Brycinus

Abstract: The family Alestidae (also referred to as the African Characidae) comprises the African dwarf forms ("Petersiini") and the genera Alestes, Brycinus, Bryconaethiops, and Hydrocynus. Although several authors have presented characters to support the monophyly of the family, a cladistic analysis of the group has not been published. Furthermore, the interrelationships of the constituent groups are the subject of some controversy. A cladistic analysis of the Alestidae is presented, including characters to support the monophyly of the family. The results of this study indicate that several species should be removed from the genus Brycinus, that Hydrocynus is the sister group of Alestes s.str. (containing only five species), and that the dwarf alestids ("Petersiini") do not form a monophyletic group.

Abstract: Baseline information on the parasites of frequently caught species of the characids namely Hydrocynus vittatus, Alestes baremoze, Brycinus macrolepidotus and Brycinus leuciscus was investigated in Anambra River from August 2004 to July 2005. The parasites recovered were the Myxosporid, Myxobolus sp (Protozoa), Polyopistocotylids, Diplozoon ghanense and Neodipolzoon polycotyleus (Monogeneans), the Caryophyllid Caryophylleus sp (Cestoda) and Rhabdochona sp (Nematoda). The prevalence of Caryophylleus sp in B. macrolepidotus (14.2%) and A. baremoze (8.1%) as well as Rhabdochon sp and Myxobolus sp in H. vittatus (9.6% and 7.8% respectively) was relatively high (>7.0%); while the other parasite species Myxobolus sp in B. leuciscus (2%), D. ghanense in B. macrolepidotus (1.9%) and N. polycotyleus in A. baremoze (1.9%) had a much lower prevalence (2.7%). Distribution of parasites was clearly seasonal. Dissolved oxygen (8.0–14.0) mg l−1 and pH (5.5–7.0) influenced the occurrence of the parasites whereas temperature (20.1–27.5 DC) showed no much effect. Resume Les informations de reference sur les parasites des especes frequemment capturees de Characides Hydrocynus vittatus, Alestes baremoze, Brycinus macrolepidotus et Brycinus leuciscus ont eteetudiees dans la riviere Anambra entre aout 2004 et juillet 2005. Les parasites retrouves sont le Myxosporide, Myxobolus sp. (Protozoaire), les Polyopistocotylides, Diplozoon ghanense et Neodipolzoon polycotyleus (Monogenes), les Caryophyllides Caryophylleus sp. (Cestodes) et Rhabdochona sp. (Nematodes). La prevalence de Caryophylleus sp. chez B. macrolepidotus (14,2%) et A. baremoze (8,1%) ainsi que de Rhabdochon sp. et Myxobolus sp. chez H. vittatus (9,6% et 7,8% respectivement) etait relativement forte (>7,0%), alors que les autres especes de parasites, Myxobolus sp. chez B. leuciscus (2%), Dipolzoon ghanense chez B. macrolepidotus (1,9%) et Neodiplozoon polycotyleus chez A. baremoze (1,9%) avaient une prevalence beaucoup plus faible (2,7%). La distribution des parasites etait nettement saisonniere. L’oxygene dissous (8,0–14,0 mg/l) et le pH (5,5–7,0) influencaient l’occurrence des parasites alors que la temperature (20,1–27,5°C) n’avait pas beaucoup d’effets.

Abstract: We studied the diet of Brycinus sadleri in Lake Victoria after extensive environmental changes during the 1980s. To check for diet expansion following these changes, as observed in some other fish species, we compared our results with data from the 1950s. Stomach contents were analysed in relation to fish size and time of the day to investigate ontogenetic and diel shifts in the diet. Comparison of diets before and after the environmental changes showed a shift to more generalist feeding. The main food sources in the 1950s were plants during daytime and surface insects at night. Hardly any plant material was eaten during the late 1980s, but chironomid larvae, chaoborid larvae and pupae, shrimps, Odonata nymphs and fish contributed to a broader daytime diet. These prey species were also commonly taken at night, though, like in the 1950s, surface insects accounted for the major part of the diet. We found dietary shifts during ontogeny. Juveniles fed exclusively on zooplankton. Chironomid larvae, relatively ...

Abstract: Mitotic chromosome sets in four fish species representing four different orders (Polypteriformes, Osteoglossiformes, Cypriniformes and Characiformes) occurring in the White Nile, Blue Nile and Omo-Turkana basins in south-western and northern Ethiopia were studied with the air-dried method of Kligerman and Bloom (1977). The following chromosome (2n) and arm (NF) numbers were found in these fishes: 2n = 36, NF = 72 in the gray bichir Polypterus senegalus (Polypteridae), 2n = 40, NF = 42 in the stonebasher Pollimyrus cf. nigricans (Mormyridae), 2n = 50, NF = 66 in the Abyssinian loach Afronemacheilus abyssinicus (Balitoridae) and 2n = 54, NF = 78 in the big-scale tetra Brycinus macrolepidotus (Alestiidae). Comparisons with the previously published data (reviewed by Arai, 2011) show general similarity in the gross karyotype features at the level of conspecific populations and congeneric species for the gray bichir, at the level of phylogenetically close genera and families for the Abyssinian loach and big-scale tetra, while substantial karyological differences were revealed between the stonebasher and two other mormyrid genera (Gnathonemus and Marcusenius) studied by Uyeno (1973).