Cryothecomonas aestivalis sp. nov., a colourless nanoflagellate feeding on the marine centric diatomGuinardia delicatula (Cleve) Hasle

Abstract

The vegetative life cycle, host specificity, morphology, and ultrastructure of a new phagotrophic nanoflagellate are described: Cryothecomonas aestivalis Drebes, Kfihn & Schnepf sp. nov. During summer and autumn it is frequently found in the North Sea phytoplankton feeding on the centric diatom Guinardia delicatula. The flagellate penetrates the diatom cell and phagocyfizes the host cytoplasm by means of a pseudopodium that emerges from the posterior cell pole. The mature trophont gives rise to eight or more biflagellate swarmers which leave the emptied diatom frustule. Transmission electron microscopy revealed a delicate theca surrounding the swarmers. The pseudopodium protrudes through a gap in the theca. The cytostome consists of a membranous labyrinth. The mitochondria are of the tubular type. The two apically inserted flagella are heretodynamic and of unequal length. They are smooth, and their basal bodies are surrounded by satellites and fibrous strands ("transitional fibres" sensu Thomsen et al., 1990). In the trophonts and dividing flagellates the transition region between the flagellum and the basal body ends apically with a massive transitional cylinder instead of distinct microtubules, and is surrounded by a funnel of the theca. The nuclear envelope disintegrates during mitosis. Due to the fine structural details the new flagellate is placed in the genus Cryothecomonas Thomsen et al., a genus of still uncertain position.

Parasitic infection of the diatom Guinardia delicatula, a recurrent and ecologically important phenomenon on the New England Shelf

“…As part of this step, for the G. delicatula category, cells and chains with visible signs of internal parasite infection were manually annotated. As described by Drebes et al (1996), the first life cycle stage of the parasite is a motile, colorless flagellate, either outside the host or inside the host before food uptake. Free cells of this stage are not likely to be imaged by IFCB since they do not contain chlorophyll (though they may have sometimes been in cluded in a G. delicatula image, e.g.…”

“…Here we present details of interactions between the centric diatom G. delicatula and a nanoflagellate parasite/parasitoid similar to Cryothecomonas aestivalis as described by Drebes et al (1996), and their recurring interactions as documented by IFCB throughout the time series from June 2006 to September 2013. While many species are present in the MVCO time series and blooms are typically multispecies events, G. delicatula represents one of the greatest contributors to phytoplankton biomass, which is also true in another temperate coastal time series (Schlüter et al 2012).…”

Food uptake and fine structure of Cryothecomonas longipes sp. nov., a marine nanoflagellate incertae sedis feeding phagotrophically on large diatoms

“…33, 34). The proximal parts of the basal bodies are, furthermore, surrounded by diffuse, electron-dense bodies ("satellites" sensu Drebes et al 1996;Figs. 27-29, 30-32).…”

“…The taxonomic position of Cryothecomonas remains enigmatic (see also Thomsen et al 1991;Drebes et al 1996).…”

“…The other species of Cryothecomonas (see Thomsen et al 1991;Drebes et al 1996) are less closely related to C. longipes. In conclusion, it is justified to erect a new species, Cryothecomonas longipes.…”