Articles
http://hdl.handle.net/11602/2143
2024-03-29T07:16:02ZThe diet of an invasive crayfish, Cherax quadricarinatus (Von Martens, 1868), in Lake Kariba, inferred using stomach content and stable isotope analyses
http://hdl.handle.net/11602/2335
The diet of an invasive crayfish, Cherax quadricarinatus (Von Martens, 1868), in Lake Kariba, inferred using stomach content and stable isotope analyses
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
2018-01-27T00:00:00ZIntermediate predator naïveté and sex-skewed vulnerability predict the impact of an invasive higher predator
http://hdl.handle.net/11602/2333
Intermediate predator naïveté and sex-skewed vulnerability predict the impact of an invasive higher predator
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.
2018-09-18T00:00:00ZMitochondrial genomes of African pangolins and insights into evolutionary patterns and phylogeny of the family Manidae
http://hdl.handle.net/11602/2332
Mitochondrial genomes of African pangolins and insights into evolutionary patterns and phylogeny of the family Manidae
Du Toit, Zelda; Du Plessis, Morne; Dalton, Desire R.; Jansen, Raymond; Grobler, J. Paul; Kotze, Antoinette
Background: This study used next generation sequencing to generate the mitogenomes of four African pangolin
species; Temminck’s ground pangolin (Smutsia temminckii), giant ground pangolin (S. gigantea), white-bellied
pangolin (Phataginus tricuspis) and black-bellied pangolin (P. tetradactyla).
Results: The results indicate that the mitogenomes of the African pangolins are 16,558 bp for S. temminckii, 16,540 bp for
S. gigantea, 16,649 bp for P. tetradactyla and 16,565 bp for P. tricuspis. Phylogenetic comparisons of the African pangolins
indicated two lineages with high posterior probabilities providing evidence to support the classification of two genera;
Smutsia and Phataginus. The total GC content between African pangolins was observed to be similar between species
(36.5% – 37.3%). The most frequent codon was found to be A or C at the 3rd codon position. Significant variations in
GC-content and codon usage were observed for several regions between African and Asian pangolin species which may
be attributed to mutation pressure and/or natural selection. Lastly, a total of two insertions of 80 bp and 28 bp in size
respectively was observed in the control region of the black-bellied pangolin which were absent in the other African
pangolin species.
Conclusions: The current study presents reference mitogenomes of all four African pangolin species and thus expands
on the current set of reference genomes available for six of the eight extant pangolin species globally and represents the
first phylogenetic analysis with six pangolin species using full mitochondrial genomes. Knowledge of full mitochondrial
DNA genomes will assist in providing a better understanding on the evolution of pangolins which will be essential for
conservation genetic studies.
2017-01-01T00:00:00ZThe complete mitogenome of a South African cryptic species of tadpole shrimp within the Triops granarius (Lucas, 1864) species group
http://hdl.handle.net/11602/2331
The complete mitogenome of a South African cryptic species of tadpole shrimp within the Triops granarius (Lucas, 1864) species group
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.
2018-11-02T00:00:00Z