Abstract
BackgroundIn an effort to characterize the fat body and other adipose tissue in the Nile crocodile and the effects of pansteatitis on the structure and composition of the adipose tissue, we evaluated the regional variation in structure and fatty acid composition of healthy farmed crocodiles and those affected by pansteatitis.MethodsAdipose tissue samples were collected from the subcutaneous, visceral and intramuscular fat and the abdominal fat body of ten 4-year old juvenile crocodiles from Izinthaba Crocodile Farm, Pretoria, South Africa while pansteatitis samples were collected from visceral and intramuscular fat of crocodiles that had died of pansteatitis at the Olifant River, Mpumalanga, also in South Africa. Histomorphology, ultrastrustucture and fatty acid composition by fatty acid methyl ester (FAME) analysis were conducted.ResultsHistological examination showed regional variations in the adipose tissue especially in the collagen content of the ECM, tissue perfusion and division into lobes and lobules by fibrous capsule. Considerable fibrosis, mononuclear cell infiltration especially by macrophages and lymphocytes and toxic changes in the nucleus were observed in the pansteatitis samples.Regional variation in lipid composition especially in Myristoleic (C14:1), Erucic acid (C22:1n9), and Docosadienoic acid (C22:2n6) was observed. Most of the saturated and trans fatty acids were found in significant quantities in the pansteatitis samples, but had very low levels of the cis fatty acid and the essential fatty acids with C18 backbone.ConclusionThis study demonstrates that there exists some regional variation in histomorphology and fatty acid composition in the healthy adipose tissue of the Nile crocodile. It also showed that pansteatitis in the Nile crocodile might have been triggered by sudden change in energy balance from consumption of dead fish; and probable exposure to toxic environmental conditions with the evidence of up scaled monounsaturated long chain fatty acids composition and toxic changes in the leucocytes observed in pansteatitis in the present study.
Highlights
In an effort to characterize the fat body and other adipose tissue in the Nile crocodile and the effects of pansteatitis on the structure and composition of the adipose tissue, we evaluated the regional variation in structure and fatty acid composition of healthy farmed crocodiles and those affected by pansteatitis
In a further study on the probable direct impact of environmental pollution and heavy metals from acid mine drainage (AMD) waters which seeps into Olifants River from Blesboak stream at a pH of 2.1 on the pathogenesis of pansteatitis, Oberholster et al [27] reported an association between accumulation of heavy metals especially aluminium and iron and development of yellow fats in Oreochromis mossambicus (Tilapia fish) and bioaccumulation of Al and Fe in filamentous algae, Spirogyra fluviatilis and S. adanata that are often consumed by the fish
Visceral adipose tissue The adipose from this region including the omental and mesenteric fat is bounded by a thick fibrous connective tissue capsule that is made up of collagen and fibroblasts, which tends to extend deep into the parenchyma to divide the tissue into lobes (Fig. 1a)
Summary
In an effort to characterize the fat body and other adipose tissue in the Nile crocodile and the effects of pansteatitis on the structure and composition of the adipose tissue, we evaluated the regional variation in structure and fatty acid composition of healthy farmed crocodiles and those affected by pansteatitis. In a further study on the probable direct impact of environmental pollution and heavy metals from AMD waters which seeps into Olifants River from Blesboak stream at a pH of 2.1 on the pathogenesis of pansteatitis, Oberholster et al [27] reported an association between accumulation of heavy metals especially aluminium and iron and development of yellow fats in Oreochromis mossambicus (Tilapia fish) and bioaccumulation of Al and Fe in filamentous algae, Spirogyra fluviatilis and S. adanata that are often consumed by the fish They suggested that the yellowness of the fat in O. mossambicus might be as a result of membrane lipid peroxidation by the pro-oxidant action of aluminium as previously suggested by Yoshino et al [36]
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