Amphetamine Response in Rat after Dopamine Neurone Destruction

AMPHETAMINE increases spontaneous locomotor activity and induces stereotyped motor responses in rats. The magnitude of these two behavioural responses varies according to the dose and which optical isomer of the drug is used^1,2. Amphetamine is known to influence the uptake and release of catecholamines in the brain both in vitro³ and in vivo^4,5 and the finding that inhibition of catecholamine synthesis by α methyl-p-tyrosine abolishes the behavioural effect of the drug^6,7 suggests that a release of catecholamines may mediate these effects. The amine transmitters noradrenaline (NA) and dopamine (DA) are localized in different anatomical systems in the brain^8,9 and attempts have been made to correlate the specific behavioural effects of amphetamine with one or other of these aminergic systems. Taylor and Snyder, on the basis of comparisons of the potency of d- and l-amphetamine in behavioural and biochemical tests, suggested that a release of NA mediates the locomotor activity and DA the stereotypy responses. We have attempted to pursue these hypotheses with lesions to aminergic pathways.     

The effect of water colour on lake hydrodynamics: a modelling study

1. The one‐dimensional equation solver, PROgram for Boundary layers in the Environment, was used to simulate the temperature structure of Lake Erken, a medium‐sized Swedish lake, assuming differing extinction coefficients for a series of modelled years driven by observed meteorological data and by a set of idealized meteorological data. 2. Results suggested that, as expected, larger extinction coefficients initially led to surface waters becoming warmer. The reverse was true late in the summer, however, as the warming induced by greater absorption of solar radiation was outweighed by the cooling effects of entrained colder hypolimnetic water. 3. There was between a two‐ and fourfold inter‐annual variation in the effects on key physical lake parameters, induced by changing extinction coefficient, such as maximum heat flux, heat content and Schmidt stability. 4. The change in surface heat flux induced by a change in extinction coefficient was up to almost 50 W m⁻². 5. In the summer, changes in extinction coefficient from 0.5 to 0.2 m⁻¹ led to a dramatic shift in the duration of the stratified period as well as to enormous changes in Schmidt stability and hypolimnetic temperature. 6. Future changes to extinction coefficients of small and medium‐sized lakes are likely to have wide‐ranging effects on lake thermal structure and ecology.     

COMMUNAL ACTIVITIES AMONG WHITE-WINGED CHOUGHS CORCORAX MELANORHAMPHUS

White-winged Choughs Corcorax melanorhamphus live in groups of 2–20 birds that nest communally. Most of the study population (82%) was composed of groups of 4–8 individuals. The oldest male in each group appears to perform a ‘linchpin’ role in group cohesion, and groups tend to disintegrate if he dies or leaves. Polygyny is shown to occur, and it is thought that some 15% of clutches are due to two females laying in the same nest. Progeny tend to stay in their natal group rather than dispersing. They help to rear subsequent offspring. All group members may help to build the nest and to incubate, brood, guard, clean and feed the young (both in and out of the nest). No correlation was found between group size and the rate of feeding young in the nest. From 186 nesting attempts, the average production was 1–4 birds of which only 16% survived to adulthood (= 4 y. o.). Besides their nesting activities, White-winged Choughs have a form of communal defence; they, also, roost, forage, drink, bathe, dust, and roost together. It is concluded that the association into groups provides the adaptive advantage of a buffer against periodic fluctuations in available food– the youngest (= smallest investment) dying first.     

Life history plasticity of Nemoura trispinosa (Plecoptera: Nemouridae) along a permanent-temporary water habitat gradient

1. The life history of the small herbivorous stonefly Nemoura trispinosa Claassen was studied in a variety of small springs in southern Ontario, Canada. Nymphs generally were able to tolerate a wide range of environmental conditions and were found in 78% of habitats sampled, although population densities differed markedly. 2. Life-cycle patterns varied from a univoltine, slow seasonal type to a univoltine, fast seasonal type with extended egg development. In one, highly stable, spring the life cycle was semivoltine. Inter-year variation was studied for 5 years in one spring and was found to be low relative to among-spring variation. 3. Differences in the life history traits of N. trispinosa populations from our spring series were most probably an expression of phenotypic plasticity rather than of genetic differentiation. 4. Maximum annual water temperature was the factor most influential on nymphal growth rate (non-linear relationship), whereas range in generation time was related to the degree of habitat permanence.     

A new species of Ramazzottius (Tardigrada, Hypsibiidae) in a rain gutter sediment from England

Five species of tardigrades were extracted from a sample of sediment from a rain gutter. Four of these, the heterotardigrade Echiniscus testudo and the eutardigrades Milnesium tardigradum, Ramazzottius oberhaeuseri , and probably Macrobiotus cf. sandrae are typical of xerophilous habitats. The fifth species, Ramazzottius varieornatus sp. nov. , is new to science, and it can be readily distinguished from the others of the same genus by egg shell morphology, placoids and the type of cuticle.     

Measuring the impact of sewage effluent on the macroinvertebrate community of an upland stream: The effect of different levels of taxonomic resolution and quantification

Abstract Benthic macroinvertebrates were sampled from four sites on upland streams in the Wentworth Falls area of the Blue Mountains, NSW. One site received effluent from a sewage treatment plant and the others were reference sites. Five replicate collections were taken from each site on four occasions at intervals of 3 months. Macroinvertebrate community data were analysed using univariate (ANOVA) and multivariate (NMDS) techniques and comparisons were made between analyses at different levels of taxonomic aggregation and using different methods of data transformation. Similar patterns were observed at both species and family levels, and even the order level showed a clear community response to effluent input. Binary (presence/ absence) data provided similar results to quantitative data for the species and family levels. However, when binary data were used at the order level, the distinctions between the reference sites became blurred. We discuss the implications of these findings for environmental monitoring.     

Frequency-dependent food selection by arthropods: a review

We review published studies in which arthropods were presented with a choice of food types at a range of relative densities. Twenty-four of 28 studies showed frequency-independent preference; 11 studies also showed frequency-dependent preference. Both pro- and anti-apostatic selection were found. In the light of these studies we discuss possible behavioural mechanisms which produce such selection; the potential benefits to the predators and the consequences of such selection for diversity both within and between species.