DAO 125:101-113 (2017)  -  DOI: https://doi.org/10.3354/dao03138

Thyroid function of steatitis-affected Mozambique tilapia Oreochromis mossambicus from a sub-tropical African reservoir

J. Dabrowski1,2,*, P. Oberholster3,4,5, J. Steyl3, G. Osthoff6, A. Hugo6, D. M. Power7, J. H. van Wyk

1Sustainability Research Unit, Nelson Mandela Metropolitan University, Private Bag x6531, George 6530, South Africa
2Department of Zoology and Entomology, University of Pretoria, Hatfield 0028, South Africa
3Department of Paraclinical Sciences, Faculty of Veterinary Science, University of Pretoria, Hatfield 0028, South Africa
4CSIR Natural Resources and the Environment, PO Box 320, Stellenbosch 7599, South Africa
5Department of Botany and Zoology, Stellenbosch University, Private Bag X1, Stellenbosch 7602, South Africa
6Department of Microbial, Biochemical and Food Biotechnology, University of the Free State, PO Box 339, Bloemfontein 9300, South Africa
7Centro de Ciencias do Mar, Universidade do Algarve, Campus de Gambelas, Faro, 8005-139, Portugal
*Corresponding author:

ABSTRACT: Thyroid function and nutritional indicators were measured in obese, steatitis-affected Mozambique tilapia Oreochromis mossambicus from Loskop Reservoir (LR), South Africa. Plasma thyroid hormones (especially T3) and thyroid follicle histomorphology revealed high levels of activity in every aspect of the thyroid cascade measured in fish from LR compared to a reference population of steatitis-free fish. Concurrent measurements of nutritional state including plasma lipids, liver lipid content and hepatocyte size showed that fish from LR had significant energy stores indicative of abundant nutritional intake. There were distinct sex and seasonal differences, with the highest plasma lipids and T3 levels observed in steatitis-affected females during spring and summer. Positive correlations were observed between plasma lipids (especially cholesterol) and T3 concentrations in fish from both populations, indicating a link between lipid metabolism and thyroid function. There was no direct evidence of thyroid disruption, but this cannot be ruled out until further research determines the factors that underlie the homeostatic shift leading to elevated plasma and liver lipids and T3 levels in steatitis-affected tilapia.


KEY WORDS: Thyroid follicle · Pansteatitis · Obesity · Yellow fat disease · Olifants River · Loskop


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Cite this article as: Dabrowski J, Oberholster P, Steyl J, Osthoff G, Hugo A, Power DM, van Wyk JH (2017) Thyroid function of steatitis-affected Mozambique tilapia Oreochromis mossambicus from a sub-tropical African reservoir. Dis Aquat Org 125:101-113. https://doi.org/10.3354/dao03138

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