枯草芽孢杆菌同种相食现象及生防应用

枯草芽孢杆菌分泌的抗菌物质在植物病害防治方面具有重要作用。在芽孢形成初期阶段,枯草芽孢杆菌通过“同种相食”（Cannibalism）推迟芽孢形成：准备形成芽孢的细胞产生并释放细菌毒素skf和sdp,杀死未形成芽孢的同类细胞,死亡细胞释放的营养可供准备形成芽孢的细胞利用,导致芽孢形成推迟。细菌毒素skf和sdp具有广谱杀菌性。综述“同种相食”的基因调控机制,该过程中新型毒素的产生及免疫机制,“同种相食”生物意义及毒素skf、sdp在生物防治应用前景。对于枯草芽孢杆菌生物防治制剂开发具有实际意义。     

Effects of stocking density and size distribution on growth, survival and cannibalism in juvenile fat snook (Centropomus parallelus Poey)

This study was carried out in order to determine the effect of stocking density and size distribution on growth, survival and cannibalism of fat snook (Centropomus parallelus Poey) juveniles. Three stocking densities (1.5, 3 and 6 fish L⁻¹) were tested in two groups of fish: homogeneous [total length (TL)=22.1 mm; coefficient of variation of length (CV)=8%] and heterogeneous (TL=22.7 mm; CV=15%). The experimental design was factorial (3 × 2) using triplicates. Fish were reared for 30 days in 80‐L circular tanks with an open flow‐through system. There was no significant interaction between the two factors (density and size distribution). The highest cannibalism rate (14.2%) was observed in the heterogeneous group, which also had a significantly higher growth rate (TL=45.6 mm) than the homogeneous group (3.2% and TL=40.9 mm). Significant differences were found between the two lowest densities and the highest density (6.2%, 6.3% and 13.4% respectively). Growth was not affected by fish density. Cannibalism was the main cause of mortality. In 90% of the occurrences, whole prey ingestion was observed. According to the results obtained, cannibalism was positively correlated to density, although size grading of fat snook juveniles is recommended to control cannibalism in all the densities tested.     

Walleye pollock egg distribution and mortality in the western Gulf of Alaska

We examine the distribution and mortality of walleye pollock ( Theragra chakogramma ) eggs in the western Gulf of Alaska. Most pollock eggs were found in mid-water, with low proportions in the neustonic and epibenthic layers during all years of sampling. A silhouette camera towed through a high egg density region provided new information on small-scale spatial distributions and provided density estimates at two depth layers similar to those of depth-discrete net sampling. Annual egg production curves and natural mortalities were estimated for 1987-92 based on the abundance of several cohorts relative to their production rate. Production during 1989 and 1990 was lower than in the other four years but 1988 was the only year to show markedly different (higher) mortality than the rest. Fertilization rate was generally very high (>99%) but several collections early in the season contained a substantial fraction of unfertilized eggs. Invertebrate egg predation was mainly due to euphausiids and was variable among locations and years. Egg cannibalism by adult pollock on the spawning grounds was inconsequential (< 1% for all years) compared to invertebrate predation.     

Reproductive costs, condition and carotenoid-based colour in natural populations of threespine stickleback (Gasterosteus aculeatus)

Abstract –  Male threespine stickleback, Gasterosteus aculeatus , display an orange/red throat during the breeding season, which is carotenoid-based colour. We examined the relationship between energy-based costs of reproduction and colour in three lacustrine populations of threespine stickleback: two benthic (Willow and Big Beaver) and one limnetic (Lynne) ecotypes. In two lakes (Willow and Big Beaver) where benthic males defend nests against cannibalistic groups, males paid higher energy costs than in the third lake (Lynne) where cannibalistic groups are absent. We then examined colour variation within each population. Males from Lynne Lake did not change colour during the parental stage, whereas males from Willow and Big Beaver lakes became more intensely coloured. In addition, colour was typically independent of condition within stages. We propose that energy-based reproductive costs could explain some of the observed variation in colour by altering the payoffs associated with signalling effort during current versus future reproduction.     

Feather pecking in laying hens housed in free-range or furnished-cage systems on French farms

ABSTRACT

1. Beak trimming is currently used in France to avoid the negative consequences of severe feather pecking (SFP). However, this practice is controversial in terms of animal welfare, and forbidden in some European countries.

2. This study aimed to assess the prevalence of SFP in French laying hen farms, to describe how farmers manage this behavioural disorder and to better understand the risk factors involved.

3. A study was carried out from April 2015 to June 2016. Visits were paid to 79 flocks kept in furnished cages (FC) and 80 flocks in a free-range (FR) system. All the hens had trimmed beaks and were genotypically brown. The information collected included feather cover, skin damage, beak condition, farm and poultry house characteristics, livestock performance and management.

4. The prevalence of SFP in FC flocks was estimated at 32.9% (IC = 95%, [22.5; 43.3]) and the prevalence of cannibalism as 2.5% (IC = 95%, [0.7; 8.8]) at 70 weeks of age. The prevalence of SFP in FR flocks was estimated to be 23.8% (IC = 95%, [14.5; 31.1]) and the prevalence of cannibalism was 8.8% (IC = 95%, [4.3; 17.0]) at 61 weeks of age.

5. In FC flocks, SFP was associated with the combination of genotype, type and length of perches, cage area per hen, type of lighting, number of hens per cage and farm location. In FR flocks, feather cover was associated with use of the outdoor run, lighting programme, genotype, farm location and date of house construction.     

Canine oral primary melanoma cells exhibit shift to mesenchymal phenotype and phagocytic behaviour

Canine oral malignant melanoma (COMM) is a potentially lethal cancer disease. We established primary cell lines from mostly amelanotic primary COMM and metastases and assessed lesions and derived cells for Melan A, PNL2 and CD146 expression. Then, migration and invasion of CD146‐enriched vs ‐depleted COMM cells were analysed. Epithelial‐to‐mesenchymal transition (EMT) was addressed by Vimentin‐staining and MMP2/MMP9 zymography. Phagocytic behaviour was analysed by histopathological examination and phagocytosis assay. While Melan A‐ and PNL2‐staining yielded inconsistent data, 100% of COMM sections and primary cells showed CD146 expression, suggesting that this protein may serve as a prognostic marker. An overall correlation between CD146‐expression and migration/invasion was not observed. All primary cell lines consistently expressed Vimentin and secreted biologically active MMP2, indicating that they had undergone EMT. Importantly, COMM sections exhibited cell‐in‐cell structures, and all primary cell lines exhibited phagocytic activity, supporting the concept that cell cannibalism may have a role in COMM progression.     

Effects of feeding conditions and size differences on aggressive behaviour and cannibalism in the Pacific bluefin tuna Thunnus orientalis (Temminck and Schlegel) larvae

We examined the effects of feeding conditions and size differences on the aggressive behaviour and cannibalism in Pacific bluefin tuna (PBT) Thunnus orientalis larvae. In a 24 h experiment, restricted feeding alone was found to remarkably increase the frequency of aggressive behaviour, which was further elevated by differences in fish size. In a 4‐day rearing experiment, while aggressive behaviour was increased by restricted feeding alone, the frequency of cannibalism did not change significantly. Although the frequency of aggressive behaviour did not increase with difference in size factor, small fish in this group gradually tended to die over 4‐day period. In the restricted feeding and size difference group, large fish were observed to bite the small fish, and almost all the small fish died on the day after the start of the experiment. These results suggest that the aggressive behaviour of PBT larvae is chiefly increased by the shortage of live food; however, deaths related to cannibalism mainly occurred in small larvae and rapidly increased with food restriction and differences in fish size.     

Application of logistic regression analysis to predict cannibalism in orange‐spotted grouper Epinephelus coioides (Hamilton) fry

Cannibalism is frequently observed in larviculture of orange‐spotted grouper Epinephelus coioides. Previously, based on measurements of morphometric characters, a linear equation of total length (TL) of prey to cannibals was proposed: TL_prey = 0.80 TL_cannibal – 1.50. To verify the reliability of the equation, experiments were performed with pairs of fish with different TLs. Cannibalism occurred only when the cannibal‐prey size ratios were equal to or larger than that predicted by the equation. To predict the probability of cannibalism among the grouper of known TLs, a logistic regression model was proposed. The logistic regression model is: The logistic regression model showed the following: when either TL_prey or TL_cannibal is constant, the probability of cannibalism increases with increase in the cannibal‐prey size ratios; if given a constant cannibal‐prey size ratio, probability of cannibalism is lower in early stages than in later stages. The prediction contrasts with that calculated from the linear equation where the minimum cannibal‐prey size ratios decrease with size of the cannibal. However, the prediction matches observed rearing experiences: cannibals prefer smaller prey to larger ones and the cannibalism rate declines as fry age.     

Improved survival and growth performances with photoperiod and feeding schedule manipulation in bagrid catfish Mystus nemurus (Cuvier & Valenciennes 1840) larvae

Manipulation of photoperiod: 24 h light (24L), 12 h light:12 h dark (12L:12D) and 24 h dark (24D); and feeding schedules: day and night feeding (DNF), day feeding (DF) and night feeding (NF) was conducted to determine effects on survival, cannibalism and growth of larval bagrid catfish Mystus nemurus 2–14 days after hatching (dAH). Photoperiod insignificantly affected all parameters. Feeding schedule significantly affected survival and total length at 6 (P < 0.049; P < 0.009), 10 (P < 0.033; P < 0.000) and 14 dAH (P < 0.013; P < 0.000), respectively, but affected cannibalism at 10 (P < 0.043) and 14 dAH (P < 0.013). Survival for DNF was significantly higher than DF. Cannibalism for DNF was significantly lower than NF at 10 and 14 dAH. Total length for DNF was significantly higher than DF and NF at 10 and 14 dAH. At 14 dAH, feeding schedule significantly affected feed intake, final weight and coefficient of variation. For feed intake and final weight, DNF was significantly higher than DF and NF. For coefficient of variation, NF was significantly higher than DF. This study suggests that larval bagrid catfish can be reared at 24L, 12L:12D or 24D but should be fed day and night for improved growth, survival and reduced cannibalism.