A Dinoflagellate Amylax triacantha with Plastids of the Cryptophyte Origin: Phylogeny, Feeding Mechanism, and Growth and Grazing Responses. (30th April 2013)

• Record Type: Journal Article
• Authors: Park, Myung Gil; Kim, Miran; Kang, Misun
• Is Part Of: Journal of eukaryotic microbiology. Volume 60:Number 4(2013:Jul./Aug.)
• Page Start: 363
• Page End: 376
• Publication Date: 2013-04-30
• Subjects: Protista -- Periodicals; Eukaryotic cells -- Periodicals; Microbiology -- Periodicals; 579.05
• DOI: 10.1111/jeu.12041
• Languages: English
• ISSNs: 1066-5234

Abstract

<abstract abstract-type="main" xml:lang="en" id="jeu12041-abs-0001"> <title>Abstract</title> <p>The gonyaulacalean dinoflagellates <italic>Amylax</italic> spp. were recently found to contain plastids of the cryptophyte origin, more specifically of <italic>Teleaulax amphioxeia</italic>. However, not only how the dinoflagellates get the plastids of the cryptophyte origin is unknown but also their ecophysiology, including growth and feeding responses as functions of both light and prey concentration, remain unknown. Here, we report the establishment of <italic>Amylax triacantha</italic> in culture, its feeding mechanism, and its growth rate using the ciliate prey <italic>Mesodinium rubrum</italic> (= <italic>Myrionecta rubra</italic>) in light and dark, and growth and grazing responses to prey concentration and light intensity. The strain established in culture in this study was assigned to <italic>A. triacantha</italic>, based on morphological characteristics (particularly, a prominent apical horn and three antapical spines) and nuclear SSU and LSU rDNA sequences. <italic>Amylax triacantha</italic> grew well in laboratory culture when supplied with the marine mixotrophic ciliate <italic>M. rubrum</italic> as prey, reaching densities of over 7.5 × 10<sup>3</sup> cells/ml. <italic>Amylax triacantha</italic> captured its prey using a tow filament, and then ingested the whole prey by direct engulfment through the sulcus. The dinoflagellate was able to grow heterotrophically in the dark, but the growth rate was approximately two times lower than in the light. Although mixotrophic growth rates of <italic>A</italic>. <italic>triacantha</italic> increased sharply with mean prey concentrations, with maximum growth rate being 0.68/d, phototrophic growth (i.e. growth in the absence of prey) was −0.08/d. The maximum ingestion rate was 2.54 ng C/<italic>Amylax</italic>/d (5.9 cells/<italic>Amylax</italic>/d). Growth rate also increased with increasing light intensity, but the effect was evident only when prey was supplied. Increased growth with increasing light intensity was accompanied by a corresponding increase in ingestion. In mixed cultures of two predators, <italic>A. triacantha</italic> and <italic>Dinophysis acuminata</italic>, with <italic>M. rubrum</italic> as prey, <italic>A</italic>. <italic>triacantha</italic> outgrew <italic>D</italic>. <italic>acuminata</italic> due to its approximately three times higher growth rate, suggesting that it can outcompete <italic>D</italic>. <italic>acuminata</italic>. Our results would help better understand the ecophysiology of dinoflagellates retaining foreign plastids.</p> </abstract>