Helogenes gouldingi Vari & Ortega 1986

Dorsal soft rays (total): 5; Analsoft rays: 39 - 43

Collected from a small black-water tributary.

fisheries: of no interest

Helogenes gouldingi

DIAGNOSIS.—The possession of 15 principal caudal-fin rays, with eight principal rays in the lower lobe of the fin, distinguishes Helogenes gouldingi from both H. uruyensis and H. marmoratus, which have 16 principal caudal-fin rays, with nine principal rays in the lower lobe of the fin. The 39 to 43 anal-fin rays of Helogenes gouldingi further separate it from H. uruyensis, which has 32 to 37 rays. Helogenes gouldingi and H. castaneus are separable in the number of anal-fin rays (39 to 43 versus 43 to 49), relative snout lengths, and relative distance between the rayed and adipose dorsal fins. Differences in the relative distances from the snout to the origin of the pelvic fin, and snout to the origin of the anal fin, and relative lengths of the base of the anal fin, and medial mandibular barbel further distinguish H. gouldingi from H. uruyensis (see “Key,” Figure 2, and Table 2).

DESCRIPTION.—Morphometrics of the holotype and paratypes are given in Table 2.

Dorsal profile of body smooth, slightly convex from snout to dorsal margin of caudal peduncle. Ventral profile of body gently curved from lower jaw to pelvic-fin origin. Base of anal fin slightly convex anteriorly, straight posteriorly. Pectoral fin with seven rays, reaching posteriorly to vertical through insertion of fourth to sixth anal-fin ray. Anal-fin margin straight anteriorly, rounded posteriorly. Anal-fin rays 39 to 43 [43]. Caudal fin with 15 principal rays; eight principal rays in lower lobe. Dorsal fin small, with five rays. Small adipose fin present in all examined specimens.

Two rows of teeth on premaxilla, inner series smaller, less evident. Lower jaw with a band of cardiform teeth, outer row distinctly larger.

Anterior and posterior nares well separated, anterior nares slightly tubular. Maxillary barbel extending posteriorly to beyond end of pectoral fin. Medial mandibular barbel extending to or slightly beyond middle of pectoral fin. Lateral mandibular barbel distinctly shorter than medial.

Five vertebrae in anterior vertebral complex; free vertebrae posterior to complex 38 (6) [38].

COLORATION.—Overall coloration dark brown, mottled; head distinctly darker dorsally. Dark body pigmentation extending onto basal one-third of caudal fin, posterior margin of pigmentation band very distinct, with a straight or slightly wavy border. Rayed dorsal fin mottled, darker at base. Caudal fin dark basally, mottled over posterior two-thirds. Anal fin dark brown at base, mottled distally, more so along posterior portion. Pectoral and pelvic fins ranging from mottled, particularly basally, to dark brown.

DISTRIBUTION.—Known only from the type-locality (Figure 4).

ECOLOGY.—The type series was collected in a small blackwater tributary of the Rio Madeira.

ETYMOLOGY.—Named for Michael Goulding, the collector of the type series, in recognition of his contributions to increasing our knowledge of the Amazonian fish fauna.

MATERIAL EXAMINED.—8 specimens (7, 27.0–46.5).

Holotype: BRAZIL. Amazonas: Igarapé 15 km from Humaitá along the Rio Madeira, (7° 31′S, 63° 02′W), collected by Michael Goulding, 7 Aug 1984, MZUSP 28854, 1 (46.5).

Paratypes: 7 specimens, taken with holotype: MZUSP 28855, 3 (27.0–37.4); USNM 269446, 4 (25.8–46.0; one specimen cleared and counterstained for cartilage and bone).

Helogenes gouldingi is a species of whale catfish endemic to Brazil where it is found in black-water tributaries of the Madeira River basin. This species grows to a length of 4.7 cm (1.9 inches).