Archolaemus ferreirai, Vari & Santana & Wosiacki, 2012

Vari, Richard P., Santana, Carlos David De & Wosiacki, Wolmar B., 2012, South American electric knifefishes of the genus Archolaemus (Ostariophysi, Gymnotiformes): undetected diversity in a clade of rheophiles, Zoological Journal of the Linnean Society 165 (3), pp. 670-699 : 683-686

ARCHOLAEMUS FERREIRAI SP. NOV.

( FIGS 3 , 4 ; TABLE 1)

Archolaemus blax, Schwassmann & Carvalho, 1985: 233 (only specimens from Brazil, Roraima, Rio Branco, Cachoeira de Bem Querer; not details of species redescription or biological information). Ferreira et al., 1988: 345 ( Brazil, Roraima, Rio Mucajaí, vicinity of Ilha Paredão; carnivorous diet). Ferreira et al., 2007: 184 ( Brazil, Roraima, Rio Branco basin).

Diagnosis: Archolaemus ferreirai is diagnosed from A. blax by the length of the gape (the rictus falling short of the vertical through the posterior naris versus extending beyond that line), the length of the coronomeckelian bone (50% or more the length of Meckel’s cartilage versus less than 20% the length of Meckel’s cartilage) and the length of the posterior ceratohyal (approximately the same length as the ventral hypohyal versus 1.5 times the length of the ventral hypohyal). Archolaemus ferreirai is diagnosed from A. janeae in the number of scales above the lateral line at the midbody (10–14 versus 15–17), by the form of the premaxilla (the anteroposterior length greater than the transverse width versus the anteroposterior length equal to the transverse width), the distribution of the teeth on the dentary (dentition restricted to anterior one-half or slightly more of the dorsal margin versus occupying most of the dorsal margin), the length of the coronomeckelian bone (50% or more the length of Meckel’s cartilage versus less than 20% the length of Meckel’s cartilage), and the length of the posterior ceratohyal (approximately the same length as the ventral hypohyal versus 1.5 times the length of the ventral hypohyal). Archolaemus ferreirai is diagnosed from A. luciae by the length of the gape (the rictus not extending posteriorly beyond the vertical through the posterior naris versus extending beyond that line) and the distribution of the teeth on the internal surface of the endopterygoid (five or six teeth arranged in single row versus between seven and ten irregularly distributed teeth). Archolaemus ferreirai is diagnosed from A. orientalis in the pigmentation pattern (the presence of a narrow dark stripe along the lateral line and a broad band of dusky to dark pigmentation overlying the basal pterygiophores of the anal fin, versus the lack of such dark pigmentation), the total number of pectoral-fin rays (18–21 versus 16), the total number of anal-fin rays (190–222 versus 164–186), the form of the premaxilla (the anteroposterior length greater than the transverse width versus the anteroposterior length equal to the transverse width), and the length of the coronomeckelian bone (50% or more of the length of Meckel’s cartilage versus less than 20% the length of Meckel’s cartilage). Archolaemus ferreirai is diagnosed from A. santosi in the form of the premaxilla (the anteroposterior length greater than the transverse width versus the anteroposterior length equal to the transverse width) and the length of the coronomeckelian bone (50% or more the length of Meckel’s cartilage versus less than 20% the length of Meckel’s cartilage).

Description: Morphometric data for the examined specimens of A. ferreirai are presented in Table 1.

Body elongate and laterally compressed. Greatest body depth located along abdominal cavity. Body profile gently convex from rear of head for approximately anterior one-third of body, and then gradually angled posteroventrally along progressively tapering body and caudal filament. Ventral profile of body slightly convex anteriorly along anterior half of abdominal cavity, and then gradually angled posterodorsally along base of anal fin and caudal filament. Anterior most perforated lateral line scale located at vertical approximately at origin of pectoral fin. Lateral line continuous, extending from immediately after vertical through origin of pectoral fin to end of caudal filament.

Head laterally compressed, widest at opercular region and deepest at nape. Head profile nearly straight dorsally. Ventral profile of head straight and posteroventrally aligned. Snout subconical and anteroventrally directed. Eye small and located laterally on dorsal half of head. Orbital rim covered by membrane and partially free of surface tissues of adjoining region of head in specimens of up to approximately 119 mm TL, but rim totally free and without membranous attachment in larger examined individuals. Anterior naris located at end of short tube and positioned short distance posterior of tip of snout, but distant from anterior margin of eye. Posterior naris elliptical, without tube and located nearer tip of snout than to anterior margin of eye. Mouth distinctly inferior, with upper jaw clearly longer than, and overlapping, lower jaw. Gape relatively short and in adults falling short posteriorly of vertical through posterior margin of posterior naris. Branchial opening moderately elongate; located along posterior margin of opercle and immediately anterior to anterior margin of pectoral-fin origin. Branchial membranes joined at isthmus and extending posteriorly to under pectoral-fin base. Anus proximate to elongate urogenital papilla, and both structures positioned approximately ventral of orbit. Position of anus and urogenital papilla shifting anteriorly ontogenetically from posterior of vertical through posterior margin of orbit to position along, or anterior of, vertical through anterior margin of orbit in larger specimens.

Scales small, cycloid, and present from immediately posterior of head to end of caudal filament. Scales along lateral line 136 to 150 (145) (N = 25). Scales above lateral line at midbody 10 to 14 (12) (N = 50). Scales absent on head.

Pectoral fin long, approximately two-thirds of head length, broad, and distally pointed with lateral rays longer. Pectoral-fin rays between ii, 16 and ii, 19 (18) (N = 50). Anal-fin elongate, extending from vertical through base of pectoral-fin base along most of length of body. Fin margin gently convex anteriorly and then straight, but with rays becoming progressively shorter posteriorly. Anal fin with 24–33 (28) unbranched rays (N = 30) and 190–222 (197) total fin rays (N = 30). Caudal filament of moderate length.

Coloration in alcohol: Overall body coloration ranging from tan to light brown, with lightly coloured specimens demonstrating a less intense version of pigmentation pattern characteristic of darker individuals. Overall brown pigmentation more developed dorsally, with narrow dark stripe extending along lateral line from vertical through tip of pectoral fin, or slightly posterior of that line to end of caudal filament. Band less apparent, but still obvious in very darkly pigmented adult male specimens. Skin overlying basal pterygiophores of anal fin with pterygiophores outlined by very narrow dark bars on body surface. Bars cumulatively form dusky to dark, broad, band running along ventral portion of body, with height of band gradually decreasing posteriorly. Dark pigmentation along centre of band often less intense, with resultant darker dorsal and ventral components to band. Dark stripe along lateral line and ventral band above anal fin separated by more lightly pigmented, broad, midlateral stripe. Lighter midlateral stripe less obvious in some overall more darkly pigmented individuals, and obscured to significant degree by overall dark pigmentation in the single examined large male specimen. Head ranging from tan ventrally and dark dorsally to dark brown over all surfaces, other than for narrow lightly coloured midventral stripe. Lips of darkly pigmented specimens distinctly lighter than proximate areas. Region anteroventral and posteroventral of pectoral-fin base more darkly pigmented than adjoining regions. Pigmentation of pectoral and anal fins ranging from tan in more lightly coloured specimens to quite dusky with dark pigmentation overlying fin rays in more intensely pigmented individuals.

Distribution: Archolaemus ferreirai is known from north-eastern portions of the Amazon basin in the Rio Mucajaí at Cachoeira Paredão 2 and the Rio Uraricoera at Ilha de Maracá, both in Roraima, Brazil ( Fig. 4 ).

Secondary sexual dimorphism: The only examined mature male of Archolaemus ferreirai (INPA 3757) has an overall body coloration ( Fig. 3B ) much darker than in the juveniles and females ( Fig. 3A ) captured at the same time. This darker pigmentation largely obscures the lighter longitudinal band present in mature females and juveniles between the dark stripe along the lateral line and the dark band overlying the basal pterygiophores of the anal fin. The upper lip of this large male is also notable in bearing some teeth, contrary to the absence of such dentition in mature females and juveniles.

Habitat: Ferreira et al. (1988: 342) reported the type region of Archolaemus ferreirai , the Rio Mucajaí at Cachoeira Paredão 2, as characterized by rapidly flowing waters and a 20 m high waterfall. The sample of A. ferreirai (reported as A. blax in that paper) was captured above these falls, in an area with many rapids and no still backwaters.

Etymology: The species name, Archolaemus ferreirai sp. nov., is in honor of Efrem Ferreira of the Instituto Nacional de Pesquisas da Amazônia, one of the collectors of the type series, in recognition of his many contributions to our understanding of the Amazonian fish fauna.

Material examined

Holotype: BRAZIL. Roraima: Rio Mucajaí, Cachoeira Paredão 2 (approximately 02°57′N, 061°27′W), collected by E. G. Ferreira & M. Jégu, 19 February 1987; INPA 3757 (183).

Paratypes: BRAZIL. Roraima: collected with holotype; INPA 36379 , 21 (119–342; 1 CS); MPEG 21683 , 1 (286); MZUSP 110183 , 1 (150); USNM 404354 , 1 (172). Rio Mucajaí, mouth of Igarapé Traira (approximately 02°57′N, 061°27′W), collected by E. G. Ferreira & M. Jégu, 21 February 1987; INPA 6422 , 12 (131–269; 4 CS) .

Non-type specimens: BRAZIL. Roraima: Rio Uraricoera, Ilha Maracá, Furo Santa Rosa (approximately 03°22′N, 061°22′W); INPA 2038 , 6 (122–176) . Rio Uraricoera, Ilha Maracá, below Furo Santa Rosa (approximately 03°22′N, 061°22′W); INPA 2054 , 4 (135–184) . Rio Uraricoera, Ilha Maracá (approximately 03°22′N, 061°22′W); INPA 2675 , 1 (54) . Rio Uraricoera, Ilha Maracá, below Furo Santa Rosa (approximately 03°22′N, 061°22′W); INPA 3747 , 1 (60) . Rio Mucajaí, station Fé-Esperança ; INPA 3758 , 3 (83– 145) . Rio Mucajaí , 2 km above Cachoeira Paredão (approximately 02°57′N, 061°27′W); INPA 6423 , 1 (338) . Rio Mucajaí , 2 km above Cachoeira Paredão, mouth of igarapé (approximately 02°57′N, 061°27′W); INPA 6495 , 1 (136) ; INPA 6500 , 7 (115–223) . Rio Mucajaí, near Cachoeira Paredão (approximately 02°57′N, 061°27′W); INPA 6496 , 11 (69–196) . Rio Mucajaí, above Cachoeira Paredão (approximately 02°57′N, 061°27′W); INPA 6499 , 1 (192).

Figures

Figure 3. A, Archolaemus ferreirai sp. nov., holotype, female, 183 mm total length, INPA 3757; Brazil, Roraima, Rio Mucajaí, Cachoeira Paredão 2 (approximately 02°57′N, 061°27′W); B, Archolaemus ferreirai sp. nov., paratype, male, 342 mm total length, INPA 36379; Brazil, Roraima, Rio Mucajaí, Cachoeira Paredão 2 (approximately 02°57′N, 061°27′W).

Figure 4. Map of upper Rio Branco and adjoining areas showing geographical distribution of Archolaemus ferreirai sp. nov. (1, holotype locality; some symbols represent more than one locality and/or lot of specimens).