Pimelodus joannis, Ribeiro & Lucena & Lucinda, 2008

Ribeiro, Frank R. V., Lucena, Carlos A. S. & Lucinda, Paulo H. F., 2008, Three new Pimelodus species (Siluriformes: Pimelodidae) from the rio Tocantins drainage, Brazil, Neotropical Ichthyology 6 (3), pp. 455-464 : 460-462

Pimelodus joannis , new species

Fig. 4

Pimelodus sp. C - Lucinda et al., 2007: 79

Holotype. MCP 41739, 51.0 mm SL, Ipueiras, rio Tocantins near the confluence with rio Manoel Alves , approximately 11º19’S 48º38’W, 20 Jan 1999, Neamb-UFT.

Paratypes. Brazil. Tocantins State. All collected by Neamb-UFT staff. MCP 41919, 5 , 42.6 -45.0 mm SL, and UNT 5641 , 34 (1 c&s), 36.2-54.5 mm SL, collected with the holotype. UNT 5644 , 1 , 53.6 mm SL , Paranã, rio Paranã, fazenda Traçadal , approximately 12º30’S 48º12’W, 26 Mar 1998 . UNT 5655 , 15 , 26.5 -40.0 mm SL, Porto Nacional, rio Tocantins, 10º43’15"S 48º25’14"W, 14 Dec 1999 . UNT 5751 , 1 , 49.9 mm SL , Paranã, rio Paranã, fazenda Traçadal , approximately 12º30’S 48º12’W, 27 Mar 1998 . UNT 5760 , 1 , 76.9 mm SL, Porto Nacional, córrego Narciso , approximately 10º43’S 48º24’W, 2 Oct 2001 . UNT 5790 , 1 , 39.1 mm SL, Pedro Afonso, rio Tocantins, near rio Sono , approximately 8º59’S 48º10’W, 15 Jan 2001 . UNT 8241 , 1 , 44.9 mm SL, Ipueiras, rio Tocantins near rio Manoel Alves , approximately 11º19’S 48º28’W, 20 Jan 2000 .

Diagnosis. Pimelodus joannis is distinguished from its congeners, except P. halisodous , P. jivaro , P. ornatus , P. pictus , and P. stewarti , by the presence of a dorsal median crest along supraoccipital process (vs. crest absent); shorter distance between the posterior nostril and the anterior orbital border (posterior nostril closer to anterior orbital border vs. posterior nostril closer to anterior nostril than to anterior orbital border); a dark spot on the distal portion of dorsal-fin rays 2-4 (vs. no spot); and two dark blotches on the base of the caudal fin (vs. absence of such spots). Pimelodus joannis differs from P. jivaro by having a shorter maxillary barbel, which extends only slightly past caudal-fin base (vs. maxillary barbel extending beyond caudal-fin base); a dark spot in the distal portion of dorsal-fin rays 2-4 (vs. absence of such spot); and two dark blotches on the base of the caudal-fin (vs. absence of such spots). The new species from P. ornatus and P. pictus by the uniform grayish to yellowish coloration (vs. presence of bands or dark dots along flanks, respectively). Pimelodus joannis differs from P. stewarti by having a shorter posterior cleithral process (10.2-12.4 vs. 12.7-15.6 % of SL); by the presence of two dark blotches on the caudal-fin base (vs. absence of such dark blotches); and by the presence of a dorsal median crest along the supraoccipital process (vs. no crest). Pimelodus joannis differs from P. halisodous by having a shorter pectoral-spine (15.5-18.5 vs. 20.0-23.5% of SL); a shorter snout (35.8-41.8 vs. 43.1-47.9% of HL); and by fewer premaxillary tooth rows (5-9 vs. 13-16).

Description. Morphometric data in Table 1. Body deeper than wide. Dorsal profile of body convex along snout; straight from orbital region to dorsal-fin origin, straight from dorsal insertion to adipose-fin origin, then gently sloping to anterior extent of caudal peduncle. Dorsal and ventral profiles of caudal peduncle slightly concave. Ventral profile of head straight to anterior region of isthmus; ventral profile of body slightly convex to anal-fin origin; anal-fin base straight. Head covered by thin skin. Skull roof ornamented with numerous small granulations, more visible in larger specimens. Snout projecting beyond mandibular symphysis by distance less than one internarial length. Mouth subterminal; margins curved in ventral view when mouth closed and exposing less than anterior half of premaxillary tooth rows; upper lip thick, fleshy, not striated. Fleshy rictal fold in pocket behind corner of mouth. Posterior nostrils closer to anterior orbital border than to anterior nostrils; anterior nostril with fleshy rim slightly raised posteriorly; posterior nostril thin, fleshy, rim elevated anteriorly. Eye large, elliptical, margin completely free and dorsolaterally positioned on head; horizontal orbital diameter greater than interorbital width; orbit oblong, horizontal orbital diameter greater than vertical orbital diameter. Premaxillary tooth patch short, broad, rectangular and transversely elongate; internal border of premaxillary tooth plate straight or slightly concave; premaxilla with eight irregular rows of slender conical teeth. Dentary with 5-9 tooth rows (n = 10). Vomerine and pterygoid tooth-plate absent. Anterior cranial fontanel triangular in dorsal view, open from mesethmoid to frontals, and terminating anterior to vertical through posterior margin of eye. Posterior fontanel welldeveloped and elongate. Supraoccipital process wide; dorsal surface with longitudinal median crest; ornamented with numerous small granulations; lateral margins of supraoccipital process converging posteriorly, process covered by narrow sheath of opaque hyaline skin. Anterior and middle nuchal plates ornamented sparsely with tuberculated ridges. Anterior nuchal plate with conspicuous anterior process fitting into bifid supraoccipital tip; posterior nuchal plate with short posterior process not trespassing line through origin of first branched dorsal-fin ray. Three pairs of barbels, flattened at base. Maxillary barbel inserted at vertical through anterior edge of lower lip; surpassing caudal-fin base origin. Mental barbels inserted anterior to gular fold apex, in curved line parallel to mandibular margin. Inner mental barbel reaching base of pectoral fin. Tip of outer mental barbel reaching to pectoral spine. Gill membranes free, diverging just behind gular fold apex and supported by eight branchiostegal rays. Gill rakers well-ossified, sharp and slender; 11-16 (mode = 13) on first branchial arch; 2- 4 on epibranchial (mode = 3), 9-13 on ceratobranchial (mode = 11; n = 52). Dorsal fin rays II,6 (mode = 6; n = 59); fin inserted near anterior one-third of SL; its origin slightly anterior to vertical through tip of innermost pectoral-fin ray. Spinelet narrow, sharply angular or exhibiting low crest anteriorly. Dorsal spine straight, strong, pungent, shorter than first branched ray, continued in filamentous ray reaching near the edge of the first soft dorsal-fin ray; approximately as long as the pectoral spine length. Dorsal spine with 1-3 anterior distal serrae (n = 11). Posterior margin of dorsal spine with moderately sharp retrorse spines distally, becoming gradually erect near spine base. First branched dorsal-fin ray longest, last dorsal-fin ray less than one-half-length of the first ray; distal margin of dorsal fin nearly straight. Adipose fin large, posterior to middle of body; its origin approximately on vertical through first branched pelvic-fin ray. Adipose-fin margin rounded and moderately deep, its apex near to vertical through base of rays 6-8 of anal fin, ending posteriorly as short free lobe slightly posterior to vertical through tip of last anal-fin ray. Caudal fin deeply forked, with pointed lobes; dorsal lobe slightly longer than ventral lobe, principal rays non-filamentous (i,7,8,i; n = 59); 19 dorsal and 20 ventral procurrent rays. Anal fin inserted on posterior one-third of SL; fin margin nearly straight, without distinct lobe anteriorly; tips of second and third branched rays longest; longest anterior and posterior branched rays meeting when depressed. Anal fin iv-vi,6-8 (mode = 7; n = 57), first and second branched rays longest. Pectoral fin i,7-9 (mode = 8; n = 59); its posterior margin obliquely truncate, first soft ray slightly longer than spine tip. Pectoral spine strong, distally pointed, dorsal and ventral surfaces smooth; numerous, regularly spaced, uniformly retrorse unicuspid dentations along most of posterior margin; anterior distal serrae weak or absent (commonly larger in juveniles), antrorse and straight dentations along proximal half of anterior margin, becoming progressively less prominent and more crowded proximally; anterior dentations much larger in juveniles. Pelvic fin i,5 (n = 11), first branched ray longest, inserted near vertical through last branched dorsal-fin ray; its posterior margin slightly rounded. Lateral-line canal complete, extending onto caudal-fin base; canal nearly straight, with superficial tubular ossicles directed posteroventrally and more developed anteriorly; no accessory laterosensory canals posterior to nuchal area. Posterior cleithral process broad, triangular, ventral margin nearly straight, dorsal margin somewhat concave; granular and osseous tubercles on lateral surface. Urogenital papilla short, located in shallow depression immediately posterior of anus. No apparent sexual dimorphism. Superficial ossifications of Weberian complex centrum not covering seventh centrum. Total vertebrae 40 (15 precaudal and 25 caudal). First pleural rib on sixth vertebra. Ten pairs of pleural ribs.

Color in alcohol. Body light brown to yellowish. Venter light to yellowish. Head surface with blackish areas. Eye dark. Some dark chromatophores on posterior cleithral process, opercle and below orbit. Dorsal fin with black spot on distal portion of rays 2-4. Pectoral, pelvic and anal fins hyaline. Black chromatophores along interradial membranes of caudal fin, concentrated on median portion of ventral lobe. Two dark blotches on base of caudal fin. Maxillary barbel dusky on dorsal surface; lighter on ventral surface. Mental barbels pale.

Distribution. Pimelodus joannis is known from the upper and medium portions of the rio Tocantins drainage ( Fig. 2 ).

Etymology. The specific name joannis is a patronym for John Lundberg, in recognition of his many contributions to catfishes systematic.

Figures

Fig. 4. Pimelodus joannis, holotype, MCP 41739, 51.0 mm SL, Ipueiras, rio Tocantins, Brazil.

Fig. 2. Rio Tocantins drainage showing the collection localities of Pimelodus stewarti (triangles, 1), P. halisodous (squares, 2), and P. joannis (circles, 3). Numbers represent type-localities. Some symbols represent more than one lot or locality.