The termiticidal activity of Sextonia rubra (Mez) van der Werff (Lauraceae) extract and its active constituent rubrynolide

BACKGROUND: Termites are degradation agents that inflict severe damage on wood. Some long‐lasting Amazonian trees can resist these insects by producing toxic secondary metabolites. These metabolites could potentially replace synthetic termiticidal products which are becoming more restricted to use. RESULTS: Sextonia rubra is resistant to termite‐induced degradation. It has been demonstrated that this species naturally produces an ethyl‐acetate‐soluble termiticidal metabolite, rubrynolide, to protect its wood. Assays in the presence of tropical and invasive termites established that both rubrynolide and crude ethyl acetate extract from S. rubra wood can be used as a treatment for the protection of sensitive woods against termites. CONCLUSION: Rubrynolide and S. rubra extract are promising candidates for the replacement of synthetic termiticides. Copyright © 2011 Society of Chemical Industry     

Yersiniosis in Atlantic cod,Gadus morhua (L.), characterization of the infective strain and host reactions

A disease outbreak in farmed Atlantic cod caused by Yersinia ruckeri is reported. Mortality started following vaccination of cod reared in two tanks (A and B). The accumulated mortality reached 1.9% in A and 4.8% in B in the following 30 days when treatment with oxytetracycline was applied. Biochemical and molecular analysis of Y. ruckeri isolates from the cod and other fish species from fresh and marine waters in Iceland revealed a high salinity‐tolerant subgroup of Y. ruckeri serotype O1. Infected fish showed clinical signs comparable with those of Y. ruckeri ‐infected salmonids, with the exception of granuloma formations in infected cod tissues, which is a known response of cod to bacterial infections. Immunohistological examination showed Y. ruckeri antigens in the core of granulomas and the involvement of immune parameters that indicates a strong association between complement and lysozyme killing of bacteria. Experimental infection of cod with a cod isolate induced disease, and the calculated LD₅₀ was 1.7 × 10⁴ CFU per fish. The results suggest that yersiniosis can be spread between populations of freshwater and marine fish. Treatment of infected cod with antibiotic did not eliminate the infection, which can be explained by the immune response of cod producing prolonged granulomatous infection.     

Patterns in the spawning of cod (Gadus morhua L.), sole (Solea solea L.) and plaice (Pleuronectes platessa L.) in the Irish Sea as determined by generalized additive modelling

Eleven ichthyoplankton cruises were undertaken covering most of the Irish Sea during the period February to June, 1995. To identify spawning localities and investigate temporal trends in egg production, the data on stage 1 A egg distributions of cod ( Gadus morhua ), plaice ( Pleuronectes platessa ) and sole ( Solea solea ) have been modelled using generalized additive models (GAMs). A two-stage approach was adopted where presence/absence was firstly modelled as a binary process and a GAM surface subsequently fitted to egg production (conditional on presence). We demonstrate that this approach can be used to model egg production both in space and in time. The spawning sites for cod, plaice and sole in the Irish Sea were defined in terms of the probability of egg occurrence. For cod, we demonstrate that by integrating under predicted egg production surfaces, a cumulative production curve can be generated and used to define percentiles of production and thus delimit the extent of the spawning season. However, for plaice and sole, the surveys did not fully cover the spawning season and the limitations that this imposes on GAM modelling of these data are discussed. Comparison of the spawning sites in 1995 with historical data suggests that the locations of cod, plaice and sole egg production in the Irish Sea have probably remained relatively constant over the last 30 years.     

3个不同地理群体黑鲷遗传变异的RAPD分析

利用RAPD技术对取自胶州湾(青岛)、台湾海峡(厦门)和北部湾(海南)3个天然群体的24尾黑鲷(Sparus macrocephalus)进行群体内与群体间的遗传变异分析.在事先优化的反应条件下,所使用的60个随机引物中,有28个引物扩增出清晰稳定的片段,共计200条,大小在200～2 500 bp,其中多态性片段135条(多态性片段的比例为67.50%).青岛、厦门和海南黑鲷群体内的遗传距离分别是0.106 8、0.093 9和0.120 6,相似系数为0.893 2、0.906 1和0.879 4;群体间的遗传距离分别是0.155 0、0.131 8和0.122 8,其中青岛和海南黑鲷群体间的遗传距离最大,青岛与厦门其次,厦门与海南最小.群体内与群体间都具有较高的遗传变异.用MEGA2.1软件的UPGMA程序和NJ程序进行聚类分析,厦门与海南群体首先聚在一起,其次是青岛群体,两者的结果相一致.     

Larval group differentiation in Atlantic cod (Gadus morhua) inside and outside the Gullmar Fjord

The spatial and temporal occurrence of pelagic fish stages and their biological variability may affect their dispersal and survival, and ultimately fish recruitment. We collected Atlantic cod larvae at one station inside and at one station outside the Gullmar Fjord, eastern Skagerrak, in order to investigate small-scale larval group differentiation. Rectangular midwater trawl hauls were taken every 6 h (during 24 h) from three separate depth intervals between the surface and 70 m depth. About 80% and 20% of all larvae occurred above the halocline at the Fjord station and the Coastal station, respectively. Hatching (at both stations) occurred from the 3rd week in February to the 1st week in May, indicating that cod larvae were present for at least 5 months (from late February to early August). The length and hatch date frequency distributions of larvae from the surface layer were unimodal inside the fjord but bimodal outside the fjord. Analyses of seven microsatellite DNA loci indicated that larvae collected inside the fjord (where local spawning occurs) were genetically distinct from larvae sampled on the outside (F_ST = 0.0026). The two age cohorts outside the fjord were not, however, genetically different, nor were larvae collected at different depths. We conclude that small-scale variability of vertical concentration and larval life history variability should have consequences for interpreting models of larval dispersal and survival, and subpopulation structure analyses.     

Technological solutions and operational measures to prevent escapes of Atlantic cod (Gadus morhua) from sea cages

Escapes of cod (Gadus morhua) from sea cages represent an economic problem for farmers and a potential environmental problem. We estimate that 0–6% of cod held in sea‐cage farms in Norway were reported to have escaped each year from 2000 to 2005, which is a high proportion compared with salmon. We interviewed employees at 19 coastal sea‐cage cod farms in Norway to investigate both how and why cultured cod escape and to document cage handling and management strategies that were effective in minimizing escapes. Based on the interviews, we describe five working hypotheses that may explain why a greater proportion of cod than salmon escape: (1) cod are more willing to escape than salmon; (2) cod bite the net cage and create wear and tear; (3) net cages have insufficient technical standards for cod culture; (4) cod are placed in sea cages at considerably smaller sizes than salmon; and (5) cod are more popular feed for predators. Preliminary testing of the hypothesis that cod bite netting and create holes was done by placing pre‐damaged net panels with cut twines and control panels inside sea cages. Holes in the pre‐damaged net panels increased in size over a period of 3 months. The type of damage indicated that biting of netting twines was the likely cause.     

Growth and gut morphology of diploid and triploid juvenile Atlantic cod (Gadus morhua)

The objective of this paper was to compare the growth and gut morphology of juvenile diploid and triploid Atlantic cod (Gadus morhua) reared under similar conditions. Individually tagged 36‐week‐old diploid (mean weight 49.3 ± 13.8 g) and triploid (mean weight 43.6 ± 11.2) juvenile cod were measured at intervals during a 29‐week growth trial. Data for weight, length, condition factor (K), hepato‐somatic index (HSI), gonado‐somatic index (GSI), Relative Gut Length (RGL) and pyloric caeca number were collected and results were analysed in relation to ploidy status, gender and family contribution. At the end of the experiment, only one family (M2xF3) had many representatives with a relatively even distribution of sexes and ploidies. Diploid females were significantly heavier and had higher K than triploid females in the M2xF3 family (body weight 371.2 ± 120.2 vs. 298.4 ± 100.7 g; K 1.1 ± 0.1 vs. 0.93 ± 0.1), but no differences were found between diploid and triploid males. In the other families (pooled data), no differences in body weight were found between the ploidy groups. In general, triploids had a shorter intestine (RGL) and fewer pyloric caeca than their diploid siblings regardless of gender suggesting possible impairments in nutrient utilization and growth.     

Copepod dynamics across warm and cold periods in the eastern Bering Sea: Implications for walleye pollock (Gadus chalcogrammus) and the Oscillating Control Hypothesis

Differences in zooplankton populations in relation to climate have been explored extensively on the southeastern Bering Sea shelf, specifically in relation to recruitment of the commercially important species walleye pollock (Gadus chalcogrammus). We addressed two research questions in this study: (i) Does the relative abundance of individual copepod species life history stages differ across warm and cold periods and (ii) Do estimated secondary production rates for copepods differ across warm and cold periods? For most copepod species, warmer conditions resulted in increased abundances in May, the opposite was observed in colder conditions. Abundances of smaller‐sized copepod species did not differ significantly between the warm and cold periods, whereas abundances of larger‐sized Calanus spp. increased during the cold period during July and September. Estimated secondary production rates in the warm period were highest in May for smaller‐sized copepods; production in the cold period was dominated by the larger‐sized Calanus spp. in July and September. We hypothesize that these observed patterns are a function of temperature‐driven changes in phenology combined with shifts in size‐based trophic relationships with primary producers. Based on this hypothesis, we present a conceptual model that builds upon the Oscillating Control Hypothesis to explain how variability in copepod production links to pollock variability. Specifically, fluctuations in spring sea‐ice drive regime‐dependent copepod production over the southeastern Bering Sea, but greatest impacts to upper trophic levels are driven by cascading July/September differences in copepod production.     

盐度对真鲷(♀)×黑鲷(♂)杂交子一代仔鱼活力的影响

比较了不同盐度梯度(5.0、10.0、15.0、20.0、25.0、30.0)下真鲷(Pagrosmus major,♂)×黑鲷(Sparus macrocephalus,♀)杂交子一代(杂交F1)初孵仔鱼的生长情况,并在此盐度梯度下对杂交F1仔鱼进行耐饥饿试验,测定不投饵存活系数(sAI).结果表明,10.0,15.0,20.0的3个盐度组的仔鱼生长速度最快,这3个盐度组下仔鱼的sAI值也最高,真鲷与黑鲷杂交F1的最适生长盐度为10.0-20.0.当自然海水盐度为20.0以上时,在允许的情况下,适当降低杂交F1仔鱼培育盐度,可以提高苗种的成活率.     

Heritability of economically important traits in the Atlantic cod Gadus morhua L

During the development of breeding programme for Atlantic cod Gadus morhua L., in Iceland, genetic parameters were estimated for 1402 individuals, which were assigned with DNA profiling to 140 dams and 70 sires. The cod was reared in cages on the eastern and western coasts of Iceland from 2004 to 2005. At the average body weight of 1.8 kg, the estimated heritability (h² ± SE) for body weight, gutted weight and the condition factor (CF) were 0.31 ± 0.06, 0.34 ± 0.04 and 0.24 ± 0.06 respectively. Genetic correlation (r_G) in body weight between the two rearing locations was estimated as 0.95, which reflects a low G × E interaction. The estimated heritability for hepatosomatic index (HSI) and fillet yields was 0.061 ± 0.04 and 0.04 ± 0.04 respectively. The HSI and fillet yields were highly genetically correlated with body weight or 0.67 and 0.82 respectively. The genetic correlation between the CF and body weight was estimated as 0.31. There appears to be substantial amount of additive genetic variation for body weight suggesting that selection is likely to be successful. Low heritability for fillet yields and the HSI indicates less promise of genetic improvement. Assigning of parentage to individuals with DNA profiling was 80% successful.