FACTORS AFFECTING PREY CHOICE AND FEEDING TECHNIQUE IN THE CARNIVOROUS SNAIL EUGLANDINA ROSEA FERUSSAC

Euglandina feeds on other gastropods either by quickly suckingthe contents from the shell, or by swallowing the prey whole,which can be more time consuming. When Euglandina were offeredprey species of various sizes, they preferentially consumedthe smaller individuals, and often swallowed these whole. Handlingtime increased with decreasing density since swallowing preywhole became more frequent at the lower densities. The relationship between prey size, predator size, handlingtime and feeding technique was examined. For the two feedingtechniques observed, handling time increased exponentially withthe size of the prey and decreased exponentially with the sizeof the predator. Predators of intermediate size tended to swallowprey whole more frequently than did the smallest and largest. These data are interpreted in terms of the animal behaving insuch a way as to balance its rate of intake of both organicmatter, which resides mainly in the soft parts, and of calcium,which resides mainly in the shell. (Received 11 July 1988; accepted 31 October 1988)     

Heterosis in Cepaea

A test has been made of the association of heterozygosity with shell breadth in the polymorphic snail Cepaea nemoralis. The material was collected by C. B. Goodhart from a series of paired sites at which individuals reached different adult breadths. Dominant phenotypes, in which a large fraction was heterozygous, had a greater breadth and lower variance than recessive phenotypes regardless of whether the measurement was of shell ground colour, banding or the double recessive vs. the rest. Most of the difference was contributed by samples from the habitat where animals reached the largest size. The result is consistent with existence of heterotic sections of chromosome that include the colour and banding loci, and may help to explain the persistence of the polymorphism.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 90 , 49–53.     

The Obsolete "Anti-Market" Mentality: A Critique of the Substantive Approach to Economic Anthropology

"Analytic work begins with material provided by our vision of things, and this vision is ideological almost by definition. It embodies the picture of things as we see them, and wherever there is any possible motive for wishing to see them in a given rather than another light, the way in which we see things can hardly be distinguished from the nay in which we wish to see them. The more honest and naive our vision is, the more dangerous it is to the eventual emergence of anything for which general validity can be claimed. The inference for the social sciences is obvious, antl it is not even true that he who hates a social system will form an objectively more correct vision of it than he who loves it. For love distorts indeed, but hate distorts still more."     

The fate of nutrients during fires in a tropical savanna

Abstract The nutrient loads contained in the grassy fuel before fires, and of ash subsequently, were compared to determine the fluxes of macronutrients, copper and zinc during fires at Kapalga in Kakadu National Park. The fluxes were estimated in three vegetation types: forest, woodland and open woodland. The magnitudes of the fluxes were greatest in the forest community where grassy fuel loads were highest at about 6.3 t ha^?1. In these sites, 54–94% of all measured nutrients in the fuel were transferred to the atmosphere during the fires. For each nutrient, the proportion transferred to the atmosphere as entrained ash was calculated by assuming that calcium was not volatilized during the fires. If the transfer of entrained ash represents local redistribution only, then rainfall accession and the deposition of these particu-lates should replace most of the losses of all nutrients except nitrogen (N). Estimated rates of biological fixation of N appear to be insufficient to replace the annual losses of N. It is therefore concluded that a regime of annual fires that completely burn the available grassy fuel would deplete N reserves in these savannas, unless there are other sources of biologically fixed N, which are unknown at present.     

Nickel and Cadmium-related Changes in Growth, Plasma Membrane Lipid Composition, ATPase Hydrolytic Activity and Proton-pumping of Rice (Oryza sativa L. cv. Bahia) Shoots

Six-day-old rice plants (Oryza sativa L. cv. Bahia) were grownin the presence of 0.5 mol m^–3 Ni or Cd for 5 or 10 d.Five days after treatment, some plants were transferred to amedium containing no heavy metal for 5 or 10 d. Plasmalemmavesicles from shoots of treated, transferred (recovery experiments)and control plants were isolated, ATPase activity and proton-pumpingwere assessed, and free sterols and phospholipids determined.The ATPase hydrolytic activity was increased by 37% and 34%in 5 and 10 d Cd-treated plants, respectively; and by 66% in5 and 10 d Ni-treated plants. However, neither the initial rateof H⁺ transport nor the proton-pumping rate at steady-statewere significantly affected by the treatments. The relativeproportion (%) of the plasmalemma sterols campesterol and ⁵-avenasteroldecreased while sitosterol increased during heavy metal treatment.The overall plasmalemma phospholipid fatty acyl chain lengthand degree of unsaturation were also reduced. In experimentswhere plants recovered from Cd and Ni treatment, differencesbetween treated and control plants were reverted, particularlyin 10 d Ni-recovered plants. The possible involvement of lipidsin the regulation of the plasmalemma ATPase as well as the relationshipbetween growth, ATPase and adaptations to stress conditionsare discussed. Key words: Cadmium, nickel, sterols, phospholipids, ATPase