亚硝酸盐对越冬红螯螯虾生理指标及肠道菌群的影响

以越冬红螯螯虾为对象,探讨其在不同亚硝酸盐浓度下的生理指标及肠道菌群变化情况。采用常规生物急性毒性试验法,得到亚硝酸盐胁迫下红螯螯虾的96 h半致死浓度为22.0 mg/L,安全浓度为2.2 mg/L。设置4个实验组,分别为A组(0 mg/L)、B组(0.5 mg/L)、C组(2.3 mg/L)和D组(5.0 mg/L),胁迫6周后取样检测。结果表明:各组成活率、肥满度、肝体指数无显著性差异(P>0.05),但D组成活率、体质量增加率、体长增加率最低。随亚硝酸盐浓度的增加,肝小管排列趋于混乱且大小出现差异,肝小管间结缔组织随之减少,产生空泡化,在D组中变化尤为明显。SOD活性随亚硝酸盐浓度升高而降低,在肝胰腺中,A组显著高于其他3组(P<0.05),D组显著低于其他3组(P<0.05);在肌肉中,A组显著高于C、D组(P<0.05),D组显著低于A、B组(P<0.05)。MDA活性随亚硝酸盐浓度升高而升高,在肝胰腺中,4组均无显著差异(P>0.05);在肌肉中,A组显著低于C、D组(P<0.05)。免疫相关指标均随亚硝酸盐浓度升高而降低,在肝胰腺中,4组ACP、AKP活性均存在显著性差异(P<0.05),A组最高,D组最低;在肌肉中,A组ACP活性显著高于其他3组(P<0.05);4组AKP活性均存在显著性差异(P<0.05),A组最高,D组最低;各组UL活性无显著性差异(P>0.05)。能量代谢指标TG活性随亚硝酸盐浓度升高而降低,A组显著高于D组(P<0.05)。亚硝酸盐胁迫在一定程度上提高了肠杆菌科(Enterobacteriaceae)的比例,且菌群多样性D组最低,A组最高,亚硝酸盐导致了肠道菌群多样性的下降。

Effects of nitrite on physiological indices and intestinal flora of parent Cherax quadricarinatus during overwintering

The physiological indexes and intestinal microflora of Cherax quadricarinatus overwintering were studied at different concentrations of nitrite. The acute toxicity of nitrite to Cherax quadricarinatus was studied by conventional bioacute toxicity test method, and the semi-lethal concentration of 96 h was 22.0 mg/L and the safe concentration was 2.2 mg/L. Four groups of nitrite experimental groups were set up, respectively, group A (0 mg/L), group B (0.5 mg/L), group C (2.3 mg/L) and group D (5.0 mg/L).Samples were taken after 6 weeks of stress. The results showed that:There was no significant difference in survival rate, hypertrophy and liver index in four groups (P>0.05), but the survival rate, weight gain rate and body length increase rate of group D were the lowest. Hepatopancreas histology analysis:With the increase of nitrite concentration, the arrangement of hepatic tubules tended to be disordered and the sizes of hepatic tubules became different. The connective tissue between hepatic tubules decreased and vacuoled, especially in group D. Physiological biochemistry indicators analysis:SOD activity decreased with the increase of nitrite concentration. In hepatopancreas, group A was significantly higher than the other three groups (P<0.05), and group D was significantly lower than the other three groups (P<0.05). In muscle, group A was significantly higher than group C and D (P<0.05), and group D was significantly lower than group A and B (P<0.05). MDA activity increased with the increase of nitrite concentration. In hepatopancreas, there was no significant difference among the four groups (P>0.05). In muscle, group A was significantly lower than group C and D (P<0.05). Immune-related indicators decreased with the increase of nitrite concentration. In hepatopancreas, ACP and AKP activities of four groups were significantly different (P<0.05), the highest in group A and the lowest in group D. In muscle, ACP activity in group A was significantly higher than that in other three groups (P<0.05). AKP activity in four groups was significantly different (P<0.05), with the highest in group A and the lowest in group D. UL activity had no significant difference in each group (P>0.05). The activity of energy metabolic index TG decreased with the increase of nitrite concentration, and the TG activity in group A was significantly higher than that in group D (P<0.05). Intestinal flora analysis:Nitrite stress increased the proportion of Enterobacteriaceae to a certain extent, and the diversity of group D was the lowest and that of group A was the highest. Nitrite caused the decrease of intestinal flora diversity.