School of Earth and Environmental Sciences, College of Natural Sciences, Seoul National University, Seoul 08826, Republic of Korea.
School of Earth and Environmental Sciences, College of Natural Sciences, Seoul National University, Seoul 08826, Republic of Korea; Advanced Institutes of Convergence Technology, Suwon, Gyeonggi-do, 16229, Republic of Korea.
Harmful Algae. 2017 Feb;62:94-103. doi: 10.1016/j.hal.2016.12.007. Epub 2017 Jan 6.
To investigate tropical roles of the newly described Yihiella yeosuensis (ca. 8μm in cell size), one of the smallest phototrophic dinoflagellates in marine ecosystems, its trophic mode and the types of prey species that Y. yeosuensis can feed upon were explored. Growth and ingestion rates of Y. yeosuensis on its optimal prey, Pyramimonas sp. (Prasinophyceae), as a function of prey concentration were measured. Additionally, growth and ingestion rates of Y. yeosuensis on the other edible prey, Teleaulax sp. (Cryptophyceae), were also determined for a single prey concentration at which both these rates of Y. yeosuensis on Pyramimonas sp. were saturated. Among bacteria and diverse algal prey tested, Y. yeosuensis fed only on small Pyramimonas sp. and Teleaulax sp. (both cell sizes=5.6μm). With increasing mean prey concentrations, both specific growth and ingestion rates of Y. yeosuensis increased rapidly before saturating at a mean Pyramimonas concentration of 109ngCmL (2725cellsmL). The maximum growth rate (mixotrophic growth) of Y. yeosuensis fed with Pyramimonas sp. at 20°C under a 14:10-h light-dark cycle of 20μEms was 1.32d, whereas the growth rate of Y. yeosuensis without added prey was 0.026d. The maximum ingestion rate of Y. yeosuensis fed with Pyramimonas sp. was 0.37ngCpredatord (9.3cellspredatord). At a Teleaulax concentration of 1130ngCmL (66,240cellsmL), growth and ingestion rates of Y. yeosuensis fed with Teleaulax sp. were 1.285d and 0.38ngCpredatord (22.4cellspredatord), respectively. Thus, Y. yeosuensis rarely grows without mixotrophy, and mixotrophy supports high growth rates in Y. yeosuensis. Y. yeosuensis has the highest maximum mixotrophic growth rate with the exception of Ansanella graniferaamong engulfment feeding mixotrophic dinoflagellates. However, the high swimming speed of Y. yeosuensis (1572μms), almost the highest among phototrophic dinoflagellates, may prevent autotrophic growth. This evidence suggests that Y. yeosuensis may be an effective mixotrophic dinoflagellate predator on Pyramimonas and Teleaulax, and occurs abundantly during or after blooms of these two prey species.
为了研究新描述的最小海洋浮游植物之一——牙海(Yihiella yeosuensis)（细胞大小约为 8μm）在热带地区的作用，探索了其营养方式和可食猎物种类。测量了 Y. yeosuensis 在其最佳猎物——Pyramimonas sp.（绿藻门）上的生长和摄食率，作为 prey concentration 的函数。此外，还在单一 prey concentration 下测定了 Y. yeosuensis 在另一种可食猎物——Teleaulax sp.（隐藻门）上的生长和摄食率，此时 Y. yeosuensis 对 Pyramimonas sp. 的生长和摄食率均已饱和。在所测试的细菌和各种藻类猎物中，Y. yeosuensis 仅以小的 Pyramimonas sp. 和 Teleaulax sp.（均为 5.6μm）为食。随着平均 prey concentration 的增加，Y. yeosuensis 的特定生长和摄食率迅速增加，然后在平均 Pyramimonas 浓度为 109ngCmL（2725cellsmL）时达到饱和。在 20°C 下，Y. yeosuensis 以 Pyramimonas sp. 为食并在 14:10 小时光暗循环（20μEms）下混合营养生长的最大生长率为 1.32d，而没有添加 prey 的 Y. yeosuensis 的生长率为 0.026d。Y. yeosuensis 以 Pyramimonas sp. 为食的最大摄食率为 0.37ngCpredatord（9.3cellspredatord）。在 Teleaulax sp. 浓度为 1130ngCmL（66,240cellsmL）时，Y. yeosuensis 以 Teleaulax sp. 为食的生长和摄食率分别为 1.285d 和 0.38ngCpredatord（22.4cellspredatord）。因此，Y. yeosuensis 在没有混合营养的情况下很少生长，混合营养支持 Y. yeosuensis 的高生长率。Y. yeosuensis 具有最高的最大混合营养生长率，除了吞噬性混合营养甲藻属（Ansanel lagranifera）之外。然而，Y. yeosuensis 的高游动速度（1572μms）几乎是所有浮游植物中最高的，可能会阻止自养生长。这一证据表明，Y. yeosuensis 可能是 Pyramimonas 和 Teleaulax 的有效混合营养性甲藻捕食者，并且在这两种猎物的大量繁殖期间或之后大量存在。
