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Browsing Articles by Author "Dalu, Tatenda"

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    The complete mitochondrial genome of Africa's largest freshwater copepod, Lovenula raynerae
    (2018-11-18) Jooste, Candice M.; Emani-Khoyi, Arsalan; Gan, Hang Ming; Wasserman, Ryan J.; Dalu, Tatenda
    Lovenula raynerae is the largest known African freshwater copepod. To date, it has only been sampled from ephemeral freshwater ecosystems. This paper reports the complete mitochondrial genome of L. raynerae, which was found to be 14,365 bp long. Base composition of 33.5% base A, 19.3% base G, 34.6% base T, and 12.5% base C was found, with 13 protein-coding genes, 22 tRNAs, and 2 rRNAs. This paper contributes to an improved understanding of phylogenetic relationships in an important crustacean group
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    The complete mitogenome of a South African cryptic species of tadpole shrimp within the Triops granarius (Lucas, 1864) species group
    (Taylor & Francis, 2018-11-02) Gan, Han Ming; Wasserman, Ryan John; Dalu, Tatenda; Rogers, D, Christopher
    The complete mitochondrial genome of a cryptic species of tadpole shrimp from South Africa (Accession Number: MG770893) was recovered by low coverage shotgun sequencing. The mitogenome consists of 15,216 bp with a GC content of 30.95%. COX1 sequence alignment indicates that this specimen is the most closely related to Triops granarius with a pairwise nucleotide identity of less than 90% (86.6%). Phylogenetic analysis using whole mitogenome dataset supports its affiliation to the genus Triops with moderate support for its relatively basal position within the clade.
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    The diet of an invasive crayfish, Cherax quadricarinatus (Von Martens, 1868), in Lake Kariba, inferred using stomach content and stable isotope analyses
    (Invasivenet, 2018-01-27) Marufu, Lighthouse T.; Dalu, Tatenda; Phiri, Crispen; Barson, Maxwell; Simango, Rutendo; Utete, Beaven; Nhiwatiwa, Tamuka
    The diet of an invasive crayfish, Cherax quadricarinatus (Von Martens 1868), in Lake Kariba, was investigated using stomach content analysis (SCA) and stable isotope analysis (SIA). The frequency of occurrence of macrophytes and detritus ranged between 63.6–97.1% and 20–45.5%, respectively, and the index of relative importance ranked these as the two most important food items across all size classes. Significant differences in the ranking of fish, macroinvertebrates and crayfish were found between size classes 29–37.9, 38–46.9 and 47–55.9 mm. Stomach content analysis showed 16% of crayfish stomachs were empty. Feeding intensity differed significantly between size classes and ranged from 3.46 to 5.21. Stable isotope analysis was done by comparing δ13C, δ15N and C/N ratios in crayfish muscle and potential dietary items in the lake. Macrophytes were the most dominant food item (57%), followed by macroinvertebrates (20%), then detritus, and finally fish and crayfish. Stable isotope analysis revealed that all crayfish size classes analysed were in the same trophic level. Nevertheless, while SCA showed high dietary overlap among all crayfish size classes (>65%), SIA showed that small crayfish (< 28.9mm) had limited overlap with large crayfish (> 56mm), with the former showing a higher proportion of macroinvertebrates in their diet. In Lake Kariba, C. quadricarinatus predominantly feeds on macrophytes, macroinvertebrates and detritus, which may bring about nutrient cycle alterations in the lake. Littoral habitat changes caused by the feeding characteristics of C. quadricarinatus might also lead to competition with, and eventual displacement of, some native littoral fishes in this lake
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    Intermediate predator naïveté and sex-skewed vulnerability predict the impact of an invasive higher predator
    (Springer Nature, 2018-09-18) Cuthbert, Ross N.; Dalu, Tatenda; Wasserman, Ryan J.; Dick, Jaimie T. A.; Mofu, Amanda Callaghan; Weyl, Olaf L. F.
    The spread of invasive species continues to reduce biodiversity across all regions and habitat types globally. However, invader impact prediction can be nebulous, and approaches often fail to integrate coupled direct and indirect invader effects. Here, we examine the ecological impacts of an invasive higher predator on lower trophic groups, further developing methodologies to more holistically quantify invader impact. We employ functional response (FR, resource use under different densities) and prey switching experiments to examine the trait- and density-mediated impacts of the invasive mosquitofish Gambusia affinis on an endemic intermediate predator Lovenula raynerae (Copepoda). Lovenula raynerae effectively consumed larval mosquitoes, but was naïve to mosquitofish cues, with attack rates and handling times of the intermediate predator unaffected by mosquitofish cue-treated water. Mosquitofish did not switch between male and female prey, consistently displaying a strong preference for female copepods. We thus demonstrate a lack of risk-reduction activity in the presence of invasive fish by L. raynerae and, in turn, high susceptibility of such intermediate trophic groups to invader impact. Further, we show that mosquitofish demonstrate sex-skewed predator selectivity towards intermediate predators of mosquito larvae, which may affect predator population demographics and, perversely, increase disease vector proliferations. We advocate the utility of FRs and prey switching combined to holistically quantify invasive species impact potential on native organisms at multiple trophic levels.