Otocinclus juruenae

Ribeiro, Alexandre Cunha & Lehmann, Pablo, 2016, A new Otocinclus (Siluriformes: Loricariidae: Hypoptopomatinae) from the Rio Juruena Basin, central Brazil, Zootaxa 4147 (3), pp. 240-246 : 241-244

Otocinclus juruenae

( Fig. 1 ).

Holotype. MZUSP 120361 , female, 29.6 mm SL, Brazil, Mato Grosso, Juara, Tapajos basin, Rio Juruena drainage, bridge over Rio São João da Barra , (10 0 18', 46,0”S/ 57 0 38' 44,0”W), Fábio Rosa & Willian Assunção, August, 6, 2007.

Paratypes. CPUFMT 839, 18 (22.3–33.0 mm SL) and MCP 49446, 3 (27.4–29.4 mm SL)+2 CS (26.2–27.8 mm SL) collected with holotype.

Diagnosis. The new species differs from all congeners (except Otocinclus cocama ) by having a complete lateral line, without gap plates. Otocinclus juruenae differs from O. bororo , O. caxarari , O. hoppei , O. huaorani , O.

macrospilus , O. mariae , O. mura , O. vestitus , and O. vittatus (previously assigned by Schaefer, 1997 to the “orbis” clade) as well as O. batmani and O. cocama by having an iris operculum (vs. iris operculum absent). It is further distinguished from all Otocinclus except O. flexilis and O. xakriaba by the lateral trunk coloration consisting of a series of three to four diffuse pigment blotches without a distinct midlateral stripe (vs. trunk with distinct midlateral stripe).

Description. Morphometric and meristic data in Table 1 and 2, respectively. Largest specimen examined 33.0 mm SL. Dorsal profile of body in lateral view gently arched from snout tip to dorsal-fin insertion; slightly concave to straight along base of dorsal fin; straight between dorsal fin and caudal peduncle and slightly concave along caudal peduncle to caudal-fin base. Ventral profile of body in lateral view straight to slightly concave along ventral margins of rostral plates, between snout tip and posteroventral margin of opercle; slightly convex to straight between that point and pelvic-fin insertion, along abdomen; straight to slightly concave between ventral fin and slightly concave from anal-fin insertion to caudal-fin base. Caudal peduncle oval to slightly rectangular in crosssection, longer along its dorsoventral axis. Greatest body depth at dorsal-fin origin. Least body depth at caudal peduncle. Greatest body width at pectoral-fin insertion, trunk gradually tapering from cleithrum to caudal-fin base.

Table 1. Morphometrics of Otocinclus juruenae . sd = standard deviation.

Head broad, elliptical anteriorly. Snout tip anteriorly pronounced. Median elongated bulge associated with mesethmoid from snout tip to transverse line between nares inconspicuous, providing flat aspect between nares. Interorbital region slightly concave. Eyes laterally placed, visible from ventral view. Iris with small semicircular operculum (iris diverticulum) extending from dorsal margin of iris and covering pupil. Oral disk (lips) elliptical, broad, reaching to vertical through anterior orbital margins, not reaching to pectoral girdle. Lower lip covered with numerous similarly-sized papillae. Oral disk with fringed margins, fringes formed by well-developed, elongated papillae. Maxillary barbel present. Buccal papilla present, moderately developed. Teeth slender, bifid, with larger medial cusp and smaller lateral cusp minute and pointed.

Body entirely covered by plates, except for ventral surface of head and insertions of pectoral and pelvic fins. Abdomen with paired series of six to eight large, sickle-shaped lateral plates; median plates in one row and seven to eight plates, extending posteriorly beyond lateral abdominal plates series to middle of branched pelvic-fin rays; pre-anal shield well developed, continuous with median abdominal plates. Plates and odontodes of head and body not arranged in crests, keels, or conspicuous rows. Tip of parieto-supraoccipital without conspicuous tuff of enlarged odontodes, odontodes just slightly enlarged. Odontodes slightly enlarged at rostral plates. Rostral and cheek plates limiting ventral margin of snout. Pectoral girdle exposed ventrally and coved with odontodes. Abdomen plated. Lateral line complete, without a gap lacking sensory pores 2). Lateral-line pores small and inconspicuous.

Tip of adpressed pectoral-fin spine reaching to about anterior one third of pelvic-fin. Odontodes of distal portion of pectoral-fin spine conspicuously larger than remaining pectoral-fin odontodes. Tip of adpressed pelvicfin spine reaching to anal-fin origin. Dorsal-fin insertion at vertical just anterior to insertion of pelvic fin. Dorsalfin spinelet V -shaped, dorsal-fin spine locking mechanism functional. Insertion of anal fin at vertical just behind posterior tip of dorsal fin. Caudal-fin margin concave, upper caudal-fin lobe slightly longer than lower caudal-fin lobe.

Character Holotype Range Mode N Dorsal plates 23 22–24 23 10 Mid-dorsal plates 17 16–18 16 10 Median plates 24 24–26 24 10 Midi-ventral plates 19 19–19 19 10 Ventral plates 20 20–21 20 10 Predorsal plates 3 3–3 3 10 Dorsal plates between posterior dorsal-fin ray and caudal-fin mambrane 16 14–16 16 10 Dorsal plates within dorsal-fin interradial membrane 4 3–4 4 10 Ventral plates within anal-fin interradial membrane 3 3–3 3 10 Ventral plates from end of anal fin to caudal–fin membrane 12 11–13 12 10 Dorsal-fin branched rays 7 7–7 7 10 Pectoral-fin branched rays 6 6–6 6 10 Pelvic-fin branched rays 5 5–5 5 10 Anal-fin branched rays 5 5–5 5 10 Caudal-fin branched rays 14 14–14 14 10 Premaxillary teeth 17 16–19 17 10 Dentary teeth 14 13–17 13 10 Color in alcohol. Ground color slightly creamy to pale yellow. Even sprinkling of melanophores between supraoccipital and origin of dorsal fin; trunk on dorsal-fin base with five or six cluster of concentrated melanophores, follow by nine or ten spots with pigment concentrated in oval shape on dorsal series plates from dorsal-fin base to first dorsal procurrent caudal-fin ray. Unbranched caudal-fin ray with three or four distinct blotches in dorsal view.

Head and trunk with diffuse sprinkling of melanophores, without distinct midlateral stripe, pigment especially concentrated in region immediately posterior to orbit and area dorsal to margin of opercle. Side of trunk composed of superficial and deep-lying melanophores arranged in distinct clusters along length of trunk between opercle and caudal fin; such clusters, in turn, concentrated into three to four diffuse blotches along length of trunk. Pigment between blotches present, inconspicuous, not appearing as stripe of uniform width and intensity. Caudal spot ovalshaped, narrow (not reaching to the dorsal and ventral margins on the caudal peduncle) intensely pigmented, extending posteriorly just along proximal half of median branched caudal-fin rays as intense concentration of melanophores, rectangular in shape. Caudal-fin rays with scattered melanophores arranged in parallel pair of diffuse pigment bands, anterior band located about midway along length of fin, posterior band located near posterior fin margin. Dorsal fin with melanophores along entire length of spine arranged in four to five blotches; pigment on branched rays concentrated in two to three faint bands, posterior one with melanophores more concentrated on ray ramifications; interradial membranes unpigmented. Anal fin unpigmented. Pectoral fin with even distribution of melanophores along pectoral spine; branched rays and interradial membranes unpigmented. Pelvic fin with few melanophores arranged in one or two blotches on distal two-thirds of unbranched ray, interradial membranes and branched rays unpigmented. Ventral surface of head and body unpigmented, except for numerous scattered melanophores on ventrolateral margin of pectoral girdle.

Distribution. Know only from its type locality in the Rio Juruena, central Brazil ( Fig. 2 ).

Etymology. Named after the Rio Juruena, a right bank tributary of the Rio Tapajós basin where the type material was collected. An adjective.

Figures

FIGURE 1. Holotype of Otocinclus juruenae, MZUSP 120361, female, 29.6 mm SL. Lateral (A) dorsal (B) and ventral (C) views.

FIGURE 2. Type locality of Otocinclus juruenae. Shaded area at left encompasses the political boundaries of Mato Grosso state, central Brazil.