Pareiorhina cepta, Roxo, Fábio Fernandes, Silva, Gabriel De Souza Da Costa E, Mehanna, Mahmoud & Oliveira, Claudio, 2012

Roxo, Fábio Fernandes, Silva, Gabriel De Souza Da Costa E, Mehanna, Mahmoud & Oliveira, Claudio, 2012, Description of a new species of Pareiorhina (Siluriformes: Neoplecostominae) from Rio São Francisco basin, Zootaxa 3512, pp. 64-74 : 65-70

Pareiorhina cepta , new species

Fig. 1 ; Table 1

Holotype: MZUSP 111095, 41.5 mm SL, Brazil, Minas Gerais State, municipality of São Roque de Minas, district of São João Batista, Córrego do Lavapés, affluent Rio Santo Antônio, affluent Rio Samburá, Rio São Francisco basin, 20°08’36”S 46°38’21”W, 18 May 2011, Mehanna, M. and Senhorini, J.

Paratypes: All from Brazil, Minas Gerais State, Rio São Francisco basin. LBP 10261, 1, 30.2 mm SL, municipality of São Roque de Minas, Córrego Maria da Prata , 20°15’51”S 46°20’57”W, 9 Apr 2010, Mehanna, M. and Senhorini, J. LBP 10287, 13, 21.5–43.6 mm SL, municipality of São Roque de Minas, district of São João Batista, Córrego do Lavapés, affluent Rio Santo Antônio, affluent Rio Samburá, Rio São Francisco basin, 20°08’36”S, 46°38’21”W, 12 Abr 2010, Mehanna, M. and Senhorini, J. LBP 11835, 1 c&s, 33.4 mm SL, 19, 25.1–44.0 mm SL. Same data as the holotype. LIRP 8950, 2, 41.9–42.7 mm SL. MCP 46896, 2, 32.5–42.7 mm SL. NUP 13578, 2, 38.8–40.6 mm SL.

Diagnosis: The new species Pareiorhina cepta differs from all its congeners by the presence of small plates covered with odontodes randomly distributed on the abdomen, Fig. 2 a (vs. abdomen completely naked) and by color pattern of caudal-fin completely dark with one hyaline bar (vs. variegated blotches corresponding to approximately three to four hyaline bars in P. brachyrhyncha and P. rudolphi and hyaline random spots in P. carrancas , Fig. 3 ). Moreover, the new species also differs from all congeners, except for P. brachyrhyncha , by presence of a minute lateral cusp in teeth (vs. unicuspid teeth in remaining species); differs from all congeners, except for P. carrancas , by having ventral surfaces of first pectoral, pelvic and anal-fin rays covered by pointed odontodes (vs. conspicuously spatulate odontodes). Additionally, P. cepta differs from P. carrancas by lacking a ridge on the postdorsal surface of trunk (vs. postdorsal surface of trunk with a low, elongate ridge formed by 10–13 raised median unpaired plates), anterior ends of the premaxillae and dentaries gently sloped inwards, Bockmann and Ribeiro (2003) (vs. strongly sloped); from P. brachyrhyncha by lacking odontodes at the ventral tip of the snout (vs. tip of snout completely covered by odontodes).

orbital diameter, PDS = predorsal, CP = caudal peduncle.

Pareiorhina cepta n=30

Holotype Range Mean/Mode SD Standard length (SL) 41.5 30.2–44.3 38.5 3.78 Percents of Standard length (SL)

Ventral plates between end of anal base and caudal-fin membrane 13 11–14 13 - Premaxillary teeth 42 32–46 36 - Dentary teeth 39 32–46 38 -

Description: Counts and measurements are summarized in Table 1. Dorsal profile of body elongated and depressed, straight from dorsal-fin to caudal-fin base. Ventral profile of body slightly convex from snout tip to caudal-fin base. Greatest body depth at dorsal-fin origin and smallest on caudal peduncle. Greatest body width at opercular region; lateral profile convex between tip snout and end of dorsal-fin; straight to caudal-fin. Body progressively narrowing from cleithrum to caudal-fin. Caudal peduncle rectangular in cross section. Dorsal profile of caudal peduncle with longitudinal depression and covered with paired plates (postdorsal plates between of 15–17). Ventral profile of caudal peduncle flat.

Head wide, rounded dorsally. Tip of snout partly naked and slightly concave towards nares. Interorbital region straight to slightly concave in frontal view. Small eyes (10.7–14.8% of head length), dorsolaterally placed. Iris with small dorsal flap covering pupil. Nares near and almost with same diameter that eyes. Lips well developed and rounded. Lower lip far from reaching pectoral girdle and covered with papillae, decreasing in size towards posterior margin, wider anteriorly. Maxillary barbel short. Upper lip folded over itself. Teeth long and bicuspid (small lateral cusp located laterally in main crow). Rami of dentaries and premaxillae strongly curved inwards. Teeth organized in single series. Dorsal-fin I,7; spinelet presented and ovoid shaped; locking mechanism not functional. Dorsal-fin base located between vertebrae 10 and 14. Pectoral-fin I,6. Pelvic-fin I,5. Pectoral and pelvic-fins without locking mechanism. Pectoral-fin unbranched ray covered with conspicuously pointed and developed odontodes, largest at ventral portion. Tip of pectoral-fin almost reaching middle of pelvic-fins. Second and third branched pectoral-fins rays surpassing tip of unbranched pectoral-fin ray. Pelvic-fin unbranched ray slightly curved. First unbranched fin ray covered with conspicuously pointed and developed odontodes, largest at ventral portion. Tip of pelvic-fin slightly surpassing insertion of anal fin first ray. Anal-fin I,5; it base located between vertebrae 16 and 19. Adipose fin absent. Dorsal portion of caudal peduncle covered with paired plates. Caudal-fin truncated with lower unbranched ray longer than upper. Caudal-fin with I,7–7,I branched rays.

Upper hypural plate (composed of epural, uroneural, and hypurals 3–5) with I+7 rays; lower hypural plate (composed of hypurals 1, 2, and parahypural) with 7+I rays. Body entirely covered by bony plates, except for ventral surface of head and most part of abdomen. Small platelets randomly distributed near urogenital opening and all abdominal regions, leaving abundant naked areas surrounding them. Dorsal plates with 24 to 27, mid-dorsal 17 to 21, median plates 24 to 27, mid-ventral 18 to 21, and ventral 20 to 23. Head with naked area beside compound pterotic. Head without crests. Head and body plates covered with developed odontodes with uniform distribution. Ventral surfaces of first pectoral, pelvic and anal-fin rays covered by pointed odontodes.

Seven pairs of ribs associated with vertebral central 8–15. First pair of ribs large and laminar; remaining ribs slender and poorly ossified. Total number of vertebrae 30. Supraorbital sensory canal with four pores s1, s3, s6+s6 and s8; s1 located on terminal portion of nasal plates; pore s3 located on anterior portion of nasal; pore s6+s6 located between frontal, on horizontal line through anteriormost limits of eyes; pore s8 on division between frontal, sphenotic and parieto-supraoccipital, just above eyes. Infraorbital sensory canals with six pores; pore io1 located on anterior end of first infraorbital; pore io2 located in medial region between first and second infraorbitals; pore io3 located in medial region between second and third infraorbitals; pore io4 located in medial region between third and fourth infraorbitals; pore io5 located in medial region between fourth and fifth infraorbitals, and pore io6 located between sixth and sphenotic. Preopercular canal with two pores; pore pm3 located between cheek plate and preopercle; pore pm4 located between preopercle and compound pterotic. Two postotic pores; pore po2 located just above branchial slit; and po3 located on region overlying opening of swim-bladder capsule.

Head osteology in Fig. 2 b. Tip of snout with four rostral plates (r). Three pairs of prenasal plates behind rostral plates (pn1–pn3) all with varied sizes and shapes and a pair of nasal plates (na). Three internasal plates (pni) between nasal plates. Five infraorbital plates (io1-io5) on lateral surface of head; all covered by latero-sensory canal system. First infraorbital largest and fifth smallest. Preopercle (pop) just below fifth infraorbital elongated, which is also covered by latero-sensory canal. Lateral of head covered by postrostral plates, (pr1–pr4); pr4 largest, triangular-shaped plate. Suprarostral plates (sprs) just below io3 and io4. Last lateral plate series in subocular cheek plates (cp1–cp2) and opercle (op). Posterior portion of skull formed by prefrontal (pf), frontal (f), sphenotic (sp), compound pterotic (cpt) and parieto-supraoccipital (soc). Several fenestrae in lateral margin of compound pterotic.

Color in alcohol: Ground color of dorsal surface of head and body light brown to yellowish brown. Ventral surface of body and head lighter than dorsal and covered by dark spots of chromatophores widely settled. Three dark bars on dorsal surface of trunk (in some specimens not evident), anterior most poorly defined. Lateral portion of body with poorly defined dark stripe from head to caudal-fin. Fins with irregularly and poorly defined bars: three on anal fin, four on pectoral and pelvic-fins, and five on dorsal-fin. Caudal-fin completely dark with one hyaline bar.

Sexual dimorphism: Males of Pareiorhina cepta have a conspicuous urogenital papilla posterior to urogenital opening (attribute absent in females).

Distribution: Known only from Córrego do Lavapés and Córrego Maria da Prata , which are two small headwater streams in the upper Rio São Francisco basin, near Serra da Canastra, Minas Gerais State, Brazil ( Figs. 4 and 5 ).

Habitat: Pareiorhina cepta was found at an altitude of about 810–1065 m.a.s.l. The streams were narrow (about 3–5 m width) and shallow (about 0.25–1.5 m deep). The stream bottom was formed of small to mediumsized rocks, loose stones, gravel and sand. The water in the sampled site was clear, cold (16.6 °C–19.5 °C), highly acidic ( pH 2.78–2.87), poorly conductive (µs/cm 0.013–0.014), highly oxygenated (5.91–13.05 mg /l OD) and moderate to fast flowing. Margins of the stream were covered by vegetation, which shadows a wide portion of its bed. In that stream, specimens of Pareiorhina cepta sympatric with other species, such as Astyanax rivularis , Neoplecostomus franciscoensis, Trichomycterus macrotrichopterus and Characidium fasciatum were captured.

Etymology: The specific name cepta is derived from CEPTA (an acronym for Centro de Pesquisa Treinamento em Aquacultura—former Centro Nacional de Pesquisa e Conservação de Peixes Continentais) from municipality of Pirassununga, São Paulo State, Brazil.

Figures

FIGURE 1. Pareiorhina cepta, MZUSP 111095, 41.5 mm SL, holotype from Córrego do Lavapés, Rio São Francisco basin, municipality of São Roque de Minas, district of São João Batista, Minas Gerais State, Brazil.

FIGURE 2. (a) Ventral view; small plates covered with odontodes randomly distributed to abdomen. (b) Dorsal view; osteology of the head. Paratype, LBP 11835, c & s, 33.4 mm SL.

FIGURE 3. Picture showing the different color pattern of the caudal-fin in species of Pareiorhina. (a) Pareiorhina cepta, (b) P. rudolphi, (c) P. brachyrhyncha, (d) P. c a r ra nc as.

FIGURE 4. Map showing the collecting site of Pareiorhina cepta in two streams in Rio São Francisco basin, Minas Gerais State. Triangle— 20 ° 08 ’ 36 ” S 46 ° 38 ’ 21 ” W, star— 20 ° 15 ’ 51 ” S 46 ° 20 ’ 57 ” W.

FIGURE 5. Field picture showing type locality of Pareiorhina cepta, Córrego do Lavapés, Rio São Francisco basin, municipality of São Roque de Minas, district of São João Batista, Minas Gerais State, Brazil.