Where ichthyofaunal provinces meet: the fish fauna of the Lake Edward system,East Africa

Based on literature, museum collections and three recent expeditions, an annotated species list of the Lake Edward, East Africa, drainage system is presented, excluding the endemic haplochromines. A total of 34 non-Haplochromis species belonging to 10 families and 21 genera are recorded from the system. Three of these are endemic and two others have been introduced in the region. Six species are new records for the Lake Edward system. A species accumulation curve indicates that we probably covered most of the non-Haplochromis species in the area sampled during the recent expeditions, but undetected species might still be present in the Congolese part of the system, which is poorly sampled. A comparison of the species list with those of neighbouring basins confirmed the placement of the Lake Edward system within the east-coast ichthyofaunal province.     

Social Reinforcement Delays in Free-Flying Honey Bees (Apis mellifera L.)

Free-flying honey bees (Apis mellifera L.) reactions were observed when presented with varying schedules of post-reinforcement delays of 0 s, 300 s, or 600 s. We measured inter-visit-interval, response length, inter-response-time, and response rate. Honey bees exposed to these post-reinforcement delay intervals exhibit one of several patterns compared to groups not encountering delays, and had longer inter-visit-intervals. We observed no group differences in inter-response time. Honey bees with higher response rates tended to not finish the experiment. The removal of the delay intervals increased response rates for those subjects that completed the trials.     

Cyclic GMP-dependent and cyclic AMP-dependent protein kinases,protein kinase modulators and phosphodieterases in arteries and veins of dogs Distribution and effects of arteriovenous fistula and arterial occlusion

Possible involvement of cyclic GMP-dependent and cyclic AMP-dependent protein kinases, protein kinase modulators and cyclic nucleotide phosphodiesterases in functions of vascular tissues were investigated in the dog. All of the above activities, localized in the smooth muscle-rich inner layer of the blood vessels, were found to be higher in the arteries than in the veins. The peripheral arteries were disproportionately richer in cyclic GMP-dependent protein kinase (as indicated by high ratios of cyclic GMP-dependent to cyclic AMP-dependent protein kinase) than were the veins, with the exception of the pulmonary artery, an atypical arterial tissue exposed to low blood pressure. Interestingly, the protein kinase ratio for the aorta, an artery with no significant role in blood pressure regulation, was not higher than that for the vena cava. Creation of femoral arteriovenous fistulae in the dogs led to preferential reductions in the cyclic GMP-dependent enzyme activity both in the proximal and distal arteries, whereas it was elevated in the stressed vein distal to the anastomotic site. The cyclic GMP-dependent enzyme was preferentially reduced in the saphenous artery distal to occlusion. Changes in the cyclic GMP-dependent enzyme activity appeared to precede gross atrophy or hypertrophy of the vessels. It is suggested that the vascular cyclic GMP-dependent protein kinase may be closely related to peripheral resistance and its regulation.     

Evaluating Hypotheses on the Evolution of Helping Behaviour in the Bell Miner (Manorina melanophrys)

In an analysis of the pattern of helping at the nest in bell miners (Manorina melanophrys), Clarke (1989) examined five hypotheses that could explain the evolution of helping behaviour in this species. We applaud the attempt by Clarke to consider many different hypotheses, but believe that more careful formulation of the hypotheses, more appropriate statistical analyses, and eventual experimental testing are required before his conclusions can be accepted.     

Modelling ultraviolet exposures in a school environment.

A technique has been developed to represent erythemally effective ultraviolet radiation exposure within a school environment. The technique models the erythemally effective exposure onto a horizontal plane representation of a mapped school environment located in Hervey Bay (25 degrees S, 153 degrees E), Australia. The input parameters used to model the ultraviolet exposures received within the school playground included the measured sky view, ground albedo and standing surface albedo. Estimates of the erythemally effective ultraviolet exposure received within the school playground during morning tea and lunch time meal breaks during a winter and summer school day are presented. The influence of tree shade and building structure was found to vary significantly with solar zenith angle modelled over the winter and summer school meal break times with horizontal plane exposures predicted to vary from between 0 and 7 SED at different locations within the playground. The technique presented provides a method that can be followed to examine the effect of surrounding buildings and surface structures of real environments on the predicted horizontal plane ultraviolet exposure.     

Leaf water relations and anatomy of a tropical rainforest tree species vary with crown position

Summary Leaf water potentials, osmotic properties and structural characteristics were examined in the Australian tropical rainforest tree species, Castanospermum australe. These features were compared for individuals growing in the understorey and canopy of the undisturbed forest and in an open pasture from which the forest had been cleared. Leaf water potentials during the day declined to significantly lower values in the open-grown and canopy trees than in the understorey trees. During most of the day the opengrown tree experienced the lowest water potentials. These differences were paralleled by significant differences in tissue osmotic properties. The tissue osmotic potential at full hydration was lowest in the open-grown tree (-1.80 MPa), intermediate in the canopy trees (-1.38 MPa), and highest in the understorey trees (-0.80 MPa). As a result, the degree to which high and positive turgor pressures were maintained as water potentials declined was highest in the open-grown tree, intermediate in the canopy trees, and lowest in the understorey trees. The differences in tissue osmotic properties between individuals in the three crown positions were paralleled, in turn, by differences in leaf structual characteristics. Relative to leaves of the canopy and open-grown trees, leaves of the understorey trees had significantly larger epidermal cells with thinner cell walls, larger specific leaf areas and turgid weight: dry weight ratios, and a higher proportion of intercellular air space.Abbreviations ₁ Leaf tissue water potential - _min Lowest value of ₁ during the day ( noon) - _{P=0 1} zero turgor - R Relative water content - P Tissue turgor pressure - Tissue osmotic potential - ₀ at full hydration