered melanophores, and a small dark spot present at the dorsal and anal fin as described above.

Sexual dimorphism. Mature males can be differentiated from adult females by the presence hooks on pelvic, anal and caudal-fin rays (Figs. 3-5). Males also present the the gill filaments from the first branchial developed into a gill gland (Fig. 7), due to the fusion of adjacent gill filaments by expansion of the epithelium that covers it (Azevedo et al., 2010). The last scale of the scale row below the lateral line is also larger and more developed in males than females (Fig. 6b). Although the females also present a homologous scale relatively large when compared to other cheirodontine species, it is still smaller than that observed in males. Mature males also have a higher number of melanophores at the distal portion of the anal-fin rays forming a tenuous dark band along the distal margin of the anal fin that it is not seen in females. The ventral profile of the anal fin also differs between males and females, being less concave on males.

Habitat and ecological notes. Macropsobrycon uruguayanae is usually found in natural flooded ponds and/or small lagoons with direct and active connection to rivers or streams. This kind of habitat is strongly affected along the area of distribution of this species by its extensive use to rice cultivation. The species is inseminating with reproductive biology described in detail by Azevedo et al. (2010).

Distribution and geographical variation. Records of Macropsobrycon uruguayanae are known from Rio Grande do Sul State in southern of Brazil, Província de Entre Ríos in Argentina (Demonte & Arias, 2005; Miquelarena et al., 2008), and Uruguay. Its geographical distribution encompasses the rio Uruguay basin, rio Negro basin (large tributary of the lower rio Uruguay), and laguna dos Patos drainage (Fig. 8).

The PCA analysis provided some morphological differences among the populations from the three studied drainages. The principal component 1 represented 72.5% of the variance, however it was found a correlation of 0.96 between its scores and the standard length values, showing to be most affected by the size. The second and third principal component represented respectively 6.2% and 4.7% of the variance. The principal component 2 showed a trend of separation between the specimens from rio Negro and from rio Uruguay basins. The individuals from rio Negro presented relatively smaller snout length and trends to bigger horizontal orbit diameter than the rio Uruguay representatives. Morphological differences between Macropsobrycon uruguayanae from laguna dos Patos basin and rio Negro basin were evidenced by the principal component 3. The laguna dos Patos basin specimens presented somewhat larger caudal peduncle length and upper jaw length, and relatively smaller anal-fin base length than specimens from rio Uruguay basin (Fig. 9). The MANOVA analysis of the PC2 and PC3 scores did not succeed in discrimitating the three populations.

Material analyzed: Macropsobrycon uruguayanae. Type material. Holotype: FMNH 57910, 36.0 mm SL, Brazil, Cacequy, 1 Feb 1909, J. D. Haseman. Paratypes: FMNH 57911, 4, 14.4-35.5 mm SL, Brazil, Cacequy, 1 Feb 1909, J. D. Haseman. FMNH 57912, 21.3 mm SL, Brazil, Cacequy, 5 Feb 1909, J. D. Haseman. Nontype material. Laguna dos Patos system, Brazil, Rio Grande do Sul: MCP 8421, 1 (m, male, 34.7 mm SL), arroio Capané at bridge on BR 290, tributary of rio Jacuí, 24 Oct 1982, C.A. S. Lucena & L. R. Malabarba. MCP 9245, 6 (2m, males, 34.8-40.6 mm SL, 3, unsexed, 39.2-40.8 mm SL, 1 c&s, 32.4 mm SL), backwater of rio Jacuí, road between Santa Maria and Vera Cruz, 16 Sep 1983, C. A. S. Lucena, L. R. Malabarba & R. E. Reis. MCP 11997, 11 (4m, males, 32.4- 39.8 mm SL, 6m, females, 31.1-39.2 mm SL, 1, unsexed, 30.9 mm SL, 1 c&s, female, 32.4 mm SL), arroio Francisquinho on highway BR 290 between Butiá and Rio Pardo, rio Jacuí basin, 24 Oct 1982, C. A. S. Lucena & L. R. Malabarba. MCP 19410, 1 (unsexed, 22.3 mm SL), lakes on left margin of rio Jacuí, at bridge on road connecting BR 290 to Cachoeira do Sulpicaré, 22 Jan 1996, L. R. Malabarba, J. R. Burns & J. F. Pezzi. MCP 20900, 87 (6m, males, 29.3-33.0 mm SL, 2m, females, 35.5-39.6 mm SL, 66, unsexed, 10.5-36.6 mm SL, 6 c&s, males, 24.6-34.2 mm SL, 2 c&s, females 33.2-35.1 mm SL, 1 c&s, unsexed, 23.4 mm SL), stream on rio Jacuí basin, at bridge on road between São Gabriel and Tiarajupuçá, 14 Jan 1997, L. R. Malabarba, J. Alves Gomes & V. Bertaco. MCP 37579, 2 (1m, male, 36.1 mm SL, 1m, female, 33.7 mm SL), Taim, Lago do Nicola, Jun 2004, A. Garcia. UFRGS 2244, 3 (unsexed, 22.9-24.7 mm SL) Rio Grande, Estação Ecológica do Taim, 8 May 1981, R. E. Reis & J. R. Stehmann. UFRGS 2245, 2 (1m, female, 34.0, 1, unsexed, 33.2 mm SL), between Taim and Mirim, channel parallel to BR 471 near a pump building in Estação Ecológica do Taim, 21 Apr 1979, L. Jardim & L. Chomenko. UFRGS 2306, 5 m (females, 30.7-36.4 mm SL), between Rio Grande and Mirim, right margin of BR 471 on Arroio Taim road, Estação Ecológica do Taim, 7 Dec 1979, N. A. Menezes et al. UFRGS 2307, 3 m (females, 33.0-35.2 mm SL), same locality as UFRGS 2306, 7 Jul 1979, P. A. Buckup. UFRGS 5604, 5 (4m, males, 34.2-35.4 mm SL, 1m, female, 34.0 mm SL), Barra do Ribeiro, arroio Ribeiro, bridge on road to Barra do Ribeiro, 19 Oct 1999. USNM 268449, 3 (2m, males, 31.3-32.0 mm SL, 1m, female, 37.3 mm SL), arroio Sarandi at stream under road crossing on road between Pelotas and Jaguarão, tributary of lago Mirim North of arroio Grande, 14 Dec 1972, N. A. Menezes et al. Rio Negro basin, Brazil, Rio Grande do Sul: MCP 11932, 1 (unsexed, 25.4 mm SL), Bagé, arroio on BR 153 km 33 between Bagé and Aceguá, 25 Oct 1982, C. A. S. Lucena & L. R. Malabarba. MCP 11938, 6 (3m, males, 28.0-28.6 mm SL, 1m, female, 31.0 mm SL, 2, unsexed, 19.5-23.4 mm SL) rio Negro, bridge on highway BR 293, between Bagé and Aceguá, 25 Oct 1982, C. A. S. Lucena, L. R. Malabarba. UFRGS 8383, 2 (1m, female, 38.9 mm SL, 1, unsexed, 25.5 mm SL) Bagé, sanga Cinco Salsos, BR 153 between Aceguá and Bagé, 29 Mar 2006, L. R. Malabarba et al. UFRGS 8430, 18 (8m, males, 30.6-32.4 mm SL, 3m, females, 28.2-34.8 mm SL, 5, unsexed, 28.2-31.3 mm SL, 1 c&s, male, 31.3 mm SL), Bagé, rio Negro on highway BR 153 between Aceguá and Bagé, 29 Mar 2006, L. R. Malabarba et al. Uruguay, Cerro Largo: ANSP 168826, 20 (20.5-34.5 mm SL), Uruguay, Depto. Cerro Largo, pool at 10 m of rio Negro, Arreria, 19 may 1984, C. A. S. Lucena & C. Chagas. MCP 11936, 120 (8m, males, 31.6-35.5 mm SL, 13m, females, 28.7-35.7 mm SL, 92, unsexed, 22.9-32.4 mm SL, 4 c&s, males, 30.2-31.4 mm SL, 5 c&s, females, 30.0-31.7 mm SL, 4 c&s, unsexed, 21.5-25.6 mm SL), same data as ANSP 168826. Uruguay, Rivera: UFRGS 7277, 2 (1m, male, 31.2 mm SL, 1m, female, 39.3 mm SL), rio Negro en el puente sobre la ruta 44, paso de Manzaneano, haci la ruta 26, 27 May 2005, L. R. Malabarba, V.A. Bertaco, P. Lehmann & F. Cantina. Uruguay, Rio Negro: UFRGS 7421, 1 (m, female, 39.3 mm SL), on bridge in Pasos del Toros, rio Negro, 28 May 2005, L. R. Malabarba, V. A. Bertaco, P. Lehmann & F. Cantuna. Rio Uruguay basin, Brazil, Rio Grande do Sul: MCP 11810, 1 (unsexed, 20.9 mm SL), rio Uruguay, 10 Nov 1987, J. Bertoletti, C. Lucena, E. Lerner & P. Azevedo. MCP 11921, 4 (unsexed, 17.9- 20.4 mm SL), rio Ibicuí-Mirim at rio Toropi mouth, 3 Jan 1983, UFSM. MCP 11922, 4 (unsexed, 18.9-22.5 mm SL), rio Ibicuí-Mirim at mouth on rio Santa Maria, 14 Jan 1983, UFSM. MCP 11923, 3 (unsexed, 24.1-36.7 mm SL), rio Ibicuí-Mirim on rio Toropi mouth, 3 Jan 1983, UFSM. MCP 11924, 1 (unsexed, 22.8 mm SL), rio Santa Maria, 26 Oct 1982, C. A. S. Lucena & L. R. Malabarba. MCP 11925, 3 (unsexed, 32.7-35.1 mm SL), rio Ibicuí-Mirim on rio Santa Maria mouth, 14 Jan 1983, UFSM (Universidade Federal de Santa Maria). MCP 11926, 7 (6m, males, 28.4-32.2 mm SL, 1m, female, 32.2 mm SL), São Francisco de Assis, rio Jaguari, 15 Sep 1983, C. A. S. Lucena, L. R. Malabarba & R. E. Reis. MCP 11927, 11 (unsexed, 24.6-35.9 mm SL), rio Ibicuí-Mirim, at road connecting Santa Maria to São Pedro, at 20 km far from Santa Maria, 20 Mar 1982, UFSM. MCP 11928, 36 (unsexed, 21.2-35.3 mm SL), rio Santa Maria, at BR 293, km 246, section Dom Pedrito / Santana do Livramento, 26 Oct 1982, C. A. S. Lucena & L. R. Malabarba. MCP 11929, 16 (5m, males, 31.2-33.6 mm SL, 2m, females, 31.5-31.9 mm SL, 9, unsexed, 30.6-33.26 mm SL), sanga on road Santa Maria / Mata, 13 Sep 1983, C. A. S. Lucena, L. R. Malabarba & R. E. Reis. MCP 11930, 10 (unsexed, 25.5-32.0 mm SL), Ponto 2, 8 Apr 1983, UFSM. MCP 11931, 51 (unsexed, 21.4-33.5 mm SL), rio Santa Maria on BR 293, km 246, section Dom Pedrito / Santana do Livramento, 26 Oct 1982, C. A. S. Lucena & L. R. Malabarba. MCP 11933, 1 (unsexed, 27.6 mm SL), rio Santa Maria, on BR 293, km 246, section Dom Pedrito / Santana do Livramento, 26 Oct 1982, C. A. S. Lucena & L. R. Malabarba. MCP 11934, 5 (unsexed, 26.1- 34.4 mm SL), rio Ibicuí-Mirim, 10 Jun 1986, UFSM. MCP 11935, 6 (unsexed, 24.0-25.9 mm SL), Itaqui, mouth of rio Ibicuí at rio Uruguai, 19 Nov 1984, L. R. Malabarba & R. E. Reis. MCP 11937, 208 (6m, males, 31.8-33.9 mm SL, 7m, females, 29.6-34.4 mm SL, 191, unsexed, 21.8-34.4 mm SL, 4 c&s, males, 27.8-32.8 mm SL), rio Santa Maria on BR 293, km 246, section Dom Pedrito / Santana do Livramento, 26 Oct 1982, C. A. S. Lucena & L. R. Malabarba. MCP 11939, 223 (219, unsexed, 21.4-34.8 mm SL, 1 c&s, male, 30.1 mm SL, 3 c&s, females, 32.4-35.1 mm SL), rio Santa Maria on BR 293, km 246, section Dom Pedrito / Santana do Livramento, 26 Oct 1982, C. A. S. Lucena & L. R. Malabarba. MCP 11998, 6 (1, males, 38.0 mm SL, 5, females, 36.5-44.6 mm SL), Santa Maria, pools on margin of rio Vacacai, 12 Sep 1983, C. A. S. Lucena, L. R. Malabarba & R. E. Reis. MCP 14158, 4 (2, unsexed, 37.6-39.5 mm SL), arroio Santo Antonio, at road Rosário do Sul / Santana do Livramento, 13 Dec 1989, C. Weber, R. E. Reis & S. Muller. MCP 14205, 1 (unsexed, 34.5 mm SL), pools on margin of rio Santa Maria, road Dom Pedrito / Santana do Livramento, 14 Dec 1989, C. Weber, R. E. Reis & S. Muller. MCP 15336, 7 (unsexed, 26.2-28.4 mm SL), Uruguaiana, affluent of rio Uruguay at PUC, 26 Feb 1991, E. Q. Chiva. MCP 16393, 2 (unsexed, 21.0-26.2 mm SL), São Marcos, marginal lake on Formosa beach, affluent of rio Uruguay, 11 Dec 1992, P. H. Wimberger, R. E. Reis & J. F. Pezzi. MCP 16399, 12 (unsexed, 20.9-28.8 mm SL), São Marcos, marginal lake on Formosa beach, affluent of rio Uruguay, 11 Dec 1992, P. H. Wimberger, R. E. Reis & J. F. Pezzi. MCP 18365, 86 (1m, male, 32.8 mm SL, 6m, females, 33.0-34.7 mm SL, 77, unsexed, 13.5-34.6 mm SL, 2 c&s, females, 29.7-35.2 mm SL), São Marcos, marginal lake on Formosa beach, affluent of rio Uruguay, 21 Nov 1995, J. F. Pezzi, W. Santos, V. Bertaco & C. Kohlmann. MCP 19602, 1 (unsexed, 27.7 mm SL), pool near Olaria on low land along side rio Santa Maria, BR 290, 15 Jan 1997, L. R. Malabarba, J. Alves Gomes & V. Bertaco. MCP 23660, 7 (2m, males, 31.3-31.6 mm SL, 4m, females, 30.2-32.7 mm SL, 1, unsexed, 28.0 mm SL), Uruguaiana, Sanchuri dam, 21 Jul 1999, R. C. Beheregaray. MCP 40723, 1 (unsexed, 20.9 mm SL), rio Touro Passo, 17 Oct 1985, C. A. S. Lucena, C. Mardini & C. Porto.