The alpha/beta subdomain of EIN is topologically similar to the phosphohistidine domain of the enzyme pyruvate phosphate dikinase, which is phosphorylated by PEP on a histidyl residue but does not interact with HPr. It is therefore likely that features of this subdomain are important in the autophosphorylation of enzyme I. The helical subdomain of EIN is not found in pyruvate phosphate dikinase; this subdomain is therefore more likely to be involved in phosphoryl transfer to HPr.
A range of chemicals are used in European marine aquaculture and these may be categorized as disinfectants, antifoulants and medicines (includes vaccines). This article provides a review of chemicals used in aquaculture in Europe, their regulatory status, and a checklist of points considered best practice in the use (and avoidance of use) of medicines in marine aquaculture. The release of antifoulants and disinfectants into the marine environment is controlled by local and/or national waste discharge regulations that may in turn be guided by wider environmental quality objectives. The authorization of veterinary medicines, biologicals (vaccines) and pharmaceuticals (chemicals), in Europe is the subject of several EC Directives. Registration dossiers address the issues of product quality, safety and efficacy and include environmental and consumer safety where the product is destined for use in a food‐producing animal. Fish farmers, like all livestock producers, must have access to a range of properly authorized medicines to safeguard animal health and welfare. The distribution and supply of medicines must be appropriately controlled and their authorization appropriately includes environmental risk assessment to a common European Union (EU) or international standard. There is progress towards the harmonization of the authorization process within the EU and this will help to ensure the continued availability of medicines for fish. Consumer safety is addressed by the setting of maximum residue limits (MRLs) derived through toxicological risk assessment and by surveillance of food for residues of veterinary medicines. The system for the environmental risk assessment of chemicals used in aquaculture is being developed and is outlined in the present article. It is recommended that the supply and use of fish medicines is uniformly regulated in the EU and supported by appropriate codes of best practice. A number of codes of practice that include reference to the use of medicines have been produced both at a European level and in member states. It is recommended that all European marine aquaculture producers adopt a code of best practice for the use of medicinal and other chemicals their industry. Medicines are one part of an integrated package in dealing with animal health. This includes environmental conditions, nutrition and hygiene. The best practice guidelines presented here are based on the outcome of three European workshops as part of the EU MARAQUA project that involved industry, government and research scientists. They cover the avoidance and minimizing of the need to use medicines and other chemicals, to recording and monitoring their use and effectiveness (in case of resistance development), exchange of experiences within the industry, and staff training. Recommendations are also included for manufacturers of medicines and other chemicals, and for regulatory authorities. Minimizing the need to use medicines and other chemicals requires attention to a healthy source of fish stock. Staff must be appropriately tra...
High shore littorinid snails exhibit complex spatial distribution patterns, forming dense aggregations both in crevices and on crevice-free sections of rocky shores. To understand how these patterns may form, an individual-based computer simulation of littorinid behaviour, similar to those used to model social insects, was used to mimic snail movement on rocky shores. Individual littorinid movement patterns were simulated, along with chance interactions with other littorinids, their trails, crevices and any resultant decisions made by the littorinids when these interactions occurred. The simulation investigated how simple behavioural rules can predict spatial aggregation patterns and the persistence and variation of these aggregation patterns over timescales of several tidal cycles. Morisita's index of dispersal showed good agreement between the simulation and observed patterns of littorinids on-shore. Trail-following was vital in the simulation, since points where trails intersected with crevices, or points where 2 or more trails met, formed the site of aggregations. Both in the simulation and in reality, aggregations often occurred in identical positions over several tidal cycles, both within and outside crevices. This temporal predictability may be due to the persistence of mucus trails on the shore over successive tidal cycles. Removal of the influence of past mucus trails from the simulation resulted in far lower persistence of aggregations over time. The simulation, therefore, is an important tool in examining behavioural mechanisms of intertidal animals. It provides insights into how simple behaviour of grazing animals can explain complex population patterns and subsequently the community dynamics of algal-herbivore interactions.
Growth and digestibility trials were conducted using African catfish, Clarias gariepinus (Burchell 1822): (1) to obtain apparent digestibility coefficient (ADC) values for capelin fish meal, soybean flour and corn meal; (2) to formulate diets based on ADC values of the protein feedstuffs; and (3) to evaluate the effects of replacing 25%, 50% and 75% of fish meal in control diets with soybean flour on growth, feed utilization efficiency and carcass composition. Supplemental methionine was added to the diet formulation in which soybean flour replaced 75% of the diet. Diets were formulated (400 g digestible protein kg−1 and 15 kJ digestible energy g−1 dry diet) and fed to catfish fingerlings (13.1 ± 0.5 g) to apparent satiation twice daily for 70 days. The protein and energy digestibilities of fish meal and soybean flour were high (>90% and >80%, respectively; P < 0.05). At 75% fish meal replacement with soybean flour (without methionine supplementation), growth and feed utilization efficiency indicators were depressed compared with other diet treatments which had a similar (P > 0.05) growth and feed utilization efficiency to those fed the control diet. The carcass compositions of catfish in all diets were similar (P > 0.05) and the liver histology of catfish fed any of the diets showed no alterations. The results obtained indicate that 50% of fish meal protein in practical catfish diets can be replaced with soybean flour and that catfish can effectively utilize supplemental methionine, thereby allowing up to 75% of the dietary fish meal protein to be replaced by soybean flour.
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