Heterotrophic nanoflagellates are ubiquitous and known to be major predators of bacteria. The feeding of free-living heterotrophic nanoflagellates on phytoplankton is poorly understood, although these two components usually co-exist. To investigate the feeding and ecological roles of major heterotrophic nanoflagellates Katablepharis spp., the feeding ability of Katablepharis japonica on bacteria and phytoplankton species and the type of the prey that K. japonica can feed on were explored. Furthermore, the growth and ingestion rates of K. japonica on the dinoflagellate Akashiwo sanguinea—a suitable algal prey item—heterotrophic bacteria, and the cyanobacteria Synechococcus sp., as a function of prey concentration were determined. Among the prey tested, K. japonica ingested heterotrophic bacteria, Synechococcus sp., the prasinophyte Pyramimonas sp., the cryptophytes Rhodomonas salina and Teleaulax sp., the raphidophytes Heterosigma akashiwo and Chattonella ovata, the dinoflagellates Heterocapsa rotundata, Amphidinium carterae, Prorocentrum donghaiense, Alexandrium minutum, Cochlodinium polykrikoides, Gymnodinium catenatum, A. sanguinea, Coolia malayensis, and the ciliate Mesodinium rubrum, however, it did not feed on the dinoflagellates Alexandrium catenella, Gambierdiscus caribaeus, Heterocapsa triquetra, Lingulodinium polyedra, Prorocentrum cordatum, P. micans, and Scrippsiella acuminata and the diatom Skeletonema costatum. Many K. japonica cells attacked and ingested a prey cell together after pecking and rupturing the surface of the prey cell and then uptaking the materials that emerged from the ruptured cell surface. Cells of A. sanguinea supported positive growth of K. japonica, but neither heterotrophic bacteria nor Synechococcus sp. supported growth. The maximum specific growth rate of K. japonica on A. sanguinea was 1.01 d⁻¹. In addition, the maximum ingestion rate of K. japonica for A. sanguinea was 0.13 ng C predator⁻¹d⁻¹ (0.06 cells predator⁻¹d⁻¹). The maximum ingestion rate of K. japonica for heterotrophic bacteria was 0.019 ng C predator⁻¹d⁻¹ (266 bacteria predator⁻¹d⁻¹), and the highest ingestion rate of K. japonica for Synechococcus sp. at the given prey concentrations of up to ca. 10⁷ cells ml⁻¹ was 0.01 ng C predator⁻¹d⁻¹ (48 Synechococcus predator⁻¹d⁻¹). The maximum daily carbon acquisition from A. sanguinea, heterotrophic bacteria, and Synechococcus sp. were 307, 43, and 22%, respectively, of the body carbon of the predator. Thus, low ingestion rates of K. japonica on heterotrophic bacteria and Synechococcus sp. may be responsible for the lack of growth. The results of the present study clearly show that K. japonica is a predator of diverse phytoplankton, including toxic or harmful algae, and may also affect the dynamics of red tides caused by these prey species.

异养纳米鞭毛无处不在，已知是细菌的主要捕食者。尽管这两种成分通常共存，但对浮游植物上自由生活的异养纳米鞭毛虫的摄食却知之甚少。为了研究主要异养纳米鞭毛Katablepharis spp。的摄食和生态作用，探讨了Katablepharis japonica对细菌和浮游植物种类的摄食能力，以及K. japonica可以摄食的猎物类型。此外，在合适的藻类捕食物—赤鞭藻赤潮（Akashiwo sanguinea）和异养细菌和蓝细菌蓝藻（Synechococcus）上，K。japonica的生长和摄食率。sp。，作为猎物浓度的函数被确定。在被测试的猎物中，日本粳稻摄食了异养细菌，Synechococcus sp。，prasinophyte Pyramimonas sp。，隐生菌Rhodomonas salina和Teleaulax sp。，鳞翅目植物Heterosigma akashiwo和Chattonella ovata，鞭毛藻，杂食藻，亚历山大藻，Cochlodinium polykrikoides，链状裸甲藻，A.荪，Coolia malayensis和纤毛虫红色中缢虫，但是，它没有寄生于甲藻链状亚历山大藻，Gambierdiscus caribaeus，Heterocapsa竹叶，Lingulodinium polyedra，具齿原甲cordatum，海洋原甲藻，和锥状尖锐湿疣和硅藻中肋骨条藻。在啄食并破坏猎物细胞的表面，然后吸收从破裂的细胞表面出现的物质之后，许多K. japonica细胞一起攻击并吞食了猎物细胞。细胞A.荪支持的正增长K.粳稻，但既不异养菌，也没有粘球菌 支持增长。粳稻在豚鼠上的最大比生长率为1.01 d ^-1。此外，最大摄取率K.粳稻为A.血红为0.13毫微克Ç捕食^-1 d ^-1（0.06细胞捕食^-1 d ^-1）。的最大摄取率K.粳稻为异养细菌为0.019纳克Ç捕食^-1 d ^-1（266种细菌的捕食^-1 d ^-1），和最高摄取率K.粳稻为粘球菌 在给定的猎物浓度高达约。10 ^7个细胞ml ^-1为0.01 ng C捕食者^-1 d ^-1（48个Synechococcus捕食者^-1 d ^-1）。每日最大的碳捕获量来自血曲霉，异养细菌和Synechococcus sp。分别占捕食者体内碳的307％，43％和22％。因此，K。japonica在异养细菌和Synechococcus sp上的摄取率较低。可能是缺乏增长的原因。本研究的结果清楚地表明日本粳稻 是各种浮游植物（包括有毒或有害藻类）的捕食者，并且还可能影响这些猎物物种引起的赤潮动态。