School of Earth and Environmental Sciences, College of Natural Sciences, Seoul National University, Seoul, Korea.
J Eukaryot Microbiol. 2011 Mar-Apr;58(2):152-70. doi: 10.1111/j.1550-7408.2011.00531.x. Epub 2011 Feb 18.
Woloszynskia species are dinoflagellates in the order Suessiales inhabiting marine or freshwater environments; their ecophysiology has not been well investigated, in particular, their trophic modes have yet to be elucidated. Previous studies have reported that all Woloszynskia species are photosynthetic, although their mixotrophic abilities have not been explored. We isolated a dinoflagellate from coastal waters in western Korea and established clonal cultures of this dinoflagellate. On the basis of morphology and analyses of the small/large subunit rRNA gene (GenBank accession number=FR690459), we identified this dinoflagellate as Woloszynskia cincta. We further established that this dinoflagellate is a mixotrophic species. We found that W. cincta fed on algal prey using a peduncle. Among the diverse prey provided, W. cincta ingested those algal species that had equivalent spherical diameters (ESDs) ≤12.6 μm, exceptions being the diatom Skeletonema costatum and the dinoflagellate Prorocentrum minimum. However, W. cincta did not feed on larger algal species that had ESDs≥15 μm. The specific growth rates for W. cincta increased continuously with increasing mean prey concentration before saturating at a concentration of ca. 134 ng C/ml (1,340 cells/ml) when Heterosigma akashiwo was used as food. The maximum specific growth rate (i.e. mixotrophic growth) of W. cincta feeding on H. akashiwo was 0.499 d(-1) at 20 °C under illumination of 20 μE/m(2) /s on a 14:10 h light-dark cycle, whereas its growth rate (i.e. phototrophic growth) under the same light conditions without added prey was 0.040 d(-1). The maximum ingestion and clearance rates of W. cincta feeding on H. akashiwo were 0.49 ng C/grazer/d (4.9 cells/grazer/d) and 1.9 μl/grazer/h, respectively. The calculated grazing coefficients for W. cincta on co-occurring H. akashiwo were up to 1.1 d(-1). The results of the present study suggest that grazing by W. cincta can have a potentially considerable impact on prey algal populations.
沃氏藻属物种是苏塞斯目甲藻纲的浮游生物，生活在海洋或淡水环境中；它们的生态生理学尚未得到很好的研究，特别是它们的营养方式尚未得到阐明。先前的研究报告称，所有沃氏藻属物种都是光合作用的，但它们的混合营养能力尚未得到探索。我们从朝鲜西部沿海地区分离出一种甲藻，并建立了这种甲藻的克隆培养物。根据形态学和小/大亚基 rRNA 基因（GenBank 登录号=FR690459）的分析，我们将这种甲藻鉴定为沃氏弯角藻。我们进一步确定，这种甲藻是一种混合营养物种。我们发现，沃氏弯角藻使用柄部摄取藻类猎物。在所提供的各种猎物中，沃氏弯角藻摄取的那些藻类的等球直径（ESD）≤12.6μm，例外的是硅藻 Skeletonema costatum 和甲藻 Prorocentrum minimum。然而，沃氏弯角藻不会摄取 ESD≥15μm 的较大藻类物种。当使用 Heterosigma akashiwo 作为食物时，沃氏弯角藻的特定生长率随着平均猎物浓度的增加而持续增加，直到在约 134ng C/ml（1,340 个细胞/ml）的浓度下达到饱和。沃氏弯角藻以 H.akashiwo 为食时的最大特定生长率（即混合营养生长）在 20°C 下光照强度为 20μE/m²/s、光暗周期为 14:10 小时时为 0.499 d⁻¹，而在相同光照条件下没有添加猎物时的生长率（即光营养生长）为 0.040 d⁻¹。沃氏弯角藻以 H.akashiwo 为食时的最大摄食和清除率分别为 0.49ng C/吞噬者/d（4.9 个细胞/吞噬者/d）和 1.9μl/吞噬者/h。沃氏弯角藻对共存的 H.akashiwo 的摄食系数高达 1.1 d⁻¹。本研究结果表明，沃氏弯角藻的摄食可能对猎物藻类种群产生相当大的影响。
