1,721,084 research outputs found
Age, growth rate and size at sexual maturity of Labeobarbus aeneus (Teleostei: Cyprinidae) in the middle Vaal River, South Africa
No full textAge structure, growth and size at sexual maturity of smallmouth yellowfish, Labeobarbus aeneus (Burchell), were assessed in 2008–2009. Despite its angling and food importance, little has been published on many aspects of its ecology and biology, specifically its age structure in the Vaal River system. Of 193 L. aeneus collected by gillnetting, 96 were assessed for sexual maturity, and ages were estimated using scales (n = 143) and whole otoliths (n = 167). Whole otoliths were found to be the most appropriate method for ageing. Both males and females were present in all age classes, which ranged from 2 to 19 years. Males may live longer (maximum 19 years) than females (maximum 16 years). Fish matured relatively late in life, the males at 3 years and females at 5 years, corresponding to lengths of 254 and 375 mm FL, respectively. Growth was shown to be fairly slow, as asymptotic growth was reached only at 8 years.http://dx.doi.org/10.2989/16085914.2012.66633
Cymothoa hermani sp. nov. (Isopoda, Cymothoidae, Crustacea), a parasitic isopod, collected off the Zanzibar coast, Tanzania from the mouth of a parrotfish (Scaridae)
No full textCymothoa hermani sp. nov., a buccal fish-parasitic isopod is described from off Unguja Island, Zanzibar, from the buccal cavity of the marbled parrotfish, Leptoscarus vaigiensis. Cymothoa hermani sp. nov. is characterised by the unique bulbous ornamentation on pereonite 1, anterolateral angles on pereonite 1 rounded and produced past frontal margin of cephalon, and pereopods with long and slender dactyli. There are no other species of Cymothoa known from parrotfishes. This description increases the number of known Cymothoa from the southwestern Indian Ocean to four
Unexpected response of a captive blackeye thicklip, Hemigymnus melapterus (Bloch), from Lizard Island, Australia, exposed to juvenile isopods Gnathia aureamaculosa (Ferreira & Smit)
No full texthttp://dx.doi.org/10.1111/j.1365-2761.2011.01261.
First record of the water mold Achlya bisexualis (Saprolegniaceae) isolated from ornamental fish in South Africa
No full textThe order Saprolegniales (Class Oomycota) is a group of fungus‐like eukaryotic microorganisms that have been associated with infections in fish and fish eggs. Infections with microorganisms from this order are clearly evident because they have a cotton wool‐like appearance. The aim of this study was to characterize and identify an oomycete that was isolated from the eye of an Orange Blotched Peacock Cichlid Aulonacara sp. A sample of cotton wool‐like mycelia was isolated and single‐spore isolations were conducted. Molecular characterization and phylogenetic analysis of the ITS1‐5.8‐ITS2 rDNA region for all isolates were used for species identification. Following molecular identification, one isolate was used to culture and characterize the reproductive structures. Physiological characterization entailed incubating the isolate on potato dextrose agar (PDA) at five different temperatures, ranging from 5°C to 25°C, to monitor growth rates. A multiple sequence alignment showed 100% similarity between all of the single‐spore isolates and alignment with other Achlya bisexualis strains. Long, coarse hyphae with zoosporangia and gemmae typical of the order Saprolegniales were observed with an optimal growth rate at 25°C. The oomycete that was isolated from an Orange Blotched Peacock Cichlid was identified as A. bisexualis, the first record of this species in South Afric
A histology-based fish health assessment of the tigerfish, **Hydrocynus vittatus** from a DDT-affected area
No full textAbstract: The Pongolapoort Dam (PPD) in the Phongola River, Kwa-Zulu Natal, South Africa and the surrounding area are classified as intermediate to low risk malaria areas and are continually being treated with DDT for malaria vector control. DDT is known as an endocrine disrupting chemical posing estrogenic and anti-androgenic properties and therefore might impact on the health of the 18 freshwater fish species found within this system. Of these species the tigerfish, Hydrocynus vittatus, is targeted by both recreational and local subsistence fishermen and was recently included in the South African threatened or protected species list. Their protected status and importance as a food source therefore emphasises the need for their health status elucidation. Previous research on H. vittatus in the Phongola floodplain highlighted DDT biomagnification in this species. Recent data show that the sum of the DDT levels in February 2009 (5403.9 ng/g lipid) and July 2009 (5537.4 ng/g lipid) is still comparable to the high levels found 30 years earlier. The aim of the current study was thus to determine the health status of H. vittatus in relation to DDT exposure by means of a histology-based fish health assessment protocol. Tigerfish were collected in February 2009 (n = 30) and July 2009 (n = 15) and gill, kidney and liver tissue were subjected to histological analyses. Mean Index values showed that the Kidney Index (IK), Gill Index (IG) and Fish Index (IFISH) were higher in fish from the February survey while the Liver Index was higher in those collected during July. Liver alterations identified included intercellular oedema, granular degeneration, vacuolation, nuclear pleomorphism and lymphocyte infiltration. Kidney alterations included dilation of the glomerulus capillaries, vacuolation and hyaline droplet degeneration. Gill alterations identified included telangiectasia and hyperplasia of the secondary lamella, congestion, and rupture of pillar cells. Although histological alterations were observed, the histology based fish health assessment protocol indicated that the H. vittatus population in PPD were in a healthy state. The histological assessment did not reflect the DDT exposure induced effects that were anticipated. However, the biomagnification effects in other tertiary consumers in the PPD such as crocodiles and fish eagles cannot be ruled out
Seasonal bioaccumulation of organohalogens in tigerfish, **Hydrocynus vittatus** Castelnau, from Lake Pongolapoort, South Africa
No full textAbstract: The study determined current exposure of tigerfish in Lake Pongolaqpoort to organohalogens. Levels of DDT, PCB, HCB, HCH, PBDE and CHLs were measured in tigerfish muscle on a seasonal basis. Historical use of DDT was reflected in the bioaccumulation patterns (5,4006,000 ng/g lipid) as well as current use of HCBs (7.715.7 ng/g lipid) in the agricultural areas. External factors, i.e. increased flow did not play a role in organic pollutant exposure. Levels are a function of the lipid content of the muscle tissue, i.e. 3.8% during low and 9% during high flow, implying that organohalogen exposure remains fairly constant throughout the year
Three-dimensional visualisation of developmental stages of an apicomplexan fish blood parasite in its invertebrate host
Get PDFThis is likely the first account of the use of 3D visualisation to study developmental stages of an apicomplexan parasite in its invertebrate vector. Elucidation of the extent of development of the haemogregarine within the leech salivary cells, together with the unusual connections between meronts and the host cell membrane, illustrates the future potential of 3D visualisation in parasite-vector biology
Is caudal fin colour in tigerfish Hydrocynus vittatus a sex or population trait?
No full textTigerfish caudal fin colours vary from yellow to red, with distinct dissimilarities previously noted. To understand these colour differences, tigerfish were collected during 2008 to 2010 from four southern African populations in the Upper Zambezi River (ZAM), Okavango Delta (OKA), Pongolapoort Dam (POD) and Phongolo River (POR), and caudal fin colouration was classified according to pattern and sex. Muscle and liver tissue were assayed by starch electrophoresis. Caudal fin colour in OKA, ZAM and POD showed significant differences between sexes. Genetics revealed closer relationships between OKA and ZAM, substantiated by their recurrent and historical links, and between POD and POR, as expected for a dam and associated river. There is an association between the genetic and geographical distance of tigerfish populations, but variation in caudal colour in this species can most likely be attributed to their environment, territorial dominance and sexual behaviour.http://www.ajol.info/index.php/aja
First report of nephrocalcinosis in a wild population of Mugil cephalus L. and Myxus capensis (Valenciennes)
No full textNo Abstract Availablehttp://onlinelibrary.wiley.com/journal/10.1111/%28ISSN%291365-276
The butterfly effect: parasite diversity, environment, and emerging disease in aquatic wildlife
No full textAquatic wildlife is increasingly subjected to emerging diseases often due to perturbations of the existing dynamic balance between hosts and their parasites. Accelerating changes in environmental factors, together with anthropogenic translocation of hosts and parasites, act synergistically to produce hard-to-predict disease outcomes in freshwater and marine systems. These outcomes are further complicated by the intimate links between diseases in wildlife and diseases in humans and domestic animals. Here, we explore the interactions of parasites in aquatic wildlife in terms of their biodiversity, their response to environmental change, their emerging diseases, and the contribution of humans and domestic animals to parasitic disease outcomes. This work highlights the clear need for interdisciplinary approaches to ameliorate disease impacts in aquatic wildlife systems
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