Dietary levamisole modulates the immune response and disease resistance of Asian catfish Clarias batrachus (Linnaeus)

In order to determine the immunomodulatory effect of dietary levamisole in Asian catfish (Clarias batrachus), fish were fed four different diets for 10 days: a formulated diet as control and the same diet supplemented with 50, 150 or 450 mg levamisole kg^?1 feed. The serum bacterial agglutination titre against Aeromonas hydrophila as a measure of specific immunity, serum haemagglutination titre, natural haemolytic complement activity (ACH₅₀), myeloperoxidase and lysozyme activities, total protein level and oxidative radical production by neutrophils as a measure of non‐specific immunity as well as disease resistance against A. hydrophila challenge to separate vaccinated and non‐vaccinated groups were evaluated at 0, 1, 2 and 3 weeks after last administration of levamisole. Levamisole supplement at the lowest level (50 mg kg^?1) significantly enhanced oxidative radical production and serum myeloperoxidase (MPO) content immediately after 10 days of feeding, which reached peak values after 3 and 2 weeks of feeding respectively. Haemolytic complement and haemagglutination titre were significantly enhanced after 3 and 1 weeks respectively. Haemolytic complement activity and MPO activities were significantly raised to 150 mg kg^?1 after 3 and 2 weeks, respectively. At the highest level of levamisole feeding (450 mg kg^?1) significant decreases in superoxide production and complement activity were measured immediately after levamisole feeding, which returned to the normal level after 1 week post‐ feeding. Fish were challenged with a virulent strain of A. hydrophila at 0, 1, 2 and 3 weeks after levamisole feeding, and the cumulative per cent survival was recorded over 10 days. Feeding levamisole at 50, 150 or 450 mg kg^?1 increased per cent survival in vaccinated fish immediately after levamisole feeding, and survival was significantly higher at 450 mg kg^?1. There was no difference in mortality patterns in non‐vaccinated fish. The results support the use of levamisole at 50 mg kg^?1 feed for 10 days as an immunostimulant in Asian catfish farming.     

Fatty acid composition of New Zealand green-lipped mussels, Perna canaliculus: Implications for harvesting for n-3 extracts

Marine bivalves offer a potentially important source of long-chained polyunsaturated fatty acids (PUFA) for human health supplements. Lipid extracts from individual New Zealand green-lipped mussels (NZGLM) were analyzed as fatty acid methyl esters (FAME) by gas chromatography to assess geographical and seasonal differences between large (86 ± 1 mm) male and female and small (44 ± 1 mm) mussels. PUFAs dominated in spring and summer, comprising ∼ 50% of total fatty acids. Moreover, the commercially important n-3 fatty acids, 20:5n-3 (eicosapentaenoic acid, EPA) and 22:6n-3 (docosahexaenoic acid, DHA) together accounted for 70-79% of total PUFAs in spring and summer. During winter there was a marked decrease in condition and total n-3 PUFAs and a concomitant increase in saturated fatty acids in mussels, suggesting they had already spawned, had increased metabolic demands and limited PUFA-rich phytoplankton as food. While total n-3 content was not significantly different, there were geographical differences in individual n-3 fatty acids. Mussels collected from the cooler waters of Stewart Island had greater levels of 20:5n-3 (EPA), while those collected in Marlborough had greater concentrations of 22:6n-3 (DHA), which was attributed mainly to differences in phytoplankton composition. Total n-3 content and the condition index varied seasonally with greater concentrations of n-3 PUFAs, especially EPA, recorded in large mussels in spring, coincident with spring diatom blooms. Total PUFA levels and condition indices remained high in summer. There was no significant difference in condition indices, total n-3 content, DHA or EPA levels between large male and female mussels. Conversely, large mussels had significantly greater amounts of n-3 PUFAs than small mussels at Marlborough Sounds, while small mussels had marginally greater total n-3 concentrations than large mussels at Stewart Island. Taken together, these results suggest that the NZGLM offers a potentially important source of n-3 PUFAs for human health supplements. Our findings suggest that optimal harvesting conditions occur in spring when mussel condition and n-3 content peak for large mussels. Although DHA and EPA levels varied geographically, total n-3 content was not significantly different between sites, which implies that harvesting mussels for n-3 extracts would be driven more by logistical considerations.     

Demand-feeding behaviour of sea bass kept in ponds: diel and seasonal patterns,and influences of environmental factors

Feeding activity was investigated from June to October in a group of 60 sea bass, Dicentrachus labrax. The fish were kept in an earthen pond in a maritime wetland subject to the fluctuations of the natural environment. The fish fed by operating a demand feeder connected to a data logger which recorded each feeding act with a time reference. Meteorological and hydrological data were also recorded. Diurnal rhythms in feeding activity changed as the months progressed. Fish fed during daylight, preferentially at dawn in June, but in the middle of the day from August to October. Most feeding took place during subdued light. Feeding was closely and positively correlated to both daylength and water temperature; daylength being the most related factor associated with rainfall and East-West wind direction.     

Genetic improvement of farmed tilapias: Biochemical characterization of strain differences in Nile tilapia

Four African wild strains (Egypt, Ghana, Senegal and Kenya) and four established Asian farmed strains of Nile tilapia, Oreochromis niloticus (popularly known in the Philippines as Taiwan, Thailand, Singapore and Israel) were analysed electrophoretically at 30 protein loci to estimate genetic differences among the strains. All strains shared alleles at 14 monomorphic and 16 variable loci. Among the African strains, characteristic allele frequency differences were observed at AAT-1 ^* 46 for Ghana and Senegal, ADH ^* 83 for Kenya, ADH ^* 120 for Senegal, G3PDH-2 ^* 300 for Egypt, IDDH ^* 67 for Senegal, sMDH-1 ^* 120 for Kenya and SOD ^* 150 for Senegal. Genetic distance values among the strains revealed a clustering of the farmed strains with Egypt and Ghana O. niloticus, a slight separation of the Senegal strain and a larger separation of the Kenya strain. This profile may reflect the origins of the few founder populations of this species previously introduced to Asia. It also confirms the wider genetic divergence of the Kenya strain (O. niloticus vulcani) from the others studied here, which are all O. n. niloticus. Observed heterozygosities of the strains ranged from 0.026 to 0.071, with the African wild strains the lower values (mean Ho = 0.036) and the farmed strains the higher ones (mean Ho = 0.056). The implications of these results to the ongoing tilapia genetic improvement programme in the Philippines are discussed.     

三角帆蚌消化系统扫描电镜观察

三角帆蚌消化系统扫描电镜观察欧阳珊，吴小平，邓宗觉，刘月英（南昌大学，３３００４７）（中科院动物研究所，北京１０００８０）关键词三角帆蚌，消化系统，扫描电镜ＳＥＭＯＢＳＥＲＶＡＴＩＯＮＯＮＴＨＥＤＩＧＥＳＴＩＶＥＳＹＳＴＥＭＯＦＨＹＲＩＯＰＳＩＳＣＵ...     

Willingness to travel to avoid recreation conflicts in Danish forests

Conflicts among forest visitors have direct effects on the quality of a recreational experience. As the number of visitors to forests close to residential areas increases, as well as the number of different activities, so does the potential for perceived conflicts. According to the literature, expanding knowledge of conflict characteristics and their causes is important for recreation planners and managers who aim to reduce conflicts.In the present study, different forest user groups were identified and categorised according to their pursued activities, and for each group, causes of conflict were identified. Furthermore, a choice experiment was constructed to estimate the distance visitors are willing to travel to encounter few visitors as opposed to many visitors, and thereby potentially experience fewer conflicts. Comparing the marginal willingness to travel (WTT) of different user groups suggests that some groups have a WTT further than the average to reach a forest with ‘Few’ visitors. The average WTT to reach a forest area with ‘Few’ visitors. ‘Mountain bikers,’ ‘Peace and nature lovers’ and ‘Horse riders’ are willing to travel 4 km more than the average per visit to reach a less crowded forest. At the other end of the scale, we find that people who are doing physical exercise are willing to travel 2 km less than the average to reach a less crowded forest.     

Reproductive biology of pink dentex Dentex gibbosus (Rafinesque) from the Adriatic Sea, Croatia

A 4‐year study (May 1997–December 2000) of the reproductive biology of pink dentex Dentex gibbosus (Rafinesque) from the Adriatic Sea revealed that this species is a rudimentary hermaphrodite. The smallest mature males and females captured were 38.70 cm in total length (T_L) and 39.80 cm in total length (T_L) respectively. The von Bertalanffy growth parameters estimated for the entire population were: L_∞=107.24, K=0.12 and t₀=−0.90. Fifty per cent of the population were sexually mature at 41.50 cm T_L, while 100% of the specimens were sexually mature at 57.00 cm T_L. Both monthly gonadosomatic index and macroscopically determined gonad stages strongly indicate that the pink dentex from the Adriatic Sea spawn partially in August, September and October. The mean value of absolute fecundity (F) was 1672 × 10⁶ eggs. The results of great fertility of the pink dentex, partial spawning and relatively late sexual maturation suggest that the pink dentex has a high potential for commercial culture.     

封闭式循环水养殖牙鲆鱼技术初步研究

将新功能滤料、高效混合净水菌团、水质自动监测及控制3项关键技术及配套设备用于封闭式循环水养殖牙鲆鱼。结果表明，封闭循环组成活率可达到90％－95．1％，平均产量为32．2kg/m^2。较对照组养殖密度增加75．6％－102．7％，成活率提高14％－17％，平均产量增加145％－187．5％。充分利用有限的水体，避免海水二次污染，利于环境保护。     

Purification and characterization of a cysteine-like protease from the body wall of the sea cucumber <Emphasis Type="Italic">Stichopus japonicus</Emphasis>

The sea cucumber (Stichopus japonicus) is able to undergo autolysis in response to a variety of environmental and mechanical cues. Within the framework of a long-term study of this phenomenon we have purified a protease from the body wall of the sea cucumber by means of ion-exchange chromatography with DE-52 cellulose and gel filtration chromatography with Sephadex G-100. The final enzyme preparation was nearly homogeneous on polyacrylamide gel electrophoresis, and its molecular weight was estimated to be approximately 35.5 kDa. The purified enzyme exhibited a maximum activity for the hydrolysis of casein at pH 7.0 and 50°C and a remarkable stability at pH 4.0–7.0 and 40–60°C. Based on the inhibition and activation profiles obtained with numerous specific protease inhibitors and an activator, the protease purified from the body wall of the sea cucumber was defined to be a cysteine-like protease.