A review of the characteristics of the dinoflagellate parasite Ichthyodinium chabelardi and its potential effect on fin fish populations

Abstract

This paper focuses on the biology and ecological impacts of Ichthyodinium chabelardi (phylum Dinophyta, class Syndiniophyceae, order Syndiniales), a virulent endobiotic parasite of yolk sacs and young larvae of many species of marine fin fish. Its infections have been observed in warm and temperate open oceanic environments and crowded marine fish tanks. The prevalence of I. chabelardi and the range of its host fishes is not well studied, and our understanding of its life cycle is incomplete. Here, we describe what is known about I. chabelardi infections in fish and we compare this with several other protistan parasites of fish, including Amyloodium ocellatum, Saprolegnia parasitica, Sphaerothecum destruens and the ‘X-cell’ clades Gadixcellia and Xcellia, all of which are considered emerging generalist parasites infecting a wide variety of fin fish species. Recent findings suggest that rising seawater temperatures might lead to higher infection rates in fishes, and we expect that these changing conditions could also expand the ranges of some of these parasitic species. Thus, it is essential that the fishing industry effectively monitors fish tanks and water in the surrounding environments for the presence of zoosporic parasites, including I. chabelardi, so as to take steps to prevent large losses in these fisheries.

Population structure and genome-wide evolutionary signatures reveal putative climate-driven habitat change and local adaptation in the large yellow croaker

“…This finding may reflect high levels of immune stress due to increased pathogen virulence (Mitchell et al 2005 ), diversity (Karvonen et al 2013 ; Luque and Poulin 2008 ), and abundances (Karvonen et al 2013 ) in warm environments. The main pathogens in large yellow croakers include Cryptocaryon irritans , Vibrio alginolyticus , Large yellow croaker iridovirus, and Ichthyodinium chabelardi (Gleason et al 2019 ), which have high incidences at high temperatures (Abdullah et al 2017 ; Yang et al 2021 ). Adaptative microevolution in immune system-related genes might improve fitness in the NH stock in tropical conditions.…”

Syndinean dinoflagellates of the genus Euduboscquella are paraphyletic

“…Rather than having a uninucleate trophont that emerges from the host to divide and produce infective/dispersal spores, I . chabelardi forms a series of plasmodia, each undergoing schizogony, with dinospores formed by the last generation of schizonts (Gleason et al, 2019).…”

“…molecular phylogeny, morphology, parasites, sporogenesis, syndinean Group I negatively impacting commercially important fisheries by causing host mortality or disease that reduces host marketability (Gleason et al, 2019;Meyers et al, 1987;Taylor & Khan, 1995;Yuasa et al, 2007). Syndinean dinoflagellates also may play important ecological roles by recycling energy and matter through or within the microbial loop (Jephcott et al, 2016;Park et al, 2004;Salomon et al, 2009).…”

“…(Cachon, 1964; Coats et al, 1994, 2012; Jung et al, 2016), syndinean dinoflagellates are parasitoids, as completion of their life cycle generally kills their host. Syndinean epizootics can thus reduce host abundances (Chambouvet et al, 2008; Choi et al, 2017; Velo‐Suárez et al, 2013), with some species negatively impacting commercially important fisheries by causing host mortality or disease that reduces host marketability (Gleason et al, 2019; Meyers et al, 1987; Taylor & Khan, 1995; Yuasa et al, 2007). Syndinean dinoflagellates also may play important ecological roles by recycling energy and matter through or within the microbial loop (Jephcott et al, 2016; Park et al, 2004; Salomon et al, 2009).…”

Microscopic marine invertebrates are reservoirs for cryptic and diverse protists and fungi

“…Ichthyodinium spp. infect fish eggs [88] whereas Euduboscquella spp. are found in tintinnid ciliates [89].…”