Browsing by Author "Gamba, Nkwengulila"

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    Determinants of the parasite community of clariid fishes from Lake Victoria, Tanzania
    (Cambridge University Press, 2008) Mwita, Chacha; Gamba, Nkwengulila
    The factors that determine parasite assemblages among the clariid fishes of Lake Victoria, Tanzania were studied between August 2003 and February 2005. Six hundred and fifty-six fish belonging to seven species were necropsied and examined for parasites, from which 31 species of metazoan parasites were recorded. The community was dominated by the nematodes both in species and numbers. Most species were generalists with only two trematodes, Diplostomum mashonense and Tylodelphys species, being specialists of Clarias gariepinus. Ten species were considered core and predictable. Parasite species richness, number of individuals per host and Shannon–Wiener diversity indices were generally high. At the compound community level, a mean number of 7.8 parasites were shared among different species of fish and the maximum number of parasites species per fish at the infracommunity level was seven. Levels of similarity in parasite species richness at the component community level ranged from 29.6 to 61.5%. The study concludes that parasite communities in clariid fishes of Lake Victoria are structured by ecological factors. At the infracommunity level, host size, diet and vagility promoted a richer parasite community. At the compound level, two factors were crucial, namely the intermixing of the waters in the lake and the predominant and mobile C. gariepinus.
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    Molecular phylogeny of the clariid fishes of Lake Victoria, Tanzania, inferred from cytochrome b DNA sequences
    (The Fisheries Society of the British Isles, Blackwell-synergy, 2008) Mwita, Chacha; Gamba, Nkwengulila
    Mitochondrial DNA cytochrome b (cyt b) sequence variation among the clariid fishes of Lake Victoria and the Malagarasi wetland Tanzania were studied between August 2003 and February 2005. Seven species were sampled and together with 26 cyt b sequences from GenBank were used to reconstruct phylogenetic relationships in the family Clariidae. The study revealed two clades: one consisting of the big-head species, Clarias gariepinus and Heterobranchus longifilis, and the other of small-sized species, Clarias werneri, Clarias alluaudi, Clarias liocephalus and Clariallabes petricola. The study further revealed that the genus Clarias is paraphyletic and that H. longifilis clusters deeply inside the Clarias group. Although H. longifilis is thought to be the oldest in evolutionary age in Tanzania, it is not close to the ancestor of the Clariidae family. The results also showed that C. werneri and C. alluaudi are genetically distinct from each other.
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    PHYLOGENETIC RELATIONSHIPS OF THE METAZOAN PARASITES OF THE CLARIID FISHES OF LAKE VICTORIA INFERRED FROM PARTIAL 18S rDNA SEQUENCES
    (Tanzania Journal of Science (TSJ), 2010) Mwita, Chacha; Gamba, Nkwengulila
    Phylogenetic relationships among twenty two metazoan parasites recovered from seven species of clariid fish from Lake Victoria were analysed using partial 18S rDNA sequences. The 18S rDNA gene was amplified by polymerase chain reaction, directly sequenced, aligned and phylogenies inferred using maximum parsimony. Heuristic bootstrap MP searches yielded one most parsimonious tree (CI = 61%, HI = 39%), which showed that clariid parasites are monophyletic at higher taxonomic levels (Cestodea, Nematodea, Digenea and Crustacea). However the position of two trematodes (Allocredium mazoensis and Clinostomum sp.) and a nematode (Contracaecum sp.) were not stable. Despite the present findings, the study utilised single species from each taxa, hence further analysis with additional sequences from a multitude of species is recommended to further resolve the phylogeny of the parasites of the clariids in Lake Victoria and elsewhere.