Hypostomus oculeus (Fowler 1943)

Jonathan W. Armbruster, 2003, The species of the Hypostomus cochliodon group (Siluriformes: Loricariidae)., Zootaxa 249, pp. 1-60 : 36-38

Hypostomus oculeus (Fowler 1943)

(Fig. 16)

Panaque oculeus Fowler 1943 : 256-258, figs. 48-51.

Material examined: AQUARIUM SPECIMEN: AUM 16090 , 1 cs . COLOMBIA. Caqueta: Río Orteguasa - Río Amazonas dr. Florencia, Caqueta, ANSP 70518, 1, (140.5), Holotype , ANSP 70519, 2, (91.8-126.3), Paratypes , and USNM 100773, 1, (143.9) . ECUADOR. State unknown: Quebrada, Río Jivino - Río Napo dr. ANSP 120350, 1, (163.6) . Río Catapino, Río Corrientes - Río Napo dr. MCNG 9724, 2, (145.8-161.3) . Río Catapino, Río Corrientes - Río Napo dr. Panayaco, MCNG 9725, 2, (149.1-190.6) . Napo: Río Aguarico, Río Napo dr. at campamento Guarmo CEPE, 00°01’S, 76°37’30”W, FMNH 106015, 1, (129.35) . Río Due, Río Aguarico dr. at site of bridge under construction 8.8 km SW Lumbaqui by road and 0.4 km N of the road, 00°00’12”S, 77°23’48”W, FMNH 106014, 1, (90.8) . Río Lushanta, Río Napo dr. 4 km E Archidona, AUM 28229, 3, 3 cs, (3) . Río Lushian, Río Napo dr. 2 km N Archidona, AUM 28221, 1, 2 cs, (1) . Río Lushian, Río Napo dr. 3 km N Archidona, AUM 28342, 2, (211.9-216.9) . Río Pano, Río Napo dr. 5.5 km NW Tena, elev. 550 m, AUM 28216, 2, (82.9-100.1) . Tributary, Río Payamino dr. few km upstream from San Jose de Payamino, 00°20’12”S, 77°18’W, FMNH 106016, 3, (152.2-185.4) . PERU. Amazonas: Río Marañon dr. Caterpiza, LACM 41873-5, 1, (175.7) . Río Cenepa, Río Marañon dr. near Río Tujushiku, LACM 39647-2, 2, (161.4-167.6) . Río Santiago, Río Marañon dr. at La Poza, LACM 41724-16, 1, (112.3) .

Diagnosis: Hypostomus oculeus can be distinguished from all other members of the H. cochliodon group except H. ericius , H. hemicochliodon , and H. sculpodon by having well developed keels. Hypostomus oculeus differs from H. hemicochliodon and H. sculpodon by a lack of a buccal papilla, by having 0-10 odontodes on the opercle (versus more than 10), and the presence of nuptial body odontodes (Fig. 2B); and from H. ericius by being dark brown with closely-placed spots (vs. tan to gray with widely separated spots) and by the following ratios: anal-fin length/SL (10.8-13.9% vs. 13.4-17.0%) and interorbital width/head length (42.4-50.2% vs. 50.5-56.6%).

Description: See Hypostomus cochliodon group description for more details. Morphometric data given in Table 3. Body almost entirely dark brown with medium to large spots present. Spots increasing in size posteriorly and almost coalescing to form stripes on caudal peduncle. Spots on abdomen large, often confluent with one another and forming crescents and rings. Abdomen slightly lighter than sides, particularly in juveniles. Individuals below 100 mm SL often entirely dark brown except for faint spots on dorsal and paired fins and with lighter abdomen.

Dorsal fin occasionally large, reaching beyond adipose fin when depressed, but dorsal fin generally reaching preadipose plate or slightly beyond when depressed. Pectoral-fin spine when depressed ventral to pelvic fin reaches beyond bases of pelvic-fin rays. Pectoral-fin spine supporting numerous stout, recurved, hypertrophied odontodes in nuptial males.

Keels sharp, strongly developed. Orbits forming ridge distinctly raised above medial surface of head; ridges of dorsal and lateral aspect of head well-developed. Longitudinal ridge on pterotic-supracleithrum beginning at posterodorsal corner of eye formed from raised bone and slightly larger odontodes absent. Opercle usually not supporting odontodes, but one to ten odontodes may be present, and odontodes on opercle more numerous in juveniles. Nuptial body odontodes present (Fig. 2B). Platelets in skin anterior to dorsalfin spine usually absent or not numerous (Fig. 6A; Table 7).

Each jaw with 7-18 teeth (mode = 8), teeth large and spoon-shaped. Average angle between dentaries 65° (SD = 10°; range: 48°-89°; N=23). Lateral line plates 27-30; dorsal plates 7-9; interdorsal plates 5-7; adipose caudal plates 9-11.

Range: Found in the Rio Marañon drainage of Peru, the Río Napo drainage of Ecuador, and the Río Orteguasa drainage of Colombia, all tributaries of the Upper Río Amazonas drainage (Fig. 17). Hypostomus oculeus is sympatric with H. ericius , H. hemicochliodon , and H. pyrineusi .