Hemiancistrus furtivus, Provenzano, Francisco & Barriga, Ramiro, 2017

Provenzano, Francisco & Barriga, Ramiro, 2017, The species of Hemiancistrus (Siluriformes: Loricariidae) from Ecuador, Zootaxa 4272 (2), pp. 221-235 : 223-228

Hemiancistrus furtivus new species

Tables 1 & 2, Figures 1 & 2

Holotype. MEPN 11569 , 83.0 mm SL, Ecuador, Pichincha Province, Esmeraldas River Basin, Río Silanche, río Blanco tributary, close to San Francisco de Silanche town , approx . 00°08´45´´N 79°16´38´´W, R. Barriga S. and A. Villacis, 0 7 November 2005, RBS05-24.

Paratypes. All from Ecuador, Esmeraldas River Basin : MEPN 18411, 1 ex ., 99.8 mm SL, Same data as holotype. MEPN 4475, 1 ex. , 79.2 mm SL, C&S, Esmeraldas Province, Estero Chipo a 11 km de Quinindé, vía Golondrinas-Buenos Aires, afluente del Río Blanco , approx. 00°16'28"N 79°24'11"W, R. Barriga, and C. Cerón, 13 March 1985, RBS 85-96 . MEPN 4488, 1 ex. , mm SL, Esmeraldas Province, Estero Mendoza, in front to Estero Cole a 1 km de la población del mismo nombre, approx. 00°27'00" N 79°24'09"W, R. Barriga, C. Cerón, and J. Caicedo, 10 March 1985, RBS 85-91 . MEPN 11421, 1 ex. , 54.4 mm SL, Esmeraldas Province, Río Quinindé. 00°18'49''N 79°29'01''W, R. Barriga S. and A. Villacis, 0 5 November 2005, RBS 05-29 . MEPN 11497, 1 ex. , 70.3 mm SL, Esmeraldas Province, Río Chamba, a 5 km de la vía Quinindé-Esmeraldas , approx. 00°15'04''N 79°21'07''W, R. Barriga S. and A. Villacis, 0 1 November 2005, RBS 05-25 . MCZ 48772, 13 ex., (12 Alc. 1 C&S), 55–97 mm SL, Esmeraldas Province, Río Tabuche , (Riachuelo) 49 km SE Esmeraldas, approx. 00°43'07''N 79°32'57''W, T. Roberts, C. Gilbert, and M. Silva, 20 October 1971 . AUM 4242 (out MCZ 48772), 1 ex., 75.7 mm SL, same data MCZ 48772 . MEPN-19058 (out MCZ 48772), 2 ex., (1 Alc. 1 C&S), 88.3–100.5 mm SL, same data MCZ 48772 .

Diagnosis. Hemiancistrus furtivus is distinguished from its unique geographical congener H. landoni and from H. medians by the totally naked abdomen and the color pattern of the dorsal and caudal fins. The dorsal fin has vertical rows of nearly rounded spots, dark (black or brown), on the interradial membranes, very near or attached to the rays, in H. landon i the dorsal fin has vertical rows of dark dots in the middle of the interradial membrane ( Fig. 2 ), while in H. medians the dorsal fin has vertical rows of dark dots on the interradial membrane near and, over the rays. In H. furtivus , the dots are smaller, near the diameter of eye or less, whereas the dots are greater than eye diameter in H. landoni and H. medians . On the caudal fin, H. furtivus has transverse rows of spots nearly rounded, dark (black) randomly dispersed on the interradial membrane and rays, mostly on the distal area, where they have the appearance of transverse dark bands. In H. landoni , the caudal fin color pattern is similar to the dorsal fin. In H. furtivus there are between 12–15 cheek odontodes, each odontode emerges from a fleshy sheath, only its tip protrudes and is visible, the length of the longest odontode is less than eye diameter. In H. landoni there are more than 15 cheek odontodes, with a similar condition as H. furtivus , but around half of each odontode is visible, the length of longest (most posterior) is greater than the eye diameter. The new species can be recognized from all other species of Hemiancistrus sensu lato (Armbruster et al. 2015) except H. medians and H. landoni by the presence of dark rounded dots on the belly vs. belly whitish or with pale color homogeneous, without dots or spots. Finally, the species grouped in the ‘H.’ chlorostistus group from Brazil have patches of small plates on the abdomen while H. furtivus has the abdomen completely naked.

Description. Morphometric data given in Table 1. Body robust, progressively compressed posteriorly. Caudal peduncle compressed, deep and robust. Dorsal profile of body from tip of snout through eyes, straight, with a slope close to 45°, from eyes to dorsal-fin origin gently convex, then gradually descending straight to caudal-fin origin. Ventral profile of body flat and straight or slightly concave. Ventral surface of head and belly naked to anus. From the anus to anal-fin origin, a straight naked band is present bordered by end of lateral plates. Urogenital papilla absent, the cloaca is a small but evident fleshy tube. Head wide and little depressed. Snout not projected with naked, oval tip. Eyes in dorsolateral position, orbits raised. Interorbital space broad. Supraoccipital slightly convex, posterior border rounded.

Cheek mobile odontodes 12–15, tiny and thin. Each odontode arises from fleshy cylindrical base, and only tip protrudes. Tips orange or amber. Mobile odontodes roughly arranged in rosette pattern. Opercular bone exposed, visible externally, its lateral margin with small odontodes.

Mouth oval or rounded. Upper lip narrow, usually covering premaxilla and only external surface is visible, edge is almost horizontal with very minute undulations. Internal surface papillose. Lower lip broad, its border crenulated. Lower lip surface papillose. Papillae smaller near border of lip increasing in size near lower jaws. Papillae of anterior lip similar in size to those near lower jaws. Maxillary barbels short, united to lower lip, leaving only tip free. Premaxilla slightly longer than dentary. Premaxillae nearly straight forming ~180° angle. Dentaries separate, forming open “V” between them, with angle 95°–105° between rami. Teeth numerous and minute, 25–35 teeth in each hemimandible. Premaxillary and dentary teeth of same size. Teeth incisor type, asymmetrically bifid, medial cusp longer and wider than lateral cusp. Medial cusp rounded or straight truncated, lateral cusp pointed. Tooth apex curved toward interior of mouth. Tooth apex yellowish, stalk whitish. Premaxillary and dentary with posterior small papillae.

Plates on sides of body with keels. Lateral line plates 27 or 28. Post-anal plates 15 or 16. Inter-dorsal plates seven or eight, just in front of adipose-fin soine one small plate with keel. Dorsal-fin origin anterior to vertical passing through pelvic-fin origin. Dorsal-fin with one spinelet, one spine, and seven branched rays; when depressed tip does not reach adipose-fin origin. Adipose-fin well developed and always present. Spine of adipose fin wide, and straight. Pectoral-fin with one spine, and six branched rays. When depressed, pectoral-fin spine reaches less than one third of pelvic-fin spine length. Spine of pectoral-fin with a fleshy tip, and slightly shorter than first branched ray. Pelvic-fin with one spine and five branched rays; its posterior margin surpassed anal-fin base when depressed. Anal-fin with one flexible spine and four branched rays. Caudal-fin rays i,14,i. Caudal-fin emarginate.

Color. Specimens preserved in 70% ethanol show little variation in base color. General color of head and dorsolateral surfaces of body dark brown. Dark (black), rectangular, ovals or rounded spots, of different sizes, and randomly arranged on head and body. Spots became smaller, concentrated, and faint or diffuse on snout. Two or three transverse, dark (black), and irregular saddles, anteriorly oriented, first at end of dorsal-fin base, second at adipose fin origin, and last at caudal-fin origin; saddles more visible in dorsal view. Patch of dark spots at caudalfin origin. Base color of abdomen uniform, creamy or whitish, with irregular, dark (black) spots. Dorsal fin with longitudinal rows of nearly rounded spots, dark (black or brown), on interradial membrane, near or attached to the rays. Caudal fin with transverse rows of spots nearly rounded, dark (black) randomly dispersed on interradial membrane and rays, mostly at distal area, where they appear to combine in transverse dark bands. Rest of fins with brown base color with dark (black) spots on spines, branched rays and interradial membranes ( Figs. 1–2 ). Smallest specimen (54.4 mm SL) with dorsal and caudal fins with longitudinal or transverse, respectively, dark bands.

Geographical distribution. The specimens were caught in the Esmeraldas River Basin, Provinces of Esmeraldas and Pichincha ( Fig. 5 ).

Etymology. The name of the species is taken from the Latin word furtivus meaning: attempting to pass unnoticed or hidden, and alludes to the fact that the species was not detected before despite being in the Ecuadorian Pacific region, one of the best known ichthyologically. An adjective.

Figures

FIGURE 1. Hemiancistrus furtivus, in lateral, dorsal, and ventral view. MEPN 11569, holotype, 83.0 mm SL.

FIGURE 2. Partial lateral view of A) Hemiancistrus furtivus, MEPN 18411, 99.8 mm SL, and B) H. landoni, MEPN 17952, 78.9 mm SL.

FIGURE 5. Geographical distribution of Hypostomus annectens (circle), Hemiancistrus furtivus (star), and Hemiancistrus landoni (triangle). Symbols may represent more than one lot.