The evolution of developmental strategy in marine invertebrates

Developmental mode varies widely in most animal phyla. These differences in developmental strategy exert a profound influence on the ecology and evolution of closely related species. The mechanistic alterations in ontogeny that lead to switches in developmental mode are coming under increasing scrutiny. Echinoids are one of the best-understood groups in this regard. Parallel modifications in direct-developing echinoids point to some of the key changes in oogenesis and embryogenesis that produce switches in developmental mode.     

Theories of sexual selection

Recent research on sexual selection in animals has begun to indicate that 'handicaps' and 'honest signalling' may play more important roles than hitherto thought. This review reappraises theories of sexual selection in the light of these new developments.     

The use of natural bacterial populations for the treatment of sulphur-containing wastewater

Pollution by inorganic and organic sulphur compounds is increasing and, because of the many environmental hazards associated with these compounds (e.g. toxicity, acidification of rain and freshwater, increase of COD, the greenhouse effect), must be taken seriously. There is a wide variety of sulphur oxidizing bacteria available in nature, and these can be used for the effective control of such pollution. The best way to break the sulphur cycle is to stop it at sulphur which, being insoluble, can be easily recovered (e.g.SO₄ ^2- S^2- S⁰). (Eco)physiological knowledge about the sulphur oxidizing bacteria has proved very useful in the prediction of the performance of sulphur oxidizing communities in actual wastewater treatment systems. Appropriate reactor design, based on this type of study, is essential if such bacterial communities are to function efficiently, especially when toxic sulphides must be treated. This paper reviews the natural and anthropogenic sources of sulphur pollution, its consequences and possible solutions.     

Prospective theoretical and experimental study towards electrochemically grafted poly(N-vinyl-2-pyrrolidone) films on metallic surfaces

Quantum chemistry calculations of equilibrium geometry, atomic charges, dipole moment, and frontier orbital energies are carried out on model N-vinyl-2-pyrrolidone, its radical anion and cation, and three protonated derivatives. Attempts to obtain poly(N-vinyl-2-pyrrolidone) films grafted on nickel and platinum electrodes, respectively by cathodic and anodic polarizations, are reported. A thin, covering and insulating film is obtained on the Pt anode, as indicated by surface characterizations carried out with UPS and IRRAS spectroscopies. The fact that the film remains adherent to the metallic surface in spite of a permanent contact with an acetonitrile solution in which poly(N-vinyl-2-pyrrolidone) is soluble suggests that chemisorption has indeed been achieved.     

Identification and sequence of a Na+-linked gene from the marine bacterium Alteromonas haloplanktis which functionally complements the dagA gene of Escherichia coli

A 4.0 kb fragment from a plasmid genomic DNA library of the marine bacterium Alteromonas haloplanktis ATCC 19855 was found in the presence of Na+ to complement the dagA gene of Escherichia coli. We have completely sequenced this fragment and the position of the Na(+)-linked D-alanine glycine permease gene (dagA) on the fragment has been determined by complementation. The predicted carrier protein consists of 542 amino acid residues (M(r) 58,955). Its hydropathy profile suggests it is composed of eight transmembrane segments with a long hydrophilic region between segments six and seven. Significant similarity has been found between this Na(+)-linked permease and the Na+/proline permeases of E. coli and Salmonella typhimurium and the human and rabbit intestinal Na+/glucose cotransporters.     

Spatial organization and monogamy in the mara Dolichotis patagonum

Maras, Dolichotis patagonum , were observed and radio-tracked in Argentina. They travelled as monogamous pairs that bred either alone at solitary burrows or communally at settlements where up to 29 pairs shared warrens.
Members of a mara settlement grazed within 2.5 km of the communal warrens, using intensively about 1 ha per day, within drifting daily ranges of 11 ha, seasonal ranges of 98 ha and annual ranges of 193 ha.
Their home ranges drifted continuously. Consequently, the long-term movements of neighbouring pairs overlapped substantially, but at any given moment they were territorially spaced.
Monogamous, drifting territoriality is explained by the patchy dispersion of food, the need to minimize interference competition, and a cycle of grazing and fallowing in the use of food plants.
Two hypotheses explaining the adaptive significance of settlements are evaluated: one relates to resource availability (through the indirect effect of ground water and sheep dung on vegetation); and the other relates to predation (through the protective influence of human dwellings). The size of sheep flocks grazing at outstations during January provide a measure of the resource richness of patches where maras graze, and the richness of these patches in the dry season appear to limit the number of maras breeding at each settlement during the following wet season.
Maras face extremes of resource dispersion between the wet and dry seasons: in the former, sparsely dispersed grazing and interference competition favour spacing out and territoriality; in the latter, clumping of resources facilitates pairs congregating in herds around outstations and dry lagoons. Superimposed upon the ecological factors favouring spacing out during the wet season are the sociological factors that cause the maras to den communally. The resulting compromise is a social system unique among mammals.