Otothyropsis biamnicus, Calegari, Bárbara B., Lehmann, Pablo & Reis, Roberto E., 2013

Calegari, Bárbara B., Lehmann, Pablo & Reis, Roberto E., 2013, Two new species of cascudinhos of the genus Otothyropsis (Siluriformes: Hypoptopomatinae) from the rio Paraná basin, Brazil, Zootaxa 3619 (2), pp. 130-144 : 136-142

Remarks. Specimens of Otothyropsis from three additional tributaries to the right margin of the rio Paraná south of the rio Verde were examined (rio Laranjaí, rio Guiraí, and some unnamed streams tributaries to the rio Otothyropsis biamnicus , sp. n.

( Figure 6 ; Tables 3–4)

Otothyropsis sp. 1.— Calegari et al. 2011: 255, 259–260 (phylogenetic analysis) Otothyropsis sp. 2.— Calegari et al. 2011: 255, 259–260 (phylogenetic analysis)

Type material: Holotype. MCP 47288, female, 38.0 mm SL, Brazil, Paraná State, Telêmaco Borba, ribeirão Harmonia, tributary to rio Tibagi basin, rio Paraná drainage, 24°18’19”S 50°36’23”W, A. Costa and D. Garcia, 26 March 2012. Paratypes. All from Brazil, rio Paraná basin. MCP 47289, 4, 21.0– 33.8 mm SL, and MZUEL 6122, 7, 24.5–34.1 mm SL, collected with holotype. MCP 39531, 5 (2 c&s), 21.5–27.8 mm SL, Santa Catarina State, Canoinhas, rio Água Verde, tributary to rio Canoinhas, affluent to rio Negro, rio Iguaçu drainage, 26°12’44”S 50°23’35”W, L. Duboc, V. Abilhoa & R. A. Torres, 3 July 2004. MCP 22602, 3, 31.8–34.0 mm SL, Paraná State, Paulo Frontin, arroio Barra Grande at road BR-153, 25°59’42”S 50°52’00”W, C. Lucena, J. Pezzi & V. Bertaco, 5 December 1998. MCP 37164, 5 (1 c&s), 25.1–38.7 mm SL, Paraná State, Lapa, rio dos Patos at road PR-427 between Lapa and Campo do Tenente, 25°50’37”S 49°43’39”W, E. Pereira, L. Duboc, V. Abilhoa & F. Torres, 29 October 2004. UFRGS 11498, 16 (2 c&s), 23.1–38.6 mm SL, Santa Catarina State, Monte Castelo, creek at BR- 116 highway, tributary to rio Negro, rio Iguaçu drainage, 23°06’03”S 50°28’15”W, L. Malabarba, V. Bertaco, L. Artioli, and J. Wingert, 17 October 2009. MCP 45755, 1, 37.5 mm SL, Paraná State, Telêmaco Borba, creek tributary to rio Tibagi, 24°10’29”S 50°39’38”W, M. Volcan, 26 July 2009. UFRGS 11495, 7 (1 c&s), 32.0– 39.9 mm SL, Paraná State, Ponta Grossa, rio Tibagi at Uvaia, approx. 100 meters from highway BR-373, 25°07’33”S 50°39’04”W, L. Malabarba and others, 17 October 2009. UFRGS 11434, 1, 34.9 mm SL, Paraná State, Porto Amazonas, rio Lageado in Porto Amazonas, tributary to rio Iguaçu, 25°54’39”S 50°29’04”W, V. Bertaco, L. Artioli, and J. Wingert, 15 October 2009. UFRGS 11464, 4, 23.2–36.9 mm SL, Paraná State, Ponta Grossa, arroio Sutil at road PR-151, tributary to rio Tibagi basin, 25°29’44”S 50°11’36”W, L. Malabarba and others, 17 October 2009. Paragenetype COI. Genbank accession nb. KC417375 from tissue voucher number 1589 on lot UFRGS 12879, Paraná State, Porto Amazonas, rio Lageado in Porto Amazonas, tributary to rio Iguaçu, 25°54’39”S 50°29’04”W, V. Bertaco, L. Artioli, and J. Wingert, 15 October 2009.

Diagnosis. Otothyropsis biamnicus is distinguished from its congeners by having shorter pectoral-fin spine (18.6–21.3 vs. 21.4–30.4% SL in remaining species). It also has a lower caudal peduncle (7.6–9.0 vs. 9.3–11.0 in O. marapoama and 9.7–11.5% SL in O. piribebuy ), deeper caudal peduncle (7.6–9.0 vs. 6.2–7.6% SL in O. polyodon ); and dorsal-fin spinelet triangular in shape (vs. spinelet rectangular or quadrangular).

Otothyropsis biamnicus is also distinguished from O. marapoama and O. piribebuy by having shorter preanal length (55.5–59.1 vs. 60.9–67.4% SL); shorter prepelvic length (36.7–39.3% vs. 40.6–46.3% SL), shorter pectoralpelvic distance (13.3–15.9 vs. 16.6–21.2% SL); shorter dorsal-fin spine (19.4–22.9 vs. 24.2–29.8% SL), longer caudal peduncle (41.3–45.1 vs. 28.1–35.9% SL), shorter prenasal length (17.6–24.4 vs. 28.9–36.4% HL), higher number of middle series lateral plates (24–26 vs. 19–22 plates), middle series of lateral plates complete (vs. middle series of lateral plates truncated at least two plates before the caudal fin); and anterior margin of the mesethmoid not covered by median rostral plate ventrally (vs. anterior margin of the mesethmoid covered by the median rostral plate in ventral view). Otothyropsis biamnicus also differs from O. marapoama by having a narrower cleithrum (20.6–23.1 vs. 23.8–25.8% SL); shorter snout (44.1–47.9 vs. 48.0–50.5% HL); and larger orbital diameter (14.5–18.3 vs. 11.3–13.8% HL). The new species also differs from O. piribebuy by having a raised crest of enlarged odontodes on the supraoccipital (vs. crest absent), shorter predorsal length (41.7–46.7 vs. 46.5–50.5% SL); longer postdorsal length (42.6–47.6 vs. 38.8–42.5% SL); shorter dorsal-fin base (9.2–12.2 vs. 12.2–14.7% SL); and narrower caudal peduncle (3.5–5.9 vs. 5.9–7.4% SL). Finally, the new species further differs from O. polyodon by having lower number of premaxillary teeth (13–20 vs. 19–31 teeth), lower number of dentary teeth (11–19 vs. 18–27 teeth), and longer anal-fin spine length (16.9–19.5 vs. 13.7–16.9% SL).

Description. Morphometrics in Table 3 and meristics in Table 4 . Dorsal body profile slightly concave along dorsal-fin length, straight from end of dorsal-fin base to caudal-fin origin. Ventral profile almost straight, slightly concave at anal region. Greatest body width at operculum and area corresponding to lateral opening of swimbladder capsule. Body gradually tapering towards caudal-fin. Greatest body depth at dorsal-fin origin and sometimes middle of suproccipital.

Otothyropsis biamnicus Otothyropsis biamnicus (rio Iguaçu basin) (rio Tibagi basin) Head wide and rounded. Snout extremely short and very depressed at nares, forming bulge in prenasal area. Portion from rostral plates to posterior margin of orbital very sloping. Nares very large, its width occupying 9.2–15.0% of HL. Dorsal margin of orbit somewhat elevated. Iris operculum present. Libs rounded and papillose, with barbel very short and laterally positioned. Odontodes at snout tip larger than those on body. Posterior margin of supraoccipital with hypertrophied odontodes in juvenile and adults.

Body entirely covered by plates, except for region of nares, lateral opening of swimbladder capsule, and central portion of abdomen. One to four small irregular lateral abdominal plates in anterior portion of abdomen. Posterior portion of abdomen with one to three small plates restricted to central area, or when more plates present, always small and distributed in single or paired rows. Abdomen rarely completely devoid of plates.

Mid-dorsal series of lateral plates truncated posteriorly; median series complete with continuous perforated plates. Mid-ventral series truncated posteriorly, reaching to same point of mid-dorsal series. Two or three transverse rows of predorsal plates not including nuchal plate.

Pectoral-fin I,6–7. Pectoral-fin axillary slit present in juvenile and adult specimens. Pectoral-fin spine slender, with odontodes distributed mostly in lateral portion and increasing gradually in size toward spine tip. Pectoral girdle exposed, except for arrector fossae covered by skin. Pelvic-fin I,5, spine thickened with larger odontodes ventrolaterally turned mesially. Dorsal-fin II,7 (three specimens with II,6 rays), its origin slightly anterior to vertical through middle of pelvic-fin length. Dorsal-fin spinelet triangular in shape and dorsal-fin locking mechanism non-functional. Anal-fin I,5, first anal-fin pterygiophore exposed anterior to anal-fin spine origin. Caudal-fin i,14,i. Total vertebrae 28 (in four c&s specimens).

Color in alcohol. Ground color of dorsal surface of head median brown with many tiny dark dots, snout lighter with dark brown spots. Posterior process of supraoccipital and dorsal surface of trunk light brown with dark chromatophores uniformly distributed. Four darker saddles usually visible between origin of dorsal fin and end of caudal peduncle. Longitudinal dark stripe from snout, crossing between middle of orbit and opercle, and continuing to lower lobe of caudal fin. All fins with series of small dark dots arranged in irregular transverse bands. Fin membranes mostly hyaline. Base and lower lobe of caudal fin with both rays and membrane mostly pigmented with dark brown. Lower portion of lower lobe with roundish to rectangular hyaline area, never with small dark dots inside ( Fig. 4 C, D). Ventral surface mostly pale yellow, with heavier concentration of dark chromatophores on snout and caudal peduncle.

Sexual dimorphism. Sexual dimorphism characterized by the presence of urogenital papilla immediately posterior to anal opening in males. Adult males also possess a fleshy flap along the dorsal margin of the pelvic-fin spine. Males have larger pelvic-fin spine (16.9–19.6% SL), vs. short pelvic-fin spine (14.1–16.2% SL) in females. Furthermore, the new species, exhibits a remarkable secondary sexual dimorphism associated with the much larger olfactory organ of males: males have wider nares diameter (13.1–15.0% vs. 9.2–11.5% HL in females); and males have shorter prenasal length ( Fig. 7 ; 17.6–20.1% vs. 22.0–24.4% in HL females).

Distribution. Otothyropsis biamnicus is known from tributaries to rio Iguaçu, in Santa Catarina and Paraná States, and to the rio Tibagi, Paraná State, both in rio Paraná basin, Brazil ( Fig. 5 ).

Ecology comments. Several specimens of Otothyropsis biamnicus from the rio Paranapanema have midge larvae ( Diptera : Chironomidae ) fixed on the operculum and more rarely on the cleithrum posterior process ( Fig. 7 ). This ecological interaction was already reported for other catfishes of the families Astroblepidae (Astrobleplus) and Loricariidae ( Chaetostoma , Hemiancistrus , Hypostomus , and Ancistrus ) and classified as commensalism by Freihofer and Neil (1967). According to those authors, the commensalism between invertebrates and fish is extremely rare. Freihofer and Neil reported on commensalism for those species based on the examination of 1,100 specimens of 10 different families of South American catfishes. The current experience, however, suggests that this interaction is not rare, as it has been also observed for other species as Pareioraphis hypsilurus (E. H. L. Pereira, pers. commun.), Microlepidogaster dimorpha , Hisonotus leucofrenatus , and H. depressicauda (F. O. Martins, pers. commun.).

The areas that chironomids usually attach themselves to loricariids are mostly the everted cheek plates, secondarily the fins (including the adipose fin), and less frequently the posterior nares ( Freihofer and Neil 1967). However, in Otothyropsis biamnicus the larvae were found attached to the gill opening or, more rarely, to the posterior process of the cleithrum, both cases not previously reported. All specimens, both males and females, were carrying the larvae along one or both sides of the body, although one single individual on each side. In some cases we found only the pupal exuviae. The fact that some loricariids have a sedentary life and the chironomids also have sedentary habits, as well as both feed on detritus, algae and organic matter, allows for this specific interaction. Freihofer and Neil (1967) suggested that the larvae are probably benefited by feeding on the detritus expelled though the gill openings.

Etymology. From the Latin bi, meaning two, and amnicus, meaning inhabitant of a river, in allusion to the fact that the species is distributed in both the Iguaçu and Tibagi basins. A noun in apposition.

Figures

FIGURE 4. Color pattern of caudal fin in Otothyropsis species. Otothyropsis polyodon, MCP 47076, (A) 37.3 mm SL, (B) 35.1 mm SL; O. biamnicus, MCP 11498, (C) 34.5 mm SL, MCP 47289, (D) 30.7 mm SL; O. marapoama, LIRP 4621, (E) 32.6 mm SL, (F) 26.6 mm SL; O. piribebuy, MCP 44394, (G) 23.9 mm SL, (H) 23.3 mm SL.

FIGURE 5. Geographic distribution of Otothyropsis marapoama (star), O. polyodon (square), O. biamnicus (dot), and O. piribebuy (triangle). Open symbols for type-localities. Some symbols represent more than one lot or locality. 1 — rio Verde; 2 — rio Tietê; 3 — rio Paranapanema; 4 — rio Iguaçu; 5 — rio Paraguay.

FIGURE 6. Otothyropsis biamnicus, holotype, MCP 47288, female, 38.0 mm SL, Brazil, ribeirão Harmonia, tributary to rio Tibagi basin, rio Paraná dranaige.

FIGURE 7. Otothyropsis biamnicus, male, paratype, MZUEL 6122, 30.5 mm SL, showing the Chironomidae larva. Scale bar = 5 mm.

Tables

TABLE 4. Frequency of distribution of meristic data for Otothyropsis biamnicus. Holotype values are marked with an asterisk. Meristic marked with double asterisks was counted in c & s specimens only. N = number of specimens.

Character	N	Range	Distribution Frequency	N	Range	Distribution Frequency
Teeth in left premaxilla	8	13–17	13(1), 14(1), 15(3), 16(1), 17(2)	10	14–19	14(1), 16(2), 17(4)*, 18(2), 19(1)
Teeth in right premaxilla	8	13–18	13(1), 14(1), 15(2), 16(2), 17(1), 18(1)*	10	14–20	14(1), 16(1), 17(2), 18(3), 19(1), 20(2)*
Teeth in left dentary	8	12–16	12(1), 13(3), 14(2), 15(1), 16(1)*	10	14–19	14(2), 15(1), 16(2), 17(2)*, 18(2), 19(1)
Teeth in right dentary	8	11–16	11(1), 13(2), 14(3)*, 15(1), 16(1)	10	13–18	13(1), 15(1), 16(3)*, 17(4), 18(1)