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The hypothesis that low skin reflectance (melanism) provides an advantage for thermoregulation under cold conditions has received mixed support in ectothermic vertebrates. We selected a model system, three allopatric closely related species of cordylid lizards that differ in skin reflectance, to test this hypothesis. Cordylus niger and Cordylus oelofseni are melanistic and inhabit peninsular and montane areas, respectively, whereas Cordylus cordylus is more widespread and inhabits low inland areas. By combining theoretical, experimental, and field data on these species, we demonstrate that the difference in body temperature (T(b)) between melanistic and non-melanistic lizards under ecologically relevant climate variation ranged from 0 degrees to 2 degrees C. Despite its small magnitude, however, the faster heating rate and higher T(b) of melanistic species relative to non-melanistic species conferred an advantage under cold conditions. Comparison of habitat thermal quality (d(e)) and thermal accuracy (d(b)) across species indicated that, in winter, melanism conferred the greatest advantage during small windows of thermal opportunity. This finding was most pronounced for C. oelofseni, which is most constrained by cold temperatures in its habitat. By contrast, due to their rock-dwelling habits, melanistic and non-melanistic species benefited from rock refugia in summer, giving similar levels of thermoregulatory effectiveness across species, regardless of skin reflectance. This study therefore demonstrates that skin reflectance variation across cordylids has significant effects on their thermal balance. Furthermore, studies investigating the role of varying skin reflectance in field populations and species should incorporate fine and broad temporal scales (daily, monthly, and seasonal), environmental variability, and cost-benefit trade-offs of thermoregulation.

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Results from this study of the white shark Carcharodon carcharias include measurements obtained using a novel photographic method that reveal significant differences between the sexes in the relationship between tooth cuspidity and shark total length, and a novel ontogenetic change in male tooth shape. Males exhibit broader upper first teeth and increased distal inclination of upper third teeth with increasing length, while females do not present a consistent morphological change. Substantial individual variation, with implications for pace of life syndrome, was present in males and tooth polymorphism was suggested in females. Sexual differences and individual variation may play major roles in ontogenetic changes in tooth morphology in C. carcharias, with potential implications for their foraging biology. Such individual and sexual differences should be included in studies of ontogenetic shift dynamics in other species and systems.

Globally, water resources are under constant threat of being polluted by a diverse range of man-made chemicals, and South Africa is no exception. These contaminants can have detrimental effects on both human and wildlife health. It is increasingly evident that several chemicals may modulate endocrine system pathways in vertebrate species, and these are collectively referred to as endocrine disrupting contaminants (EDCs). Although the endocrine-disrupting effect of water pollutants has been mainly linked to agricultural pesticides and industrial effluents, other pollutants such as pharmaceuticals and personal care products (PPCPs) are largely unnoticed, but also pose a potentially significant threat. Here we present for the first time in a South African context, a summarised list of PPCPs and other EDCs detected to date within South African water systems, as well as their possible endocrine-disrupting effect in-vitro and in-vivo. This review addresses other factors which should be investigated in future studies, including endocrine disruption, PPCP metabolites, environmental toxicology, and antibiotic resistance. The challenges of removing EDCs and other pollutants at South African wastewater treatment works (WWTWs) are also highlighted. The need for focused research involving both in-vitro and in-vivo studies to detect PPCPs in water systems, and to delineate adverse outcome pathways (AOPs) of priority PPCPs to aid in environmental impact assessment (EIA), are discussed.

The epidermal glandular structures in lizards belonging to the family Cordylidae are described. In addition to the large tubulo-follicular holocrine glands in the femoral region, "glandular scales" in the femoral, pre-cloacal, dorsal body and anterior antebrachial regions resembling epidermal "generation" glands are for the first time described histologically. In contrast to generation glands described in other lizards, a sequential buildup of glandular generations occur in these structures. Based on histological features, two types of cordylid generation glands are recognized, depending on whether the sequential buildup of the glandular generations is above ("protruding" type) or below ("pit" type) the stratum germinativum profile of the normal epidermis.

1993. Sexual dimorphism in cordylid lizards: a case study of the Drakensberg crag lizard, Pseudocordylus melanotus. Can. J . Zool. 71: 17 15 -1723. In a high-altitude population of the Drakensberg crag lizard, Pseudocordylus melanotus, most adult males, unlike adult females, are brightly coloured, and they are larger in body size and have relatively larger heads than females. Three basic colour phases can be distinguished among the brightly coloured adult males. No apparent differences in reproductive activity, number and differentiation state of the generation glands and femoral pores, or scar frequency were noted among the three colour phases. In males the development of bright colours and the differentiation of the epidermal glands coincide with the onset of sexual maturity. Sexual dimorphism in head size of adults is due to a decrease in female head size relative to juvenile head size as well as an increase in relative head size of males. Preliminary data indicate a social structure of territorial polygyny in P. melanotus and suggest that the dimorphism can partly be ascribed to sexual selection. There are also, however, indications of altitudinal variation in the expression of sexual dimorphism, which may be explained in terms of differential energy allocation by females at different altitudes. MOUTON, P. LE EN., et VAN WYK, J.H. 1993. Sexual dimorphism in cordylid lizards: a case study of the Drakensberg crag lizard, Pseudocordylus melanotus. Can. J . Zool. 71 : 17 15 -1723. Chez une population de haute altitude du lezard Pseudocordylus melanotus, la plupart des miles adultes, contrairement aux femelles, sont trks colores et ils sont aussi plus gros et ont la ttte relativement plus grosse. I1 existe trois types de coloration chez les miles adultes trks colores, mais il ne semble pas y avoir de differences entre ces trois types quant B l'activite reproductrice, quant au nombre ou au stade de differenciation des glandes genitales ou des pores femoraux, ou quant B la frkquence des cicatrices. Chez les mQles, l'apparition des couleurs vives et la differenciation des glandes Cpidermiques coincide avec l'avknement de la maturite sexuelle. Le dimorphisme sexuel de la taille de la tCte chez les adultes est attribuable B la fois B une reduction de la taille de la tCte chez les femelles comparativement B celle des juveniles et B une augmentation de la taille relative de la tCte chez les miles. D'aprks des donnees preliminaires, il semble que la structure sociale de P. melanotus soit basee sur la polygynie territoriale et que le dimorphisme soit attribuable en partie B la selection sexuelle. Cependant, il existe aussi des indices d'un gradient altitudinal dans l'expression du dimorphisme sexuel qui peut peut-etre s'expliquer par une variation dans la repartition de la depense Cnergetique chez les femelles B differentes altitudes.[Traduit par la redaction]