| Deteriorations of germplasm, disease, environment and product quality are becoming more serious problems, not yet to be resolved in Chlamys farreri culture. In view of this, studies on defence and neuroendocrine mechanism of C. farreri were carried out. The interaction among environmental stress, stress hormone and haemocyte immune functions was investigated systematically. To explore the cause of massive mortality of C. farreri from the ecological immunology point of view, it will be benefit for disease prevention and germplasm optimization in the long term. The main results are as follows:1. The recent progress derived largely from the mechanism analysis of molluscan ecological immunity was reviewed in this paper. The immune suppression effect of stress hormones on the molluscan immunity has been analyzed, and the relationship between the cost investment in defence system and other ecological factors was expounded. The interaction mechanism between pathogen and host was clarified. Furthermore, the future studies in molluscan ecological immunology for inspiring the new thoughts in controlling mollusks disease were suggested.2. According to the special characteristic of C. farreri haemocyte, a desirable anticoagulant solution was selected (Glucose 20.8 gL-1,EDTA 20mM,Sodium chloride 20 gL-1,Tris-HCl 0.05M,pH=7.4).3. Investigating the effects of major environmental stressors, including air exposure (5°C,17°C and 25°C for 24h period), acute temperature variation (increased directly from 17°C to 23°C and 28°C, or decreased directly from 17°C to 11°C), acute salinity variation (increased directly from 31 to 35, or decreased directly from 31 to 25 and 20), starvation (sustained for 40 days) and stocking density (low, medium and high), on haemocyte immune conditions of C. farreri. The results showed that air exposure has a negative effect on haemocyte immune functions of scallops, this may lead to scallop vulnerability to fight against any pathogen during the first 24h after re-immersion. Air exposure at 25°C was demonstrated to markedly reduced survival rate in scallops. The homeostatic capabilities appear to be compromised for C. farreri transferred directly from 17°C to 28°C, it is supposed that the overall health of the scallop would be compromised and the likelihood of being affected by pathogens might increased. By contrast, scallops showed possessing high tolerance to a rapid decrease of seawater temperature (from 17°C to 11°C). Acute salinity decrease (from 31 to 20) could significantly inhibit the haemocyte immune conditions of scallop and accelerate the propagation of pathogen, which will greatly increase the probability of mass mortality of scallops. Starvation (sustained for 40 days) could also significantly inhibit the haemocyte immune functions. Considering the superfluous feeding factor in experimental condition, no significant effect of stocking density was observed on haemocyte immune functions except the percentage of phagocytic haemocytes.4. The ultrastructural alterations taking place in C. farreri haemocytes resulting from air exposure (exposed to air for 24hours at 17°C), temperature variation (transferred directly from 17°C to 11°C and 28°C and sustained for 7 days), salinity variation (transferred directly from salinity 31 to 20 and sustained for 7 days) and starvation for 40 days, were examined by transmission electron microscopy (TEM). The results showed that serious damages appeared in the haemocytes ultrastructure after air exposure (17°C for 24hours), hypotonic (salinity 20 for 7days) and starvation stress (40 days).5. Enzyme immunoassay revealed that stable presence of catecholamines (including adrenaline, noradrenaline and dopamine) in the haemolymph of the scallop, the basic values were 0.088±0.11, 18.63±1.96 and 2.59±0.46ng/ml respectively. The method was also used to investigate these catecholaminergic responses to environmental stress. The results showed that both adrenaline and noradrenaline concentrations increased significantly in response to all the stress, including air exposure, acute temperature increase (from 17°C to 28°C) and acute salinity decrease (from 31 to 20). However, the dopamine concentration showed reverse variation trend in response to stress compared with adrenaline and noradrenaline.6. Based on the basic concentration and fluctuation amplitude of catecholamines in response to stress in circulating haemolymph, different concentrations of adrenaline and noradrenaline were designed for investigating the influence of these two catecholamines on haemocyte immune activities. The results showed that noradrenaline had a dose-dependent inhibitory effect on phagocytosis at physiological concentrations of 30ng/ml and 50ng/ml, and on reactive oxygen species at concentration of 50ng/ml. But no significant effect of adrenaline on haemocyte immune activities was observed. |
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