Published online at www.m.elewa.org on 31 st March 2018 https://dx.doi.org/10.4314/jab.v123i1.2 RÉSUMÉ Objectif : En vue de contribuer à une meilleure connaissance des myxosporidioses pour à terme élaborer des méthodes de lutte, 350 spécimens d'Oreochromis niloticus (tilapia du Nil) ont été échantillonnés de Mai 2016 à Mai 2017 au barrage de retenue de la Mapé (Adamaoua-Cameroun) et autopsiés. Méthodologie et résultats : La collecte, conservation des poissons et l'identification des espèces de Myxosporidies ont été classiques. Douze espèces de Myxosporidies appartenant au genre Myxobolus ont été identifiées. Au total 159 poissons (45, 43%) ont été parasités. Les espèces parasites ont été rares (Prévalence < 10%) à l'exception de Myxobolus camerounensis, M. israelensis, M. tilapiae et M. brachysporus qui ont été intermédiaires (10% ≤ Prévalence ≤ 50%). La prévalence d'infestation a varié significativement entre les espèces parasites. La prévalence la plus élevée (15, 14%) et la plus faible (0,86%) a été observée chez Myxobolus tilapiae et Myxobolus pharyngeus respectivement. Les poissons âgés ont été les plus infestés et les mâles plus parasités que les femelles toutefois, sans différence significative. Au total 10 organes ont été infestés. Indépendamment de l'espèce parasite, les reins ont été significativement les plus parasités (36, 57%) et ont hébergé 11 espèces parasites. M. camerounensis a montré un large spectre d'infestation des organes. La prévalence a été significativement plus élevée en saison sèche (52,94%) qu'en saison de pluie (39,59%). Au total, 59, 94 % de poissons parasités ont été poly infestés pour 5 catégories d'infestations multiples (2 ; 3 ; 4 ; 5 et 6 espèces). La prévalence des associations d'infestations a baissé avec le nombre d'espèces parasites associées. Conclusion et application : Les prévalences de myxosporidioses chez O. niloticus ont été affectées par les facteurs endogènes et les saisons. Les données permettent de développer des stratégies de lutte afin de booster la production en poisson. Fonkwa et al., J. Appl. Biosci. 2018 Prévalences des Myxosporidioses Chez Oreochromis niloticus Linné, 1758 (Cichlidae) au barrage réservoir de la Mapé (Adamaoua-Cameroun) 12333 Prevalence of Myxosporidiosis in Oreochromis niloticus Linnaeus, 1758 (Cichlidae) at Mapé reservoir dam (Adamawa-Cameroon) Objectives: in order to contribute to a better understanding of Myxosporean infections to develop control strategies, 350 Oreochromis niloticus (Nile tilapia) specimens were sampled from May 2016 to May 2017 from the Mapé dam (Adamawa-Cameroon). Methodology and results: Classical methods were used for fish's sampling, conservation and Myxosporean species identification. An overall total of 12 Myxosporean species belonging to the genus Myxobolus were identified. A total of 159 fish (45.43%) were infected. Parasite species were scarce (Prevalence < 10%) apart from Myxobolus camerounensis, M. israelensis, M. tilapiae and M. brachysporus which were intermediate (10% ≤ Prevalence ≤ 50%). The Prevalence di...

In order to improve fish productivity, an essay on the evaluation of the comparative effect of chicken and pig manure on the composition and structure of zooplankton was conducted at the Application and Research farm from the University of Dschang (LN: 5º44'-5 °36 and LE: 10º06'-9 ° 85'). For this purpose, 15 ponds (5.7 x 5.7 x 1m), three doses of 0 (control); 800 and 1000kg/ha of chicken manure as well as pig dung were used. At each of the randomly selected ponds was administered one of the fertilizer doses every 7 days. Each of the doses and type of fertilizer representing a treatment was repeated three times. The physicochemical characteristics of the water and the zooplankton population were measured every 14 days. With respect to the physicochemical characteristics of water, the values of nitrites (7.92 ± 0.05mg/l), nitrates (8.03 ± 0.24mg/l), phosphates (4.68 ± 0, 05mg/l) were significantly (p <0.05) higher in ponds fertilized at 1000kg/ha pig dung, the lowest being obtained in the control treatment. For zooplankton, the highest specific (64.51% of total species), generics (87.87% of total genera) and families (82.35% of total) zooplanktonic abundances were obtained in ponds fertilized at the rate of 1000kg/ha of chicken manure. The species of rotifers were the most diverse survived those of cladocerans whatever the type or the dose of fertilizer. The use of the 1000kg/ha dose of chicken droppings makes sense for a large production of zooplankton diversity.

The study on the phenotypic polymorphism of Heterotis niloticus was undertaken from February to May 2020 in the rain forest region of Cameroon. The  main objective was to contribute to a better understanding of the genetic diversity of this adapted species for adequate breeding and preservation  strategies. More specifically, the investigation aimed at evaluating the variability of phenotypic, morphometric and meristic features according to the  study sites. Further, it was also in order to analyse the phenotypic variability, the structure, as well as the phylogenetic relationships among the Heterotis  niloticus subpopulations. A total of 125 adult individuals were collected in three localities and characterized. Two (2) phaneroptic traits were observed,  while 16 morphometric traits were measured and 5 meristic characters were counted. The results showed that there is a colour variability of eyes and  body in Heterotis niloticus from the study area with a predominance of golden eyes (97.60%) and grey body (96.80%). The number of scales on the lateral  line was higher in the individuals collected in Mbalmayo (38.67±1.46) than those in Ayos (37.70±0.95). Discriminant factor analyses and phylogenetic  analyses revealed that the overall population studied is made up of 3 morphotypes cohabiting in the three localities; thus it was possible to establish the  phylogenetic relationships that exist between them. Morphotypes 1 and 2 are closer while morphotypes 2 and 3 are far apart, showing a tendency of  splitting genetic make up. The recorded diversity suggests that Heterotis niloticus from the study area constitutes a natural genetic resource having the  interesting variability for further improvement and sustainable management.

In order to improve fish productivity, an essay on the evaluation of the comparative effect of chicken and pig manure on the composition and structure of zooplankton was conducted at the Application and Research farm from the University of Dschang (LN: 5º44'-5 °36 and LE: 10º06'-9 ° 85'). For this purpose, 15 ponds (5.7 x 5.7 x 1m), three doses of 0 (control); 800 and 1000kg/ha of chicken manure as well as pig dung were used. At each of the randomly selected ponds was administered one of the fertilizer doses every 7 days. Each of the doses and type of fertilizer representing a treatment was repeated three times. The physicochemical characteristics of the water and the zooplankton population were measured every 14 days. With respect to the physicochemical characteristics of water, the values of nitrites (7.92 ± 0.05mg/l), nitrates (8.03 ± 0.24mg/l), phosphates (4.68 ± 0, 05mg/l) were significantly (p <0.05) higher in ponds fertilized at 1000kg/ha pig dung, the lowest being obtained in the control treatment. For zooplankton, the highest specific (64.51% of total species), generics (87.87% of total genera) and families (82.35% of total) zooplanktonic abundances were obtained in ponds fertilized at the rate of 1000kg/ha of chicken manure. The species of rotifers were the most diverse survived those of cladocerans whatever the type or the dose of fertilizer. The use of the 1000kg/ha dose of chicken droppings makes sense for a large production of zooplankton diversity.