University of Delaware, 1044 College Dr., Lewes DE 19958, United States.
BioImaging Center, University of Delaware, Delaware Biotechnology Institute, 590 Avenue 1743, Newark, DE 19713, United States.
Harmful Algae. 2022 Jan;111:102168. doi: 10.1016/j.hal.2021.102168. Epub 2021 Dec 24.
In laboratory culture, the toxic dinoflagellate Dinophysis acuminata acquires plastids from the ciliate, Mesodinium rubrum, which, in turn, acquires plastids from the cryptophyte, Teleaulax amphioxeia. Reports of D. acuminata from field samples found plastids of the raphidophyte, Heterosigma akashiwo within D. acuminata cells, suggesting a broader range of prey. Dinophysis blooms often co-occur with H. akashiwo in Delaware's inland bays. In the study presented here, predation on H. akashiwo by D. acuminata was investigated. Growth rates of D. acuminata were measured when cultured with H. akashiwo either alone or with its known prey, M. rubrum. M. rubrum was also cultured with H. akashiwo to examine predation by the ciliate as a vector for Heterosigma plastids. Ingestion rates by D. acuminata were measured when presented with H. akashiwo as prey, and retention of plastids from H. akashiwo was investigated by measuring chlorophyll a fluorescence intensities in D. acuminata cells presented with H. akashiwo as prey compared to M. rubrum. Additionally, a fluorescence-based method was developed to identify the presence of the accessory pigment fucoxanthin from H. akashiwo plastids in cells of D. acuminata. Results showed that the growth rate of D. acuminata was significantly lower when offered H. akashiwo as prey compared the growth rate when offered M. rubrum as prey. Likewise, no predation was observed when D. acuminata was offered H. akashiwo as prey. Intensity of chlorophyll a fluorescence was lower when H. akashiwo was offered as prey compared to M. rubrum, and fucoxanthin was not detected in any of the Dinophysis cells examined after incubation with H. akashiwo. Results of this investigation do not support the hypothesis that D. acuminata preys on H. akashiwo and highlight the need for further research on factors that stimulate the growth of Dinophysis in field populations.
在实验室培养中，有毒双鞭甲藻从纤毛虫 Mesodinium rubrum 中获得叶绿体，而纤毛虫 Mesodinium rubrum 又从隐藻 Teleaulax amphioxeia 中获得叶绿体。从野外样本中报告的双鞭甲藻中发现了双鞭甲藻细胞内的甲藻 Heterosigma akashiwo 的叶绿体，这表明其猎物范围更广。双鞭甲藻水华经常与 Delaware 内陆湾的甲藻 Heterosigma akashiwo 同时出现。在本研究中，研究了双鞭甲藻对甲藻 Heterosigma akashiwo 的捕食作用。当单独培养或与已知猎物纤毛虫 Mesodinium rubrum 一起培养时，测量了双鞭甲藻的生长率。还培养了纤毛虫 Mesodinium rubrum 与甲藻 Heterosigma akashiwo 一起，以研究纤毛虫作为 Heterosigma 叶绿体载体的捕食作用。当将甲藻 Heterosigma akashiwo 作为猎物时，测量了双鞭甲藻的摄食率，并通过测量提供甲藻 Heterosigma akashiwo 作为猎物的双鞭甲藻细胞中的叶绿素 a 荧光强度与提供纤毛虫 Mesodinium rubrum 作为猎物的细胞中的叶绿素 a 荧光强度来研究从甲藻 Heterosigma akashiwo 中保留的叶绿体。此外，还开发了一种基于荧光的方法来鉴定双鞭甲藻细胞中来自甲藻 Heterosigma akashiwo 叶绿体的辅助色素叶黄素的存在。结果表明，当提供甲藻 Heterosigma akashiwo 作为猎物时，双鞭甲藻的生长速度明显低于提供纤毛虫 Mesodinium rubrum 作为猎物时的生长速度。同样，当提供甲藻 Heterosigma akashiwo 作为猎物时，没有观察到双鞭甲藻的捕食作用。与提供纤毛虫 Mesodinium rubrum 作为猎物相比，提供甲藻 Heterosigma akashiwo 作为猎物时叶绿素 a 荧光强度较低，并且在用甲藻 Heterosigma akashiwo 孵育后，在任何检查过的双鞭甲藻细胞中均未检测到叶黄素。本研究结果不支持双鞭甲藻捕食甲藻 Heterosigma akashiwo 的假设，并强调需要进一步研究刺激野外双鞭甲藻种群生长的因素。
