Apteronotus pemon, 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 : 586-592

APTERONOTUS PEMON SP. NOV.

( FIGS 16–18 ; TABLE 3)

Diagnosis: Apteronotus pemon is distinguished from A. anu by the condition of the fifth infraorbital (present as a tubular laterosensory canal segment versus absent), the interorbital distance (9.7–14.6% of HL versus 14.7–36.5%), the number of caudal-fin rays (18–20 versus 10–13), the number of scales along the lateral line (74–83 versus 59–63), and the condition of the lateral ethmoid (ossified versus cartilaginous). Apteronotus pemon differs from A. baniwa in the number of scales above the lateral line at the midbody N, number of specimens; H, holotype. Range includes holotypes if examined.

Sexually dimorphic features for A. pemon are presented as two entries. First entry is for sexually dimorphic males with information for females and immatures in second entry. Holotypes for A. rostratus or A. spurrellii are not available for examination.

(nine to ten versus seven to eight), the number of scales along the lateral line (74–83 versus 61–70), and the number of precaudal vertebrae (18–19 versus 16–17). Apteronotus pemon is differentiated from A. ferrarisi by the mouth length (30–44.5% of HL versus 49.4–56.3%), the tail length (13.0–17.5% of LEA versus 6.9–9.9%), the tail depth (9.9–15.4% of CL versus 22.2–28.7%), the number of scales above the lateral line at the midbody (nine to ten versus 10–13), and the number of caudal-fin rays (18–20 versus 15–17). Apteronotus pemon is distinguished from A. galvisi by the ocular diameter (4.0–6.3% of HL versus 6.4–11.3%), the number of scales above the lateral line at the midbody (nine to ten versus 11–12), and the number of caudal-fin rays (18–20 versus 10–16). Apteronotus pemon differs from A. leptorhynchus in the number of scales above the lateral line at the midbody (nine to ten versus 12–13) and the number of pectoral-fin rays (16 versus 17–18). Apteronotus pemon is differentiated from A. macrostomus by the number of scales above the lateral line at the midbody (nine to ten versus 11–14). Apteronotus pemon is distinguished from A. rostratus by the condition of the fifth infraorbital (present as a tubular laterosensory canal segment versus absent), the number of scales along the lateral line (74–83 versus 63–67), the number of caudal-fin rays (18–20 versus 14–16), and the condition of the lateral ethmoid (ossified versus cartilaginous). Apteronotus pemon can be differentiated from A. spurrellii by the condition of the fifth infraorbital (present as a tubular laterosensory canal segment versus absent), the number of pectoral-fin rays (16 versus 12–13), the number of anal-fin rays (152–160 versus 171–173), the number of caudal-fin rays (18–20 versus 14), and the condition of the lateral ethmoid (ossified versus cartilaginous).

Description: Head, body, and fin shape and pigmentation illustrated in Figures 17 and 18 . Morphometrics for holotype and paratypes presented in Table 3. 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 74*(1), 79(1), 82(1), or 83(1). Scales above lateral line to mid-dorsal line at midbody 9(2) or 10*(2).

Head laterally compressed, widest at opercular region and deepest at nape. Dorsal profile of head slightly convex. Snout longer in sexually mature male than 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 reaching vertical through anterior border of eye in small individuals and extending posterior of that vertical in adults. Branchial opening located anterior to vertical through pectoral-fin insertion. Anus and urogenital papillae located posterior to vertical through eye without ontogenetic variation in position.

Pectoral fin elongate, with 16*(3) rays. Anal-fin origin located anterior to vertical through posterior margin of opercle. Unbranched anal-fin rays 22*(1), 24(1), or 32(1); total anal-fin rays 152(1), 157(1), 160(1), or 162*(1). Tail compressed and short; ending in small, elongate caudal fin. Caudal-fin rays 18(1), 19(1), or 20*(2).

Origin of dorsal sagittal electroreceptive filament located on posterior half of body. Filament inserted into narrow mid-dorsal groove extending 4*(3) or 9(1) scales beyond vertical through posterior terminus of anal-fin base. Precaudal vertebrae 18*(2) or 19(2). Total vertebrae 63(1), 67*(1), 73(1), or 82(1).

Secondary sexual dimorphism: The single examined sexually mature male (206 mm TL; Fig. 17 ) and female of A. pemon (165 mm TL; Fig. 18 ) differ in several aspects of head morphology, with the distance from the posterior naris to the eye and mouth greater in the male than in the female and immatures ( Table 3). In addition, the interorbital distance is narrower in the male than in the female and immatures ( Table 3).

Coloration in alcohol: Body and head brown. Prominent, broad, lightly coloured longitudinal band extending from chin along dorsal midline of head and body to beginning of dorsal filament. Pectoral- and anal-fin rays dark brown with inter-radial membranes translucent. Light band encircling base of caudal fin. Caudal fin pale at base, dark brown posteriorly.

Distribution: Apteronotus pemon is only known from the type locality at the Techiné-meru waterfall along a tributary of the upper Río Caroni basin, Venezuela ( Fig. 16 ).

Etymology: The species name, pemon , is in reference to the Pemon indigenous group whose traditional lands included much of the Río Caroni basin, which includes the type locality of the species.

Remarks: The report of A. leptorhynchus from the Río Claro, a left bank tributary of the lower Río Caroni, by Taphorn & García Tenía (1991: 35) may be based on samples of A. pemon , which is the only member of the species-group known from that river system. The same may be the case with the report of A. leptorhynchus from the Gran Sabana region of the upper Rio Caroni basin by Lasso et al. (1989: 116).

Material examined: Holotype: Venezuela. Bolivar. FMNH 70012 , male, 206 mm; Techiné-meru waterfall, along tributary of Río Caroni , approximately 05°01′N, 62°17′60′′W, J. Steyermark, 16.iii.1955 . Paratypes: Venezuela. Bolivar. FMNH 121159 , 4 (one female, two immature), 1 c&s, 121–165 mm; same locality as holotype .

APTERONOTUS ROSTRATUS (MEEK & HILDEBRAND)

( FIGS 16 , 19 ; TABLE 3)

Sternarchus rostratus Meek & Hildebrand, 1913: 85 [original description; type-locality: Rio Grande near Cana, Panama]. – Eigenmann & Fisher, 1914: 236 [ Colombia, Girardot, Apulo, Cartago, Río Cauca at Cali]. – Meek & Hildebrand, 1916: pl. 27 [based on Meek & Hildebrand, 1913; first illustration of species; Rio Grande near Cana, Panama; Río Cauca at Cali, Colombia]. – Eigenmann, 1922: 176, pl. 35, figs 3–5 [ Colombia, Río Magdalena; Panama, Río Tuyra]. – Hildebrand, 1938: 292 [ Colombia, Río Magdalena; Panama, Río Tuyra]. – Dahl, 1971: 99, unnumbered fig. [ Colombia, Río Cauca, Río Magdalena and Río Sinú; maximum size and habitat].

Apteronotus rostratus, Miles, 1947: 185 [comb. nov.; Colombia, Río Magdalena and upper Río Cauca; Panama, Río Tuyra]. – Mago-Leccia, 1994: 29, fig. 30 [in listing of species]. – Roman-Valencia, 1995: 4 [ Colombia, Alto Cauca, Río La Vieja]. – Mojica-C, 1999: 563 [ Colombia]. – Cardona, Roman-Valencia, Jimenez & Hurtado T., 1998: 17 [ Colombia, upper Río Cauca]. – Albert, 2003: 499 [in listing of species; Río Grande basin, Panama]. – Maldonado-Ocampo et al., 2008: 213 [ Colombia, Pacific and Caribbean drainages]. – de Santana & Cox-Fernandes, 2012: 284 [Río Magdalena basin; occurrence in streams].

Diagnosis: Apteronotus rostratus is distinguished from A. anu by the tail length (10.6–12.4% of LEA versus 17.1–37.5%) and the number of caudal-fin rays (14–16 versus 10–13). Apteronotus rostratus is differentiated from A. baniwa by the condition of the fifth infraorbital (absent versus present as a tubular laterosensory canal segment), the condition of the lateral ethmoid (cartilaginous versus ossified), the number of precaudal vertebrae (18–19 versus 16–17), and the tail length (10.6–12.4% of LEA versus 13.0–24.3%). Apteronotus rostratus differs from A. ferrarisi in the condition of the fifth infraorbital (absent versus present as a tubular laterosensory canal segment), the condition of the lateral ethmoid (cartilaginous versus ossified), the tail length (10.6–12.4% of LEA versus 6.9-9.9%), and the number of scales along the lateral line (63–67 versus 73–80). Apteronotus rostratus is distinguished from A. galvisi by the condition of the fifth infraorbital (absent versus present as a tubular laterosensory canal segment), the condition of the lateral ethmoid (cartilaginous versus ossified), and the number of scales above the lateral line at the midbody (nine to ten versus 11–12). Apteronotus rostratus is differentiated from A. leptorhynchus by the condition of the fifth infraorbital (absent versus present as a tubular laterosensory canal segment), the condition of the lateral ethmoid (cartilaginous versus ossified), the number of scales above the lateral line at the midbody (nine to ten versus 12–13), the number of caudal-fin rays (14–16 versus 17–21), the number of scales along the lateral line (63–67 versus 78–82), and the tail length (10.6– 12.4% of LEA versus 17.1–18.6%). Apteronotus rostratus differs from A. macrostomus in the condition of the fifth infraorbital (absent versus present as a tubular laterosensory canal segment), the condition of the lateral ethmoid (cartilaginous versus ossified), the number of scales above the lateral line at the midbody (nine to ten versus 11–14), the number of anal-fin rays (153–162 versus 140–152), the number of caudal-fin rays (14–16 versus 18–21), and the tail length (10.6– 12.4% of LEA versus 13.9–20.6%). Apteronotus rostratus is distinguished from A. pemon by the condition of the fifth infraorbital (absent versus present as a tubular laterosensory canal segment), the number of scales along the lateral line (63–67 versus 74–83), the number of caudal-fin rays (14–16 versus 18–20), and the condition of the lateral ethmoid (cartilaginous versus ossified). Apteronotus rostratus is differentiated from A. spurrellii by the number of pectoral-fin rays (15–17 versus 12–13), the number of total anal-fin rays (153–162 versus 171–173), the number of scales along the lateral line (63–67 versus 73–76), and the tail length (10.6–12.4% of LEA versus 12.5–13.7%).

Description: Head, body, and fin shape and pigmentation illustrated in Figure 19 . Morphometrics for holotype and paratypes presented in Table 3. 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 63(1), 64(2), 66(2), or 67(3). Scales above lateral line to mid-dorsal line at midbody 9(6) or 10(6).

Head laterally compressed, widest at opercular region and deepest at nape. Dorsal profile of head nearly straight. 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 located posterior of vertical through anterior border of eye. Branchial opening located slightly 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 15(10) or 17(2) rays. Anal-fin origin located at, or slightly anterior to, vertical through posterior margin of opercle. Unbranched anal-fin rays 14(3), 18(5), 23(2), or 27(2); total anal-fin rays153(2), 154(2), 156(1), 157(1), 160(1), or 162(1). Tail compressed and short; ending in small, elongate caudal fin. Caudal-fin rays14(3), 15(1), or 16(1).

Origin of dorsal sagittal electroreceptive filament located on posterior half of body. Filament inserted into narrow mid-dorsal groove extending 2(2), 3(1), 8(2), or 11(4) scales beyond vertical through posterior terminus of anal fin. Precaudal vertebrae 18(3) or 19(3). Total vertebrae 72(1), 74(2), 75(1), or 77(1).

Coloration in alcohol: Body and head grey to dark brown. Prominent, broad, lightly coloured longitudinal band extending from chin along dorsal midline of head and body to over dorsal filament. Pectoral- and anal-fin rays dark brown with inter-radial membranes translucent. Lightly coloured band encircling base of caudal fin. Caudal fin pale basally, grey to dark brown in central portion and translucent posteriorly.

Distribution: Apteronotus rostratus is known from the Ríos Magdalena and Cauca, Colombia, and several rivers of the Pacific versant of Panama ( Fig. 16 ).

Common name: Cardona et al. (1998: 17) reported that A. rostratus has a common name of ‘Boca da perra’ in the upper Río Cauca, Colombia.

Remarks: Apteronotus anu and A. rostratus are morphologically the most similar members of the A. rostratus- clade but can be differentiated on the basis of various features (see Remarks for A. anu ).

Geographical variation: Apteronotus rostratus demonstrates considerable variation in some features across its geographical range; most notably differences in the posterior extent of the dorsal sagittal electroreceptive filament. Whereas the filament extends only two scales beyond the vertical through the posterior terminus of the anal fin in some examined specimens from the Río Pirre, Panama, in the northern portion of the species range, it continues up to 11 scales beyond that point in a specimen that originated in the Río Cauca in the southern portion of the range. Continuity between these extremes occurs in intervening populations. Such variation is expected given the highly dissected geographical isolation of the river basins and parallels variation previously reported in other groups of fishes from the region ( Bermingham & Martin, 1998). The report by Cala (1986) of A. rostratus from the Río Meta basin is erroneous under available information as to the distribution of the species and most likely is based on congeners inhabiting that river basin.

Material examined: Colombia. Choco. USNM 317229 , 3 , 109–157 ; Rio Salado near Teresita (approximately 7°06′N, 77°23′W). USNM 324044 , 1 , 112 ; Río Pavarando , tributary of Rio Salaqui. USNM 317230 , 1 , 183 ; creek of Río Parado , approximately 10 min by helicopter from village of Parado . Panamá. Chepo. AUM 31623, 1 , Bahia de Panamá, Pan American Highway, 17.7 km north-east of Chepo. FMNH 7592 , 1 , 94 , holotype (specimen in poor condition and morphometrics not included in Table 3); Rio Grande near Cana , Panama. MBUCV-V 10926 , 4 (2 c&s), 115–162; Río Pirre, tributary of Río Tuyra. Colon. USNM 324045 , 2 , 108–132 , Río Membrillo , 08°41′N, 77°41′W .

APTERONOTUS SPURRELLII (REGAN)

( FIGS 16 , 20 ; TABLE 3)

Sternarchus spurrellii Regan, 1914: 32 [original description; type locality: Río Condoto, Colombia].

Sternarchus leptorhynchus , (not of Eigenmann, 1912), Eigenmann & Fisher, 1914: 236 [ Colombia, Pacific Slope, Calima, Río Dagua at Cordova]. – Eigenmann, 1922: 177, pl. XXXV, fig. 1 [illustration].

Apteronotus spurrellii, Albert, 2003: 499 [comb. nov.; in listing of species; Colombia, Río San Juan basin]. – de Santana & Crampton, 2006: 116 [Río Condoto, Colombia]. – Maldonado-Ocampo et al., 2008: 213 [ Colombia, Pacific drainages]. – de Santana & Cox-Fernandes, 2012: 284 [Río San Juan basin; occurrence in streams].

Diagnosis: Apteronotus spurrellii is distinguished from A. anu by the number of pectoral-fin rays (12–13 versus 14–16), the number of caudal-fin rays (14 versus 10–13), the number of scales along the lateral line (73–76 versus 59–63), the extent of the middorsal groove (extending four scales beyond the vertical through the posterior terminus of the anal fin versus seven to eight scales) and the tail length (12.5–13.7% of LEA versus 17.1–37.5%). Apteronotus spurrellii differs from A. baniwa in the condition of the fifth infraorbital (absent versus present as a tubular laterosensory canal segment), the condition of the lateral ethmoid (cartilaginous versus ossified), the number of scales along the lateral line (73–76 versus 61–70), and the number of pectoral-fin rays (12–13 versus 14–16). Apteronotus spurrellii is differentiated from A. ferrarisi by the condition of the fifth infraorbital (absent versus present as a tubular laterosensory canal segment), the condition of the lateral ethmoid (cartilaginous versus ossified), the mouth length (42.9–48.4% of HL versus 49.4–56.3%), the tail length (12.5–13.7% of LEA versus 6.9-9.9%), the number of scales above the lateral line at the midbody (eight to nine versus 10–13), the number of anal-fin rays (171–173 versus 150–167), and the number of caudal-fin rays (14 versus 15–17). Apteronotus spurrellii is distinguished from A. galvisi by the ocular diameter (3.7-5.8% of HL versus 6.4–11.3%), the condition of the fifth infraorbital (absent versus present as a tubular laterosensory canal segment), the number of scales above the lateral line at the midbody (eight to nine versus 11–12), the number of anal-fin rays (171–173 versus 145–165), and the condition of the lateral ethmoid (cartilaginous versus ossified). Apteronotus spurrellii differs from A. leptorhynchus in the condition of the fifth infraorbital (absent versus present as a tubular laterosensory canal segment), the condition of the lateral ethmoid (cartilaginous versus ossified), the number of pectoral-fin rays (12–13 versus 17–18), the number of anal-fin rays (171–173 versus 151–156), the number of scales along the lateral line (73–76 versus 78–82), and the extent of the mid-dorsal groove (extending four scales beyond the vertical through the posterior terminus of the anal fin versus eight scales). Apteronotus spurrellii is differentiated from A. macrostomus by the condition of the fifth infraorbital (absent versus present as a tubular laterosensory canal segment), the condition of the lateral ethmoid (cartilaginous versus ossified), the number of pectoral-fin rays (12–13 versus 15–17), the number of scales above the lateral line at the midbody (eight to nine versus 11–14), the number of anal-fin rays (171–173 versus 140–152), and the number of caudal-fin rays (14 versus 18–21). Apteronotus spurrellii is distinguished from A. pemon by the condition of the fifth infraorbital (absent versus present as a tubular laterosensory canal segment), the number of pectoral-fin rays (12–13 versus 16), the number of anal-fin rays (171–173 versus 152–160), the number of caudal-fin rays (14 versus 18–20), and the condition of the lateral ethmoid (cartilaginous versus ossified). Apteronotus spurrellii differs from A. rostratus in the number of pectoral-fin rays (12–13 versus 15–17), the number of scales along the lateral line (73–76 versus 63–67), the total number of anal-fin rays (171–173 versus 153–162), and the tail length (12.5–13.7% of LEA versus 10.6–12.4%).

Description: Head, body, and fin shape and pigmentation illustrated in Figure 20 . Morphometrics for holotype and paratypes presented in Table 3. 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 73(1) or 76(1). Scales above lateral line to mid-dorsal line at midbody 8(2) or 9(2).

Head laterally compressed, widest at opercular region and deepest at nape. Dorsal profile of head nearly straight. 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 posteriorly beyond vertical through anterior border of eye. Branchial opening located slightly 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 12(3) or 13(1) rays. Analfin origin located at, or slightly anterior to, vertical through posterior margin of opercle. Total anal-fin rays 171(1) or 173(2). Tail compressed and short; ending in small, elongate caudal fin. Caudal-fin rays 14 (1).

Origin of dorsal sagittal electroreceptive filament located on posterior half of body. Filament inserted into narrow mid-dorsal groove extending 4(2) scales beyond vertical through posterior terminus of anal fin. Precaudal vertebrae 17(2) or 18(2). Total vertebrae 74 (1).

Coloration in alcohol: Body dark brown. Prominent, lightly coloured, broad longitudinal band extending from chin along dorsal midline of head and body to beginning of dorsal filament. Pectoral- and anal-fin rays dark brown, with inter-radial membranes translucent. Lightly coloured band encircling base of caudal fin. Caudal fin pale basally and dark brown distally.

Distribution: Apteronotus spurrellii inhabits the Ríos Condoto and Dagua of the Pacific versant of Colombia ( Fig. 16 ).

Material examined: Colombia. Choco. BMNH 1914.5.18:90-3, 4, syntypes, 142–189; Río Condoto. Valle del Cauca. CAS 72124 [IU 13374], 1, 185; Río Dagua, 19.3 km above its mouth at Buenaventura , 36.6 m elevation. FMNH 56773 , 1 , 128 , creek near mouth of Río Calima .

Figures

Figure 16. Map of north portion of South America showing geographical distribution of Apteronotus macrostomus (1 = holotype locality); Apteronotus pemon (2 = holotype locality); Apteronotus rostratus (3 = holotype locality); and Apteronotus spurrellii (4 = type locality). Some symbols represent more than one locality and/or lot of specimens.

Figure 17. Apteronotus pemon, 206 mm total length, male, holotype, FMNH 70012; Venezuela, Bolivar, Techiné-meru waterfall, tributary of Río Caroni, approximately 05°01′N, 62°03′W.

Figure 18. Apteronotus pemon, 165 mm total length, female, FMNH 121159; Venezuela, Bolivar, Techiné-meru, tributary of Río Caroni, approximately 05°01′N, 62°03′W.

Figure 19. Apteronotus rostratus, 132 mm total length, MBUCV V-10926; Panama, Río Pirre, tributary of Río Tuyra.

Figure 20. Apteronotus spurrellii, 189 mm total length, syntype, BMNH 1914.5.18:90-3; Colombia, Choco.