Rhyacoglanis epiblepsis, Shibatta & Vari, 2017

Shibatta, Oscar Akio & Vari, Richard P., 2017, A new genus of Neotropical rheophilic catfishes, with four new species (Teleostei: Siluriformes: Pseudopimelodidae), Neotropical Ichthyology 15 (2), No. e 160132, pp. 1-30 : 8-11

Rhyacoglanis epiblepsis , new species

urn:lsid:zoobank.org:act:20173235-94FE-4571-BBAA-C3D3744692A2

Figs. 5-6; Tab. 2

Pimelodus zungaro zungaro . - Mees, 1974:132, 202, fig. 39, pl. 5 (partim; Bolivia, río Popoi, upper río Beni).

Holotype. AMNH 266401 , 53.3 mm SL, Bolivia, Beni, río Itenez, cachuelo approximately 300 m above mouth of río Machupo , ca. 12°29’S 64°24’W, 14 Oct 1964, R. M. Bailey, A. Ximenez, R. Ramos & D. Anez.

Neotropical Ichthyology, 15(2): e160132, 2017 New genus and four new species of Pseudopimelodidae

Paratypes. AMNH 40127 , 116 (25 measured), 41.0- 54.2 mm SL, collected with holotype .

Diagnosis. Rhyacoglanis epiblepsis can be distinguished from all congeners by having rounded caudal-fin lobes (vs. pointed lobes). Rhyacoglanis epiblepsis can be differentiated from R. annulatus by possessing a uniform caudal-peduncle band (vs. an unpigmented region in the band) and lower total vertebrae (31-33 vs. 34-35). Rhyacoglanis epiblepsis differs from R. paranensis by the intensely spotted lateral surface of body (vs. presence of only a few dark spots). Rhyacoglanis epiblepsis is differentiated from R. seminiger by the distinct separation of the dark subdorsal and subadipose bands (vs. fusion of those bands) and well developed serrations along the entire anterior pectoral-spine margin (vs. weak serrations limited to the basal portion of the margin). Rhyacoglanis epiblepsis differs from R. pulcher in the possession of numerous dark spots on the body (vs. limited spots) and lower number of total vertebrae (31-33 vs. 34-35).

Description. Body proportions are presented in Tab. 2. Body depressed from snout tip to dorsal-fin origin; progressively more compressed from that point to caudal-fin base. Dorsal profile of head and body posterodorsally nearly straight from snout tip to dorsal-fin origin. Dorsal-fin base slightly straight; profile nearly straight from limit of dorsal-fin base to adipose-fin origin. Ventral profile of head and body very slightly convex from margin of lower jaw to end of anal-fin base. Caudal peduncle concave dorsally and ventrally.

Head depressed, slightly longer than wide. Anterior margin very slightly convex in dorsal view. Head with unculiferous tubercles mainly dorsally. Mouth terminal, wide, more than one-half of HL. Upper jaw slightly longer than lower jaw. Lips thick, well developed primarily on lateral surface of jaws. Premaxillary tooth plate with posteriorly pointed projection. Anterior nostril immediately posterior of vertical through rictus. Eye small, superior, covered by skin, slightly posterior of anterior one-third of HL. Opercular membrane well developed; margin reaching pectoral-fin base. Maxillary-barbel base enlarged. Tip of adpressed barbel falling short of opercular margin. Adpresssed inner mental barbel extending beyond base of outer mental barbel but falling short of barbel tip. Tip of adpressed outer mental barbel reaching margin of opercular membrane.

Dorsal fin trapezoidal; distal margin rounded; length of longest ray shorter than fin base. Dorsal-fin origin immediately posterior to anterior one-third of body length and anterior to one-half of SL. Tip of adpressed dorsal fin falling short of midpoint between bases of dorsal and adipose fins. First dorsal-fin ray (spinelet) small, rigid, and forming dorsal-fin locking-mechanism. Second ray a spine with anterior margin smooth and posterior margin bearing retrorse serrations. Dorsal-fin rays I,6* rays (15). Adipose fin long; base longer than that of all other fins; posterior extremity free and rounded. Pectoral fin slightly triangular overall with distal margin rounded. Tip of adpressed pectoral fin falling short of pelvic-fin origin. First pectoral-fin ray strong, rigid, and forming spine with retrorse serrations along anterior and posterior margins. Serrations of posterior margin slightly larger, more so distally ( Fig. 3b). Pectoralfin rays I,6* (15). Pelvic fin almost triangular with distal margin rounded. Pelvic-fin origin at vertical through base of penultimate dorsal-fin ray. Tip of adpressed pelvic fin falling short of anal-fin origin and of vertical through adipose-fin origin. Pelvic-fin rays i,5*(15). Anal fin rounded distally. Anal-fin rays iii,5(2), iv,5(5), iii,6(7), iv,6*(6), iii,7(2). Caudal fin forked with rounded lobes; lower lobe slightly longer than upper lobe. Principal caudal-fin rays i,6,7,i(2), i,6,8,i*(18), i,7,8,i(5).

Posterior cleithral process well developed and pointed. Axillary pore present. Lateral line with pored portion of variable length; extending posteriorly beyond vertical through posterior limit of adipose-fin base, but falling short of caudal-fin base. Total vertebrae 30(1), 31*(8), 32(14), 33(2). Ribs 9*(21), 10(4). Gill rakers 1,1,2(1); 1,1,3(6); 1,1,4(2); 1,1,5(6).

Color in alcohol. Ground color brown. Head with dark spots dorsally, on opercle, and ventral to orbit. Region over adductor mandibulae muscle lightly colored in many specimens. Lateral and dorsolateral surface of body covered by small dark spots. Subdorsal band nearly triangular; subadipose band trapezoidal; caudal-peduncle band with straight anterior and biconcave posterior margins. Dorsal fin with dark stripes basally and across midsection with lightly colored stripes along distal margin and ventral one-third of posterior five rays. Adipose fin with central portion entirely dark brown. Caudal-fin ground coloration light; each lobe with posteriorly arching dark band and lobe margins lightly pigmented. Pectoral, pelvic and anal fins with thin, incomplete, dark stripes. Completely spotted individuals with spots extending onto fins ( Fig. 6).

Geographical distribution. Rhyacoglanis epiblepsis is known only from the río Madeira-Mamoré system in Bolivia ( Fig. 4).

Etymology. The specific name, epiblepsis , is an adjective from the Greek epi (= up), and blepsis (= act of sight) in reference to the dorsal position of the eyes.

Conservation status. Several specimens of R. epiblepsis were collected, potentially indicating that the species is locally common. However, because R. epiblepsis , is known only from the type locality, is it not possible to estimate its actual distribution. Considering the absence of information about its distribution and population dynamics, R. epiblepsis should be assigned a Data Deficient (DD) IUCN (2016) status.