Cordylancistrus nephelion, Provenzano, Francisco & Milani, Nadia, 2006

Provenzano, Francisco & Milani, Nadia, 2006, Cordylancistrus nephelion (Siluriformes, Loricariidae), a new and endangered species of suckermouth armored catfish from the Tuy River, north­central Venezuela, Zootaxa 1116, pp. 29-41 : 31-35

Cordylancistrus nephelion new species

Figs. 1–2 , Table 1

Holotype: MBUCV­V­ 21800, 129.1 mm SL; Venezuela, Caribbean Sea basin, Tuy River system, Mesia River, tributary of the Guare River, near Village Corocito, approximately 10°12'N, 67°05'W; N. Padilla and H. Camejo; 26 January 1992.

Paratypes: All from Venezuela, Caribbean Sea basin, Tuy River system. Miranda State: MBUCV­V­21801, 1 ex., 121.2 mm SL; collected with the holotype. MBUCV­V­ 12526, 1 ex., 61.0 mm SL; Grande River approximately 500 m upstream from its mouth in Santa Cruz River, a tributary of Taguaza River, Guatopo National Park, approx. 10°05'N, 66°29'W; R. Royero and party; 0 1 March 1981. MBUCV­V­16382, 1 ex., 55.2 mm SL; Mesia River, tributary of the Guare River, Paso del Viento, near the road to Tácata, approx. 10°12'N, 67°02'W; N. Padilla and L. Aguana; 30 January 1992. MBUCV­V­21806, 1 ex., 31.1 mm SL; Cagua River, Boca de Cagua, approximately 10 km E of Village Guayas, approx. 10°14'N 67°07'W; R. Royero, F. Gil and C. Navarrese, 0 6 April 1991. MBUCV­V­ 27872, 1 ex, 76.4 mm SL; Mesia River, tributary of the Guare River, Pozo El Cirilo, near Village El Salado, approx. 10°13'N 67°03'W; N. Padilla and E. Camejo; 29 May 1994. Aragua State: MBUCV­V­22700, 1 ex., 75.9 mm SL; Quebrada Agua Amarilla, a tributary of the Cagua River, Village Agua Amarilla, SE of Tejerias, approx. 10°12'N, 67°03'W; N. Padilla; 23 February 1992.

Diagnosis. Cordylancistrus nephelion can be distinguished from the other species assigned to its genus by its unique color pattern. Head and body blackish to greenish brown with white irregular spots. Abdomen uniformly white. All fins with whitish spots that simulate bands.

Description. Morphometric data are given in Table 1 . Head wide and slightly depressed. Snout edge covered with small plates, its contour oval. Eyes in dorsal position, dorsal edge of the orbits slightly raised, small odontodes found around orbits. Interorbital space flat. Posterior edge of the supraoccipital without a fleshy keel. Mouth wide, lips papillose, papillae of the anterior lip slightly larger. Edge of the posterior lip with marked undulations. Maxillary barbels very short and joined to lower lip by a fleshy flap, leaving tip of barbel free. Premaxilla and dentary enlarged. Inside mouth behind premaxilla with three to five larger papillae. Also behind the dentary three to five larger and smooth papillae present that increase in size toward center of mouth ( Fig. 2 ). Teeth numerous, 49 to 105 teeth on each premaxilla and 53 to 129 on each dentary. Teeth are very thin and elongated, with apex curved toward interior of mouth. Teeth bifurcate, one lobe slightly longer than other, both tips are pointed. Tooth apex yellowish, stalk whitish. Interopercular hypertrophied evertible odontodes vary in size; longest odontode sometimes reaches the cleithrum but surpasses it in only one specimen. Hypertrophied odontodes vary in number from six on smallest specimen to 25 on the largest. Body robust and relatively deep. Caudal peduncle compressed. Lateral plates of the body without spiny keels. Lateral line plates 23 to 24. Post­anal plates 10 to 11. Inter­dorsal plates six, the last with a slight keel. Ventral surface of body naked to origin of anal fin. Dorsal fin I8. Pectoral fin I6, pectoral spine relatively short, reaching one­third length of pelvic spine or less. In all examined specimens, pectoral spine with odontodes on posterodorsal surface. Anal fin with four branched rays, three on one specimen. Pelvic fin I5. Caudal fin I14 I, obliquely truncate.

Color. In specimens preserved in 70% ethanol head and body color varies from blackish to greenish brown with white irregular spots; abdomen uniformly white. Dorsal surface of head with small spots that become larger posteriorly. Spots along body approximately as wide as the eye; in some cases two or more spots unite to form a spot of greater size. Spine and branched rays of dorsal fin with four to five whitish spots. Interradial membrane with irregular translucent spots, more evident towards the distal margin. In largest specimens (121 and 129 mm SL), pectoral­fin and pelvic­fin spine have six to seven whitish spots and branched rays have five to six, while in smaller specimens (76.4 mm SL or less) spines with four to five and branched rays with three to four. Interradial membrane hyaline. Anal fin generally whitish with dark distal border. Adipose fin with whitish band. Caudal­fin spines with six to seven whitish spots and branched rays with four to six. Interradial membrane with pattern similar to dorsal fin.

Range. The specimens of Cordylancistrus nephelion were captured in three tributaries of the Tuy River: the Cagua River, the Mesia River (a tributary of the Guare River) and the Santa Cruz River (a tributary of the Taguaza River) at 40 km, 55 km and 130 km east of the headwaters of the Tuy River respectively ( Fig. 3 ). This distribution suggests that the species may be present throughout the Tuy River basin. The species seems to inhabit small rivers of the north slope of the Serranía del Interior, Cordillera de La Costa. These rivers have transparent waters, with moderate to strong flow and a temperature of 15° to 20° C. The bottom generally consists of stone, gravel and sand. The predominant vegetation in this mountainous area is cloud forest.

An exhaustive review of the Venezuelan fish collections shows that the geographic distribution of the three species of Cordylancistrus present in the country is restricted and disjunct. Cordylancistrus torbesensis inhabits the foothill rivers of the south slope of the Cordillera de Mérida; C. perijae is found in rivers of the eastern slope, north of the Sierra of Perijá and C. nephelion inhabits the Tuy River basin, in rivers of the north slope of the Serranía of the Interior, Cordillera de La Costa ( Fig. 3 ).

Etymology. The name of the species is taken from the Greek word nephelion , meaning cloudlike spots, in reference to the color pattern of the species.

Figures

FIGURE 1. Cordylancistrus nephelion MBUCV­V­ 21800, 129. 1 mm SL, holotype, A: lateral, B: dorsal, and C: ventral views. Photos by N. Milani.

FIGURE 2. Cordylancistrus nephelion MBUCV­V­ 21800, 129. 1 mm SL, holotype, Detail of the ventral surface of head. Photo by N. Milani

FIGURE 3. Geographical distributions of Cordylancistrus species in Venezuela. C. nephelion circles, white circle is the type locality. C. torbesensis white square. C. perija black square.

Tables

TABLE 1. Morphometric data of Cordylancistrus nephelion. Morphometric data 1 – 15 are expressed as percentage of standard length, 16 – 20 as percentage of the head length, and 21 – 24 in ratios. MIN: minimum, MAX: maximum, AVE: average, STD: standard deviation, HL: head length, IOW: interorbital width, MRL: mandibular ramus length, OD: orbital diameter.

	Holotype	MIN	MAX	AVE	STD
SL (mm)	129,10	31,10	129,10	78,56	35,33
1 Head length	35,24	34,32	41,16	36,32	2,41
2 Predorsal length	43,14	42,90	46,62	44,17	1,37
3 Postdorsal length	36,64	35,05	37,68	35,98	0,95
4 Interdorsal length	14,79	10,13	15,31	13,29	1,93
5 Preanal length	64,14	64,14	69,45	67,36	1,84
6 Postanal length	28,43	28,43	35,11	30,50	2,20
7 Thoracic length	20,99	20,58	23,44	21,93	1,00
8 Abdominal length	22,46	19,61	24,01	21,69	1,40
9 Dorsal fin base	22,08	18,49	22,53	20,91	1,49
10 Dorsal spine length	24,98	21,34	25,50	23,50	1,67
11 Pectoral spine length	32,61	24,77	33,00	27,77	3,65
12 Pelvic spine length	25,64	25,00	27,31	25,94	0,86
13 Cleithral width	36,17	32,80	36,17	34,61	1,14
14 Caudal peduncle depth	14,64	12,50	14,64	13,43	0,84
15 Head depth	19,33	17,21	20,16	18,81	1,02
16 Snout length	69,67	59,38	70,55	66,67	4,29
17 Interorbital width	29,23	27,34	30,29	28,45	1,03
18 Orbital diameter	13,63	13,63	16,52	15,37	0,94
19 Longest interopercular odontode	40,88	11,72	40,88	21,23	9,81
20 Mandibular ramus length	29,89	23,44	30,77	28,36	2,51
21 IOW/MRL	0,98	1.17	0.93	1.0 1	0.0 8
22 HL/IOW	3,42	3.66	3.30	3.52	0.13
23 IOW/OD	2,15	2.15	1.73	1.86	0.17
24 HL/OD	7,34	7.34	6.0 5	6.53	0.42