Abstract
Petrocephalus similis n. sp. is described from the Djerem River, upper Sanaga basin, in Cameroon. It can be distinguished from all other Petrocephalus from West and Central Africa by an unique combination of morphological characters including: body without melanin mark, 22–24 branched rays in the dorsal fin and 28 or 29 branched rays in the anal fin, mouth commissure under the posterior half of the eye. Petrocephalus similis mostly resembles Petrocephalus sullivani. Yet, P. similis has proportionally a larger mouth and a wider head, and reaches a longer maximum standard length. The electric organ discharge waveform of this species is not known. Molecular comparisons based on cytochrome b nucleotide sequences are congruent with morphological comparisons in independently supporting the distinctiveness of this species from 17 other species of Petrocephalus. Within the genus Petrocephalus, P. similis belongs to a group that is almost exclusively composed of endemic species of Central Africa, pointing out its likely origin from this region. Additional examinations of museum specimens from the Sanaga River basin demonstrate the occurrence of at least two other species of Petrocephalus: Petrocephalus microphthalmus, and a second species which is conservatively assigned to Petrocephalus cf. christyi, pending additional evidence.
References
Bass, A.H. (1986) Electric organs revisited: evolution of a vertebrate communication and orientation organ. In: Bullock, T.H. & Heiligenberg, W. (Eds.) Electroreception. John Wiley and Sons, New York, pp. 13–70.
Bigorne, R. & Paugy, D. (1991) Note sur la systématique des Petrocephalus (Teleostei, Mormyridae) d'Afrique de l'Ouest. Ichthyological Exploration Freshwaters, 2, 1–30.
Boden, G., Teugels, G.G. & Hopkins, C.D. (1997) A systematic revision of the large-scaled Marcusenius with description of a new species from Cameroon (Teleostei; Osteoglossomorpha; Mormyridae). Journal of Natural History, 31, 1645–1682.
Boulenger, G.A. (1887) On new fishes from the lower Congo. Annals and Magazine of Natural History, 19, 148–149.
Boulenger, G.A. (1899) Poissons nouveaux du Congo. Quatrième Partie. Polyptères, Clupes, Mormyres, Characins. Matériaux pour la faune du Congo. Zoologie--Série I. Annales du Musée du Congo, Zoologie, 1, 59–96.
Boulenger, G.A. (1903) Second account of the fishes collected by Dr. W. J. Ansorge in the Niger Delta. Proceedings of the General Meetings for Scientific Business of the Zoological Society of London, 2, 324–330.
Boulenger, G.A. (1912) Poissons recueillis dans la région du Bas-Congo par le Dr. W. J. Ansorge. Annales du Musée du Congo, Zoologie, 2, 1–25.
Boulenger, G.A. (1914) Descriptions of three new fishes from South Cameroon. Annals and Magazine of Natural History, 14, 383–385.
Boulenger, G.A. (1920) Poissons recueillis au Congo Belge par l'expédition du Dr C. Christy. Matériaux pour la faune du Congo. Annales du Musée du Congo, Zoologie, 2, 1–38.
Cuvier, G. & Valenciennes, A. (1847) Histoire Naturelle des Poissons. Tome dix-neuvième. Pitois, Paris, 544 pp.
Brummet, R.E. & Teugels, G.G. (2004) Rivers of the Lower Guinean rainforest: Biogeography and sustainable exploitation. In: R. L. Welcomme & T. Petr (Eds), Proceedings of the second international symposium on the management of large rivers for fisheries. FAO Regional Office for Asia and the Pacific, Bangkok, Thailand, pp. 149–171.
Daget, J. (1979) Contribution à la faune de la République Unie du Cameroun. Poissons de l'Ayina, du Dja et du Bas Sanaga. Cybium, 3, 55–64.
Daget, J. & Depierre, D. (1980) Contribution à la faune de la République Unie du Cameroun. Poissons du Sanaga Moyen et Supérieur. Cybium, 3, 53–65.
Fowler, H.W. (1936) Zoological Results of the George Vanderbilt African Expedition of 1934. Part III,– The Fresh Water Fishes. Proceedings of The Academy of Natural Sciences of Philadelphia, 88, 243–335.
Günther, A. (1862) Eine neue art von Mormyrus. Archiv für Naturgeschichte, 28, 64.
Harder, W. (1968) Zum Aufbau der epidermalen Sinnesorgane der Mormyridae (Mormyriformes, Teleostei). Zeitschrift für Zellforschung, 89, 212–224.
Hopkins, C.D., Lavoué, S. & Sullivan, J.P. (2007) Mormyridae. In: M.L.J. Stiassny, G.G. Teugels & C.D. Hopkins (Eds), Faune des poissons d'eaux douces et saumâtres de l'Ouest de l'Afrique Centrale (Cameroun, Guinée Equatoriale, Gabon, Congo Brazzaville). IRD, Paris, pp. 219–334.
Lacepède, B.G.E. (1803) Histoire Naturelle des Poissons. Tome cinquième. Saugrain, Paris, 803 pp.
Lavoué, S., Arnegard, M.E., Sullivan, J.P. & Hopkins, C.D. (2008) Petrocephalus of Odzala offer insights into evolutionary patterns of signal diversification in the Mormyridae, a family of weakly electrogenic fishes from Africa. Journal of Physiology-Paris, 102, 322–339.
Lavoué, S., Hopkins, C.D. & Kamdem Toham, A. (2004) The Petrocephalus (Pisces, Osteoglossomorpha, Mormyridae) of Gabon, Central Africa, with the description of a new species. Zoosystema, 26, 511–535.
Lavoué, S., Sullivan, J.P. & Arnegard, M.E. (2010) African weakly electric fishes of the genus Petrocephalus (Osteoglossomorpha: Mormyridae) of Odzala National Park, Republic of the Congo (Lekoli River, Congo River basin) with description of five new species. Zootaxa, 2600, 1–52.
Lévêque, C. (1997) Biodiversity dynamics and conservation: the freshwater fish of tropical Africa. Cambridge: Cambridge University Press, 438 pp.
Lévêque, C., Paugy, D. & Teugels, G.G. (1990) Faune des poissons d'eaux douces et saumâtres de l'Afrique de l'Ouest. MRAC, ORSTOM, Tervuren, Paris, 384 pp.
Marcusen, J. (1854) Vorläufige Mittheilung aus einer Abhandlung über die Familie des Mormyren. Bulletin de l'Académie des Sciences de St. Petersbourg, 12, 1–14.
Pellegrin, J. (1908) Sur une seconde collection de poissons recueillis par M. E. Haug à Ngomo. Bulletin de la Société Philomatique de Paris, 11, 184–190.
Pezzanite, B. & Moller, P. (1998) A sexually dimorphic basal anal-fin ray expansion in the weakly discharging electric fish Gnathonemus petersii. Journal of Fish Biology, 53, 638–644.
Roberts, T.R. (1975) Geographical distribution of African freshwater fishes. Zoological Journal of the Linnean Society, 57, 249–319.
Sauvage, H.E. (1879) Notice sur la faune ichthyologique de l'Ogooué. Bulletin de la Société Philomatique de Paris, 7, 90–103.
Sauvage, H.E. (1883) Descriptions de quelques poissons de la collection du Muséum d'Histoire Naturelle. Bulletin de la Société Philomatique de Paris, 7, 156–161.
Silvestro, D. & Michalak, I. (2010) raxmlGUI: a graphical front-end for RAxML. available from: http://sourceforge.net/projects/raxmlgui/ (December 2010).
Stamatakis, A. (2006) RAxML-VI-HPC: maximum likelihood-based phylogenetic analyses with thousands of taxa and mixed models. Bioinformatics, 22, 2688–2690.
Stiassny, M.L.J., Teugels, G.G. & Hopkins, C.D. (2007) Faune des poissons d'eaux douces et saumâtres de l'Ouest de l'Afrique Centrale (Cameroun, Guinée Equatoriale, Gabon, Congo Brazzaville). IRD, Publication Scientifique du Muséum, MRAC, Paris, 800 pp.
Sullivan, J.P., Lavoué, S. & Hopkins, C.D. (2000) Molecular systematics of the African electric fishes (Mormyroidea: Teleostei) and a model for the evolution of their electric organs. Journal of Experimental Biology, 203, 665–683.
Van den Bergh, E.C. & Teugels, G.G. (1998) Description of new small-sized Barbus species from the Sanaga Basin in Cameroon. Comments on B. jae and on the taxonomic status of B. condei (Ostariophysi; Cyprinidae). Journal of Natural History, 32, 1367–1401.