Symbioses of Ciliates (Ciliophora) and Diatoms (Bacillariophyceae): Taxonomy and Host–Symbiont Interactions

Abstract

The nature of the plankton symbioses between ciliates and diatoms has been investigated from the tropical South Atlantic Ocean, and Mediterranean and Caribbean Seas. The obligate symbioses of the diatoms Chaetoceros dadayi or C. tetrastichon with the tintinnid Eutintinnus spp., and Chaetoceros coarctatus with the peritrich ciliate Vorticella oceanica are the most widespread, and the consortium of Chaetoceros densus and Vorticella sp. have been rediscovered. Facultative symbioses between Eutintinnus lususundae and Chaetoceros peruvianus, Hemiaulus spp., and Thalassionema sp. are less frequent, often containing three or four partners because Hemiaulus can also harbor the diazotrophic cyanobacteria Richelia intracellularis. Another three-partner consortium is the peritrich ciliate Zoothamnium pelagicum, ectobiont bacteria, and the diatom Licmophora sp. The predominantly oligotrophic conditions of tropical seas do not favor the survival of large diatoms, but large species of Coscinodiscus and Palmerina in facultative symbiosis with Pseudovorticella coscinodisci have a competitive advantage over other diatoms (i.e., reduction of sinking speed and diffusive boundary layer). Symbioses allow sessile peritric ciliates to extend their distribution in the pelagic environment, permit boreal-polar related diatoms such as C. coarctatus or Fragilariopsis doliolus to inhabit tropical seas, and help large diatoms to extend their survival under unfavorable conditions.

Whole-genome scanning reveals environmental selection mechanisms that shape diversity in populations of the epipelagic diatom Chaetoceros

“…It is moreover evident that other localisations harbour Chaetoceros populations, such as for instance in the Southern Ocean where diatoms dominate photosynthetic protist assemblages [ 13 , 35 ]. In the same vein, associations between Chaetoceros and tintinnid ciliates have been observed in the Pacific Ocean and Caribbean Sea [ 42 , 91 ] https://www.zotero.org/google-docs/?lxqQIn , which were only partially sampled during the Tara Oceans expeditions [ 13 ]. Future oceanographic campaigns should help reveal the distribution of Chaetoceros populations and the extent of their genomic variability.…”

“…Some associated bacteria have even been observed to favour resistance of Chaetoceros cells against viral infection and lysis compared to axenic controls [ 41 ]. Chaetoceros can be involved in photosymbioses with epibiotic peritrich and tintinnid ciliates [ 42 ], interact with nitrogen-fixing cyanobacteria in diatom–diazotroph associations [ 43 , 44 ] and is globally highly connected with other plankton members in the Tara Oceans network of planktonic associations [ 45 ]. Therefore, given the ecological significance of Chaetoceros and its prevalence in regions particularly predicted to be vulnerable to climate change, the present study focuses on describing patterns of genetic diversity and population structure of this diatom genus.…”

Responses of attached bacterial communities to blooms of the swimming shelled pteropod Creseis acicula in Daya Bay, southern China

“…Reasonably, some bacteria attach to C. acicula shells. For example, in the present study, the abundance of Halioglobus and Haloferula spp., which were proven to be the dominant bacteria in mussel feces (Griffin et al 2021 ), was positive, although the correlation efficiency did not reach a significant level, related to the density of C. acicula in the waters; (2) the C. acicula shells also served as the substratum for some epizoic diatom Licmophora sp., which have specialized mucilage pads and stalks favoring them to adhere on shells (Russell and Norris 1971 , Hiromi et al 1985 , Gómez et al 2018 , 2020 ). Therefore, the abundance of Licmophora sp.…”

Whole-genome scanning reveals selection mechanisms in epipelagic Chaetoceros diatom populations

“…It is moreover evident that other localisations harbour Chaetoceros populations, such as for instance in the Southern Ocean where diatoms dominate photosynthetic protist assemblages (Malviya et al 2016;Sommeria-Klein et al 2021). In the same vein, associations between Chaetoceros and tintinnid ciliates have been observed in the Pacific Ocean and Caribbean Sea (Gómez 2007;Gómez 2020), which were only partially sampled during the Tara Oceans expeditions (Malviya et al 2016). Future oceanographic campaigns should help reveal the distribution of Chaetoceros populations and the extent of their genomic variability.…”

“…Some associated bacteria have even been observed to favour resistance of Chaetoceros cells against viral infection and lysis compared to axenic controls (Kimura and Tomaru 2014). Chaetoceros can be involved in photosymbioses with epibiotic peritrich and tintinnid ciliates (Gómez 2020), interact with nitrogen-fixing cyanobacteria in diatom-diazotroph associations (Foster et al 2011; Pierella Karlusich, Pelletier, et al 2021) and is globally highly connected with other plankton members in the Tara Oceans network of planktonic associations (Vincent and Bowler 2020). Therefore, given the ecological significance of Chaetoceros and its prevalence in regions particularly predicted to be vulnerable to climate change, the present study focuses on describing patterns of genetic diversity and population structure of this diatom genus.…”