Pimelodus luciae, Rocha, Marcelo Salles & Ribeiro, Frank Raynner V., 2010

Rocha, Marcelo Salles & Ribeiro, Frank Raynner V., 2010, A new species of Pimelodus LaCépède, 1803 (Siluriformes: Pimelodidae) from rio Itacaiunas, rio Tocantins basin, Brazil, Zootaxa 2343, pp. 57-65 : 58-61

Pimelodus luciae , new species

Fig. 1,2; Table 1

Holotype: MPEG 3174 (78.4 mm SL), Brazil, state of Pará: rio Itacaiúnas, Cachoeira Carreira Comprida, Caldeirão, Poço de Pedral, Serra dos Carajás, municipality of Parauapeba, rio Tocantins basin, 1 Nov 1983, Michael Goulding.

Paratype: INPA 33831 (87.2 mm SL), collected with holotype.

Diagnosis. The unique color pattern of Pimelodus luciae includes five regular or irregular rows of dark spots on anterior portion of sides of body; dark brown spots, generally smaller than those on body sides, present on supraoccipital process, dorsal surface of head and cheeks; dark longitudinal band on ventral lobe of the caudal fin; pectoral, pelvic and anal fins hyaline, without spots. Pimelodus luciae differs further from its congeners, except P. halisodous Ribeiro , Lucena and Lucinda, 2008, P. jivaro Eigenmann and Pearson, 1942 , P. joannis Ribeiro , Lucena and Lucinda, 2008, P. ornatus Kner, 1858 , P. pictus Steindachner, 1877 , and P. stewarti Ribeiro , Lucena and Lucinda, 2008, by having shorter distance between the posterior nostril and the anterior orbital border (vs. posterior nostril closer to anterior nostril than to anterior orbital border). Pimelodus luciae differs further from P. halisodous , P. jivaro , P. joannis , and P. pictus by having dorsal surface of the supraoccipital process rounded in cross section (vs. supraoccipital process with a middorsal crest). Pimelodus luciae differs further from P. ornatus by having horizontal orbital diameter greater than interorbital distance (vs. smaller than interorbital distance). Pimelodus luciae differs further from P. stewarti by having distal portion of dorsal fin hyaline (vs. dark spot in the distal portion of dorsal-fin rays 2–4) and longer maxillary barbells (reaching middle caudal-fin rays vs. slightly surpassing anal-fin base).

Description. Morphometric data in Table 1 . Body deeper than wide. Dorsal profile of body convex from snout tip to dorsal-fin origin; straight to slightly concave from dorsal-fin insertion to adipose-fin origin. Ventral profile of body straight to convex to anal-fin origin. Dorsal and ventral profiles of caudal peduncle concave. Ventral profile of head straight to anterior region of isthmus.

Head conical, covered by thin skin. Skull roof ornamented with numerous small osseous granulations. Snout relatively short, tapering convexly in dorsal view, 43.5 or 44.7% of HL. Mouth subterminal, opening anteroventrally; margins curved in ventral view when mouth is closed with some premaxillary tooth rows exposed; upper lip not very developed, fleshy and striated. Distance between anterior and posterior nostrils shorter than that between posterior nostrils and longer than that between anterior nostrils; anterior nostril with tubular rim; posterior nostril with an anteriorly elevated membrane. Posterior nostril located closer to anterior orbital border than to anterior nostril.

Anterior cranial fontanel triangular in dorsal view, terminating before vertical through posterior margin of eye. Premaxillary tooth patch wide, broad, rectangular and transversely elongated; premaxilla with 10* or 12 irregular rows of conical and slender teeth. Dentary with eight tooth rows. Vomerine teeth absent. Pterygoid tooth patch absent. Eye large, elliptical, with margin completely free and situated laterodorsally on head; horizontal orbital diameter greater than interorbital distance; horizontal orbital diameter greater than vertical diameter.

Supraoccipital process wide, reaching anterior nuchal plate; dorsal surface rounded in cross section, ornamented with numerous small granulations; sides of supraoccipital process tapering posteriorly; covered by narrow band of opaque hyaline skin. Anterior and middle nuchal plates ornamented with small granulations.

Gill membranes free, diverging just behind gular fold apex. Gill rakers well-ossified, sharp and slender; 18* or 19 rakers on first branchial arch; four on epibranchial, 14* or 15 on ceratobranchial. Three pairs of barbels, proximally depressed. Maxillary barbels inserted immediately posterior to vertical through posterior edge of anterior nares; reaching between base and posterior tip of middle caudal-fin rays. All mental barbels inserted in advance of gular fold apex, in a curved line parallel to mandibular margin. Inner mental barbels reaching slightly beyond base of pectoral fin. Outer mental barbels reaching pelvic-fin base. Posterior cleithral process broad, posteriorly pointed; ventral margin nearly straight; dorsal margin somewhat concave; granular and osseous tubercles on lateral surface. Urogenital papilla short, located in a shallow depression immediately behind anus, between pelvic fins.

Dorsal fin inserted approximately in second third of standard length; its origin slightly posterior to vertical through tip of the posterior cleithral process. Eight dorsal-fin rays: spinelet, spine, and six soft, branched rays. Spinelet narrowing distally, rounded in front; its tip gently rounded. Dorsal spine straight, strong, pungent, shorter than first branched ray; longer than pectoral spine. Dorsal spine with anterior distal serrae. Posterior margin of dorsal spine with moderately sharp retrorse spines distally, becoming gradually smaller and erect near spine base. First branched dorsal-fin ray longest, remaining rays decreasing in length posteriorly.

Adipose-fin origin inserted near vertical through tip of innermost pelvic-fin ray. Adipose fin moderately deep with rounded margin, ending in short free lobe anterior to vertical through tip of last anal-fin ray.

Caudal fin deeply forked with pointed lobes; dorsal lobe slightly longer than ventral lobe; its outer principal rays not filamentous. Dorsal lobe with nine rays, one unbranched plus eight branched; ventral lobe with eight rays, one unbranched plus seven branched.

Anal fin inserted on last third of standard length; fin margin slightly concave, not forming distinct lobe; tips of longest anterior and posterior rays meet when depressed. Anal-fin rays 14 or 15*, five and six* unbranched rays; second branched rays longest. Pelvic fin with an unbranched ray and five branched rays, inserted at or slightly posterior to vertical through end of the dorsal-fin base; second branched ray longest.

Pectoral fin with spine plus 10 branched rays; first soft ray longer than pectoral spine length. Pectoral spine strong, distally pointed, dorsal and ventral surfaces smooth; numerous, regularly spaced, uniformly retrorse unicuspid dentations along most of posterior margin; antrorse and straight dentations along proximal half of anterior margin, becoming progressively less prominent and more crowded proximally.

Lateral line canal complete, extending onto caudal-fin base; declining on anterior body until vertical through dorsal-fin origin, nearly straight from there to caudal-fin base; superficial tubular ossicles directed posteroventrally and more developed anteriorly.

Total number of vertebrae, 38–39* including the Weberian complex. First pleural rib on 6th vertebra. Nine pairs of ribs.

Color in alcohol. Body ground color light brown to light yellow, with five regular or irregular rows of dark spots on anterior portion of flanks, three or four rows of spots on posterior portion, and two on caudal peduncle; spots more abundant on anterior part of body. Smaller dark spots on head surface and supraoccipital process, opercle, posterior cleithral process and below orbital region. Venter light. Dorsal fin hyaline or with spots localized in proximal region; black chromatophores along interradial membranes. Pectoral, pelvic and anal fins hyaline. Adipose fin with very faint spots, localized along base. Caudal-fin base with very faint spots; dark longitudinal band on ventral lobe; remaining fin hyaline. Maxillary barbel dusky on dorsal surface; lighter on ventral surface. Mental barbels all light, yellowish.

Distribution. Pimelodus luciae is known only from its type locality in the rio Itacaiunas, rio Tocantins basin ( Fig. 3 ).

Figures

FIGURE 3. Partial map of South America showing the type locality of Pimelodus luciae. Black circle showing the type locality.

Tables

TABLE 1. Morphometric data of Pimelodus luciae, new species.

Measurement	Holotype	Paratype
Standard length (mm)	78.4	87.2
Percents of standard length
Predorsal length	40.6	39.4
Pre-pectoral length	25.0	25.1
Body depth	22.5	21.2
Body width	20.3	20.0
Head length	27.3	26.1
Dorsal spine length	22.3	21.9
Dorsal-fin base length	17.0	15.7
Dorsal-fin to adipose-fin distance	13.3	14.3
Adipose-fin base length	20.2	22.4
Adipose-fin height	7.4	7.5
Caudal peduncle length	18.1	16.9
Caudal peduncle depth	8.0	7.5
Anal-fin height	17.1	19.4
Anal-fin base length	11.4	9.9
Pectoral spine length	18.8	17.0
Pelvic-fin length	16.3	18.1
Anus to anal fin distance	11.0	13.1
Percents of head length
Snout length	43.5	44.7
Mouth width	32.2	34.2
Interorbital distance	23.4	22.4
Horizontal eye diameter	32.7	33.3
Vertical eye diameter	25.7	27.6
Eye to posterior nostril distance	13.1	14.9
Distance between anterior nostrils	12.6	12.3
Distance between anterior and posterior nostrils	16.4	15.4
Distance between posterior nostrils	21.0	22.8