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INTRODUCTION
Crocodiles – why do humans have an interest in these reptiles? First of all, they are man-eaters! These charismatic cold-blooded animals have been called giant lizards, and described as living fossils from dinosaur-time (Grigg and Kirshner, 2015). Expanding populations of both humans and crocodilians may lead to the invasion of each others’ territories, resulting in human-crocodile conflict (Caldicott et al., 2005; Wallace et al., 2011). In addition, economic interest in crocodilian skins and meat has promoted the establishment of numerous commercial crocodile farms in southern Africa, focusing on raising large numbers of crocodiles (Davis, 2001; Blessing, 2014).
The group, Archosaurs (meaning “ruling reptiles”), has traditionally been regarded as a subclass of the class Reptilia, the taxonomic status of which required revision during recent decades (Benton, 1982). Together with the extinct theocodants (includes phytosaurs), dinosaurs and pterosaurs (flying reptiles, ancestors of birds), crocodilians belong to the great group of archosaurs. The phytosaurs, believed to have preyed upon Triassic crocodilians, died out at the end of the Triassic (195 million years ago). Crocodilian fossils started appearing ±200 million years ago, in the Upper Triassic, a time when turtles, lizards and dinosaurs (another important group of reptiles) came into prominence (Bellairs, 1987).
The Triassic crocodilians were primitive reptiles and belong to the order Protocuchia, consisting of Protosuchus (Colbert and Mook, 1951), Orthosuchus (Nash, 1975) and Lesothosuchus (Whetstone and Whybrow, 1983). The Protocuchia were true crocodilian descendants and differed in many ways from modern forms, superficially lizard-like creatures less than one meter in length, presenting with heavy armour of bony plates, a broad head with a rather short, narrow snout and fairly long legs. The hind legs were longer than the front legs, as in modern crocodiles. The long bony palate which separates the mouth from the nose is a very characteristic crocodilian adaptation to amphibious life (Bellairs, 1987). In Orthosuchus, the bony palate was quite short, but Nash (1975) believes that it was functionally completed by soft tissue, indicating that the animal may have been partially aquatic.
Some 230 to 65 million years ago, during the Mesozoic period, adaptive radiation of the crocodilians involved diversity in habits and snout form, presuming specialisation in catching fish by the slender-snouted types (Bellairs, 1987). The sub-order Mesosuchia, appearing in the Jurassic (195 to 140 million years ago), showed quite extensive bony palates, with internal nostrils “pushed” towards the posterior parts of the skull. Gharial-like teleosaurs and metriorhynchids (a truly marine group which had evolved paddle-like limbs and finned tails) were among the mesosuchians. In the late Jurassic, a generalized “mainstream” group, the goniopholids, and the little broad-snouted atoposaurs (average length of fourty centimetres; may have been terrestrial) appeared (Bellairs, 1987).
CHAPTER 1: INTRODUCTION
CHAPTER 2: AIM AND OBJECTIVES
2.1. Aim
2.2. Objectives
CHAPTER 3: LITERATURE REVIEW
3.1. Urine sample analysis for diagnostic tools
3.1.1. Introduction
3.1.2. Laboratory analysis of urine
3.1.3. Specific laboratory analyses
3.1.4. Routine testing of urine samples in veterinary medicine
3.2. Urine from crocodilians
3.3. Crocodilian blood parameters
CHAPTER 4: JUSTIFICATION
CHAPTER 5: Nile crocodile (Crocodylus niloticus) urine and plasma biochemistry investigation
5.1. Introduction
5.2. Materials and methods
5.3. Results
5.4. Discussion
5.5. Conclusion
5.6. Acknowledgements
5.7. Proposed publication from this chapter
CHAPTER 6: Clinical validation of the analysis of steroids and steroid metabolites in Nile crocodile urine
CHAPTER 7: Steroid profiling of crocodilian urine
8. CHAPTER 8: Adrenocorticotropic hormone study in Nile crocodiles
9. CHAPTER 9: General discussion and conclusions
CHAPTER 10: References
