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This communication details the maternal care of Hemisus marmoratus and Hemisus guttatus. A Hemisus mother stays with the eggs, protecting them during their time in the nest chamber, and ensures their ultimate arrival in a body of water, at varying stages of development, via a variety of different techniques, ranging from nest placement and slide construction to tadpole transportation. We confirm that a sticky glue-like substance is used during inguinal amplexus of H. guttatus, with only the hands of the male being glued to the female. Field observations indicate that H. marmoratus females carry their offspring to the water, gluing her hind legs together to increase the surface area for the tadpoles to adhere to during the journey.
The effect of invasive species on local parasite dynamics is often overlooked. The African Clawed Frog Xenopus laevis (Daudin, 1802) (Anura: Pipidae) is a global invader, with established populations on four continents and is a domestic exotic in southern Africa. Despite a century of parasitological surveys, the current study reports seven previously unrecorded nematode species parasitising X. laevis across South Africa. These are adult Capillaria sp. and Falcaustra sp. from the intestine, third stage larvae of Contracaecum sp. encysted in the body cavity, third stage larvae of Paraquimperia sp. and Tanqua sp. from the intestine and two different species of second stage nematode larvae from the lungs and kidneys, respectively. Morphological descriptions, photomicrographs and molecular data of the 18S and 28S rRNA and COI genes are provided to aid future investigations. We propose that these nematodes could well be using X. laevis as a definitive, paratenic and intermediate host, probably involving native fish, piscivorous birds, semi-aquatic reptiles and invertebrates in their life cycles. All recovered nematodes are recorded for the first time herein in association with X. laevis, except for the genus Contracaecum, members of which have previously been recorded from invasive X. laevis from California and Chile. The current study illustrates that X. laevis is an important parasite reservoir in its native range, with implications for its role in the invasive range. The fact that none of these nematodes could be identified to species level underscores the importance of providing morphological descriptions and molecular data when reporting on parasitological surveys, especially those of known invasive species.
Animal behavioural traits determine trophic interaction strength, which in turn structures ecological communities. Behavioural responses to prey cues can inform upon how prey are perceived and detected and therefore determine whether certain stimuli can increase or dampen predatory efficiency and therefore community structuring. We examined the functional foraging traits of an amphibian predator Xenopus laevis on mosquito larvae (Culex sp.), with regard to responses towards different prey cues. We assessed a suite of foraging behaviours exhibited when supplied with three abundances of live prey (2, 4 and 20); non-injury prey cues; prey injury kairomones from mechanically damaged prey in order to determine the importance of cues in stimulating foraging. High abundance of live prey caused frogs to visit the top of the arena significantly more than in the other treatments. This suggests that hydromechanical and visual cues alert X. laevis to prey items in different spatial zones, which results in foraging where the prey have aggregated, while the non-injury prey cue resulted in a decrease in foraging behaviours. The injury kairomone cue elicited a significantly farther distance travelled, and similar responses in terms of velocity of movement and duration of time spent moving when supplied with 20 live prey items. Previous work on X. laevis predation has focused on prey detection via lateral line sensitivity, however, the strength of response elicited by the prey injury kairomone treatment indicates that there are also complex olfactory pathways involved in detecting prey items. This is possibly related to abiotic context (i.e. turbid ponds) and high predator density in the wild.
The mining industry plays a key role in the economic development of South Africa as one of the largest exporters of valuable resources, such as gold, platinum group metals and other metals and minerals. Unfortunately, mining produces large volumes of solid waste in the form of tailing disposal facilities (TDFs), which contain a variety of metals that are hazardous to the soil environment. The aim of this study was to use earthworm bioassays and avoidance-behaviour tests to assess the effects of gold mine tailings on soil organisms. Six random soil samples were taken from four different sites on a gold mine viz. two different TDFs and two grassy pasture sites. Earthworms (Eisenia andrei) were exposed for a period of 28 days to the soils from these different sites. Soil from the TDFs was also diluted to 25%, 50%, 75% and 100%, respectively. Soil chemical analysis showed that the TDFs had the lowest pH levels and that only Cr concentrations were higher than proposed benchmarks in two of the sites. Earthworms exposed to the TDF material showed significantly lower earthworm biomass, allied with a very low cocoon production. The avoidance-behaviour test showed similar results, where earthworms generally preferred natural and control soils over the TDF material. It can be concluded, that even though the gold mine was inactive for a long period of time, it still remains a highly contaminated area.
Brominated flame-retardants (BFRs), including polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane (HBCD), were analysed in 77 eggs of 13 wild bird species from Gauteng and northern Free State (the industrial heartland of South Africa). BFRs were in all eggs, but not all BFRs were quantifiable. Concentrations ranged between 2.9 and 46 ng g–1 wm (wet mass) and the predominant congeners were BDE-47, -153, -154, -183 and -209. The BFR compositional patterns of the congeners in eggs differed between species, feeding guilds, and habitats. Differences in associations of birds with humans seemed to have as much an influence as the trophic levels occupied by the maternal animals. The congener pattern of BFRs differed between terrestrial and aquatic species. The congener concentrations and patterns also differed from eggs from other countries, suggesting differences in sources. BFR concentrations in eggs from the current study area were below a reported no observed effect level (NOEL; 1 000 ng g–1 wm). Although this suggests that the BFRs do not pose a risk, the NOEL was mostly based on information from birds from moderate and colder climates. This NOEL might not apply to birds from warmer climates with different life histories, as in the current study, because there are currently only draft regulations on importing BFRs or BFR-containing products in South Africa. The BFR-containing products otherwise destined for countries with BFR restrictions in place may now find their way to South Africa. The additional waste these poorly regulated products generate will eventually find their way to landfills ensuring that release to the environment and consequent exposures to biota will continue without effective interventions and waste management. Our findings indicate the need for on-going environmental monitoring to assess trends, identify hot spots, investigate effects, strengthen waste management, and the need to urgently implement the commitments under the Stockholm Convention.
Production, use and disposal of products containing nanomaterials can lead to an increased presence of these particles in the environment and exposure to the organisms found there. It is therefore becoming increasingly necessary to develop methods for screening these materials for possible toxic effects. Behavioural analyses have proven to be a dependable and accurate measure of ecotoxicological risk factors. The aim of the current study was to investigate the toxicological effect of two types of nanomaterials (carbon- and metal-based) on zebrafish larvae. Individual larvae, seven days post fertilisation, were transferred to wells on 24-well plates containing OECD ISO fish media. Sections of the plate to be exposed were randomly arranged and incrementally dosed with sublethal stock concentrations of suspended CdTe (functionalised cadmium-tellurium) quantum dots (QDs) and nanodiamonds (NDs). Subsequently, the 24-well plate was loaded into a DanioVision® system and the behaviour of the larvae recorded for 12 h. The recordings were then analysed using Noldus™ EthoVision® software. Exposure to QDs affected various locomotor and behaviour endpoints over time, i.e. distance travelled, swimming speed, mobility and acceleration states. A significant increase in locomotor activity, coupled with erratic and hyperactive swimming bouts, were observed in zebrafish larvae exposed to QDs, a nanomaterial associated with cadmium dissolution toxicity. However, behaviour remained largely unaffected in zebrafish exposed to NDs. The results support the use of zebrafish in acute toxicological studies, as a result of its sensitivity to environmental toxins. Their relatively small size permits the use of multi-well plates to allow rapid, high-throughput screening of pollutants.
Although temporary wetlands are often biodiversity hotspots that deliver multiple ecosystem services, they are also threatened by human exploitation. We conducted a comparative field study to investigate the impact of reserve protection on the diversity and community structure of aquatic macroinvertebrates of temporary wetlands (pans) in South Africa. Specifically, we compared the diversity and community composition of macroinvertebrates with a special focus on large branchiopod crustaceans in pans of a protected nature reserve (Ndumo Game Reserve) with that of pans in the surrounding anthropogenically disturbed area (Ndumo Communal Area). Our results show that reserve protection has a significant positive effect on the diversity and community structure of the aquatic macroinvertebrates. The taxon diversity for macroinvertebrates in general and large branchiopods in particular was significantly higher in the Ndumo Game Reserve, compared with the Ndumo Communal Area. Overall, our results illustrate the need for continued protection of reserve areas and pans in this tropical region in South Africa for the conservation of macroinvertebrate species.
Southern Africa has one of the highest densities of temporary pools and some of the most understudied temporary wetlands in the world. Additionally, the eastern African annual killifishes (Nothobranchius spp.) are rare in southern Africa and found exclusively in temporary habitats. There is a notable lack of literature regarding the diet of these fish, as well as the foodweb structures of temporary ecosystems. The current study aimed to address this paucity in literature by assessing the foodweb of a temporary pool located in the Ndumo Game Reserve (NGR) in northern Kwa-Zulu Natal using stable isotopes analysis. In addition, Bayesian mixing models were used to assess the diet of the spotted killifish Nothobranchius orthonotus over two seasons (dry and wet seasons). The foodweb consisted of only three trophic levels and comprised different foodweb items between the two seasons. Stable isotope analysis indicated significant increases in δ 15N from the dry to wet season. It further revealed the diet of N. orthonotus to be more varied and omnivorous with primary producers contributing a much greater percentage toward their diet than previous studies have reported. This study contributes valuable information to the paucity of knowledge regarding foodweb structure and food-chain length of temporary pools in South Africa, as well as new insights into the extended diet of N. orthonotus. The analytical techniques used in this study could also be utilised as part of future research in ecological assessments of temporary pools and other aquatic ecosystems in Africa and globally.
Information about the non-target effects of glyphosate, a broad-spectrum systemic herbicide on soil-borne nematodes is scarce and not well documented for South African agricultural fields. In the present study, the abundance and identity of plant-parasitic nematodes in roots and rhizosphere soil of commercial glyphosate-tolerant (genetically modified; GM) and conventional (non-glyphosate-tolerant) soybean cultivars from cultivated fields were obtained for two consecutive growing seasons. Grass and soil from adjacent natural vegetation were sampled, representing the reference system. Thirty plant-parasitic nematode species, belonging to 13 genera were identified in the roots and rhizosphere soil of soybean cultivars and natural vegetation. In rhizosphere soil, Meloidogyne (for glyphosate-tolerant and conventional soybean), followed by Helicotylenchus (for glyphosate-tolerant soybean) and Scutellonema (for conventional soybean), were the predominant genera. Seven species, namely Pratylenchus flakkensis, Pratylenchus scribneri, Pratylenchus vulnus, Rotylenchus brevicaudatus, Telotylenchus avaricus, Tylenchorhynchus brevicaudatus and Quinisulcius capitatus are first reports for soybean in South Africa. Although it was not possible to define the impact of each ecosystem on the plant-parasitic nematode assemblages, this study suggested that glyphosate had no deleterious effects on plant-parasitic nematodes.
Praying mantids (Mantodea) are not only apex predators with a ‘mystical' status, but are also regarded as a kind of oracle and, in some cultures, as omens associated with good or bad. In the future, the cultural, mystical and religious values allocated to mantids over millennia can contribute not only to their own conservation, but also to conservation of arthropods in general. Historically, Mantodea influenced African, Greek, Egyptian, Japanese and Chinese cultures and they affected human culture in a variety of ways. Some of these are coin designs, hairstyles, swords, death rituals, war strategies, advertisements, children's books and even modern music. Despite human fascination with mantids, this group of arthropods is unfortunately overlooked in terms of conservation and research. Conservation as a mitigation strategy to protect threatened and endangered species is influenced by philosophical and psychological aspects and requires more than a purely scientific approach. This paper highlights the role of praying mantids in human culture and the historical relationships between humans and other arthropods. Acknowledgement of these cultural aspects of the mantids may contribute to a positive change in people's perceptions of arthropods and eventually in insect conservation. It is suggested that mantids could be used as a flagship or gateway species to advance awareness of insect conservation. We can generate much needed insect appreciation by building on the existing ‘global’ cultural values, fascination and intrigue of the charismatic mantid, therefore increasing wonderment of the small things that dominate the world we live in.
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