Neoplecostomus corumba, Zawadzki, Cláudio Henrique, Pavanelli, Carla Simone & Langeani, Francisco, 2008

Zawadzki, Cláudio Henrique, Pavanelli, Carla Simone & Langeani, Francisco, 2008, Neoplecostomus (Teleostei: Loricariidae) from the upper Rio Paraná basin, Brazil, with description of three new species, Zootaxa 1757, pp. 31-48 : 32-36

Neoplecostomus corumba , n. sp.

Figure 2 ; Table 1

Neoplecostomus sp.: Zawadzki et al., 2004:574 (photo; Goiás, Rio Corumbá , tributary to Rio Paranaíba; comparison to N. paranensis ; allozymes).

Neoplecostomus sp.—“cascudinho”: Pavanelli et al., 2007:61 (citation; Goiás, Rio Corumbá , tributary to Rio Paranaíba).

Holotype. DZSJRP 6713 [male], 78.3 mm SL, Goiás State, Corumbaíba, Córrego Gameleira, affluent of Rio Corumbá , Rio Paranaíba basin, 17o59’S / 48o29’W, 17 Sep 1996, Nupélia.

Paratypes. (same data as the holotype, excepting date: March 1996 to March 2000) DZSJRP 6193, 5 [3 m, 2 f], 44.0– 73.8 mm SL; MZUSP 86208, 9 [4 m, 5 f], 45.7–77.6 mm SL; NUP 2528, 5 [3 m, 2 f], 53.0– 66.8 mm SL.

Diagnosis. Neoplecostomus corumba can be distinguished from N. selenae by lacking enlarged odontodes and distinct swollen skin along lateral margins of snout and along ridges before the eyes in mature males (vs present); from N. yapo by lacking enlarged odontodes and distinct swollen skin along lateral margins of snout (vs present), by having smaller interdorsal length/SL (18.4–20.5 vs 20.7–23.0), and greater mandibullary width/HL (16.3–18.1 vs 14.1–15.2); from N. paranensis by having well-developed adipose fin (vs reduced or absent), greater orbital diameter/HL (12.2–13.0 vs 7.9–12.0), and greater mandibullary width/HL (16.3–18.1 vs 8.4–12.4); from N. espiritosantensis by having 10–18 dentary teeth (vs 19–38), greater cleithral width/SL (24.9–27.6 vs 17.0–19.0), and greater orbital diameter/HL (12.2–13.0 vs 6.0–9.0); from N. franciscoensis and N. ribeirensis by having a well-developed dorsal-fin spinelet, wider than dorsal-fin spine base (vs absent or narrower than dorsal-fin spine base); from N. granosus by having 27–29 lateral-line plates (vs 34–43), and greater orbital diameter/HL (12.2–13.0 vs 9.0–11.0); from N. microps by having greater orbital diameter/HL (12.2–13.0 vs 8.0–11.0); and from N. variipictus by having smaller caudal peduncle depth/SL (6.0–6.5 vs 7.3– 7.8), greater orbital diameter/HL (12.2–13.0 vs 9.1–9.9), 15–24 premaxillary teeth (vs 12–14), and 10–18 dentary teeth (vs 7).

Description. Counts and measurements are presented in Table 1 . Body elongated and depressed. Greatest width at cleithrum, narrowing to caudal peduncle. Dorsal body profile gently convex, elevating from snout tip to dorsal-fin origin and descending to first caudal-fin procurrent spine. Greatest body depth at dorsal-fin origin. Trunk and caudal peduncle dorsally rounded in cross-section; body ventrally flattened to anal-fin origin, flattened to slightly rounded to caudal fin. Dorsal body surface completely covered by dermal plates, excepting for a naked area around dorsal-fin base. Snout tip naked. Ventral head surface naked except by a plate bearing odontodes in front of gill openings. Abdomen with conspicuous, small dermal platelets between insertions of pectoral and pelvic fins, forming a thoracic shield surrounded by naked areas; in some specimens also some isolated platelets near pectoral-fin base.

Character N. corumba n = 20 N. selenae n = 15 Head wide and moderately depressed. Head and snout weakly obtuse in dorsal view. Interorbital space slightly straight in frontal view. Median ridge from snout tip to area between nares weak or not evident. A ridge from naris to superior margin of orbit. Snout convex in lateral profile. Eye moderately small (12.2–13.0 of HL), dorsolaterally placed. Lips well developed and rounded. Lower lip almost reaching pectoral girdle and covered by papillae, wider anteriorly; two or three irregular and conspicuous rows of large and transversally flattened papillae, just posterior to dentary teeth. Maxillary barbel short and mostly coalesced with lower lip, generally with free tip. Teeth long, slender and bicuspid; mesial cusp longer than lateral. Dentary rami forming an angle of approximately 120o.

Dorsal-fin origin slightly posterior to vertical passing through pelvic-fin origin; nuchal plate not covered by skin; dorsal-fin spinelet half-moon shaped and wider than dorsal-fin spine base; dorsal-fin locking mechanism absent. Dorsal-fin with spine flexible, followed by seven branched rays; its posterior margin straight or slightly falcate, reaching about vertical through end of pelvic-fin rays when adpressed. Moderate to well developed and always present adipose fin, not preceded by azygous plate. Pectoral fin with six branched rays and a depressed and inward curved spine (more pronounced in larger specimens) shorter than longest branched ray; its posterior margin slightly falcate, reaching (in smaller specimens) or almost reaching half pelvic-fin length when adpressed. Pelvic fin with one spine and five branched rays; its posterior margin nearly straight, reaching or almost reaching anal-fin insertion when adpressed. Pelvic-fin spine ventrally flattened, with dermal flap on its dorsal surface in males. Anal fin with one flexible spine and five branched rays; its posterior margin straight. Caudal fin bifurcate; lower lobe longer than upper; 14 branched rays. Pectoral and pelvic-fin spines with odontodes on lateral and ventral portions. Anal-fin spine with odontodes only ventrally.

Color in alcohol. Ground color of dorsal surface of head and body yellowish. Head, dorsum, flanks and fins covered by many inconspicuous darker dots or blotches of variable shapes and sizes. Dorsal color pattern, even in mature larger individuals, retains the generic juvenile color pattern of five transverse dark bars: the first through supraoccipital, the second anterior to dorsal fin, the third posterior to dorsal fin, the fourth at adipose fin, and the last at caudal-peduncle posterior portion. Head usually with two light, short and parallel lines anterior to nares, bordering the naked area on snout tip. Orbital margin lighter, mainly on its superior portion. Small light spot on interorbital space, inconspicuous in some specimens. Few specimens with two almost parallel small lighter lines on suppraoccipital posterior part. Body lateral portion with an upper darker region and a lower lighter one, just below lateral line, not easily visualized in large specimens.

Dorsal fin with irregular series of dark dots on rays. Caudal fin irregularly dark at base and distal portion of rays, leaving two lighter areas on median portion and rays tips. Pectorals, pelvics, and anal fins with dark dots forming irregular bands usually diffuse. Adipose fin generally dark laterally and light on spine dorsal portion.

Ventral surface of head and body mostly unpigmented, except for some brown, faded scattered chromatophores near body lateral margins and from pelvic fin to caudal-fin base; upper lip dark brown, except for its light narrow margin.

Etymology. The specific name refers to the Rio Corumbá , type-locality’s drainage. It is treated as a noun in apposition.

Distribution. Neoplecostomus corumba is known only from the type-locality ( Fig. 3 ).

Figures

FIGURE 2. Neoplecostomus corumba, holotype, DZSJRP 6713, male, 78.3 mm SL.

FIGURE 3. The type localities of N. corumba (dot), N. selenae (lozenge), N. yapo (star), and N. paranensis (triangle).

Tables

TABLE 1. Morphometric data and counts of Neoplecostomus corumba, N. selenae, N. yapo, and N. paranensis from the upper Rio Paraná basin. CP = caudal-peduncle, IO = interorbital length, OD = orbital diameter, PDS = predorsal, SL = standard length, ad = adipose-fin, an = anal-fin, cd = caudal-fin, ds = dorsal-fin.

	Holotype	Low	High	Mean/ Mode	SD	Holotype	Low	High	Mean/ Mode	SD
Standard length	78.3	45.5	78.3	60.7	11.21	101.7	52.2	101.7	66.7	15.79
Percents of SL