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Feeding by the Newly Described Mixotrophic Dinoflagellate Paragymnodinium shiwhaense : Feeding Mechanism, Prey Species, and Effect of Prey Concentration
Author(s) -
YOO YEONG DU,
JEONG HAE JIN,
KANG NAM SEON,
SONG JAE YOON,
KIM KWANG YOUNG,
LEE GITACK,
KIM JUHYOUNG
Publication year - 2010
Publication title -
journal of eukaryotic microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.067
H-Index - 77
eISSN - 1550-7408
pISSN - 1066-5234
DOI - 10.1111/j.1550-7408.2009.00448.x
Subject(s) - biology , dinoflagellate , mixotroph , heterosigma akashiwo , predation , botany , isochrysis galbana , red tide , diatom , alexandrium tamarense , gymnodinium , algae , ecology , phytoplankton , algal bloom , heterotroph , bacteria , genetics , nutrient
. To investigate the feeding by the newly described mixotrophic dinoflagellate Paragymnodinium shiwhaense (GenBank accession number=AM408889), we explored the feeding process and the kinds of prey species that P. shiwhaense is able to feed on using several different types of microscopes, including a transmission electron microscope and high‐resolution video‐microscopy. In addition, we measured the growth and ingestion rates of P. shiwhaense on its optimal algal prey Amphidinium carterae as a function of prey concentration. We also measured these parameters for edible prey at a single concentration at which the growth and ingestion rates of P. shiwhaense on A. carterae were saturated. Paragymnodinium shiwhaense feed on algal prey using a peduncle after anchoring the prey by a tow filament. Among the algal prey offered, P. shiwhaense ingested small algal species that had equivalent spherical diameters (ESDs) ≤11 μm (e.g. the prymnesiophyte Isochrysis galbana , the cryptophytes Teleaulax sp. and Rhodomonas salina , the raphidophyte Heterosigma akashiwo , and the dinoflagellates Heterocapsa rotundata and A. carterae ). However, it did not feed on larger algal species that had ESDs ≥12 μm (e.g. the dinoflagellates Prorocentrum minimum , Heterocapsa triquetra , Scrippsiella trochoidea , Alexandrium tamarense , Prorocentrum micans , Gymnodinium catenatum , Akashiwo sanguinea , and Lingulodinium polyedrum ) or the small diatom Skeletonema costatum . The specific growth rates for P. shiwhaense feeding upon A. carterae increased rapidly with increasing mean prey concentration before saturating at concentrations of ca. 350 ng C/ml (5,000 cells/ml). The maximum specific growth rate (i.e. mixotrophic growth) of P. shiwhaense on A. carterae was 1.097/d at 20 °C under a 14:10 h light–dark cycle of 20 μE/m 2 /s, while its growth rate (i.e. phototrophic growth) under the same light conditions without added prey was −0.224/d. The maximum ingestion and clearance rates of P. shiwhaense on A. carterae were 0.38 ng C/grazer/d (5.4 cells/grazer/d) and 0.7 μl/grazer/h, respectively. The calculated grazing coefficients for P. shiwhaense on co‐occurring Amphidinium spp. was up to 0.07/h (i.e. 6.7% of the population of Amphidinium spp. was removed by P. shiwhaense populations in 1 h). The results of the present study suggest that P. shiwhaense can have a considerable grazing impact on algal populations.