Hypostomus hemicochliodon, Jonathan W. Armbruster, 2003

Jonathan W. Armbruster, 2003, The species of the Hypostomus cochliodon group (Siluriformes: Loricariidae)., Zootaxa 249, pp. 1-60 : 29-31

Hypostomus hemicochliodon new species

(Fig. 12)

Holotype: PERU. Río Nanay, Río Amazonas dr. at Pampa Chica, 4.54 km from Iquitos center, 269° bearing, 03°45’07”S, 73°16’59”W, MUSM 17442, 1, (126.2 mm SL).

Paratypes: PERU. Amazonas, Río Marañon dr. 500 m upstream from Caterpiza, LACM 42013-4, 1, (87.8) . Río Marañon dr. Caterpiza, LACM 41886-2, 1, (100.3) and LACM 41893-4 , Amazonas, Quebrada, Río Santiago - Río Marañon dr. quebrada enters Río Santiago from east, 2/3 length of island downstream of La Poza, LACM 39862-5, 1, (80.1) . Quebrada Kayamasa, Río Marañon dr. 40 km upstream from Caterpiza, LACM 41853-3, 1, (206.9) . Quebrada Pastazilla, Río Santiago - Río Marañon dr. LACM 39947-5, 2, (109.7-118.9) and LACM 39937-6, 1, (162.6) . Río Santiago, Río Marañon dr. at La Poza, FMNH 97010, 1, (115.1) and LACM 41729-34, 1, (91.3) . Loreto, Caño Sacarito, Río Orosa - Río Amazonas dr. about 35 min by boat upstream from mouth of Tonche Caño, 67.1 mi ENE Iquitos, 03°36’50”S, 72°16’55”W, INHS 39690, 1, (84.6) , AUM 28907, 1 (82.8) . Río Itaya, Río Amazonas dr. approx. 10 km S Santa Clara, INHS 36878, 1, 1 cs, (99.8) and SIUC 36690, 1, (93.8) . Río Itaya, Río Amazonas dr. ca. 4-5 km upstream from Iquitos ( Belém) above and below mouth of Quebrada Manzana, 03°47’71”S, 73°17’29”W, INHS 39962, 1, (100.5) . Río Itaya, Río Amazonas dr. near Iquitos, AMNH 218019, 1, (82.1) . Río Nanay, Río Amazonas dr. at Pampa Chica, 4.54 km from Iquitos center, 269°bearing, 03°45’07”S, 73°16’59”W, INHS 50131, 2, 1 cs, (80.6- 107.8) .

Nontype material: BRAZIL. Mato Grosso, Rio Juruena, Rio Tapajos dr. upper Rio Juruena, USNM 199225, 1, (119.3) . Rio Xingu, Rio Amazonas dr. São Felix, USNM 207509, 1, (82.7) . ECUADOR: Napo, Río Jivino, Río Napo dr. lower 4 km (mostly) to 0.6 km upstream from mouth (most between the two ports of Limoncocha), 00°24’36”S, 76°39’00”W, FMNH 106021, 1, (105.3) . Río Shushufindi, Río Aguarico dr. lower reaches, about 2 km from mouth in Río Aquarico, 00°17’30”S, 76°25’36”W, FMNH 106025, 2, (141.5-157.9) . Tributary, Río Payamino dr. few km upstream from San Jose de Payamino, 00°20’12”S, 77°18’W, FMNH 106024, 1, (158.0) . Tributary, Río San Miguel dr. km 50, 4.5 km S of Tipischa, FMNH 106022, 1, (208.7) . Tributary, Río Churuyacu - Río Payamino dr. Tiuyacu, first tributary of Río Churuyacu upstream from mouth in Río Payamino and near mouth of Río Churuyacu, 00°29’30”S, 77°18’W, FMNH 106023, 3, (112.6-197.2) . Río Corrientes, Río Napo dr. eastern Ecuador, FMNH 92633, 3, 1 cs, (78.6- 89.8) . VENEZUELA. Amazonas, Caño Jenita, Río Ocamo dr. Oramo department, in an old meander 1 km river km above the Río Ocamo, 02°46’N, 64°54’W, MCNG 24332, 1, (142.3) . Laguna Pacón, Río Orinoco dr. in pools behind beach along Río Ventuari about 0.5 hr above mouth, MBUCV V-23092, 1, (165.2) . Río Cataniapo, Río Orinoco dr. in Las Palvas, MBUCV V-24501 (none measured) . Río Mavaca, Río Orinoco dr. river above camp base, MBUCV V-19239, 1, (186.1) . Río Siapa, Rio Casiquiare - Río Negro dr. Departmento Río Negro, at campsite near Laguna Cumicapi between Río Emoni and Río Manipitare, MCNG 37041, 1, (100.3) . Río Siapa, Río Casiquiare dr. near and downstream of confluence with Río Manipitare, 01°54’06”N, 65°57’05”W, MCNG 37032, 1, (199.5) .

Diagnosis: Hypostomus hemicochliodon differs from all other members of the H. cochliodon group except H. sculpodon by the presence of a medium-sized buccal papilla (condition intermediate between those shown in figures 4A and 4B), intermediately developed teeth (Fig. 1B; juvenile H. cochliodon also occasionally have intermediate teeth), and a large patch of odontodes on the opercle. Hypostomus hemicochliodon differs from H. sculpodon by coloration (dark brown with closely spaced spots vs. brownish-red with widely spaced spots), by having a greater dorsal-anal length to anal-fin length ratio (average= 111.1 ± 8.4%, 92.5-132.6% vs. average = 79.2 ± 7.6%, 69.6-89.7%), and almost completely by having a larger interorbital width/HL ratio (average = 49.9 ± 2.7%, 44.1- 55.6% vs. average = 51.4 ± 3.1%, 38.5-45.4%).

Description: See description of the Hypostomus cochliodon group for more details. Morphometric data given in Table 2. Color brown with medium to large spots. Spots become larger posteriorly, often coalescing on caudal peduncle to form large, longitudinally oval dashes or stripes. Some adults with spots on body absent. Spots on abdomen variable; fairly large specimens often have few or no spots on the abdomen; abdomen often significantly lighter than sides, almost white. Four faint dorsal saddles often present: first below anterior rays of dorsal fin, second below posterior rays of and slightly posterior to dorsal fin, third slightly anterior to and ventral to adipose fin, and fourth at base of caudal fin. One captive Hypostomus hemicochliodon demonstrated well-developed ability to change color, particularly ability to lighten coloration of abdomen and intensify lateral spots or dorsal saddles (either spots or the saddles dominant, but never both dark at same time).

Dorsal fin fairly short, usually falls short of preadipose plate when depressed. Depressed pectoral-fin spine ventral to pelvic fin reaches 2-3 plates beyond bases of pelvic-fin rays. Tip of pectoral-fin spine of nuptial males with stout, recurved, hypertrophied odontodes.

Keels strong, sharp. Orbit forming ridge distinctly raised above medial surface of head; ridges of dorsal and lateral aspect of head well-developed. Longitudinal ridge formed of raised bone and slightly larger odontodes present on pterotic-supracleithrum beginning at postdorsal corner of orbit. Opercle broadly exposed, always supporting much more than ten odontodes. Nuptial body odontodes absent (Fig. 2A). Plates in skin anterior to dorsal-fin spine absent or few (Fig. 6A; Table 7).

Each jaw with 7-23 teeth (mode = 15), teeth of intermediate size (Fig. 1B). Average angle between dentaries 63° (SD = 7°; range: 45°-75°; N=23). Lateral line plates 28-30; dorsal plates 8-9; interdorsal plates 6-8; adipose caudal plates 8-10.

Range: Has a wide range across central South America in the Ríos Marañon, Itaya, Nanay, Napo, and Orosa of the upper Río Amazonas of Peru, the Río Napo drainage of the Upper Río Amazonas drainage of Ecuador, the Rios Tapajos and Xingu of the lower Rio Amazonas drainage of Brazil, and the upper Río Negro drainage (middle Río Amazonas drainage) and upper Río Orinoco drainage of Venezuela. (Fig. 8). Hypostomus hemicochliodon is sympatric with H. ericius , H. oculeus , H. pyrineusi , and H. sculpodon .

Etymology: From the Latin, hemi, for half, the Latin, coclea (coch-), for spoon, and the Greek, odon, for tooth in reference to the fact that the teeth are about half as spoonshaped as those of wood-specializing members of the Hypostomus cochliodon group.