Comprehensive DescriptionRead full entry
Figs. 1-2, Table 1
Holotype : MBUCV-V- 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 : MBUCV-V- 21801, 1 ex., 121.2 mm SL; collected with the holotype . MBUCV-V- 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; 01 March 1981 . MBUCV-V- 16382, 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 . MBUCV-V- 21806, 1 ex., 31.1 mm SL; Cagua River, Boca de Cagua, approximately 10 km E of Village Guayas, approx. 10°14'N67°07'W ; R. Royero, F. Gil and C. Navarrese, 06 April 1991 . MBUCV-V- 27872, 1 ex, 76.4 mm SL; Mesia River, tributary of the Guare River, Pozo El Cirilo, near Village El Salado, approx. 10°13'N67°03'W ; N. Padilla and E. Camejo; 29 May 1994 . Aragua State : MBUCV-V- 22700, 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 ZBK 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. Post-anal plates 10 to 11. Inter-dorsal 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 one-third 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 I14I, 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), pectoral-fin and pelvic-fin 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. Caudal-fin 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 ZBK 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 ZBK 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 ZBK is found in rivers of the eastern slope, north of the Sierra of Perijá and C. nephelion ZBK 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.
Comparisons. The external morphology of C. nephelion ZBK most closely resembles C. perijae ZBK . Both species possess a robust body and both reach a similar maximum size that is larger than the maximum size of other Cordylancistrus ZBK species. The remaining species possesses a more depressed body. Cordylancistrus nephelion ZBK separates easily from C. platycephalus by the absence of keels on lateral plates of the body. Cordylancistrus nephelion ZBK can be distinguished from C. platyrhynchus in the number of odontodes in the interopercular area (six or more large odontodes vs. two or three smaller ones). Cordylancistrus nephelion ZBK differs from C. torbesensis and C. perijae ZBK because the latter two species have the edge of the posterior lip without undulations and the edge of the posterior lip of C. nephelion ZBK has undulations. Finally, in C. nephelion ZBK the exposed area of the opercle is small, while in C. daguae the exposed area of the opercle is of greater size, very evident and extended posteriorly. Table 3 shows the morphometric data of the species currently assigned to Cordylancistrus ZBK . The morphometric data that distinguish C. nephelion ZBK from the other species are postdorsal distance, postanal length, cleithral width, length of dorsal-fin base and caudal peduncle depth.
Observations. Collections in the Tuy River basin (Eigenmann, 1920; Schultz, 1944; FernándezYépez , 1945) have produced a list of fish species inhabiting this basin and the description of three new species of loricariid catfishes, Ancistrus brevifilis ZBK and Chaetostoma pearsei Eigenmann 1920 and Chaetostoma dupouii Fernandez-Yepez 1945 ZBK . Additionally, Chaetostoma guairense Steindachner, 1881 was described from the basin. Other loricariid catfishes that apparently came from the Tuy River basin are: Farlowella acus (Kner, 1853) ZBK , Lasiancistrus mystacinus (Kner, 1854) , Rineloricaria caracasensis (Bleeker, 1862) , and Squaliforma villarsi ( Luetken , 1874) . Mago-Leccia (1968) presented an inventory of the fishes from the Guaire River and the Tuy River basin and included the following additional species: Loricaria ZBK sp., Hypostomus plecostomus and Hypostomus emarginatus ZBK (probably Squaliforma emarginata ). The discovery of a species new to science in the Tuy River basin, despite the prior inventories and the basin’s relatively small size, suggests the following non-exclusive possibilities: 1) The population density of C. nephelion ZBK has been continuously low and is not a recent result or sampling artifact; 2) The species inhabits restricted areas of the basin where peculiar environmental conditions are found. At the moment, C. nephelion ZBK and other fish species of this basin are obliged to live in the few remaining small rivers that have not been contaminated with pollution or rendered impassable by dams. The Tuy River basin is extremely altered, and the Tuy River proper and almost all of its tributaries (Guaire, Caucagua Rivers and others) are highly contaminated by the urban and industrial waste of human conglomerates and industries. Other tributaries, including the Lagartijo, Taguaza and Taguazita Rivers have been dammed for water supply. Because of this environmental degradation, there are very few areas where the autochthonous fish fauna can take refuge and survive. If government institutions fail to establish recovery or protection plans, the extinction of this new species and others that are endemic to the basin will be a very distinct possibility. The extinction of these species would imply not only the loss of the biological information that it represents, but also the loss of information on the evolutionary history of the Tuy River and of the La Costa mountain range. Such a loss would reduce the biodiversity of northern Venezuela significantly.