三亚湾近岸两种优势砂壳纤毛虫对硅藻的摄食初探

浮游纤毛虫是近岸生态系统中的重要原生动物，对初级生产者有较高的摄食压力，其摄食行为对物质在食物网中的传递至关重要。近岸生态系统中浮游植物群落多以硅藻为优势类群，为更好地认识纤毛虫对初级生产者尤其是硅藻的摄食调控作用，本研究于2015年4月在三亚湾近岸采集了两种优势砂壳纤毛虫（妥肯丁拟铃虫Tintinnopsis tocantinensis和斯氏拟铃虫T.schotti），运用分子生物学方法分析其食物组成。结果表明，两种纤毛虫中共检测到8属13种硅藻来源的食物，分别隶属于骨条藻（Skeletonema）、细柱藻（Leptocylindrus）、根管藻（Rhizosolenia）、海链藻（Thalassiosira）、拟菱形藻（Pseudo-nitzschia）、波纹藻（Cymatosira）、星杆藻（Asterionellopsis）和角毛藻（Chaetoceros）。两种纤毛虫均摄食骨条藻、细柱藻、根管藻和海链藻，其中对中肋骨条藻（S.costatum）的摄食比例最高（达>60%，序列数百分比）。粒径较大的斯氏拟铃虫摄食多样性（11种）略高于粒径较小的妥肯丁拟铃虫（7种），而且环境中最优势的拟菱形藻（49.12%，浮游植物丰度百分比）仅在斯氏拟铃虫中检测到（15.55%，序列数百分比），说明两种纤毛虫具有一定的摄食选择性且存在种间差异。本研究表明以纤毛虫为代表的原生动物对硅藻的广泛摄食是初级生产者在食物链传递的重要环节，这对理解近岸生态系统的物质传递和砂壳纤毛虫重要生态作用具有重要意义。

Preliminary study on two dominant tintinnids feeding on diatoms in the coastal waters of Sanya bay

Planktonic ciliates, which play important roles in transferring materials in food webs by grazing on primary producers, are considered as an important group of protozoans in coastal waters.Diatoms are important primary producers dominating phytoplankton community in coastal ecosystem.To better understand the role of ciliates in the transmission of primary producers (especially diatoms) along the food chain, two dominant species of tintinnids (Tintinnopsis tocantinensis and T.schotti) were collected from coastal water of Sanya bay in April, 2015, and in situ feeding diversity of these ciliates were analyzed by molecular techniques.In total, 13 diatom species belonging to 8 genera were detected in the diet of ciliates, including Skeletonema, Leptocylindrus, Rhizosolenia, Thalassosira, Pseudo-nitzschia, Cymatosira, Asterionellopsis and Chaetoceros. Two species of ciliates had the same preys as Skeletonema, Leptocylindrus, Rhizosolenia and Thalassosira, among which Skeletonema (S.costatum) was the most abundant prey items (>60%, percent of total squences).T.schotti, a larger size species, had a more diverse diet (11 species) than that in the smaller T.tocantinensis (7 species).Furthermore, the most abundant phytoplankton species (Pseudo-nitzschia) in the ambient water (49.12%, percent of phytoplankton abundance) was only detected in T.schotti(15.55%, percent of total sequences), which suggested ciliates have a selective feeding behavior in the natural environment.The results directly proved that ciliates could widely feed on diatoms and indicated that ciliates were an important link of diatom transfer along food chain in coastal ecosystem.These findings are helpful to understand the ecological role of ciliates and materials transfer in coastal ecosystems.