The Cardiovascular Control of Heat Exchange: Consequences of Body Size

For blood flow to be an effective agent for the control of heatexchange, it must occur in a region of the body where conductionresistance in the tissues is relatively high, and in an environmentwhere external resistance to heat exchange is relatively low.If either of these conditions is not met, control of heat exchangeby blood flow is not possible. Very small reptiles should notbe able to control heat exchange by blood flow in any environment,unless they control blood flow specifically to appendages. Verylarge reptiles should be able to control heat exchange by bloodflow only under certain conditions, such as in water, very highwinds, or intense radiative heating. Otherwise, they shouldhave little control. An optimum body size should exist for areptile's ability to control heat exchange using blood flow.In air, this optimum body size for alligators appears to beabout 5 kg. Theoretically, the optimum size should be substantiallylarger than 5 kg for reptiles heating and cooling in water.     

Precocene II modifies maternal responsiveness in the burrower bug, Sehirus cinctus (Heteroptera)

Abstract. The anti-Juvenile Hormone agent precocene II was used to investigate the relationship of corpora allata activity to subsocial behaviour in a burrower bug Sehirus cinctus Palisot (Heteroptera: Cydnidae). Egg-brooding females treated with a range of dosages of precocene II exhibited reliably depressed maternal defensive behaviour when treated with at least 70 μg of precocene II, but attraction to eggs was only depressed at higher dosages. This effect was not due to precocene II toxicity, as demonstrated by the prevention of depression effects through simultaneous treatments of precocene II and the Juvenile Hormone analogue methoprene. Methoprene, however, failed to reinstate maternal responsiveness in maternally depressed females that had been previously treated with precocene II. This study provides the first clear evidence that insect parental behaviour can be modified by treatment with anti-Juvenile Hormone agents, and suggests that the role of the corpora allata in governing care in S. cinctus is different from that of other maternal insects, such as earwigs.     

Naegleria lovaniensis tarasca New Subspecies, and the Purepecha Strain, a Morphological Variant of N. I. lovaniensis, Isolated from Natural Thermal Waters in Mexico

Amoebae were isolated from a natural thermal water source in Michoacaan, Mexico, in September 1986. Two 500-ml samples were taken from pools with water at 45°C and 46°C and concentrated at 2,000 g for 15 min. The sediment was seeded on nonnutritive agar plates and incubated at 42°C. The isolates were axenized in bactocasitone-serum medium. The identification of the isolates was based on their morphology, total protein and isoenzyme patterns by agarose isoelectric focusing, serology, fine structure, agglutination with Concanavalin A, sensitivity to trimethoprim, capacity to kill mice, and their cytopathic effect in Vero cells. The results showed several morphophysiological, biochemical and serological differences between the isolates and the type strain Aq/9/1/ 45D of Naegleria lovaniensis. These remarkable differences provide sufficient evidence to consider one of the isolates a new subspecies, and the other one a morphological variant of N. l. lovaniensis, which can be differentiated from other Naegleriae by their morphology, biochemistry, serology and physiology. The authors propose the name tarasca for the subspecies and purepecha for the morphological variant.     

Lion density and population structure in the Selous Game Reserve: evaluation of hunting quotas and offtake

In 1992, tourist hunting in the Selous Game Reserve generated 1.28 million dollars for the Tanzanian government, of which 0·96 million dollars were returned to wildlife conservation. Lions ( Panthera leo ) are one of three critical species for tourist hunting, consistently generating 12%–13% of hunting revenue from 1988 to 1992. Because of their ecological and economic importance (and intrinsic value), it is important that lion quotas be set so that offtake is sustainable. The population density of lions in Selous ranges from 0·08 to 0·13 adults km⁻², comparable to unhunted ecosystems. The adult sex ratio (36–41% male) and the ratio of cubs to adults (29% cubs) are similar to those of unhunted populations. The ratio of lions to hyaenas is lower in heavily hunted areas (0·17 lions/hyena) than in unhunted areas (0·43 lions/hyena). Hunting levels between 1989 and 1994 took 2·7–4·3% of adult males annually, which is sustainable. The current quota is 10–16% of the adult male population, which exceeds natural mortality rates for male lions. To remain stable if the quota was filled, the population would have to compensate via increased fecundity, increased juvenile survival, or an altered sex‐ratio. Compensation occurs in Selous by producing (or raising) more male than female cubs (66–81% of juveniles are male). Only 28% of the Selous quota was filled in 1992. The percentage of quota filled (both in Selous and nationwide) has dropped since 1988 as quotas have increased. The current intensity of lion hunting in Selous is sustainable, but the quota cannot be filled sustainably.