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Thesis (MSc) -- Stellenbosch University, 2004. / ENGLISH ABSTRACT: Standard histological procedures revealed that there are two types of glands in the cloacal complex of the viviparous Cordylus cataphractus. These occur in the urodeal region of the complex (called urodeal glands), and in the posterior proctodeum region (called proctodeal glands). Urodeal glands are found in females only and differentiate at sexual maturity. Proctodeal glands occur in both sexes and the dorsal and ventral proctodeal glands are identical in structure. Seasonal activity in cloacal gland structure and secretory was studied. Urodeal glands show distinct seasonal variation in development and secretory activity, they become enlarged in vitellogenic females, remain active during pregnancy, with glandular activity peaking around parturition. Proctodeal glands, in contrast, show little or no seasonal variation in development or secretory activity in both sexes. Secretion quantity, however, is highly variable among individuals of the same sex, time of year, as well as reproductive stage, but evidently much less in females than in males. Although the possible functions of the cloacal glands are still unclear, two main functions are suggested: a) mechanical function such as lubrication or a substrate for genital products and b) pheromonal communication. I propose that urodeal glands are involved in some reproductive function rather than in social communication, because very little secretion is found during the mating season and peak glandular activity are evident around parturition. The opposite may be true for proctodeal glands, but further investigation is needed, particularly chemical analysis of secretion and behavioural manipulation, to determine the role of these glands in social communication. / AFRIKAANSE OPSOMMING: Standaard histologiese tegnieke dui aan dat daar twee tipes kliere voorkom in die kloakale kompleks van die lewendbarende akkedis, Cordylus cataphractus. Die een kliertipe word in die urodeale omgewing aangetref en staan bekend as die urodeaalkliere, terwyl die ander groep in die posterior area van die proktodeum voorkom en proktodeaalkliere heet. Urodeaalkliere word slegs in wyfies aangetref en ontwikkel eers na volwassenheid bereik is. Proktodeaalkliere kom in albei geslagte voor en dorsale en ventrale aspekte van hierdie kliere is identies aan mekaar. Die seisoenale aktiwiteit in struktuur en sekresie-aktiwiteit van hierdie kloakale kliere is ondersoek in mannetjies en wyfies wat gedurende verskillende maande van die jaar versamel is en dus in verskillende voorplantingstadia was. Urodeaalkliere het duidelike seisoenale variasie vertoon wat beide ontwikkeling van die klier en sekretoriese aktiwiteite betref. Die klier vergroot tydens vitellogenese, bly aktief tydens swangerskap en bereik maksimale aktiwiteitsvlakke rondom geboorte. In teenstelling hiermee het die proktodeaalkiere van beide geslagte weinig of self geen seisonale variasie in hul ontwikkeling of sekretoriese aktiwiteit getoon nie. Die hoeveelheid sekreet vrygestel was merkbaar minder in wyfies as in mannetjies, maar hoogs veranderlik tussen individue van dieselfde geslag of voortplantingstadium; of wat in dieselfde tydperk van die jaar versamel is. Alhoewel funksies van kloakale kliere steeds onduidelik bly, word twee hooffunksies voorgestel: a) ‘n meganiese funksie, byvoorbeeld as smeermiddel of as ‘n substraat vir geslagsprodukte en b) ‘n kommunikasie funksie, byvoorbeeld in die vrystelling van feromone. Ek stel voor dat die urodeaalkliere eerder by ‘n voortplantingsfunksie betrokke is, aangesien baie min sekreet gedurende die paarseisoen vervaardig word terwyl klieraktiwiteit rondom geboorte ‘n piek bereik. Die teenoorgestelde mag geld vir proktodeaalkliere, maar vereis verdere ondersoek. Veral ‘n chemiese analise van die sekresie en gedragsmanipulasie sal nuttig wees om ‘n moontlike rol van hierdie kliere in sosiale kommunikasie te bepaal.

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[Truncated abstract] In ecomorphological or ecophysiological studies, variation in `design? traits (e.g. size, morphology and physiology) is thought to determine variation in ecologically-relevant performance traits, which in turn determines fitness in a particular habitat (Arnold 1983). Thus, natural selection is thought to act most directly on intermediate traits such as measures of locomotory performance. This thesis examined this process in the closely related group of Australian varanids lizards (Squamata: Varanidae). Phylogenetically, varanids are divided into three major clades. Size (mass and snout-to-vent length) is strongly correlated with these three clades. Two clades, (Gouldii and Komodoensis) are large, while the third clade (Odatria) has a smaller body size. Thus, there is considerable variation in size for various species. Size varied for species by three orders of magnitude. Size is also related to two ecological characteristics, foraging mode and habitat openness. Widely-foraging species were larger than sit-and-wait strategists, while species from open habitats were larger than species from semi-open or closed habitats. However, given the tight link between size and phylogeny we cannot separate adaptation of size to ecological traits from that of phylogenetic patterns. Of interest throughout this thesis was how variations in design (e.g. morphology and physiology) were related to ecological characteristics. Since body size also influences many of these morphological and physiological characteristics it is often necessary to remove the effects of size. Three design traits were examined in detail: body dimensions, vertebral number and metabolic rates. …Curiously, no performance variable linked differences in size-free body dimensions to retreat sites. This suggests that there is either a direct link between design and ecology (e.g. dorso-ventral compression), or some unmeasured performance variable related to retreat site. Given that most performance traits are thought to involve kinematic movements of the hindlimb limb and pelvis, and these were not best related to retreat site, then a direct link between design and ecology with respect to retreat site seems possible. In summary, this thesis provides evidence not only for links between design and ecology mediated by locomotory performance traits, but also direct links between design and ecology, for Australian varanid lizards.

The effect of total metabolic cost expenditures on the precision of behavioral thermoregulation was investigated for the purportedly eurythermic Northern Alligator lizard (Gerrhonotus coeruleus). An operant apparatus was designed to test metabolic output at different heat reinforcement magnitudes. The mean TB reflected in each trial was positively correlated to the length of reinforcement. The shuttle rate during each trial was inversely correlated to the length of reinforcement. The standard deviation and total metabolic costs did not vary significantly between trials undertaken at the same ambient temperature. Eurythermality in G. coeruleus is caused by fluctuations in preferred body temperature and not by fluctuations around this temperature. The metabolic cost of behavioral thermoregulation did not change with corresponding changes in reinforcement magnitude. This indicates that eurythermality is the recorded effect of lizards behaviorally regulating to different TB in a stenothermic manner, rather than of random TB fluctuations in a wide range of normal activity (the classical view of eurythermality).

Reptiles are polyphyletic, and previous studies of renal anatomy and physiology in reptiles have covered a wide diversity of species of different phylogeny and habitat. To date, no study has examined the renal morphology and function of a group of closely related reptiles from different environments, yet this design has a number of advantages. Firstly, phylogenetic effects are reduced while adaptive specialisations in renal function or structure can be elucidated, and secondly, the variation in renal form and function between closely related species may be quantified in an effort to appreciate better the variation between more distantly related species. In this thesis, kidney morphology and renal function were studied in three Western Australian agamid lizards inhabiting environments differing in the availability of water. These key species were Pogona minor, Ctenophorus nuchalis and Ctenophorus salinarum. The renal anatomy of the three key lizards was characterised by determining glomerular diameter, volume density, surface area and number in each. Allometric relationships between kidney, colon and body mass were investigated in these and an additional 11 species of agamid lizard. Patterns of response to osmotic challenge were recorded by measuring renal variables such as urine flow rate, glomerular filtration rate and fractional reabsorption of filtrate among the three key species, and concurrent measurements of circulating arginine vasotocin in P. minor and C. nuchalis allowed the response of this hormone to homeostatic imbalance in these species to be gauged. The gross morphology and the glomerular characteristics of the kidneys was remarkably similar between species. Glomerular number and other characters varied as a function of body size rather than species, contrasting with reports in the literature suggesting that a given species has a particular number of glomeruli. ... Thus, kidney morphology is constrained among species and the response of each species to osmotic perturbation is similar. However, the mechanisms underlying antidiuresis and the hormonal control of this process differ subtly between species, and there is some evidence to suggest that P. minor is more adapted to a mesic environment than the other two lizards examined in this study. The hypothesis that renal form and function reflect the environment in which a lizard lives therefore receives partial support, although the reptilian bauplan is able to mitigate many of the forces that could potentially lead to renal specialisation.