Lasiancistrus heteracanthus (Günther, 1869)

Armbruster, Jonathan W., 2005, The loricariid catfish genus Lasiancistrus (Siluriformes) with descriptions of two new species, Neotropical Ichthyology 3 (4), pp. 549-569 : 558-559

Lasiancistrus heteracanthus (Günther, 1869) Fig. 6

Chaetostomus heteracanthus Günther, 1869:425 . UpperAmazon, Peru.

Material Examined: Ecuador, Napo: FMNH 111719 , 1, 108.3 mm SL, río San Miguel- río Putumayo- río Amazonas drainage, río San Miguel , río Conejo at bridge on road from Lago

Agris to Lumbaqui, near Santa Cecilia , 0°3’30"N, 77°2’0"W, 17 Sep 1983 . Peru, no department given: BMNH 1869.5 .21.3, 1, 149.2 mm SL, holotype, upper Amazon, Bartlett. Loreto: SIUC 27970 , 1 , 66.2 mm SL, río Amazonas drainage, río Napo at Mazan , 3°47.48’S, 73°14.90’ W, 19 Jul 1995 .

Diagnosis. Lasiancistrus heteracanthus can be separated from L. caucanus , L. saetiger , and L. tentaculatus by having abdominal plates (vs. abdominal plates absent), from L. schomburgkii and L. saetiger by having dark spots in the dorsal and caudal fins (vs. white spots or all dark), and from L. guacharote by not having the abdominal plates restricted to a region near the insertion of the pectoral-fin spine.

Description. See genus description for more information. Morphometrics in Table 2. Largest specimen 149.2 mm SL. Abdomen with small platelets anteriorly. 23-25 (mode = 24) plates in median series. 10-19 whiskerlike odontodes in evertible cheek mass (N = 3); 24-32 (N = 3) total hypertrophied odontodes in cheek mass.

Color. Large, light spots barely visible on brown head, becoming mottling on dorsal and lateral surfaces of body. Distinct, midlateral stripe in larger specimen with more diffuse stripe located down middle of dorsal plates, both stripes beginning at vertical through dorsal-fin spine. Small spots present along dorsal spine and rays, spots not extending onto membrane. Medium spots on paired-fin rays and spines combining to form bands, but spots lighter on membranes. Lower lobe of caudal darker than upper lobe. Large spots on lower lobe of caudal combining to form bands that angle anteroventrally in upper half of lower lobe and posteroventrally in lower half. Small spots only on rays of upper caudal lobe, spots not connected to form bands, but if bands were formed, they would be angled posteroventrally. Abdomen slightly lighter tan than sides. Color of larger recently collected specimen (FMNH 111719) more intense than that of smaller specimen (SIUC 27970) collected from muddy waters of lower río Napo (pers. obs.). Color of holotype gone except for some faint, dark spots in dorsal and caudal fins.

Sexual dimorphism. No sexual dimorphism observed; specimens might not be mature. The holotype appears to be developing whiskerlike odontodes on the snout.

Range. The type locality of Lasiancistrus heteracanthus is stated as the upper Amazon of Peru. Only two specimens are available with good localities ( FMNH 111719 and SIUC 27970 ) from the upper río Napo of Ecuador and the lower río Napo of Peru ( Fig. 3 ) .

Comments: Lasiancistrus heteracanthus appears to be very rare, and only three specimens were examined. The type of L. heteracanthus has the color almost absent; however, some faint, dark spots are visible on the dorsal and caudal fins. The only specimens examined from theAmazon drainage that have dark spots are FMNH 111719 and SIUC 27970, and these two specimens were used for the color description.

Figures

Fig. 6. Dorsal, lateral, and ventral views of Lasiancistrus heteracanthus, FMNH 111719, 108.3 mm SL.

Fig. 3. Range of species of Lasiancistrus. Open symbols are type localities except for in L. heteracanthus where the type locality is not specific. Triangles = L. schomburgkii, squares = L. caucanus, upside down triangles = L. guacharote, diamonds = L. heteracanthus, cross = L. saetiger, and circles = L. tentaculatus. The following are type localities for species in synonymy that have good locality information: 1. L. castelnaui (locality approximate), 2. L. guapore, 3. L. maracaiboensis, 4. L. mayoloi, 5. L. planiceps, 6. L. scolymus, 7. L. volcanensis.