Nutritional status and diet composition affect the value of diatoms as copepod prey

The role of diatoms as key food for copepods at the base of pelagic food chains has been questioned recently on the grounds of toxicity. We show, using unialgal versus mixed algal diets of different nutritional status (i.e., nitrogen:carbon ratio) fed to Acartia tonsa, that diatoms per se are not toxic but that single-diatom diets are inadequate. Additionally, the nutritional state of the phytoplankton has a profound effect on copepod growth and growth efficiency. The ecological significance of laboratory demonstrations of diatom toxicity needs to be reconsidered.     

Gender and property rights in the commons: Examples of water rights in South Asia

In many countries and resource sectors, the state is devolving responsibility for natural resource management responsibility to ``communities' or local user groups. However, both policymakers and researchers in this area have tended to ignore the implications of gender and other forms of intra-community power differences for the effectiveness and equity of natural resource management. In the irrigation sector, despite the rhetoric on women's participation, a review of evidence from South Asia shows that organizations often exclude women through formal or informal membership rules and practices. Women may have other ways to obtain irrigation services, but even if they are effective, these other informal ways of obtaining irrigation services are typically less secure. As resource management – and rights to resources – are transferred from the state to local organizations, ensuring women's participation is essential for gender equity in control over resources. Greater involvement of women can also strengthen the effectiveness of local organizations by improving women's compliance with rules and maintenance contributions. Further detailed and comparative research is required to identify the major factors that affect women's participation and control over resources, if devolution policies are to be both equitable and sustainable. This revised version was published online in June 2006 with corrections to the Cover Date.     

Host-bacterial mutualism in the human intestine

The distal human intestine represents an anaerobic bioreactor programmed with an enormous population of bacteria, dominated by relatively few divisions that are highly diverse at the strain/subspecies level. This microbiota and its collective genomes (microbiome) provide us with genetic and metabolic attributes we have not been required to evolve on our own, including the ability to harvest otherwise inaccessible nutrients. New studies are revealing how the gut microbiota has coevolved with us and how it manipulates and complements our biology in ways that are mutually beneficial. We are also starting to understand how certain keystone members of the microbiota operate to maintain the stability and functional adaptability of this microbial organ.     

Gendered participation in water management: Issues and illustrations from water users‘ associations in South Asia

The widespread trend to transferirrigation management responsibility from the stateto communities or local user groups has byand large ignored the implications ofintra-community power differences for theeffectiveness and equity of water management. Genderis a recurrent source of such differences. Despitethe rhetoric on womens participation, a review ofevidence from South Asia shows that femaleparticipation is minimal in water usersorganizations. One reason for this is that theformal and informal membership criteria excludewomen. Moreover, the balance between costs andbenefits of participation is often negative forwomen because complying with the rules and practicesof the organization involves considerable time costsand social risks, whereas other ways to obtainirrigation services may be more effective for femalewater users. Although effective, these other andoften informal ways of obtaining irrigation servicesare also typically less secure. More formalparticipation of women can strengthen womensbargaining position as resource users withinhouseholds and communities. Greater involvement ofwomen can also strengthen the effectiveness of theorganization by improving womens compliance withrules and maintenance contributions. Furtherdetailed and comparative research is required toidentify the major factors that affect womensparticipation and control over resources, ifdevolution policies are to address the tensionbetween objectives of transferring control overresources to community institutions, and ensuringthe participation of all members of the community,especially women.     

Differences and similarities in DNA-binding preferences of MyoD and E2A protein complexes revealed by binding site selection

A technique was developed for studying protein-DNA recognition that can be applied to any purified protein, partially purified protein, or cloned gene. From oligonucleotides in which particular positions are of random sequence, that subset to which a given protein binds is amplified by the polymerase chain reaction and sequenced as a pool. These selected and amplified binding site (SAAB) "imprints" provide a characteristic set of preferred sequences for protein binding. With this technique, it was shown that homo- and heterooligomers of the helix-loop-helix proteins MyoD and E2A recognize a common consensus sequence, CA--TG, but otherwise bind to flanking and internal positions with different sequence preferences that suggest half-site recognition. These findings suggest that different combinations of dimeric proteins can have different binding sequence preferences.     

Effects of no‐take area size and age of marine protected areas on fisheries yields: a meta‐analytical approach

Marine protected areas (MPAs) are often promoted as tools for biodiversity conservation as well as for fisheries management. Despite increasing evidence of their usefulness, questions remain regarding the optimal design of MPAs, in particular concerning their function as fisheries management tools, for which empirical studies are still lacking. Using 28 data sets from seven MPAs in Southern Europe, we developed a meta‐analytical approach to investigate the effects of protection on adjacent fisheries and asking how these effects are influenced by MPA size and age. Southern European MPAs showed clear effects on the surrounding fisheries, on the ‘catch per unit effort’ (CPUE) of target species, but especially on the CPUE of the marketable catch. These effects depended on the time of protection and on the size of the no‐take area. CPUE of both target species and the marketable catch increased gradually by 2–4% per year over a long time period (at least 30 years). The influence of the size of the no‐take area appeared to be more complex. The catch rates of the entire fishery in and around the MPA were higher when the no‐take areas were smaller. Conversely, catch rates of selected fisheries that were expected to benefit most from protection increased when the no‐take area was larger. Our results emphasize the importance of MPA size on its export functions and suggest that an adequate, often extended, time frame be used for the management and the evaluation of effectiveness of MPAs.     

Comparison of two- and three-way rotational crossing and synthetic variety production involving inbred lines of Hereford cattle: postweaning traits

Data for this linecrossing study were the postweaning growth and weight records of calves born from 1967 through 1975. The records consisted of 264 bull (M) and 263 heifer (F) straightline (SL) calves; 108 M and 100 F two-line rotational cross (2W) calves; 130 M and 102 F three-line rotational cross (3W) calves and 58 M and 51 F synthetic variety (SV) calves, all in the Hereford breed. Average inbreeding percentages of calves and dams in Lines 1, 4, 6 and 10 were 24, 28, 34 and 28; respectively. The M calves were fed a growing-fattening diet for 196 d after a 14-d period of adjustment to postweaning environment. The F calves were fed to gain approximately .5 kg daily during winter from weaning to about 12 mo of age and were then grazed on native pasture until about 18 mo of age. For M, average percentage increases over SL by 2W, 3W and SV combined over three generations were respectively, 9.0, 11.0, 11.6 for initial weight; 5.9, 8.1, 8.8 for 140-d weight; 4.8, 7.2, 7.7 for final 196-d weight and 1.5, 4.2, 4.7 for 196-d gain. All above estimates of increased weight or gain over SL were significant except for 196-d gain in 2W. For F, average percentage increases over SL by 2W, 3W and SV, respectively, were 9.0, 10.9, 11.3 for initial weight; 8.2, 9.2, 8.4 for 12-mo weight; 7.5, 7.7, 9.1 for 18-mo weight; 5.2, 5.3, 5.7 for 18-mo score. All these estimated increases over SL were significant.(ABSTRACT TRUNCATED AT 250 WORDS)