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Gerber R, de Necker L, van Vuren JHJ, Ikenaka Y, Nakayama SMM, Ishizuka M, Wepener V, Smit NJ. A stable isotope analysis of the dietary patterns of the aquatic apex predator, the African tigerfish (Hydrocynus vittatus). J Fish Biol 2023; 103:1129-1143. [PMID: 37498144 DOI: 10.1111/jfb.15516] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Revised: 07/19/2023] [Accepted: 07/26/2023] [Indexed: 07/28/2023]
Abstract
Stable isotope analyses, specifically δ13 C and δ15 N, are useful tools increasingly used to understand ecosystem function, food web structures, and consumer diets. Although the iconic tigerfish Hydrocynus vittatus is regarded as an apex predator in southern African freshwater systems, little information is available regarding their feeding behavior and how this may change with growth or differ between ecosystems, with most information stemming from stomach content analyses (SCA). The aim of the present study was to address this lack of information through a baseline study of the diet of large and small tigerfish in various lentic and lotic ecosystems in South Africa using stable isotope methods. Fish and various food web components and food sources were collected from two river and two lake ecosystems in South Africa. The δ13 C and δ15 N values for all samples were determined and multivariate analyses and Bayesian analytical techniques applied to determine the feeding ecology of H. vittatus and how this may differ with size and habitat type. Analyses revealed a substantial difference in the type and abundance of food sources contributing to the diet of H. vittatus between ecosystems, most prominently between the lotic systems, where less dietary specialization was observed, and lentic systems where more specialization was observed. Furthermore, there was a distinct difference in diet between small and large tigerfish, especially in the lotic system, indicating an ontogenetic diet shift as tigerfish grow and further supporting previous SCA studies. This is the first study of its kind on the African continent for H. vittatus and the findings illustrate the value of stable isotope analysis in providing in-depth information into the feeding ecology of consumers and how this may differ between size classes and habitat types.
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Grants
- 127549 Department of Science and Innovation Professional Development Programme
- 22KK0163 Grants-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology of Japan
- 17KK0009 Grants-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology of Japan
- 18KK028708 Grants-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology of Japan
- 17K2003807 Grants-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology of Japan
- 18H0413208 Grants-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology of Japan
- 20K20633 Grants-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology of Japan
- 105979 National Research Foundation of South Africa
- 85505 National Research Foundation of South Africa
- 105122 National Research Foundation of South Africa
- K5-1922 Water Research Commission of South Africa
- K5-2185 Water Research Commission of South Africa
- JPMJSA1501 JST/JICA SATREPS (Science and Technology Research Partnership for Sustainable Development
- JPMJAS2001 aXis (Accelerating Social Implementation for SDGs Achievement
- PJ36210002 JST AJ-CORE
- JSPS CORE to CORE program
- Hokkaido University SOUSEI Tokutei Research
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Affiliation(s)
- Ruan Gerber
- Water Research Group, Unit for Environmental Sciences and Management, North-West University, Potchefstroom, South Africa
| | - Lizaan de Necker
- Water Research Group, Unit for Environmental Sciences and Management, North-West University, Potchefstroom, South Africa
- South African Institute for Aquatic Biodiversity (NRF-SAIAB), Makhanda, South Africa
| | - Johan H J van Vuren
- Water Research Group, Unit for Environmental Sciences and Management, North-West University, Potchefstroom, South Africa
| | - Yoshinori Ikenaka
- Water Research Group, Unit for Environmental Sciences and Management, North-West University, Potchefstroom, South Africa
- Laboratory of Toxicology, Department of Environmental Veterinary Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan
- Translational Research Unit, Veterinary Teaching hospital, Faculty of Veterinary Medicine, Hokkaido University, Sapporo, Japan
- One Health Research Center, Hokkaido University, Sapporo, Japan
| | - Shouta M M Nakayama
- Laboratory of Toxicology, Department of Environmental Veterinary Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan
| | - Mayumi Ishizuka
- Laboratory of Toxicology, Department of Environmental Veterinary Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan
| | - Victor Wepener
- Water Research Group, Unit for Environmental Sciences and Management, North-West University, Potchefstroom, South Africa
| | - Nico J Smit
- Water Research Group, Unit for Environmental Sciences and Management, North-West University, Potchefstroom, South Africa
- South African Institute for Aquatic Biodiversity (NRF-SAIAB), Makhanda, South Africa
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Dahms-Verster S, Nel A, van Vuren JHJ, Greenfield R. Mortality and malformation effects of acute vanadium (V) exposure on the African clawed frog (Xenopus laevis) embryos. Environ Sci Pollut Res Int 2023; 30:55730-55741. [PMID: 36899118 PMCID: PMC10121540 DOI: 10.1007/s11356-023-26196-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Accepted: 02/24/2023] [Indexed: 06/18/2023]
Abstract
Vanadium (V) is a transition metal that is found in low concentrations in aquatic ecosystems. These levels increase due to anthropogenic activities. The mortality and teratogenicity effects of V remain unexplored in amphibian species. To address this gap in the knowledge base, a standard Frog Embryo Teratogenic Index - Xenopus (FETAX) assessment was conducted. Vanadium pentoxide (V2O5) was chosen for its known toxicity in other aquatic biota and its solubility in water. A range-finding test was conducted in two different mediums, V2O5 in distilled water (VDH2O) and V2O5 in FETAX medium (VMED), to determine concentration ranges where effects occurred. Thereafter, definitive tests were conducted using two separate breeding pairs, with two replicate dishes per concentration containing 15 embryos each. Multiple endpoints were assessed including mortality, malformations, minimum concentration to inhibit growth (MCIG), and the teratogenic index (TI). Mortality and malformation effects occurred at different ranges, and therefore, the exposures were conducted in low dose and high dose ranges. The high dose range for mortality effects was conducted at 0, 10, 20, 40, 80, and 160 mg/L of V. The low dose exposures to assess malformation effects were conducted at 0.0001, 0.00025, 0.0005, 0.00075, and 0.001 mg/L. Binary logistic regression was used to determine the LC50 and EC50 for the two sets of definitive tests. The LC50s were determined to be 46.10 mg/L and 26.91 mg/L for VDH2O and 34.50 and 25.25 for VMED for the two breeding pairs respectively. The EC50 was calculated as 0.00053 mg/L and 0.00037 mg/L for VDH2O and 0.00036 mg/L and 0.00017 mg/L for VMED for the two definitive tests respectively. The TI was calculated as 86,981 and 72,729 for VDH2O and 95,833 and 148,526 for VMED. Ultimately, there were severe malformation effects in embryos exposed to low doses of V and V was determined to be a very strong teratogen.
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Affiliation(s)
- Simone Dahms-Verster
- Department of Zoology, University of Johannesburg, Cnr. Kingsway and University Rd, Auckland Park, Johannesburg, 2092, Gauteng, South Africa
| | - Amina Nel
- Department of Zoology, University of Johannesburg, Cnr. Kingsway and University Rd, Auckland Park, Johannesburg, 2092, Gauteng, South Africa
| | - Johan H J van Vuren
- Department of Zoology, University of Johannesburg, Cnr. Kingsway and University Rd, Auckland Park, Johannesburg, 2092, Gauteng, South Africa
| | - Richard Greenfield
- Department of Zoology, University of Johannesburg, Cnr. Kingsway and University Rd, Auckland Park, Johannesburg, 2092, Gauteng, South Africa.
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Gerber R, Smit NJ, van Vuren JHJ, Ikenaka Y, Wepener V. Biomarkers in tigerfish (Hydrocynus vittatus) as indicators of metal and organic pollution in ecologically sensitive subtropical rivers. Ecotoxicol Environ Saf 2018; 157:307-317. [PMID: 29627415 DOI: 10.1016/j.ecoenv.2018.03.091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Revised: 03/19/2018] [Accepted: 03/30/2018] [Indexed: 06/08/2023]
Abstract
Studies have shown high levels of contamination of both metals and organochlorine pesticides (OCPs) in aquatic systems of the world renowned Kruger National Park, South Africa. With effects evident in top predators, including, unexplained Crocodylus niloticus deaths and organ level and histological changes in Hydrocynus vittatus. A suite of biomarkers reflecting exposure and were selected to evaluate biological responses of H. vittatus to anthropogenic stressors as well as to evaluate whether the chosen suite of biomarkers could successfully distinguish between the different pollution profiles present in the selected rivers. During this study a clear relationship was found between exposure to environmental contaminants and the concomitant responses of H. vittatus to these stressors. The ensuing biomarker responses indicated that there is a physiological attempt to deal with, and mitigate the deleterious effects that metals and OCPs may induce. In the Luvuvhu River there is a clear indication in H. vittatus of the stimulation of anti-oxidant protective mechanisms in response to internal OCP exposure. This is reflected by the increasing cytochrome P-450, superoxide dismutase, and more specifically reduced glutathione, which resulted in decreased lipid and protein breakdown (reflected in decreased lipid peroxidation and protein carbonyl levels). Consequently H. vittatus populations of the Luvuvhu River are under greater cumulative stress and this is reflected in the lower energy budgets. Our results further show the integrated application value of the current suite of biomarkers in assessing responses of subtropical fish to metal and OCP exposure as the entire suite of biomarkers when used in conjunction were able to explain 100% of the variation in the data.
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Affiliation(s)
- R Gerber
- Water Research Group, Unit for Environmental Sciences and Management, North-West University, Private Bag X6001, Potchefstroom 2520, South Africa
| | - N J Smit
- Water Research Group, Unit for Environmental Sciences and Management, North-West University, Private Bag X6001, Potchefstroom 2520, South Africa
| | - Johan H J van Vuren
- Water Research Group, Unit for Environmental Sciences and Management, North-West University, Private Bag X6001, Potchefstroom 2520, South Africa
| | - Y Ikenaka
- Water Research Group, Unit for Environmental Sciences and Management, North-West University, Private Bag X6001, Potchefstroom 2520, South Africa; Laboratory of Toxicology, Department of Environmental Veterinary Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Kita 18, Nishi 9, Kita-ku, Sapporo 060-0818, Japan
| | - Victor Wepener
- Water Research Group, Unit for Environmental Sciences and Management, North-West University, Private Bag X6001, Potchefstroom 2520, South Africa
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Gerber R, Smit NJ, van Vuren JHJ, Wepener V. Metal concentrations in Hydrocynus vittatus (Castelnau 1861) populations from a premier conservation area: Relationships with environmental concentrations. Ecotoxicol Environ Saf 2016; 129:91-102. [PMID: 27003617 DOI: 10.1016/j.ecoenv.2016.03.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2015] [Revised: 02/17/2016] [Accepted: 03/07/2016] [Indexed: 06/05/2023]
Abstract
Metals are known to have deleterious effects on aquatic ecosystems, so monitoring the bioaccumulation of these pollutants is important for the assessment of potential impacts. The aim of the study was therefore to determine the degree to which aquatic biota in selected rivers of the world renowned Kruger National Park (KNP) are exposed to metals entering from the catchments outside the KNP and to determine how these metal levels reflect what is occurring within the environment. Many of these rivers have never previously been assessed and those which have, have not been assessed within the past two decades. Tigerfish (Hydrocynus vittatus) is an economically important apex predator and was selected as the bioindicator for this study. Fish were sampled from the KNP sections of the Luvuvhu, Letaba and Olifants Rivers during the high and low flow periods from 2009 to 2011. The analysis of various metals from the aforementioned systems revealed spatial and temporal related variation in metal level patterns of the chosen bioindicator, with concentrations in fish from the Olifants River>Letaba River>Luvuvhu River and 2009>2010>2011. Although there were differences between rivers, metal concentrations were comparable and indicate that all of the studied KNP rivers, even those considered to be in a natural state are affected to some degree by anthropogenic activities. However, concentrations found during this study were much lower than previous studies in the area, as well as contaminated sites across the world, but were higher than concentrations in fish from contaminated sites in the Vaal River, South Africa. Bioaccumulated metals showed no correlation to metals in the water column, but some were correlated to sediment metal concentrations and the contamination and bioavailability of these metals within the sediments. This is of concern when managing the water resources of the conservation area since the contaminants enter the park from outside the borders and pose potential risks to the mandated conservation of aquatic biota within the KNP.
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Affiliation(s)
- Ruan Gerber
- Department of Zoology, Kingsway Campus, University of Johannesburg, PO Box 524, Auckland Park 2006, South Africa.
| | - Nico J Smit
- Water Research Group, Unit for Environmental Sciences and Management, Potchefstroom Campus, North-West University, Private Bag X6001, Potchefstroom, South Africa
| | - Johan H J van Vuren
- Department of Zoology, Kingsway Campus, University of Johannesburg, PO Box 524, Auckland Park 2006, South Africa
| | - Victor Wepener
- Water Research Group, Unit for Environmental Sciences and Management, Potchefstroom Campus, North-West University, Private Bag X6001, Potchefstroom, South Africa
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Gerber R, Smit NJ, van Vuren JHJ, Nakayama SMM, Yohannes YB, Ikenaka Y, Ishizuka M, Wepener V. Application of a Sediment Quality Index for the assessment and monitoring of metals and organochlorines in a premier conservation area. Environ Sci Pollut Res Int 2015; 22:19971-19989. [PMID: 26296506 DOI: 10.1007/s11356-015-5206-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Accepted: 08/10/2015] [Indexed: 06/04/2023]
Abstract
The physical and chemical characteristics of surface sediments from a leading conservation area, namely the Kruger National Park, were determined in order to identify potential stressors in the systems that may contribute to overall deterioration in sediment quality within the reserve, leading to potential threats to the aquatic biota conserved within these stretches of river. Sediment samples were collected during four surveys (two low flow and two high flow) from 2009 to 2011. Samples were analysed for organic content, grain size determination, metals and various organochlorine pesticides. Results indicated that the Olifants River sediments did not show any great improvement over the years and point towards the continued input of pollutants into this system. Sediment quality in the Luvuvhu and Letaba Rivers is better than that of sediments from the Olifants River in terms of metals, but metal concentrations are still comparable and point towards anthropogenic inputs of metals into these rivers. Even though the data indicate that these systems are being contaminated with both metals and organochlorine pesticides (OCPs), levels were still below contaminated sediments from around the globe. Sediment Quality Index scores showed that the sediment quality of these rivers is in a relatively good state. High metal concentrations were the drivers behind lowered sediment quality, and in some cases certain OCPs played a role. Both metals and OCP concentrations were highly correlated with finer grain sizes. Sediment assessments are not routinely applied in South Africa resulting in very little reference or background data available for the area. The metal concentrations for the study area were generally lower than those for other studies in more polluted regions. The study also contributes to the available knowledge on surrounding metal pollution in riverine sediments in South Africa.
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Affiliation(s)
- Ruan Gerber
- Department of Zoology, Kingsway Campus, University of Johannesburg, Box 524, Auckland Park, 2006, South Africa.
| | - Nico J Smit
- Unit for Environmental Sciences and Management, Potchefstroom Campus, North West University, Private Bag X6001, Potchefstroom, South Africa
| | - Johan H J van Vuren
- Department of Zoology, Kingsway Campus, University of Johannesburg, Box 524, Auckland Park, 2006, South Africa
| | - Shouta M M Nakayama
- Laboratory of Toxicology, Department of Environmental Veterinary Sciences, Graduate school of Veterinary Medicine, Hokkaido University, Kita 18, Nishi 9, Kita-ku, Sapporo, 060-0818, Japan
| | - Yared B Yohannes
- Laboratory of Toxicology, Department of Environmental Veterinary Sciences, Graduate school of Veterinary Medicine, Hokkaido University, Kita 18, Nishi 9, Kita-ku, Sapporo, 060-0818, Japan
| | - Yoshinori Ikenaka
- Unit for Environmental Sciences and Management, Potchefstroom Campus, North West University, Private Bag X6001, Potchefstroom, South Africa
- Laboratory of Toxicology, Department of Environmental Veterinary Sciences, Graduate school of Veterinary Medicine, Hokkaido University, Kita 18, Nishi 9, Kita-ku, Sapporo, 060-0818, Japan
| | - Mayumi Ishizuka
- Laboratory of Toxicology, Department of Environmental Veterinary Sciences, Graduate school of Veterinary Medicine, Hokkaido University, Kita 18, Nishi 9, Kita-ku, Sapporo, 060-0818, Japan
| | - Victor Wepener
- Unit for Environmental Sciences and Management, Potchefstroom Campus, North West University, Private Bag X6001, Potchefstroom, South Africa
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Mlambo SS, van Vuren JHJ, Barnhoorn IEJ, Bornman MS. Histopathological changes in the reproductive system (ovaries and testes) of Oreochromis mossambicus following exposure to DDT. Environ Toxicol Pharmacol 2009; 28:133-139. [PMID: 21783993 DOI: 10.1016/j.etap.2009.03.011] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2008] [Revised: 03/23/2009] [Accepted: 03/26/2009] [Indexed: 05/31/2023]
Abstract
This study assesses the effects of 1,1-bis (4-chlorophenyl)-2,2,2-trichloroethane (DDT) on the reproduction and gonadal histology of adult Mozambique tipalia (Oreochromis mossambicus). The fish were allowed to breed, following exposure to 2 and 5μg/l of waterborne technical-grade DDT for 40 days. Fertilized eggs were artificially incubated. In the 5μg/l exposure, posthatch survival was significantly lower, and prevalence of larval skeletal deformities significantly higher, compared to the control (p<0.05). Incomplete axial development was the common gross deformity in posthatch larvae, caused by failure to develop chondroblasts posterior to the buccopharyngeal cavity. There were no significant differences in the gonadosomatic index of exposed and non-exposed male and female adults. The exposure caused increased oocyte atresia in the ovaries and disorganization of seminiferous lobules in the testes of adults. DDT exposure reduced survival and increased deformities in larvae, at levels that did not cause severe histopathological changes to parental gonads.
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Affiliation(s)
- Sibonani S Mlambo
- Department of Zoology, University of Johannesburg, Auckland Park 2006, South Africa
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