Scalytail Bulldog

description

Description. Measurements and meristic counts are given in Table 5. Head with terminal mouth well in front of eye; mental lobe on lower jaw protruding in front of upper jaw; snout rounded and blunt; pre-anal distance shorter than pre-dorsal distance; distance from origin of anal fin to origin of dorsal fin greater than middle body depth; pre-pelvic distance twice as long as distance between pelvic and anal fin; dorsal and anal fins set well back on the body, dorsal fin situated about three fourths of standard length from snout and opposite anal fin; dorsal fin shorter, originating on vertical at 4 th or 5 th anal fin ray and ending before anal fin base; distal margin of dorsal and anal fins obliquely orientated, with rays becoming gradually shorter posteriorly; dorsal fin rays 20 (20 – 22), its anterior rays highest, with distal margin rounded and slightly concave; anal fin rays 27 (27 – 28); males at sexual maturity have kink in the base of the anal fin distinctly curving inward; anterior anal fin rays of sexually mature males strong and sometimes darker, 3 rd – 5 th rays longer than the first two rays, crescentic and rounded or curved backwards, but are anteriorly sharp or pointy

Descriptions of three new species of Marcusenius Gill, 1862 (Teleostei: Mormyridae) from South Africa and Mozambique

diagnosis

Diagnosis. Middle body depth 23.8 – 25.9 % SL; dorsal fin length 15.4 – 19.2 % SL; anal fin length 23.0 – 24.9 % SL; pre-dorsal length 61.7 – 66.7 % SL; pre-anal length 60.7 – 62.8 % SL; caudal peduncle depth 40.4 – 51.7 % of its length (greater than and non-overlapping with M. krameri and M. lucombesi); dorsal fin rays 20 – 22; anal fin rays 27 – 28; scales around caudal peduncle 19; lateral line scales 72 – 73; anterior GR (4) + (5 – 6) = (9 – 10); posterior GR (6) + (9) = 15; conical teeth on upper / lower jaws 5 – 5.

Descriptions of three new species of Marcusenius Gill, 1862 (Teleostei: Mormyridae) from South Africa and Mozambique

discussion

Remarks. Marcusenius caudisquamatus can easily be distinguished by its shorter and thicker caudal peduncle, (40.4 – 51.37 % of peduncle length as opposed to 26.0 – 40.6 % in M. krameri and 28.7 – 45.66 % in M. pongolensis). The deeper caudal peduncle has more circumpeduncular scales than in other species (19 vs 16 in M. krameri and 16 – 17 for M. pongolensis, Table 7). The dorsal profile of the head of M. caudisquamatus specimens from the Mhlatuze River has a steep, nearly vertical hump in front of the eye. It is slightly concave behind the eye (Fig. 2 c) as compared to being convex in M. pongolensis and M. lucombesi (Figs. 2 a and 2 d, respectively), and straight in M. krameri (Fig. 2 b). The number of GR on the posterior side of the first arch is constant and a reliable character to distinguish this species from both M. pongolensis and M. krameri (Table 6). Compared to M. krameri and M. pongolensis in which the scales series across their body are easily visible, M. caudisquamatus appears smooth and the scales are almost fully embedded in the skin (observed both in live and preserved specimens). The species is genetically closely related to M. krameri (Fig. 4). Sequence divergence

Descriptions of three new species of Marcusenius Gill, 1862 (Teleostei: Mormyridae) from South Africa and Mozambique

distribution

Distribution and ecology. Currently this species is known only from the Nseleni and the Mhlatuze rivers in KwaZulu-Natal, South Africa (Fig. 1). The Nseleni River was generally deep with strong currents and all the specimens were collected with gill nets. The Mhlatuze River was wide and shallow, about 1.5 m deep, with a sandy or rocky bottom with dense reed beds on the periphery. Water current was moderate to fast in sections where M. caudisquamatus was collected. The water conductivity was relatively high (503 µS / cm to 707 µS / cm) in summer (November 2009) as compared to the 134 µS / cm recorded by Kramer et al. (2007) in winter (12 August 1999). The water temperature at noon was around 25 – 26 ° C in November 2009, the water was clear and specimens were caught at various depths depending on the sampling station. The Mhlatuze River system has the southernmost record of mormyrids in Africa (Kramer et al. 2007). The biology and ecology of the species is unknown, but the characteristic anal fin notch of sexually mature males was observed from about 96.7 mm SL. The largest male was 250 mm and the largest female was 215 mm SL.

Descriptions of three new species of Marcusenius Gill, 1862 (Teleostei: Mormyridae) from South Africa and Mozambique