Cryptomyrus ogoouensis, 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 : 130-131

Taxon classification Animalia Osteoglossiformes Mormyridae

Cryptomyrus ogoouensis sp. n. Fig. 7; Table 4

Holotype.

CUMV 98155, tag no. JPS-1194, 132 mm TL, 111.6 mm SL, female; Ogooué–Lolo Province, Gabon: Ogooué River at Doumé falls, off rocks on left bank near village of Doumé, approx. 1.5 meters depth, 0°50.4822'S, 12°57.9288'E, earthworm-baited fish trap, J.P. Sullivan, B. Sidlauskas, J.H. Mve Beh, J. Cutler, & A. Dolé, 17 September 2014.

Diagnosis.

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

Description.

Morphometric and meristic data for holotype (female, 111.6 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 very nearly straight from back of head to above eye, a slight indentation above anterior margin of eye and abruptly angled at tip of snout. In lateral view, upper lip to tip of snout nearly a straight line, forming a 90° angle with top of head. Ventral profile of head with marked concavity between gular region and chin, body depth increasing rapidly from there to below mid level of pectoral fin. Snout blunt, deep and broad, rounded from above. Tip of snout on level with center of eye, projecting beyond upper lip. Nostrils well separated from each other and from eye; posterior naris at level of bottom of orbit, anterior naris just 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 beneath posterior naris in advance of eye. Chin swelling present: expansive, but not protruding beyond snout. Premaxillary teeth 5, notched, dentary teeth 6, broad, squarish, spatulate, center four oriented horizontally. Center two projecting beyond neighboring pair, longest along inner edges (Fig. 6). Eye large, laterally positioned on head. Predorsal distance greater than preanal distance; anal-fin origin well in advance of dorsal fin: first dorsal ray above anal-fin ray 7 (branched ray 4); dorsal-fin base shorter than anal-fin base; dorsal-fin rays 3+21, anal-fin rays 3+28; 3 anal-fin rays beyond last dorsal-fin ray. Dorsal fin with strongly falcate posterior margin. Longest dorsal-fin ray is second branched ray; next 10 rays successively shorter; final 8 rays equal in length. Anal fin with gently falcate posterior margin. Longest anal-fin ray is third branched ray; next 13 rays successively shorter, final 12 rays equal in length. Pectoral fin long and pointed distally, with 10 rays, extending to vertical through middle of pelvic fin. Pelvic fin with 6 rays, closer to pectoral-fin origin than to anal-fin origin. Caudal peduncle narrow, depth at middle equal to depth at origin. Caudal fin deeply forked with 20 rays in each lobe, lobes long with rounded ends, scaled at bases; distance from caudal flexion to caudal tips roughly equal to CPL. Body covered by thin, cycloid scales, head naked. Body scales large along sides, smaller dorsally: 43 pierced lateral line scales + 2 unpierced along midlateral line, 19 scales in transverse series between origins of dorsal and anal fins, 9 from pelvic fin to midlateral line, 12 around caudal peduncle. Total vertebrae 43; epineurals associated with vertebrae 1-9, vertebral centra 2-13 with pleural ribs directly attached, vertebrae 14-17 with pleural ribs displaced beneath haemal arches; caudal vertebrae 18-43. Hypurals 1 & 2 unfused.

Color.

In life, a light cinnamon brown along sides, darker along dorsum, reflective coppery pigment on lower half of head and along belly to anal fin, mouth and chin whitish. Eye with golden iris, dark center. Faint, diffuse broad band of pigment between dorsal and anal fin occupying 4-5 scales, darker above. Numerous depigmented spots over electroreceptors conspicuous on snout, top of head, belly and upper back. Fins with very lightly pigmented rays, interradial membranes hyaline. In preservation, light brown.

Electric organ discharge.

EOD waveform recorded from the holotype specimen is very short, about 0.55 millisecond total duration (recorded at 23.2 °C) if measured from the onset of the first very weak head-negative phase (P0) and only 0.28 milliseconds if measured from the rising phase of the head-positive phase (P1) to the end of the large head negative phase (P2) using a 2% departure-from-baseline threshold (Fig. 4A). P1 is twice the duration and 85% of the amplitude of P2. Both P1 and P2 rise and fall smoothly with no inflection points. In advance of P1 there is a weak head-negative (P0) phase, only 0.2% of the peak-to-peak height of P1 and P2, difficult to see without additional amplification. The presence of a P0 indicates that the electrocytes of this species’ electric organ have penetrating stalks innervated on the posterior side of the electrocyte (type Pa) unlike the non-penetrating stalk electrocytes (type NPp) of species of sister genera Boulengeromyrus and Ivindomyrus ( Sullivan et al. 2000). The power spectrum of the EOD (Fig. 4B) exhibits a broad plateau between 1700 and 8200 Hz with peak power at 4300 Hz.

Etymology.

The specific epithet is a Latinized noun in the genitive case and refers to the Ogooué River of Gabon.

Distribution and ecology.

Currently known only from the Ogooué River at Doumé falls. At the collection site, we recorded a water temperature of 26.7 °C, a pH of 6.89, water conductivity of 13.8 μS /cm and dissolved oxygen of 84.7%.