饥饿对南方鲇幼鱼胃排空及其数学模型选择的影响

Effect of starvation on gastric evacuation and associated mathematical models in juvenile southern catfish (Silurus meridionalis)

为研究饥饿对南方鲇幼鱼胃排空及其数学模型选择产生的影响,实验在(25±0.5)℃条件下,在对照组(饥饿0 d,S0)和饥饿组(饥饿16 d,S16;饥饿32 d,S32)实验鱼摄入6%BW(百分比体质量)泥鳅饵料后的不同时间分别测定胃内容物重量及其百分比,用常见3个数学模型对实验数据进行拟合并比较。结果发现,随摄食后时间的增加,3个实验组的胃内容物重量及其百分比均呈现阶段性减少变化特征,但饥饿组(S16,S32)胃内容物重量百分比的下降速率明显慢于S0对照组(P<0.05);S0对照组和饥饿组(S16,S32)胃排空的最优数学模型均为平方根模型;S32饥饿组的胃排空率(0.188%/h)明显小于S0对照组(0.239%/h)(P<0.05),两个饥饿组的胃排空时间(均为64 h)显著长于S0对照组(36 h),二者都延长了近78%。研究表明,饥饿对南方鲇幼鱼的胃排空特征及其最优数学模型未产生显著影响,但明显降低该种鱼的胃排空率并延长胃排空时间。

To investigate the effects of starvation on gastric evacuation and associated mathematical mod- els in juvenile southern catfish （Silurus meridionalis）, experimental fish of both control group （starved 0 d, SO） and starvation groups （starved 16 d, S16; starved 32 d, S32） were all fed a 6%BW loach diet at （25 ＋ 0.5）℃. After diet offered, the wet masses of stomach content at each sampling time were collected and determined. The percentages （wet mass of residual diet/wet mass of total diet） of residual diet in stomach were also calculated and fitted to three common mathematical equations （linear, exponential and square-root）. The results of present study showed that the wet masses of stomach content and percentages of residual diet of both control group and starvation groups decreased significantly, exhibiting a phased trend whereas the decrease rate of percentages of residual diet in starvation groups was lower than that in the SO control group （P〈0.05）. Based on the three evaluation standards, the good fit mathematical equation of both the S0control group and the two starvation groups （S 16, $32） was the square-root model. The gas- tric evacuation rate （0.188 %/h） of the $32 group was much lower than that （0.239 %/h） of the SO control group whereas the gastric evacuation time （all 64 h） of the two starvation groups was much longer than that （36 h） of the SO control group, prolonging approximately 78%. Our results suggest that the gastric evacua- tion and its associated mathematical models did not change after starvation while starvation can decrease significantly the gastric evacuation rate and prolong significantly the evacuation time. All of these findings are adaptive consequences of the natural selection in the southern catfish.