Feeding by phototrophic red-tide dinoflagellates: five species newly revealed and six species previously known to be mixotrophic

Abstract

We report here for the first time that 5 red-tide dinoflagellates (Gymnodinium catenatum, G. impudicum, Lingulodinium polyedrum, Prorocentrum donghaiense, and P. triestinum) which had been previously thought to be exclusively autotrophic dinoflagellates are mixotrophic species. We investigated the feeding behaviors, the kinds of prey species that 11 mixotrophic red-tide dinoflagellates (Akashiwo sanguinea, Alexandrium tamarense, G. catenatum, G. impudicum, Heterocapsa triquetra, L. polyedrum, P. donghaiense, P. micans, P. minimum, P. triestinum, and Scrippsiella trochoidea) fed on, and the effects of the prey concentration on the growth and ingestion rates of P. donghaiense, H. triquetra, P. micans, and L. polyedrum when feeding on algal prey. We have also calculated grazing coefficients by combining field data on abundances of P. donghaiense, H. triquetra, P. micans, and L. polyedrum and co-occurring prey species. All algal predators tested in the present study ingested small phytoplankton species that had equivalent spherical diameters (ESDs) < 12 μm. A. sanguinea and L. polyedrum were able to ingest large phytoplankton species such as H. triquetra, S. trochoidea, and A. tamarense. Prorocentrum spp. fed on prey by engulfing the prey cell through body sutures, while S. trochoidea engulfed prey through the apical horn as well as through the sulcus. Specific growth rates of P. donghaiense, H. triquetra, and P. micans on a cryptophyte and L. polyedrum on P. minimum and S. trochoidea increased with increasing mean prey concentration, with saturation occurring at mean prey concentrations of 110 to 480 ng C ml , respectively. Maximum ingestion rates of P. donghaiense, H. triquetra, and P. micans on the cryptophyte were much lower than those of L. polyedrum on S. trochoidea and P. minimum. The calculated grazing coefficients of P. donghaiense, H. triquetra, and P. micans on the cryptophyte were up to 2.67, 0.091, and 0.041 h

Most harmful algal bloom species are vitamin B1and B12auxotrophs

“…Given the frequent occurrence of HABs, processes such as algal/bacterial symbiosis (15), delivery from external sources (e.g., benthic fluxes, terrestrial run-off) (22), regeneration from microbial processes, and/or vitamin assimilation via phagotrophy must be crucial processes for maintaining vitamin replete conditions for HABs. Although dinoflagellates are well known phagotrophs (58,59), the stability and subsequent bioavailability of large, complex macromolecules such as vitamins following the digestion of algal prey is unknown.…”

The acquisition of phototrophy: adaptive strategies of hosting endosymbionts and organelles

“…phagotrophic phototrophs) (Schnepf and Elbrachter 1992;Jeong et al 2005). Nearly all organelle retaining dinoflagellate species sequester their plastids from free-living cryptophyte algae (Larsen 1988;Fields and Rhodes 1991;Horiguchi and Pienaar 1992;Skovgaard 1998;Park et al 2006;Koike and Takishita 2008;Garcia-Cuetos et al 2009, 2010.…”

“…So why are dinoflagellates so prone to novel plastid acquisitions? About half of all dinoflagellate species are heterotrophic or parasitic, and most of the photosynthetic species are mixotrophic (Schnepf and Elbrachter 1992;Jeong et al 2005). Many dinoflagellates that lack stable plastids, practice organelle retention and temporarily enslave algal plastids for photosynthesis (Skovgaard 1998;Jakobsen et al 2000;Stoecker et al 2009).…”

Bioactive compounds of marine dinoflagellate isolates from western Greenland and their phylogenetic association within the genus Alexandrium

“…A number of allelochemically active microalgae, including species of Alexandrium and Fragilidium, have been shown to be mixotrophic (Jacobson and Anderson, 1986;Tillmann, 1998;Jeong et al, 2005;Stoecker et al, 2006;Yoo et al, 2009;Sheng et al, 2010;Blossom et al, 2012) and it has been speculated that allelochemicals can be deployed for predation. In the present experiments, however phagotrophic uptake of Rhodomonas by Alexandrium was not observed.…”