Marcusenius pongolensis ( Fowler, 1934 )

Kramer, Bernd, Skelton, Paul, Bank, Herman Van Der & Wink, Michael, 2007, Allopatric differentiation in the Marcusenius macrolepidotus species complex in southern and eastern Africa: the resurrection of M. pongolensis and M. angolensis, and the description of two new species (Mormyridae, Teleostei), Journal of Natural History 41 (9 - 12), pp. 647-708 : 684-686

publication ID	https://doi.org/ 10.1080/00222930701250987
persistent identifier	https://treatment.plazi.org/id/C512B407-FFDA-A04E-E716-1481FC5FDC73
treatment provided by	Carolina
scientific name	Marcusenius pongolensis ( Fowler, 1934 )
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Marcusenius pongolensis ( Fowler, 1934) View in CoL

( Figures 1D, 1M View Figure 1 )

Gnathonemus macrolepidotus: Gilchrist and Thompson 1913, pp. 330–331 View in CoL .

Gnathonemus pongolensis Fowler, 1934 p. 419 View in CoL , his Figure 6 View Figure 6 ; Crass 1960, p. 416 (synonymy with Gnathonemus macrolepidotus View in CoL ).

Marcusenius pongolensis: Taverne 1971a, p. 103 View in CoL .

Type specimens. Holotype (unique): ANSP 54950 ( Figure 1D View Figure 1 ).

Type locality. South Africa: KwaZulu-Natal Province: Pongola River at Paulpietersburg district (no. 4, Figures 4 View Figure 4 and 8 View Figure 8 ) .

The first South African record is that of three specimens of Gnathonemus macrolepidotus ( Peters, 1852) , one each from the Waterberge District (Limpopo System), the Crocodile River and the Sabie River (the latter two rivers form part of the Incomati System) by Gilchrist and Thompson (1913, pp. 330–331). Without reference to Gilchrist and Thompson (1913, 1917), Fowler (1934) described a new species of bulldog, Gnathonemus pongolensis , from the Pongola River in KwaZulu-Natal ( South Africa), a river south of the Incomati System. Gnathonemus pongolensis was synonymized with G. macrolepidotus ( Peters, 1852) by Crass (1960, p. 416): ‘‘Fowler’s pongolensis was described from a single specimen taken in the upper Pongola, near Paulpietersburg. It appears to differ from typical macrolepidotus only in its more slender shape. Other species such as Barbus aureus , are commonly more slender in headwaters than farther downstream, and there seems no reason to regard pongolensis as a valid species’’. Gnathonemus pongolensis is resurrected here, as Marcusenius pongolensis ( Fowler, 1934) .

Diagnosis. A median 73 (70–76) scales in lateral series, median 18.5 (15–20) scales around caudal peduncle, median 23 (21–24) dorsal fin rays, median 28.5 (27–29) anal fin rays, mean BD 22.6% (19.1–26.2%) of SL, EOD lacking a weak head-negative pre-potential, in females and juveniles Ndur of short duration (typically, 140¡S.E. 2.8 Ms at 25 u C and ‘‘5% threshold criterion’’), no striking sexual dimorphism in EOD waveform present, but longer EOD duration and statistically significant increase with SL in males.

Description. Head with terminal mouth well in front of eye, mental lobe on lower jaw protruding beyond upper jaw. Head and body dorsolaterally compressed. Dorsal fin situated about three fourths of standard length from snout, obliquely orientated, anteriorly higher and posteriorly lower, distal margin sometimes only slightly crescentic with anterior two or three rays longer than posterior rays, number of rays 18 (N 52), 19 (N 51), 20 (N 51), 21 (N 516), 22 (N 524), 23 (N 513), 24 (N 52); anal fin opposite dorsal fin with distinctly more anterior origin, obliquely orientated, anteriorly lower and posteriorly higher, anterior rays longer than posterior ones, especially in males where they also appear stronger and often darkened, distal margin crescentic (in males only posterior to rounded, elongated anterior part of fin), number of rays 24 (N 51), 25 (N 51), 26 (N 56), 27 (N 515), 28 (N 523), 29 (N 512), 30 (N 51). Scales cycloid with reticulate striae, scales extending anteriorly to operculum and pectoral fins (beyond pelvics). Scales on caudal peduncle circumference, 15 (N 51), 16 (N 519), 17 (N 57), 18 (N 510), 19 (N 511), 20 (N 511). Caudal peduncle subcylindrical entire length, usually 20% (18–22%) in SL. Electric organ discharge biphasic lacking a weak pre-potential, in females and juveniles Ndur of short duration (140¡2.8 Ms at 25 u C and ‘‘5% threshold criterion’’). In large males, statistically longer EOD duration and significant tendency for increase of both Pdur and Ndur with SL, however, no sexual dimorphism when compared to Upper Zambezi males (effect not seasonal, and no sudden growth spurt at sexual maturity; however, some plasticity observed when spawning). Males approaching sexual maturity develop a striking kink in the base of the anal fin, with several of its first rays longer, stronger and often curved backwards compared to females and juveniles, where the anal fin base is straight and its rays are similar amongst each other. The kink is distinctly curving inward in many specimens. Colour in life ranging from an almost homogeneous medium brown to grey-brown with yellow-golden shimmer, sometimes going into purple, underside lighter, a few strongly faded, darker blotches on sides detectable, fins yellowish.

Colour in preservation. Light to medium brown; fins whitish; irregular fair spots on body sides (from aggression?).

Ecology. Although transformed by some river impoundment, the Sabie and the Crocodile rivers in the Lowveld are fast-flowing, major, perennial rivers, bordered by dense, subtropical or tropical vegetation. Water conductivity appears to be raised by human settlements and activities, both inside and especially outside the Kruger National Park. Similar for the Pongola in the Lowveld, where the water conductivity is very high. During the day M. pongolensis is often encountered below undercut river banks, especially in dense networks of tree roots; places where there is a countercurrent seem to be especially attractive. In Swaziland M. pongolensis has been observed high up in river systems with rapid water flow and rocky substrate (R. Bills, pers. comm.).

Distribution. Marcusenius pongolensis occurs in coastal rivers draining into the Indian Ocean, ranging from the Incomati system in the north (Mpumalanga Province of South Africa, and Mozambique) to the Mhlatuze System in KwaZulu-Natal (.28 u S) as its southern limit, including the Pongola which is the type river. Marcusenius pongolensis is the mormyrid

ranging farthest south for the whole of Africa. The form of bulldog occurring in the Limpopo River System could not be determined with certainty .

Relationships. Marcusenius pongolensis is considered closest to M. macrolepidotus based largely on the confusion of the identity of both species. Marcusenius pongolensis is distinguished by a higher median count of SLS (70–73 vs. 55.5), of SPc of 16–20 (range, 15–20) vs. 16 (range, 12–18 for M. macrolepidotus ). Although there is considerable geographic variation, M. pongolensis when compared to M. macrolepidotus is more slender (elongated, lower body depth) with PAL shorter (anal fin origin situated closer to head), pD longer, CPL longer, head length shorter, and chin length greater. Female and juvenile EODs with Ndur of shorter duration than in M. macrolepidotus (represented by Buzi fish); the EOD of M. pongolensis does not exhibit striking sexual dimorphism but a clear sex difference in pulse duration that increases with SL in the male sex.

Fowler (1934) described a single specimen from the Pongola River in KwaZulu-Natal, the type specimen (his Figure 6 View Figure 6 ). The morphology of this fish is in good agreement with the present sample of 10 Pongola bulldogs. An anal fin ray count of only 24 by Fowler as opposed to a minimum of 27 (N 54) in the present fish from the Pongola was incorrect, as shown by a recount of nA by one of us (P.S.) that yielded 27 in Fowler’s specimen. A pericaudal scale count of 16 in Fowler’s fish is identical to the lower limit in our fish (N 52), likewise the number of 21 rays of the dorsal fin (N 52). HL/ Na in Fowler’s fish is greater than the maximum of the present sample, but this is not of great concern because of the Na measurement being very small and, hence, less reliable. CPL is slightly greater and LA slightly lower than the range limits of our sample; this should not be considered a reason of much concern because our sample comprises only 10 fish, and then we could not compare the type specimen with our own specimens side by side. The type specimen was kindly measured by Museum personnel and not by one of us (except for nA, see above, unconnected with the present study), in order to avoid the potentially damaging shipping of the valuable type specimen, or else overseas travel. The identity of Limpopo system specimens could not be established with certainty and needs more research .