基于肌肉和肝脏脂肪酸分析的热带大西洋中上层鲨鱼营养生态位分化研究

Trophic niche partitioning of pelagic shark of tropical Atlantic based on muscle and liver fatty acid profile analysis

多组织脂肪酸组成分析可反映生物不同时间尺度的摄食信息,对探讨大型顶级捕食者群落内物种间的营养生态位分化具有重要指示作用。通过测定热带大西洋中上层鲨鱼——大青鲨(Prionace glauca)、长鳍鲭鲨(Isurus paucus)、拟锥齿鲨(Pseudocarcharias kamoharai)和尖吻鲭鲨(I.oxyrinchus)肝脏和肌肉的脂肪酸组成,探究4种鲨鱼短期(肝脏)和长期(肌肉)摄食策略及营养关系的变化情况。结果显示,4种鲨鱼存在不同程度的食性或栖息地差异,长鳍鲭鲨与拟锥齿鲨营养生态位重叠度较高,两者存在激烈的摄食与栖息地竞争;而长鳍鲭鲨与尖吻鲭鲨生态位分离,两者存在摄食隔离。大青鲨营养生态位宽度较大,表明其对环境的适应性较强,而拟锥齿鲨营养生态位宽度较小,表现为食性特化。比较肝脏和肌肉脂肪酸组成发现,鲨鱼在不同时期的资源分配模式不同,尖吻鲭鲨与大青鲨肌肉的营养生态位重叠最高,而肝脏却分离,说明二者在较长的时间尺度上存在摄食竞争。该研究结果有助于揭示大洋性鲨鱼的共存机制。

Multi-tissue fatty acid profile analysis reflects dietary information of organisms at different time scales,which plays an important indicative role in exploring trophic niche partitioning among large apex predators.In this study,we investigated the trophic niche partitioning of four shark species in the upper middle layer of tropical Atlantic Ocean(Prionace glauca,Isurus paucus,Pseudocarcharias kamoharai,I.oxyrinchus)by measuring the fatty acid profiles of their muscle and liver,to reveal the short-term and long-term feeding strategies and nutritional relationships.The results show that the four shark species had di-verse degrees of dietary or habitat variation,and high trophic niche overlap was found between I.paucus and P.kamoharai,with intense dietary and habitat competition.However,there was trophic niche partitioning between I.paucus and I.oxyrinchus,indi-cating their dietary separation.P.glauca had relatively longer trophic niche width,indicating greater environmental plasticity,while the smaller one of P.kamoharai indicates dietary specialization.Comparison of liver and muscle fatty acid profiles reveals variable resource allocation patterns among sharks over time,with the highest overlap of trophic niche between the muscle of I.oxyrinchus and P.glauca,but separation of livers suggests intense competition for long-term feeding.The results help to un-derstand the coexistence mechanisms of pelagic sharks.