Mise en evidence d'une reponse humorale antibacterienne chez T. t., semblable a celle observable chez les insectes. Parmi les proteines produites, seule une d'entre elles possede une activite bactericide

The lizard Angolosaurus skoogi inhabits the surface and subsurface environments of sand dunes of the northern Namib Desert. We have related posture, locomotion, and other aspects of surface activity to the microclimate prevailing above and below the surface. Globe temperature was the best microclimatic correlate of surface activity. From our analysis, we concluded that surface thermoregulatory behaviour of A. skoogi is facultative, and aimed at maintaining a body temperature compatible with foraging and other obligatory surface activities.

The Namib Desert beetle, Onymacris plana developed a behavioural fever when given injection of highly purified lipopolysaccharide isolated from E. coli. The beetles sought a higher preferred temperature in a thermal gradient after injection of the pyrogen than they had previously chosen. The elevation of thermal preference was observed within 1 h after injection and remained elevated for at least 12 h. The peak amplitude was 1.5°C, about 5 h after injection of lipopolysaccharide doses of around 250 mg. kg−1. This is the second report of febrogenesis in an insect and the first using a highly purified lipopolysaccharide pyrogen.

Flower scarabs can warm up endothermically from 20 C to flight temperatures near 36 C in 3 min. Despite their impressive capacity for endothermy, however, foraging beetles stop heat production immediately on landing on a flower. In addition, they seek shade within seconds of landing and allow body temperatures to follow ambient thermal conditions. Foraging beetles spend at least 98% of their time perched and feed slowly. In the laboratory, beetles that are handled or otherwise disturbed warm up repeatedly by endothermic shivering, but in the field undisturbed beetles generally warm up to fly to another flower only when they have the opportunity to warm up by basking. Unlike other large strong-flying insects so far examined, these beetles do not regulate (stabilize) their thoracic temperature in flight, and they restrict flight to a narrow range of ambient temperature. We speculate that their lack of maintenance of an elevated body temperature ("hypothermia") when not in flight and their seemingly lackadaisical foraging is related to low foraging competition leading to a minimization of energy expenditure.

Lipopolysaccharides (LPS) from Gram-negative bacteria are potent pyrogens in mammals. Polymyxin B (PB), a cationic polypeptide antibiotic, binds lipid A, the active moiety of LPS, with high affinity and abrogates several biological responses to LPS. We studied the effect of PB on pyrogenicity of purified LPS from E. coli 0111:B4 in rabbits. PB reduced the pyrogenic response to LPS in a dose-dependent manner at mass ratios (PB:LPS) from 5:1 to 100:1. Previous reports have suggested that PB is effective only at much higher doses. In our hands, PB itself is pyrogenic, unless previously gamma-irradiated. Our results confirm in vivo the anti-endotoxic action of PB.

Twenty—six species of adult Namib tenebrionid beetles belonging to the tribes Adesmiini and Zophosini have an extracuticular wax bloom covering either part or all of their body surface. These species occur in the dunes, dry river bed, and adjacent gravel plains of the central Namib. The percentage of species possessing a wax bloom increases from the coastal fog desert to the inland hot dry desert. The amount of bloom and its distribution over the integument also increase in a similar manner along the climatic gradient. Despite considerable diversity in coloration and patterns of the wax blooms, the chemical composition of the lipid components showed little variation. Hydrocarbons were the predominant lipid class, with the size of constituent molecules ranging from 19 to 40 carbon atoms. In all species tested, n—alkanes were more abundant than branches alkanes. Odd—numbered carbon chains (e.g., C27, C29, C31) comprised the bulk of the hydrocarbon fractions. The possible functional roles of these blooms in water balance, thermoregulation, predator avoidance, and chemical communication are discussed.

The dynamics of the extracuticular was bloom in a ‘winter’ species of tenebrionid beetle, Cauricara phalangium, from the Namib Desert were monitored in the field and under laboratory conditions. The beetles possessed a full complement of the white wax material after adult emergence. The amount of this material on the integument declined towards the end of the season. The wax bloom was regenerated in both the field and laboratory, with high temperatures and low humidities bringing about greatest renewal. End of the season decline appears tobe related to the senescence of these seasonal beetles. Water loss rates differed significantly for individuals collected in May, when fully bloomed, and in August when little or no wax bloom was present. The wax bloom material contributes to the protection of these diurnal beetles against the high temperatures and radiant heat loads in the Namib Desert.