Does sunlight enhance the effectiveness of avian preening for ectoparasite control?

Preening is a bird's first line of defense against harmful ectoparasites. Ectoparasites, in turn, have evolved adaptations for avoiding preening such as hardened exoskeletons and escape behavior. Earlier work suggests that some groups of ectoparasites, such as feather lice, leave hiding places in feathers that are exposed to direct sunlight, making them more vulnerable to preening. It is, therefore, conceivable that birds may choose to preen in direct sunlight, assuming it improves the effectiveness of preening. Using mourning doves and their feather lice, we tested 2 related hypotheses; (1) that birds with access to direct sunlight preen more often than birds in shade, and (2) that birds with access to direct sunlight are more effective at controlling their ectoparasites than birds in shade. To test these hypotheses, we conducted an experiment in which we manipulated both sunlight and preening ability. Our results provided no support for either hypothesis, i.e., birds given the opportunity to preen in direct sunlight did not preen significantly more often, or more effectively, than did birds in shade. Thus, the efficiency of preening for ectoparasite control appears to be independent of light intensity, at least in the case of mourning doves and their feather lice.     

Acute toxicity effects of ibuprofen on behaviour and haematological parameters of African catfish Clarias gariepinus (Burchell, 1822)

Indiscriminate discharge of pharmaceutical waste into the aquatic ecosystem may pose serious health challenges to aquatic biota. The effect of acute exposure to ibuprofen was evaluated using changes in behaviour and haematological parameters under static bio-assay method in Clarias gariepinus. Test specimens were exposed to acute concentrations of ibuprofen (0.28, 0.33, 0.38, 0.43 and 0.48 mg l^?1) for 24, 48, 72 and 96 h durations respectively. Behavioural and phenotypic changes were observed in surviving fish. There were significant (p < 0.05) concentration and duration-dependent increases in erythrocyte (RBC), haemoglobin (Hb), pack cell volume (PCV) and leukocytes (WBC) in treated fish compared to the control. Insignificant decreases (p > 0.05) in mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC) were observed in treated fish compared to the control. Ibuprofen elicited dose and duration- dependent decrease in neutrophil counts with the decreases being significant (p < 0.05) in the higher doses of 0.43 and 0.48 mg l^?1. Ibuprofen did not elicit any significant changes in monocytes, basophils and eosinophils. Changes observed in this study showed that ibuprofen negatively affected the health of the fish and we recommend that discharge of ibuprofen into the aquatic environment should be monitored and controlled.     

Vegetative reproduction of trees in some European natural forests

Various means of vegetative reproduction in unexploited forests in western Europe are illustrated with examples. Root suckers are sometimes almost the only method of forest regeneration near the limits of tree growth on the Wadden islands and they can play an important role in forest gaps and riverine forests. Trunk suckers finally replacing their parent trees occur in Alnus, Tilia and Ulmus. Partial uprooting of trees, favoured by special soil conditions, was shown to be an important condition for vegetative reproduction. Temporary survival after uprooting gives opportunity for development of reiterative sprouts, that can replace the vertical axis of a fallen tree. Contact of living branches or even whole stems with soil or mouldering logs favours the growth of adventitious roots. Thus vegetatively reproduced individual trees establish before the uprooted parent tree finally dies. Examples of the clonal spreading of trees are given and a special strategy of layering its branches in pasture woods has been described for beech. Modern forestry rigorously eliminates conditions suitable for the vegetative reproduction of forest trees so their abilities in this respect are often underestimated. Vegetative reproduction seems to be particularly important under circumstances where natural growth is difficult e.g. near the limits of tree growth, on dynamic sites and under heavy shade.     

Protoplasmic streaming in the giant unicellular green algaAcetabularia mediterranea

Summary Protoplasmic Streaming inAcetabularia mediteranea has been studied by microcinematography in 1. germinating zygotes, 2. germlings before the differentiation of rhizoids and apices, 3. young cells with rhizoids and apices, 4. vegetative cells-several centimeters in length, 5. cells with a maximum sized cap, containing secondary nuclei, and 6. cells after cyst formation. Intracellular transport is found to occur at a network-system of thin filaments and at a different system of headed streaming bands. At the network of filaments chloroplasts are found to move at a velocity of 1–2 m/sec. Headed streaming bands move along the filaments and may lead without interruption from the rhizoid to the apex of the cell andvice versa. The front zone of the streaming bands is occupied by a leading cytoplasmic head-structure. Small vesicles, polyphosphate granula and secondary nuclei are the predominant moving structures in headed streaming bands. The velocity of these particles is found to be 3–11 m/sec. The filament system is found during all developmental stages. Headed streaming bands are undetectable in germinating zygotes and develop from small cytoplasmic droplets in germlings to broad heavily loaded bands in the huge vegetative cell.Transport of secondary nuclei by headed streaming bands is not observed during mitotic divisions and after cyst formation, though moving bands are still present for several weeks after cyst formation.     

Regeneration from intact and sectioned immature embryos of barley (Hordeum vulgare L.): the scutellum exhibits an apico-basal gradient of embryogenic capacity

Immature zygotic embryos from spring barley cv. Dissa were used to induce somatic embryogenenesis. Up to 158 germinated somatic embryos could be recovered per plated zygotic embryo. Critical factors for obtaining a high yield of regenerants were the size of the explant, the level of 2,4-D used for callus induction and the careful division of callus at each subculture. Use of microsections of immature embryos as explants revealed a pronounced gradient of callus formation and embryogenic response across the scutellum. Sections from the scutellar tissue at the coleoptilar end of the embryo gave the most callus and were highly embryogenic. The regeneration response of sectioned explants was comparable to that recovered from intact embryos of similar size.     

Eutrophication in Australian Rivers, Reservoirs and Estuaries – A Southern Hemisphere Perspective on the Science and its Implications

Australian science has made rapid advances in the last decade in understanding eutrophication processes in inland waters and estuaries. The freshwater research on which these advances are based was triggered by well-publicised blooms of cyanobacteria during the 1980s and early 1990s, particularly a 1000 km long bloom on the Darling River. In estuaries the study which greatly enhanced our understanding but simultaneously served to stimulate further research into estuarine eutrophication, the Port Phillip Bay Study, was initially designed to address perceived problems of toxicants in the Bay but provided profound insights into drivers for, and ecosystem responses to, eutrophication. Subsequent estuarine research has largely been stimulated by management questions arising from Australia’s increasing coastal development for residential purposes. The research has shown that some of the beliefs extant at the time of the blooms were incorrect. For example, it is now clear that stratification and light penetration, not nutrient availability, are the triggers for blooms in the impounded rivers of southeastern Australia, although nutrient exhaustion limits the biomass of blooms. Again, nitrogen seems to play as important a role as phosphorus does in controlling the biomass of these freshwater blooms. The research has also shown that aspects of eutrophication, such as nutrient transport, are dominated by different processes in different parts of Australia. Many of the biophysical processes involved in eutrophication have now been quantified sufficiently for models to be developed of such processes as sediment-nutrient release, stratification, turbidity and algal growth in both freshwater and estuarine systems. In some cases the models are reliable enough for the knowledge gained in particular waterbodies to be applied elsewhere. Thus, there is now a firm scientific foundation for managers to rely upon when managing algal blooms. Whilst these findings have already been presented to managers and communities throughout Australia, there is still a considerable way to go before they are absorbed into their modus operandi.