Mormyrops (Oxymormyrus) zanclirostris (Günther, 1867)
Original Published Description:
Trumpet-like snout, long, straight, and tubular, its length about 0.75–0.85 times the post-orbital HL. Mouth terminal, submental swelling absent. Truncate teeth in a single row around margin of upper and lower jaws, more than 12 in each. Body relatively elongate, depth 5–8 times into SL. Head about 3.1–3.3 times into SL. Snout elongate, as much as 12.9% SL, 40–42% HL, or about equal to the post-orbital length. Mouth terminal and very small. Teeth truncate, more than 12 in each jaw. Eye diameter small, 9–13% of snout length. Nostrils close to one another near tip of snout, far from eye. Dorsal fin with 19–21 rays (one simple + 18–20 segmented) about 59% of the anal fin length, anal with 34–39 rays (one simple + 33-38 segmented). Origin of dorsal posterior to origin of anal fins; dorsal originates over 12th or 14th anal ray. Pectoral fin about 40% HL. Caudal peduncle twice as long as deep, its length about 30% of the length of the head. 70–74 scales in lateral line. Color: dark chocolate-brown, fin rays and membranes darkly pigmented.
Electric Organ Discharge
The EOD waveform has three phases, beginning with a small head-positive prepulse of small amplitude, P0, followed by a head-negative phase, P1, ending with a head-positive phase, P2. The total duration is about 1 msec. The polarity of this EOD is ‘inverted’ compared to most other mormyrids. The cause of the inversion is that the electrocytes have penetrating stalks innervated on the posterior side (Type Pp) rather than the anterior side (Type Pa), and this switches the polarity of each phase of the EOD waveform.
M. zanclirostris differs from Mormyrops boulengeri from the Congo basin by having a slightly shorter snout, which is straight rather than curved, and by having more circumpeduncular scales (12 versus 8 for M. boulengeri). Furthermore, the EOD waveforms of the two species are quite distinct.
Ecology and Distribution
In Lower Guinea found in the Ntem River, throughout the Ogowe basin, including the Ivindo River, the Nyanga River and in the Kouilou River. Elsewhere, known from the Congo River basin, where it overlaps in distribution with M. boulengeri. See FishBase for museum records and localities. Common in a wide range of habitats, from deepest parts of rivers to smaller streams and swamps. Isolated individuals are often found along the banks of small streams during the rainy season floods.
- Mormyrops zanclirostris (Günther, 1867) (synonym)
Syntypes: BMNH 18184.108.40.206-12 (2), RMNH 5250 (1)
|Hopkins, Lavoué, Sullivan 2007.pdf||932.9||2010-11-27T21:38:42Z|
|Günther 5 1896.pdf||4845.5||2011-02-02T22:30:19Z|