Apteronotus baniwa, Santana & Vari, 2013

Santana, Carlos David De & Vari, Richard P., 2013, Brown ghost electric fishes of the Apteronotus leptorhynchus species-group (Ostariophysi, Gymnotiformes); monophyly, major clades, and revision, Zoological Journal of the Linnean Society 168 (3), pp. 564-596 : 575-576

APTERONOTUS BANIWA SP. NOV.

( FIGS 5 , 7 , 8 ; TABLE 1)

Diagnosis: Apteronotus baniwa is distinguished from A. anu by the condition of the fifth infraorbital (present as a tubular laterosensory canal segment versus absent), the number of caudal-fin rays (14–17 versus 10–13), the condition of the lateral ethmoid (ossified versus cartilaginous), and the number of precaudal vertebrae (16–17 versus 18–19). Apteronotus baniwa is differentiated from A. ferrarisi by the number of scales above the lateral line at the midbody (seven to eight versus 10–13), the number of scales along the lateral line (61–70 versus 73–80), the mouth length (36.6–47.2% of HL versus 49.4–56.4%), the tail length (13.3–24.2% of LEA versus 6.9–9.9%) and the tail depth (8.2–15.3% of CL versus 22.2– 28.7%). Apteronotus baniwa differs from A. galvisi in the number of scales above the lateral line at the midbody (seven to eight versus 11–12). Apteronotus baniwa is distinguished from A. leptorhynchus by the number of scales above the lateral line at the midbody (seven to eight versus 12–13), the number of scales along the lateral line (61–70 versus 78–82), the number of pectoral-fin rays (14–16 versus 17–18), the number of precaudal vertebrae (16–17 versus 18), and the number of total vertebrae (68–77 versus 78–81). Apteronotus baniwa is differentiated from A. macrostomus by the number of scales above the lateral line at the midbody (seven to eight versus 11–14), the number of caudal-fin rays (14–17 versus 18–21), and the number of precaudal vertebrae (16–17 versus 18). Apteronotus baniwa differs from A. pemon in the number of scales above the lateral line at the midbody (seven to eight versus nine to ten), the number of scales along the lateral line (61–70 versus 74–83), the number of caudal-fin rays (14–17 versus 18–20), and the number of precaudal vertebrae (16–17 versus 18–19). Apteronotus baniwa is distinguished from A. rostratus by the condition of the fifth infraorbital (absent versus present as a tubular laterosensory canal segment), the condition of the lateral ethmoid (ossified versus cartilaginous), the number of precaudal vertebrae (16–17 versus 18–19) and the tail length (13.3–24.3% of LEA versus 10.6–12.4%). Apteronotus baniwa is differentiated from A. spurrellii by the condition of the fifth infraorbital (absent versus present as a tubular laterosensory canal segment), the condition of the lateral ethmoid (ossified versus cartilaginous), and the number of scales along the lateral line (61–70 versus 73–76).

Description: Head, body, and fin shape and pigmentation illustrated in Figures 7 and 8 . Morphometrics for holotype and paratypes presented in Table 1. Body laterally compressed, greatest body depth located at, or slightly posterior to, abdominal cavity. Dorsal profile of body nearly straight. First perforated scale of lateral line located above pectoral-fin origin. Lateral line extending posteriorly to base of caudal fin. Scales along lateral line 61(1), 63(1), 66(1), 67(1), 70*(1). Scales above lateral line to mid-dorsal line at midbody 7(1), 8*(5).

Head laterally compressed, widest at opercular region and deepest at nape. Dorsal profile of head overall slightly convex. Dorsal margin of snout straight in single examined mature male but slightly convex in mature female and immatures. Eye small, located laterally on head and completely covered by thin membrane. Anterior naris located at end of small tube and close to tip of snout. Posterior naris ellipsoidal, without tube and positioned closer to tip of snout than to anterior margin of eye. Mouth terminal with rictus extending posterior of vertical through anterior margin of eye. Branchial opening located anterior to vertical through pectoral-fin insertion. Anus and urogenital papillae located posterior to vertical through eye and without ontogenetic variation in position.

Pectoral fin elongate, with 14*(4) or 16(2) rays. Anal-fin origin located anterior to vertical through posterior margin of opercle. Unbranched anal-fin rays 16(1), 20*(1), 22(2) or 31(1); total anal-fin rays 136(1), 142(1), 143(1), 144(1), 151*(1) or 159(1). Tail compressed and short; ending in small, elongate, caudal fin. Caudal-fin rays 14(1), 15*(2), 16(1) or 17(1).

Origin of dorsal sagittal electroreceptive filament located on posterior half of body. Filament inserted into narrow mid-dorsal groove and extending 6(2), 9*(3) scales posterior of vertical through posterior terminus of anal fin. Precaudal vertebrae 16*(2) or 17(4). Total vertebrae 68(2), 72(1), 73(1) or 77*(2).

Secondary sexual dimorphism: The single examined sexually mature male (N = 1, 155 mm TL) of A. baniwa differs from mature females (N = 4, 94– 111 mm TL) in diverse aspects of head morphology. The dorsal margin of snout is nearly straight in the male ( Fig. 7 ) versus slightly convex in mature females ( Fig. 8 ) and immature specimens. The snout length, the distance from the posterior naris to the eye, the internarial distance, and the length of the mouth are proportionally greater in the male than in the females and immatures ( Table 1). The proportional interorbital distance is smaller in the male than in females and immatures, with this reflecting the more elongate head in the male ( Table 1).

Coloration in alcohol: Body and head dark brown. Narrow, pale, longitudinal band extending from chin along mid-dorsal surface of head and body to, or slightly posterior of, vertical through tip of pectoral fin. Pectoral- and anal-fins rays dark brown with inter-radial membranes translucent. Pale band encircling base of caudal fin. Caudal fin pale at base and dark brown posteriorly.

Distribution: Apteronotus baniwa is known from the Ríos Orinoco and Ventuari in the southern portions of the Río Orinoco basin, Venezuela ( Fig. 5 ).

Etymology: The species name, baniwa , is based on the name of the indigenous people whose home territory is in the vicinity of the type-locality for the species.

Material examined: Holotype: Venezuela. Amazonas. AUM 43275, male, 155 mm; Río Orinoco, 147 km east-south-east of San Fernando de Atabapo , 03°18′23′′N, 66°36′12′′W, N. Lujan et al., 4.iii.2005 . Paratypes: Venezuela. Amazonas. AUM 44075, 1 (immature), 71.1 mm; USNM 406841 , 1 (female), 111 mm; Río Ventuari, near ornamental fish market, 04°45′23′′N, 66°53′34′′W, N. Lujan et al., 3.iv.2005. MCNG 52994 , 3 (females), 94–101 mm; AUM 43276, 2 , 82–103 ; same data as holotype. Nontype: Ven- ezuela. Amazonas. FMNH 102100 , 8 , 48–131 mm; rocks and rapids in Río Orinoco at Isla Cupaven , approximately 03°05′N, 67°40′W .

Figures

Figure 5. Map of north portion of South America showing geographical distribution of Apteronotus anu (1 = holotype locality); Apteronotus baniwa (2 = holotype locality); Apteronotus ferrarisi (3 = holotype locality); Apteronotus galvisi (4 = holotype locality), and Apteronotus leptorhynchus (5 = holotype locality). Some symbols represent more than one locality and/or lot of specimens.

Figure 7. Apteronotus baniwa, 155 mm total length, male, holotype, AUM 43275; Venezuela, Amazonas, Río Orinoco, 147 km east-south-east of San Fernando de Atabapo, 03°18′23′′N, 66°36′12′′W.

Figure 8. Apteronotus baniwa, 101 mm total length, female, paratype, MGNC 52994; Venezuela, Amazonas, Río Orinoco, 147 km east-south-east of San Fernando de Atabapo, 03°18′23′′N, 66°36′12′′W.