Mixotrophy in the newly described dinoflagellate Ansanella granifera: feeding mechanism, prey species, and effect of prey concentration

doi:2014.29.2.137

Algae > Volume 29(2); 2014 > Article

Algae 2014;29(2): 137-152. doi: https://doi.org/10.4490/algae.2014.29.2.137

Sook Kyung Lee¹, Hae Jin Jeong²^,3^,*, Se Hyeon Jang², Kyung Ha Lee², Nam Seon Kang², Moo Joon Lee² and Éric Potvin²

¹KHNP-Central Research Institute, Korea Hydro & Nuclear Power Corporation, Daejeon 305-343, Korea
²School of Earth and Environmental Sciences, College of Natural Sciences, Seoul National University, Seoul 151-747, Korea
³Advanced Institutes of Convergence Technology, Suwon 443-270, Korea

*Corresponding Author

Email: hjjeong@snu.ac.kr

ABSTRACT

Mixotrophic protists play diverse roles in marine food webs as predators and prey. Thus, exploring mixotrophy in phototrophic protists has emerged as a critical step in understanding marine food webs and cycling of materials in marine ecosystem. To investigate the feeding of newly described mixotrophic dinoflagellate Ansanella granifera, we explored the feeding mechanism and the different types of species that A. granifera was able to feed on. In addition, we measured the growth and ingestion rates of A. granifera feeding on the prasinophyte Pyramimonas sp., the only algal prey, as a function of prey concentration. A. granifera was able to feed on heterotrophic bacteria and the cyanobacterium Synechococcus sp. However, among the 12 species of algal prey offered, A. granifera ingested only Pyramimonas sp. A. granifera ingested the algal prey cell by engulfment. With increasing mean prey concentration, the growth rate of A. granifera feeding on Pyramimonas sp. increased rapidly, but became saturated at a concentration of 434 ng C mL-1 (10,845 cells mL-1). The maximum specific growth rate (i.e., mixotrophic growth) of A. granifera feeding on Pyramimonas sp. was 1.426 d-1, at 20°C under a 14 : 10 h light-dark cycle of 20 μE m-2 s-1, while the growth rate (i.e., phototrophic growth) under similar light conditions without added prey was 0.391 d-1. With increasing mean prey concentration, the ingestion rate of A. granifera feeding on Pyramimonas sp. increased rapidly, but slightly at the concentrations ≥306 ng C mL-1 (7,649 cells mL-1). The maximum ingestion rate of A. granifera feeding on Pyramimonas sp. was 0.97 ng C predator-1 d-1 (24.3 cells grazer-1d-1). The calculated grazing coefficients for A. granifera feeding on co-occurring Pyramimonas sp. were up to 2.78 d-1. The results of the present study suggest that A. granifera can sometimes have a considerable grazing impact on the population of Pyramimonas spp.

Key words: engulfment; feeding; growth; ingestion; mixotrophy; protist; red tide