Genetic Analyses of the rbcL and psaA Genes From Single Cells Demonstrate a Rhodophyte Origin of the Prey in the Toxic Benthic Dinoflagellate Ostreopsis

Abstract

Phagotrophy of the harmful benthic dinoflagellates of the genus Ostreopsis has long been inferred based on observations of food particles present inside cells, but the prey has not yet been identified. This study aimed to investigate the seasonal dynamics of benthic dinoflagellates Ostreopsis spp. in temperate Korean coastal sites, with special emphasis on their phagotrophy. Further, prey species were identified by extracting the ingested food particles from single Ostreopsis cells and determining their rbcL and psaA gene sequences. High concentration of Ostreopsis cells was observed between June and October at all sites, when the water temperatures were higher than 19 • C, exhibiting a marked temporal seasonality. The percentage of Ostreopsis cells containing ingested food particles exhibited large spatial and temporal variations among sampling sites, ranging from undetectable level to 29.5%, and was not always associated with Ostreopsis cell abundance. Phylogenetic analyses performed using both plastid-encoded rbcL and psaA genes revealed that all sequences obtained from the ingested food particles of Ostreopsis cells grouped within the class Florideophyceae, Rhodophyta. Our result clearly demonstrates that Ostreopsis species consume various macroalgae from Rhodophyta, but not protists, which have long been thought to be the potential prey. The results of this study provide a basis for better understanding the mixotrophic behavior and nutritional ecology of the harmful benthic dinoflagellate Ostreopsis species.

Temporal and Spatial Distribution of the Toxic Epiphytic Dinoflagellate Ostreopsis cf. ovata in the Coastal Waters off Jeju Island, Korea

“…Ostreopsis species around Jeju Island has been reported since 2010 [44,50]. Moreover, Hwang et al [13,51] reported the novel cytotoxic non-PLTX compounds Ostreol A and B in the strain isolated from Jeju Island, which have not both been reported in any other strain.…”

Chemical Ecology of the Benthic Dinoflagellate Genus Ostreopsis: Review of Progress and Future Directions

“…ovata were also found on the turf dominated community i.e., in a complex intricate matrix of small Corallinales, Ceramiales (both Florideophyceae) and other filamentous algae (Meroni et al, 2018) as reported in Vila et al (2001) for Ellisolandia elongata and in Blanfuné et al (2015) for Jania rubens. Lee and Park (2018) also showed that Ostreopsis sp. ingested rhodophytes because of their soft cell membrane containing microfibrillar and sulfated galactans (see section 4.2).…”

“…Almada et al (2017) showed evidence of phagotrophy using LysoSensor staining even if the prey inside the cells were not discernable. More recently, using molecular approaches, Lee and Park (2018) defined the red bodies as digestive vacuoles containing ingested red macroalgae (Class Florideophyceae).…”

Benthic dinoflagellates in Korean waters

“…2). Under these circumstances, it is critical to determine whether these dinoflagellates can survive and overwinter in the South and Baek (2012aBaek ( , 2012b, Shah et al (2013aShah et al ( , 2013bShah et al ( , 2014a, and Lee and Park (2018).…”