水位变化影响蝌蚪存活、形态表型和植物血凝素反应

为探究黑斑侧褶蛙蝌蚪形态和生理特征对水位变化的响应,对480只大小相似的蝌蚪进行快速、中速和慢速干涸处理,统计各发育时期时长和存活率,测定变态完成后幼蛙的身体和内脏器官大小,以及对植物血凝素(PHA-P)的反应。结果表明: 对照组蝌蚪的变态时长最长,显著长于快速、中速和慢速干涸组;不同处理变态存活率在72.5%～90.8%,其中对照组最高,快速干涸组最低。对照和慢速干涸组幼蛙的体重和体长均显著高于中速和快速干涸组,快速干涸组体宽、体重与体长的比值、胴体湿重以及肺和脂肪体的湿重系数均最低,但心、脾、肾和消化器官的湿重系数和消化道各段的长度系数均无明显的组间差异。不同处理幼蛙对PHA-P的最大反应值均出现于注射后3 h,且中速和慢速干涸组的最大反应值均显著高于对照组,而快速干涸组与各组均无显著差异。表明黑斑侧褶蛙蝌蚪可通过加速变态发育进程来应对干旱胁迫,但会出现个体变小、细胞介导的免疫能力下降,不利于其成功登陆。

Effects of water level variations on survival,morphological phenotype and responsiveness of tadpoles to phytohemagglutinin

To investigate the responses of morphological and physiological characteristics in tadpoles of Pelophylax nigromaculatus to various water levels, a total of 480 tadpoles with similar sizes were treated with rapid, moderate and slow desiccation. Both the metamorphosis duration and average metamorphosis survival rate of specific developmental stages were counted. Their body and internal organ sizes, as well as the responsiveness to phytohemagglutinin (PHA-P) of froglets were measured after complete metamorphosis. The results showed that the metamorphosis duration of tadpoles in the control group was the longest. The average metamorphosis survival rate of different treatment groups ranged from 72.5% to 90.8%, which was the highest in the control group and the lowest in the rapid desiccation group. Body weight (BW) and body length (BL) of froglets in control and slow desiccation groups were significantly higher than those of moderate or rapid desiccation groups. Body width, ratio of BW to BL, carcass wet weight and the wet weight index of lung and fat body were the lowest in rapid desiccation group. There was no significant difference in the wet weight index of heart, spleen, kidneys and digestive organs, as well as the length index of different segments of whole digestive tract between groups. The maximal response value of froglets to PHA-P appeared at 3 h after injection in different treatments, which was significantly higher in moderate and slow desiccation groups than the control group. There was no significant difference between rapid desiccation group and any other groups. The tadpoles of P. nigromaculatus might accelerate the metamorphosis developmental process to cope with desiccation stress, accompanying with decreased atrophic body size and weakened cell-mediated immunity, which would harm tadpoles to successfully land.