Curculionichthys sabaji, Roxo, Fabio F., Silva, Gabriel S. C., Ochoa, Luz E. & Oliveira, Claudio, 2015

Roxo, Fabio F., Silva, Gabriel S. C., Ochoa, Luz E. & Oliveira, Claudio, 2015, Description of a new genus and three new species of Otothyrinae (Siluriformes, Loricariidae), ZooKeys 534, pp. 103-134 : 107-111

Taxon classification Animalia Siluriformes Loricariidae

Curculionichthys sabaji sp. n. Figure 3; Table 1

Holotype.

MZUSP 117379, female, 23.3 mm SL, Pará State, municipality of Altamira, Rio 13 de Maio, tributary of Rio Curuá, Rio Iriri drainage, 08°43'41"S, 55°01'38"W, 22 October 2007, coll. Birindelli JLO, Netto-Ferreira AL, Sabaj-Perez MH, Lujan NK.

Paratypes.

All from Brazil, Rio Xingu basin. LBP 19763 (1, female, 23.4 mm SL), Pará State, municipality of Altamira, Rio Curuá, Rio Iriri drainage, 08°19'07"S, 55°05'23"W, 22 October 2007, coll. Birindelli JLO, Netto-Ferreira AL, Sabaj-Perez MH, Lujan NK. MZUSP 95711 (5, 16.3−20.0 mm SL, 2 c&s, sex not determined, 18.7−19.9 mm SL), Mato Grosso State, municipality of Gaúcha do Norte, Rio Coronel Vanick, 13°31'34"S, 52°43'52"W, 08 October 2007, coll. Lima FCT, Moreira CR, Ribeiro AC, Moraes L, Leite CMC. MZUSP 96959 (2, 19.1−20.7 mm SL), Pará State, municipality of Altamira, Rio 13 de Maio, tributary of Rio Curuá, Rio Iriri drainage, 08°38'53"S, 55°01'41"W, 22 October 2007, coll. Birindelli JLO, Netto-Ferreira AL, Sabaj-Perez MH, Lujan NK. MZUSP 97039 (5, 17.0−19.2 mm SL), Mato Grosso State, municipality of Campinápolis, Rio Couto de Magalhães, 13°48'02"S, 53°03'43"W, 10 October 2007, coll. Lima FCT, Moreira CR, Ribeiro AC, Moraes L, Leite CMC. MZUSP 97138 (1, 23.6 mm SL), collected with holotype. MZUSP 97198 (2, 20.0−22.3 mm SL), Pará State, municipality of Altamira, Rio Curuá, Rio Iriri drainage, 08°19'07"S, 55°05'23"W, 22 October 2007, coll. Birindelli JLO, Netto-Ferreira AL, Sabaj-Perez MH, Lujan NK.

Diagnosis.

Curculionichthys sabaji differs from all congeners by having several dark-brown spots distributed on the body (vs. a variety of pigment patterns, but none of which includes dark-brown spots). Moreover, the new species differs from all congeners, except Curculionichthys coxipone and Curculionichthys paresi by having the cleithrum with an area free of odontodes, Fig. 4A (vs. cleithrum completely covered with odontodes, Fig. 4 D–F). The new species further differs from Curculionichthys piracanjuba , Curculionichthys sagarana , and Curculionichthys oliveirai by having some papillae of the lower lip arranged in a medial longitudinal series extending posterior to dentaries through the middle portion of the lower lip (vs. lower lip with all papillae randomly distributed); from Curculionichthys coxipone and Curculionichthys oliveirai by having the anterior profile of the head pointed (vs. rounded); from Curculionichthys piracanjuba by having odontodes forming longitudinally aligned rows on head and trunk (vs. odontodes not forming longitudinally aligned rows on head and trunk); from Curculionichthys insperatus and Curculionichthys sagarana by having the caudal fin hyaline, with one dark strip extending from caudal peduncle base to the median caudal fin rays, and for dark chromatophores irregular distributed almost forming two bands, Fig. 5A (vs. caudal fin hyaline, with dark blotch limited to caudal peduncle base, Fig. 5B and 5C respectively); from Curculionichthys sagarana by the absence of one unpaired platelet on the dorsal portion of caudal peduncle (vs. one unpaired platelet on the dorsal portion of the caudal peduncle, Fig. 6); from Curculionichthys insperatus by having small, inconspicuous odontodes forming rows on the head and trunk (vs. large, conspicuous odontodes forming rows on the head and the trunk); from Curculionichthys oliveirai by having 6−9 lateral abdomen plates (vs. 4−5 lateral abdomen plates); from Curculionichthys paresi by lacking contrasting dark geometric spots on the anterodorsal region of body (vs. presence of geometric spots); from Curculionichthys piracanjuba by not having hypertrophied odontodes on the snout tip (vs. hypertrophied odontodes on the snout tip). Additionally, Curculionichthys sabaji is distinguished by having a shorter dorsal fin spine (18.5−22.7% of SL, vs. 25.2−27.0% of SL in Curculionichthys paresi ; 23.2−26.9% of SL in Curculionichthys insperatus ); a shorter pectoral-fin spine (18.9−23.4% of SL, vs. 27.0−30.1% of SL in Curculionichthys paresi ); a deeper caudal peduncle (7.0−10.0% of SL, vs. 10.8−12.5% of SL in Curculionichthys oliveirai ; 10.2−11.3% of SL in Hisonotus paresi ); a deeper head (40.9−49.1% of HL, vs. 51.6−59.2% of HL in Curculionichthys oliveirai ); a longer head (34.3−38.6% of SL, vs. 27.9−32.2% of SL in Curculionichthys piracanjuba ; 28.8−33.3% of SL in Curculionichthys luteofrenatus ); a shorter snout (45.5−56.9% of HL, vs. 67.7−72.7% of HL in Curculionichthys piracanjuba ; 67.0−75.3% of HL in Curculionichthys luteofrenatus ) and a shorter interorbital width (30.3−35.7% of HL, vs. 36.7−40.9% of HL in Curculionichthys piracanjuba ; 67.0−75.3% of HL in Curculionichthys luteofrenatus ).

Description.

Morphometric and meristic data are given in Table 1. Small-size loricariid; maximum body length reached 23.6 mm SL. In lateral view, dorsal profile of body straight from snout tip to interorbital region; slightly convex to dorsal fin origin; and almost straight and decreasing to end of caudal peduncle. Ventral surface of body concave at tip of snout to anal fin insertion; concave to caudal fin insertion. Greatest body depth at dorsal fin origin. Greatest body width at opercular region; progressively narrowing towards snout and caudal fin. Trunk and caudal peduncle almost ellipsoid; rounded laterally and almost flat dorsally and ventrally.

Head elliptical in dorsal view; snout long (45.5−56.9% HL), slightly pointed, its tip rounded, flat to slightly convex between orbits. Dorsal and ventral series of odontodes completely covering anterior margin of snout; odontodes of snout slightly larger in size than remaining ones found on head. Snout tip completely covered with odontodes. Odontodes on head and trunk well defined and arranged into longitudinal rows (one odontode after the other, but not necessarily forming parallel series). Eye small and round (10.2−17.9% HL), situated dorsolaterally in midpoint of head. Iris operculum present but poorly developed. No ridge between eyes and nares. Nostril small. Supraoccipital process not elevated and without tuft of odontodes in specimens of all size. Mouth wide; oral disk roundish with papillae arranged in a medial longitudinal series extending posterior to dentaries through middle portion of lower lip. Lower lip larger than upper; almost reaching cleithrum region; its border strongly fringed. Maxillary barbel short, slender and free distally. Teeth slender and bicuspidate. Cusps symmetrical; medial cusp larger than lateral. Premaxillary teeth 7-12. Dentary teeth 5-12.

Dorsal fin rays ii, 7; in lateral view dorsal fin originating slightly posterior through origin of pelvic fin; distal margin slightly convex. Tip of adpressed dorsal fin rays surpassing end of anal fin base. Dorsal fin spinelet short and V-shaped (Fig. 7A); lock mechanism functional. Pectoral fin rays i, 6; tip of longest tip of longest pectoral-fin ray almost reaching pelvic fin insertion, when adpressed. Pectoral axillary slit present between pectoral fin insertion and lateral process of cleithrum. Pelvic fin rays i, 5; distal margin slightly convex; tip of adpressed pelvic fin almost reaching anal fin origin. Adipose-fin absent. Anal fin rays i, 4; distal margin slightly convex. Caudal fin rays i, 7-7, i; slightly emarginate; both unbranched rays of same size. Adpressed rays of all fins covered with pointed odontodes. Total vertebrae 28.

Body completely covered by bony plates, except on ventral part of head, around pectoral and pelvic fin origins and on dorsal fin base. Abdomen entirely covered by plates (Fig. 7B), abdomen formed by lateral plate series with elongate and large plates, formed by two lateral plates series, similar in size; median plates formed by one to three plates series reaching anal shield. Lateral of body entirely covered by plates (Fig. 7C); mid-dorsal plates poorly developed, almost reaching end of dorsal fin base; median plates not interrupted in median portion of body; mid-ventral plates almost reaching middle of caudal peduncle. Cleithrum and coracoid totally exposed. Arrector fossae partially enclosed by ventral lamina of coracoids.

Parts of dorsal head bone plates presented in Fig. 7D. Snout tip formed by one pair of rostral square-shaped plates (r). Nasal (n) almost rectangular forming anterior medial nostril margin in contact posteriorly with frontals (f) and anteriorly and laterally with pre-nasals (pn). Pre-nasals (pn) positioned posteriorly of rostral plates (r), formed by two large and two small rounded-shaped plates between nares. Top of head composed by compound pterotic (cpt), parieto supraoccipital (soc) and frontal (f), largest bones of head, and prefrontal (pf) and sphenotic (sp). Compound pterotic (cpt) fenestrated randomly distributed. Posterior rostrum plates pr1-pr2 small, and rectangular shaped; pr4-pr3 largest, and rectangular shaped. Infraorbital plate series complete (io1-io5), present just above posterior rostrum series, all covered by latero-sensory canal system; io2 largest and io5 smallest; io3, io4 and io5 forming inferior orbital margin of eyes; preopercle (pop) elongated and rectangular, covered by latero-sensory canal; preopercle present under io4 and io5, and upper cp1, cp2. Supra-opercular plate (spop) present just above preopercle, covered by latero-sensory canal. Subocular cheek plates (cp1-cp2) and opercle (op) form posterior lateral margin of head.

Color in alcohol. Ground color of dorsal and ventral region of head and trunk pale yellowish; dorsal portion darker than ventral. Four dark saddle along dorsal portion of body: one at dorsal fin origin; second at end of dorsal fin; third at middle of caudal peduncle; and fourth at upper caudal peduncle adpressed ray origin. Dorsal end ventral surface covered with small dark-dots smaller then eyes diameter. Unpigmented portion of snout appears as two hyaline parallel stripes from rostral plate to nares. Dorsal, pectoral, and pelvic fins with dark chromatophores forming irregular sets of bands: three on dorsal and pectoral fin, two on pelvic fin and one on anal fin. Caudal fin hyaline, except for dark stripe on origin of rays, and for dark chromatophores irregularly distributed forming two diffuse bands.

Sexual dimorphism. Adults males have a papilla in urogenital opening (vs. absent in females); have a long pelvic fin that extends beyond anal fin origin (vs. pelvic fin not reaching anal fin origin in females); and have an unbranched pelvic fin ray supporting a dermal flap along its dorsal surface. Both sexes have a membrane on anal opening; however, this membrane is more developed in females than in males, covering almost the entire urogenital opening (see reference to this last character in Roxo et al. 2014b).

Distribution.

The new species Curculionichthys sabaji are known from five localities in the Rio Xingu basin: two at Rio 13 de Maio, one at Rio Coronel Vanick, one at Rio Couto de Magalhães and one at Rio Curuá (Fig. 8).

Etymology.

The specific name “sabaji” is a patronym honoring Dr. Mark Henry Sabaj Pérez, Collection Manager of Ichthyology, Academy of Natural Sciences of Philadelphia, in recognition of his dedication and contributions to study of Neotropical fishes especially from Rio Xingu basin (iXingu Project).

Comparative remarks.

Curculionichthys sabaji from the Xingu basin is morphologically very similar to Curculionichthys paresi from Rio Paraguai basin. Both species share a low number of teeth in the premaxillaries and dentaries, the form of papillae in the lower lip and the general pattern of body coloration. However, Curculionichthys sabaji , can be distinguished from Curculionichthys paresi by having several dark-brown spots distributed on the body, a shorter dorsal fin spine, a shorter pectoral fin spine, a deeper caudal peduncle and the lack of dark geometric spots on the anterodorsal region of body. The similarity in morphology among both species suggests a close relationship between them and that they may have once shared a common ancestor. Furthermore, the presence of these close related species in the Rio Paraguay and the Rio Xingu is not a surprise, since several authors (e.g. Pearson 1937; Carvalho and Albert 2011) historically have reported that those two hydrographic systems share several lineages of fishes, and that most species lineage present in the Rio Paraguay originated in Amazonian drainages ( Carvalho and Albert 2011).