Rineloricaria misionera, Mónica S. Rodríguez & Amalia M. Miquelarena, 2005

Mónica S. Rodríguez & Amalia M. Miquelarena, 2005, A new species of Rineloricaria (Siluriformes: Loricariidae) from the Paraná and Uruguay River basins, Misiones, Argentina., Zootaxa 945, pp. 1-15 : 5-13

Rineloricaria misionera new species

Fig. 1

Loricaria (Rineloricaria) phoxocephala : Ringuelet et al., 1967 (in part): 411 (3 specimens from Pindapoy, Misiones; 69.0-72.0 mm SL)

Holotype. ILPLA 1698, 97.4 mm SL, female, arroyo Cuña - Pirú (27º08’S 54º54’W) Cainguas Department, Misiones Province, Argentina, September 2000, A. Miquelarena et al.

Paratypes. ARGENTINA: ILPLA 1064, (1) 51.1 mm SL, May 1997, R. Filiberto & N. Perelmuter ; ILPLA 1065 (2 cleared and stained) 89.6-90.2 mm SL, July 1998, R. Filiberto et al. ; ILPLA 1190, (7) 36.9-92.1 mm SL, September 2000, A. Miquelarena et al. ; ILPLA 1210, (1) 59.6 mm SL, September 1997, F. de Durana & H. Oñatibia ; ILPLA 1684, (1) 79.9 mm SL, March 2000, R. Filiberto et al., same locality as holotype ; ILPLA 1189, (2) 35.2-55.1 mm SL, March 2000, H. Povedano ; ILPLA 1191, (6) 43.6-84.8 mm SL, arroyo Tateto (27º10’S 54º57’W) Cainguás Department, Misiones Province, September 2000, A. Miquelarena et al. ; ILPLA 1336, (1) 86.7 mm SL, San Pedro (26º39’S 54º08’W) San Pedro Department, Misiones Province, November 1972, A. Acosta ; ILPLA 1546, (2) 57.8-59.2 mm SL, Salto Horacio and arroyo Pepirí Miní at the end of Provincial Road 21 (27ºS 54ºW) San Pedro Department, Misiones Province, January 2001, R. Filiberto et al. ; ILPLA 1551, (1) 70.0 mm SL, arroyo Santa Ana, on National Road 12 (27º23’S 55º36’W) Santa Ana Department, Misiones Province, January 2001, R. Filiberto et al. ; ILPLA 1681, (2) 52.5-85.8 mm SL and MCP 35793, (3) 66.6-84.3mm SL, arroyo Liso (27º06’S 54º59’W), Cuña-Pirú valley, Cainguás Department, Misiones Province, March 2000, H. Povedano ; MLP 3368, (1) 72.0 mm SL and MLP 3370, (2) 69.0-70.0 mm SL, Pindapoy (27º45’S 55º48’W) Apóstoles Department, Misiones Province .

Diagnosis: The new species differs from all other Rineloricaria species by its unique pattern of abdominal plates: anterior abdominal region covered by plates, except for the pectoral girdle, which generally lacks plates. When present in this region, the plates are relatively small, few, well-defined and grouped as shown in Figure 2. The posterior plates of this complex are arranged in one or two regular series. The posterior abdominal complex comprises a well-developed preanal plate, bordered anteriorly by a series of 3-5 usually polygonal plates. In addition, the following combination of characters permits the differentiation of this species: premaxillary and dentary teeth with unequal-sized cusps (Fig. 3 a; b); upper caudal ray barely longer than the lower ray (not prolonged as a filament), and snout tip with an oval naked area not reaching the last pore of the infraorbital sensory canal.

Among the species that partially lack abdominal plates, R. latirostris (Boulenger, 1900) is most similar to R. misionera . However, this species differs from R misionera in the following characters: wider caudal peduncle (4.0-4.5 vs. 2.9-3.9 % SL); smaller orbital diameter (17.0-19.5 vs. 19.6-26.2 % HL); and margin of caudal fin truncated vs. concave.

Description: Morphometrics in Table 1. Head and body strongly depressed. Trunk and caudal peduncle ventrally flattened and becoming more compressed caudally. Dorsal profile of body straight or slightly concave at snout level; convex at eye level, straight or somewhat convex to dorsal fin, straight from dorsal fin to penultimate plate of caudal peduncle. Upper edge of orbit slightly raised. Well-developed triangular postorbital notch.

Outline of head triangular in dorsal view, with straight or convex sides. Odontodes small, densely arranged in lines covering head, trunk, and fin rays. Tip of snout with oval area of naked skin. In all examined individuals (n= 30), area between naked area on snout tip and upper lip with odontodes, except for three juvenile specimens. Naked skin area not reaching anterior pore of infraorbital branch of sensory canal. Lower lip bearing very short digitiform papillae on its outer edge shallow median notch present. Maxillary barbel shorter than eye diameter. Rostral border poorly developed. Premaxilla with 4-10 (mean= 6.7, n=32) bilobed teeth in functional series. Dentary with 4-9 (mean= 6.3, n=32) bilobed teeth in functional series. All teeth with uneven cusps. Five to 10 (mean= 7.5) thoracic plates between origin of pectoral and pelvic fins (except in one individual with four plates on right side and another with eleven plates on left side). Posterior abdominal plate complex formed by one preanal plate anteriorly, surrounded by 3 to 5 plates, usually polygonal, although sometimes irregularly shaped. Anterior abdominal region with plates, except on pectoral girdle skeleton. When present on pectoral girdle, these plates are relatively small, few, and well-defined. Lateral plates ranging from 26 to 29 (mean= 27.5) with welldeveloped keels formed by hypertrophied odontodes, coalesced in last 8 to 13 (mean= 11.1) plates. Supraoccipital and predorsal plates with low ridges.

Posterior margin of dorsal fin straight or slightly convex, with first unbranched ray and/or second or third branched rays longest. Tip of dorsal fin, when depressed, reaches third or fourth plate posterior to fin insertion. Posterior margin of pectoral fin straight or slightly convex longer first ray reaching to or slightly beyond level of pelvic fin origin. Posterior margin of pelvic fin rounded; third and fourth rays longest, reaching to or falling short of anal fin origin. Posterior margin of anal fin rounded, with longer second and/or third fin rays. Tip of anal fin, when depressed, reaches fifth plate posterior to fin insertion; three ventral plates along its base. Posterior margin of caudal fin concave; upper unbranched ray slightly longer than lower, not extended as filament.

Color in alcohol: Background color of dorsal surface of head and body tan with six transverse black bands; first or anteriormost crossing supraoccipital process, second at dorsal fin base, and third through fifth variable in position between dorsal and caudal fins. Ventral surface light brown or yellowish. Sides of head frequently with dots or vermiculate black spots. Pectoral, pelvic, dorsal, and anal fins with round black spots arranged in rows. Caudal fin with conspicuous dark spot on its base and numerous dots near distal margin forming a black stripe. Ventral snout, upper lip, and barbels with black pigmentation.

Sexual dimorphism: Males have hypertrophied odontodes on the sides of head, especially on the opercular area, and on the dorsal surface of branched pectoral-fin rays. Pectoral spine (or leading unbranched pectoral ray) is hypertrophied and the anterodorsal odontodes are markedly enlarged. Cusps of premaxillary teeth have smoothly rounded edges in males, whereas females have sharper, less rounded cusps (Fig. 3 a b, respectively).

Habitat: Small streams having swift current over rocky and sandy bottoms (Fig. 4). Individuals seek shelter between rocks, gravel, and crevices during the day, and are active mainly during the night.

Etymology: The specific name, misionera, refers to Misiones, the Argentinian Province containing the type-locality.

Distribution: Paraná and Uruguay River basins in Misiones Province, Argentina (Fig. 5).

Discussion

The partial or total absence of plates on the abdomen has only been described for three species of Rineloricaria : R. latirostris , from a tributary of the upper Paraná River in Brazil, R. aequalicuspis Reis & Cardoso, 2001 , and R. maquinensis Reis & Cardoso, 2001 , the last two species described from southeastern Brazil. Among these species, R. misionera appears more closely related to R. latirostris based on similarities in the anterior abdominal plate complex. However, the new species differs from R. latirostris in several characters: narrower caudal peduncle (2.9-3.9 vs. 4.0-4.5 % SL); greater orbital diameter (19.6- 26.2 vs. 17.0-19.5 % HL), greater number of plates in the anterior abdominal complex (20-45 vs. 13-23), and posterior margin of the caudal fin (concave vs. truncate). In addition, odontode development surrounding the area of naked skin on the snout of R. misionera is less pronounced than the broad, caramel-colored odontodes in R. latirostris .

Tooth morphology differentiates R. misionera from R. aequalicuspis , with the former having asymmetrical cusps and the latter with symmetrical cusps. Differences in the development of plates in the anterior abdominal region further distinguish these two species: R. misionera always has 20-45 plates in this area, whereas in R. aequalicuspis this area is either naked or has up to 25 plates.

Rineloricaria misionera differs from R. maquinensis in having plates on the anterior abdomen, greater predorsal distance (31.9-36.2 vs. 28.2-31.5 % SL), shorter postanal distance (44.1-53.1 vs. 55.5-62.5 % SL), posterior margin of caudal fin concave vs. truncate, and, sexually dimorphic teeth.

Rineloricaria misionera differs from all other species recorded in Argentina ( R. lima , R. catamarcensis , R. microlepidogaster , R. felipponei , R. thrissoceps , R. pareiacantha , R. parva and R. lanceolata ) in having the anterior abdominal area only partially covered by plates.

Rineloricaria catamarcensis , a species occurring in central and northwestern Argentina, resembles R. misionera in some morphometrical characters. However, R. misionera is distinguished from R. catamarcensis , in addition to the aforementioned characters, in having the upper caudal ray not prolonged as a filament, and densely distributed silk-like body odontodes vs. sparsely distributed, coarse or hispid-like odontodes. In addition, these species occur in different habitats: while R. catamarcensis occurs in small streams to large rivers with muddy or sandy bottoms, R. misionera inhabits fast-flowing streams with rocky and sandy bottoms.

The distributional range of three Rineloricaria species, R. lanceolata , R. microlepidogaster and R. parva , is similar to that of R. misionera . Rineloricaria parva , distributed in Upper and Lower Paraná and Lower Uruguay basins in Argentina, differs from R. misionera in having more fused plates (12-16 vs. 8-13), shorter head (16.7-21.2 vs. 21.3-25.7 % SL), shorter abdominal length (11.4-15.4 vs. 14.4-19.2 % SL), shorter cleithral width (11.5-16.6 vs. 15.7-21.4 % SL), less deep caudal peduncle (1.0-1.6 vs. 1.4-2.2 % SL) and upper and lower caudal rays prolonged as filaments.

Rineloricaria lanceolata , reported for Upper and Lower Paraná basins, differs from R. misionera in having more fused lateral plates (13-8 vs. 8-13), shorter abdominal length (12.2-14.4 vs.14.4-19.2 % SL), upper and lower caudal rays prolonged as filaments, dissimilar color pattern and different sexual dimorphism ( Isbrücker, 1973).

Rineloricaria misionera differs from R. microlepidogaster , distributed in the Lower Uruguay basin, in having well-developed orbital notch and shorter pectoral fin (tip reaching or barely exceeding pelvic fin origin).

Rineloricaria felipponei , R. pareiacantha and R. thrissoceps have only been nominally cited by de Buen (1950) for Río de La Plata. Rineloricaria lima was cited for Río de La Plata by Van Der Stigchel (1947). This author redescribed the species based on two female specimens (one from Caracas, Venezuela, and one from Río de La Plata) and one male specimen from Rio de Janeiro (Brasil). Subsequently several authors (Ringuelet et al, 1967; López, 1970; Cordini, 1977; Cordiviola de Yuan, 1992; Liotta et al., 1995/96; López et al., 1996; del Barco, 1997; Almirón et al., 2000, Nieva et al, 2001; López et al., 2003; Monasterio de Gonzo, 2003; Menni, 2004) reported the species for diverse basins in Argentina. The presence of these species in Argentina could not be confirmed from the revision of type specimens, materials from ichthyological collections and field-collected specimens.

The Province of Misiones along with the Yungas cloudforest, is one of the areas of highest biodiversity in Argentina (Bertonatti & Corcuera, 2000). From an ichthyofaunistic standpoint, it is part of the Paranoplatensean Province (Ringuelet, 1975) and the Misioneran ecoregion ( López et al., 2002). During the last seven years, increased sampling efforts of interior streams within this territory has led to the discovery of new taxa in the orders Characiformes, Silurifomes, and Perciformes. For example, in Cuña - Pirú Creek seven new species, including R. misionera , have been recorded in the last three years within the genera Astyanax , Bryconamericus , Gymnogeophagus , Rhamdella , Rineloricaria and Crenicichla (Miquelarena et al., 2002).