Cryptomyrus ona, Sullivan, John P., Lavoue, Sebastien & Hopkins, Carl D., 2016

Sullivan, John P., Lavoue, Sebastien & Hopkins, Carl D., 2016, Cryptomyrus: a new genus of Mormyridae (Teleostei, Osteoglossomorpha) with two new species from Gabon, West-Central Africa, ZooKeys 561, pp. 117-150 : 131-134

Taxon classification Animalia Osteoglossiformes Mormyridae

Cryptomyrus ona sp. n. Figs 8, 9; Table 4

Holotype.

MNHN 2003-0425, 120.6 mm TL, 107.8 SL, male; Nyanga Province, Gabon: Moukalaba River very near its confluence with the Nyanga River, just above ferry landing on Tchibanga-Digoudou road, 2°47.3400'S, 10°43.7160'E, gill net at night, S. Lavoué & V. Mamonekene, 23 July 2001.

Other (non-type) specimen.

CUMV 98647, 115.1 mm TL, 98.1 mm SL, male; Ngounié Province, Gabon: Mabounié River (Lower Ngounié-Ogooué River basin), Station HBG-010, 0°45.1692'S, 010°32.9202'E, gill net at night, Y. Fermon, J.H. Mve Beh, & J.D. Mbega, 21 February 2012.

Diagnosis.

Cryptomyrus ona sp. n. is readily differentiated from its sole congener, Cryptomyrus ogoouensis sp. n., in having an anal-fin origin located only just in advance of the dorsal fin (first dorsal ray above anal-fin ray 3 vs. first dorsal-fin ray above anal-fin ray 7), a deep caudal peduncle (6.0-6.8% SL vs. 5.1% SL), and lobes of caudal fin markedly shorter than caudal peduncle (vs. nearly as long as peduncle).

Description.

Morphometric and meristic data for holotype (male, 107.8 mm SL) presented in Table 4. Maximum size of this species unknown. Body fusiform with dorsal and ventral profiles gently convex, greatest body depth between terminus of pelvic fin and urogenital pore. Body compressed, widest at head. Dorsal head profile gently convex with shallow slope downwards to snout, slight inflection between snout and head above eye. Ventral profile of head with marked concavity between gular region and chin, with body depth increasing rapidly from here to below pelvic fin origin. Snout bulbous, rounded, tip below horizontal through center of eye, projecting above upper lip. Nostrils well separated from each other and from eye; posterior naris at level of bottom of orbit, anterior naris below line through center of eye; straight line drawn through nostrils passes through tip of snout and just below pectoral-fin origin. Mouth subinferior, small; rictus below posterior naris, in advance of eye. Chin swelling modest, but broad, nonprotrusive. Premaxillary teeth 5, strongly notched, dentary teeth 6, spatulate, center four oriented horizontally, center two with broad contact between inner edges which are longer than outer edges, projecting well beyond neighboring pair to which they are closely appressed, trowel-like (Fig. 6). Eye large, laterally positioned on head. Predorsal distance equal to preanal distance; anal fin only slightly in advance of dorsal fin: first dorsal-fin ray above first or second branched anal-fin ray; dorsal and anal fins with short bases. Dorsal-fin rays 3+18, anal-fin rays 3+21; 2 anal-fin rays beyond last dorsal-fin ray. Dorsal fin with falcate posterior margin. Longest dorsal-fin ray is first branched ray; next 10 rays successively shorter; next 5 rays approximately equal in length, final 2 rays longer. Anal-fin ray with gently falcate posterior margin. Longest anal-fin ray is second branched ray; next 10 rays successively shorter, next 6 rays more or less equal in length, final 3 successively longer. Pectoral fin with 10 rays, tip pointed, extending beyond the origin of the pelvic fin, but short of halfway. Pelvic fin with 6 rays, closer to pectoral than to anal. Caudal peduncle deep, depth at middle of peduncle slightly deeper than at origin. Caudal fin deeply forked with 20 rays in each lobe, lobes short, scaled at their bases with bluntly pointed ends; distance from caudal flexion to caudal tips shorter than CPL. Body scales thin, cycloid, head naked. Body scales large along sides, smaller dorsally: 42 pierced lateral line scales + 2 unpierced along midlateral line, 18 scales in transverse series between origins of dorsal and anal fins, 9 from pelvic fin to midlateral line, 12 around caudal peduncle. Total vertebrae 41, epineurals associated with vertebrae 1-8, pleural ribs directly attached to vertebral centra 2-13, ribs displaced beneath haemal arches on vertebrae 14-17, caudal vertebrae 18-41. Hypurals 1 & 2 unfused.

Color.

Photo of holotype specimen recovered from gill net, several hours post-mortem, shows a purplish-gray body, darker along dorsum, with whitish marbling/speckling on lower half of head and along belly to anal fin and diffuse band of pigment below dorsal fin occupying 4 scales, darker above, lighter or absent above anal fin. Numerous depigmented spots over electroreceptors conspicuous on snout, top of head, belly and upper back. Fins with darkly pigmented rays, interradial membranes hyaline. In preservation, body yellowish tan.

Electric organ discharge.

Unknown.

Etymology.

The specific epithet is a noun in apposition that honors Marc Ona Essangui, Gabonese environmental and civic activist, founder and executive director of the NGO Brainforest and recipient of the 2009 Goldman Environmental Prize, in appreciation for his efforts to protect Gabon’s equatorial forests and wetlands.

Distribution and ecology.

Known from the type locality in the Moukalaba River at its confluence with the Nyanga River. A second specimen referred to this species comes from the Mabounié River, a small right-bank affluent of the lower Ngounié River, below Samba Falls. Both specimens were caught by gill net at night. At the type locality we recorded water temperature of 23.6 °C, pH of 8.0, water conductivity of 116.0 μS /cm and dissolved oxygen of 4.98 mg/l. Water conductivity at the Mabounié River at time of collection of that specimen was 48 μS /cm.