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) Author Kramer, Bernd Author Skelton, Paul Author Bank, Herman Van Der Author Wink, Michael text Journal of Natural History 2007 2007-06-30 41 9 - 12 647 708 http://dx.doi.org/10.1080/00222930701250987 journal article 10.1080/00222930701250987 1464-5262 4658362 Marcusenius devosi , sp. n. ( Figure 1 G ) Type specimens. Holotype : SAIAB 79138 (specimen Ta13na), Kenya : Tana River . Paratypes : SAIAB 79139 (14), ZSM 35091 (3) , ZSM 35092 (1) , ZSM 35093 (4) , ZSM 35094 (7). Type locality. Kenya : Lower Tana River near village Wenje : 1 u 52938.10S, 40 u 8922.50E (no. 14, Figure 4 ) . The presence of G. macrolepidotus , or a form of this species, in the equatorial Tana River of East Africa was suggested by Whitehead and Greenwood (1959) and Whitehead (1959, 1962); for M. macrolepidotus adopted by Seegers (1996 , p. 76). However, a critical comparison with M. macrolepidotus has not been made. Diagnosis. Longest mean pD of 41% (39.5–43.4%) of SL, shortest mean PAL of 59.1% (57–61%) of SL, shortest mean PDL of 62.3% (59.8–64%), long mean CPL of 20.2% (19.2–22.1%), median SLS of 62.5 (56–66) vs. 55.5 (52–62) in M. macrolepidotus , a median 22 (21–24) dorsal fin rays, 28 (26–30) anal fin rays, 16 (14–18) scales around caudal peduncle; EOD lacking weak head-negative pre-potential, strongest Namp relative to Pamp among samples from all origins (typically 137%), but short Ndur (about 140 Ms at 25 u C and ‘‘5% threshold criterion’’), Pdur of long duration (typically greater than 230 Ms), brief PNsep (typically 76 Ms). Fish from Rovuma River: anal and dorsal fin ray counts, one ray more each, SPc identical, CPD/CPL ratio significantly lower, LD and HL higher. 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 two thirds 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 21 ( N 53), 22 ( N 518), 23 ( N 55), 24 ( N 54); 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 26 ( N 51), 27 ( N 59), 28 ( N 514), 29 ( N 54), 30 ( N 52). Scales cycloid with reticulate striae, scales extending anteriorly to operculum and pectoral fins (beyond pelvics). Scales on caudal peduncle circumference, 14 ( N 52), 15 ( N 51), 16 ( N 526), 17 ( N 50), 18 ( N 51). Caudal peduncle relatively deep, subcylindrical entire length, usually 20% (19–21%) in SL. Electric organ discharge biphasic lacking a weak pre-potential, Pamp of relatively long duration (around 230–235 Ms at 25 u C and ‘‘5% threshold criterion’’), increasing with SL at least in females and juveniles, Ndur of very short duration (usually around 140 Ms), but very strong Namp (137% of Pamp). No sexual dimorphism recognized. Males approaching sexual maturity develop a kink in the base of the anal fin which is absent in juveniles and females where the anal fin base is straight. Colour in preservation. Head and back when seen from above, dark. Body sides light brown to light ochre, the ochre found especially on lower parts and underside. Dorsal fin usually darker than anal fin. Homogeneous coloration without any blotches, increasingly lighter from back to belly. Ecology. The Tana River is a major, perennial river of about 700 km length that originates from the equatorial Mt. Kenya and flows into the Indian Ocean. In its final part close to the sea the river is bordered by gallery forest, surrounded by dry savannah on both sides. In August the water was murky and brown, and visibility very low. River borders are high and steep and difficult to climb up or down. Even though the water level was low the current was strong. Distribution. Presently only known from the Tana River but range extension both to the north and south likely. Samples from the Rovuma River System more than 1000 km to the south are more similar to M. devosi than M. macrolepidotus in anatomical characters but take an intermediate, independent position in ISSR-PCR genetic analysis. Relationships. Marcusenius devosi is considered closest to M. macrolepidotus based largely on the confusion of the identity of both species. Marcusenius devosi is distinguished most easily by its longer posterior body part relative to the anterior body part, as evidenced by higher lengths for the caudal peduncle and for pD, and lower lengths for PDL, PAL, and HL. BD was also lower in M. devosi . Marcusenius devosi when compared to M. macrolepidotus carries a longer mental lobe on the lower jaw, and has an EOD of shorter N phase duration and much greater strength relative to P phase (than Buzi specimens); the EOD of M. devosi shows no evidence for sexual dimorphism. There is also very little affinity with G. moeruensis whose morphological parameters are outside the range observed in the Tana River sample for: PDL, PAL, LD, pD, CPL, CPD, BD, nA, and SPc. Etymology. Marcusenius devosi is named in honour of Dr. Luc De Vos, late curator of fishes at Nairobi Museum (born 8 December 1957 at Sint-Niklaas/ Belgium , deceased 14 June 2003 at Nairobi/ Kenya ), for his contributions to African ichthyology and promotion of ichthyology in East Africa (see obituary by J. Snoeks).