Use of Cell Cultures to Study the Interactions of Ciliates with Fish

Abstract

How the ciliates of fish can be cultured and be used to study ciliate/fish interactions are reviewed. The culturing of ciliates is currently done in basal solutions based on either freshwater, seawater, or bodily fluids of vertebrates. These are supplemented either with bacteria, fish cells, or organic matter, which can be defined or more commonly undefined, with proteose peptone being a prominent example. Among pathogenic ciliates, the most difficult to culture has been Ichthyophthirius multifiliis. To contrast, Cryptocaryon irritans caused a similar disease and has been maintained successfully in co-cultures with fish cells. Pathogenic scuticociliates and tetrahymenas are more amenable to culture, and can be grown axenically. These cultures have been used to study pathogenic mechanisms and to screen drugs for their potential chemotherapeutic value. Ciliates may act directly on fish to cause disease, but may also influence fish health indirectly through their interactions with other types of fish pathogens, for example bacteria and fungi. For example, in culture Tetrahymena spp. have been shown to phagocytose pathogenic bacteria, Yersinia ruckerii, and microsporidia, Glugea hertwigi, where ciliates are not linked to disease, very different ciliate/fish interactions are possible. For some fish larvae, free-living ciliates are a source of nutrients. Large-scale cultures of both freshwater and marine ciliates have been achieved and could be a source of feed for fish larvae in aquaculture. Finally, ciliates have the potential to feed on fish carcasses and in doing so make nutrients available to the ecosystem. In the future cell cultures should be invaluable in studying these and other possible relationships between fish and ciliates.

Current status of parasitic ciliates Chilodonella spp. (Phyllopharyngea: Chilodonellidae) in freshwater fish aquaculture

“…Artificial cultures of some protozoan parasites in vivo and/or in vitro are exceptionally challenging (Crosbie et al . ; Pinheiro & Bols ) and most parasitic ciliates need the presence of their host to grow under artificial conditions (e.g. Cryptocaryon irritans ).…”

Development of a continuous cell line from larval Atlantic cod (Gadus morhua) and its use in the study of the microsporidian, Loma morhua

“…Given the market value of live fish and the relative complexity of in vivo studies, additional research tools are required for timely and efficient means of improving livestock management and production methods. Cell culture and other in vitro methodologies have proven invaluable tools for studies into fish physiology and parasitology, advancing our understanding of piscine pathogens, facilitating the production of vaccines and preliminary evaluations of therapeutic treatments (Bols, ; Bols, Pham, Dayeh, & Lee, ; Hightower & Renfro, ; Lee, Dayeh, Schirmer, & Bols, ; McConnachie, Sheppard, Wright, & Speare, ; Monaghan et al., ; Pinheiro & Bols, ; Villena, ; Woo & Li, ).…”

“…physiology and parasitology, advancing our understanding of piscine pathogens, facilitating the production of vaccines and preliminary evaluations of therapeutic treatments (Bols, 1991;Bols, Pham, Dayeh, & Lee, 2017;Hightower & Renfro, 1988;Lee, Dayeh, Schirmer, & Bols, 2009;McConnachie, Sheppard, Wright, & Speare, 2015;Monaghan et al, 2009;Pinheiro & Bols, 2013;Villena, 2003;Woo & Li, 1990).…”

Some but not All Tetrahymena Species Destroy Monolayer Cultures of Cells from a Wide Range of Tissues and Species

“…One way to study ciliate/fish interaction at the cellular level is to use cocultures of ciliates and fish cells using a variety of potential methods (reviewed in Pinheiro and Bols ). This was recently done with Tetrahymena thermophila (Pinheiro and Bols ), which is a species that is widely used as a model organism in cell biology but usually not considered a fish pathogen.…”