Jeong Hae Jin, Du Yoo Yeong, Kim Jae Seong, Kim Tae Hoon, Kim Jong Hyeok, Kang Nam Seon, Yih Wonho
School of Earth and Environmental Sciences, College of Natural Sciences, Seoul National University, Seoul 151-747, Republic of Korea.
J Eukaryot Microbiol. 2004 Sep-Oct;51(5):563-9. doi: 10.1111/j.1550-7408.2004.tb00292.x.
We first reported here that the harmful alga Cochlodinium polykrikoides, which had been previously known as an autotrophic dinoflagellate, was a mixotrophic species. We investigated the kinds of prey species and the effects of the prey concentration on the growth and ingestion rates of C. polykrikoides when feeding on an unidentified cryptophyte species (Equivalent Spherical Diameter, ESD = 5.6 microm). We also calculated grazing coefficients by combining field data on abundances of C. polykrikoides and co-occurring cryptophytes with laboratory data on ingestion rates obtained in the present study. Cocholdinium polykrikoides fed on prey cells by engulfing the prey through the sulcus. Among the phytoplankton prey offered, C. polykrikoides ingested small phytoplankton species that had ESD's < or = 11 microm (e.g. the prymnesiophyte Isochrysis galbana, an unidentified cryptophyte, the cryptophyte Rhodomonas salina, the raphidophyte Heterosigma akashiwo, and the dinoflagellate Amphidinium carterae). It did not feed on larger phytoplankton species that had ESD's > or = 12 microm (e.g. the dinoflagellates Heterocapsa triquetra, Prorocentrum minimum, Scrippsiella sp., Alexandrium tamarense, Prorocentrum micans, Gymnodinium catenatum, Akashiwo sanguinea, and Lingulodinium polyedrum). Specific growth rates of C. polykrikoides on a cryptophyte increased with increasing mean prey concentration, with saturation at a mean prey concentration of approximately 270 ng C ml(-1) (i.e. 15,900 cells ml(-1)). The maximum specific growth rate (mixotrophic growth) of C. polykrikoides on a cryptophyte was 0.324 d(-1), under a 14:10 h light-dark cycle of 50 microE m(-2) s(-1), while its growth rate (phototrophic growth) under the same light conditions without added prey was 0.166 d(-1). Maximum ingestion and clearance rates of C. polykrikoides on a cryptophyte were 0.16 ng C grazer(-1)d(-1) (9.4 cells grazer(-1)d(-1)) and 0.33 microl grazer(-1)h(-1), respectively. Calculated grazing coefficients by C. polykrikoides on cryptophytes were 0.001-0.745 h(-1) (i.e. 0.1-53% of cryptophyte populations were removed by a C. polykrikoides population in 1 h). The results of the present study suggest that C. polykrikoides sometimes has a considerable grazing impact on populations of cryptophytes.
我们在此首次报道，有害藻类多环旋沟藻（Cochlodinium polykrikoides），此前一直被认为是一种自养性甲藻，实际上是一种混合营养型物种。我们研究了多环旋沟藻在以一种未鉴定的隐藻物种（等效球径，ESD = 5.6微米）为食时的猎物种类，以及猎物浓度对其生长和摄食率的影响。我们还通过将多环旋沟藻和共生隐藻的现场丰度数据与本研究中获得的摄食率实验室数据相结合，计算了摄食系数。多环旋沟藻通过沟吞噬猎物细胞来摄食猎物。在所提供的浮游植物猎物中，多环旋沟藻摄食ESD ≤ 11微米的小型浮游植物物种（例如等鞭金藻Isochrysis galbana、一种未鉴定的隐藻、隐藻盐生红胞藻Rhodomonas salina、针胞藻赤潮异弯藻Heterosigma akashiwo以及甲藻卡特亚单鞭金藻Amphidinium carterae）。它不摄食ESD ≥ 12微米的大型浮游植物物种（例如甲藻三角异帽藻Heterocapsa triquetra、微小原甲藻Prorocentrum minimum、斯克里普藻Scrippsiella sp.、塔玛亚历山大藻Alexandrium tamarense、米氏原甲藻Prorocentrum micans、链状裸甲藻Gymnodinium catenatum、血红裸甲藻Akashiwo sanguinea以及多边舌甲藻Lingulodinium polyedrum）。多环旋沟藻在以隐藻为食时的特定生长率随平均猎物浓度的增加而增加，在平均猎物浓度约为270 ng C ml⁻¹（即15,900个细胞ml⁻¹）时达到饱和。在50 μE m⁻² s⁻¹的14:10小时光暗周期下，多环旋沟藻在以隐藻为食时的最大特定生长率（混合营养生长）为0.324 d⁻¹，而在相同光照条件下无添加猎物时其生长率（光养生长）为0.166 d⁻¹。多环旋沟藻对隐藻的最大摄食率和清除率分别为0.16 ng C食草动物⁻¹ d⁻¹（9.4个细胞食草动物⁻¹ d⁻¹）和0.33 μl食草动物⁻¹ h⁻¹。多环旋沟藻对隐藻的计算摄食系数为0.001 - 0.745 h⁻¹（即1小时内多环旋沟藻种群可去除隐藻种群的0.1 - 53%）。本研究结果表明，多环旋沟藻有时对隐藻种群具有相当大的摄食影响。
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