The aphelids are a small group of intracellular parasitoids of common species of eukaryotic phytoplankton with three known genera Aphelidium, Amoeboaphelidium, and Pseudaphelidium, and 10 valid species, which form along with related environmental sequences a very diversified group. The phyla Microsporidia and Cryptomycota, and the class Aphelidea have recently been considered to be a deep branch of the Holomycota lineage forming the so called the ARM-clade which is sister to the fungi. In this review we reorganize the taxonomy of ARM-clade, and establish a new superphylum the Opisthosporidia with three phyla: Aphelida phyl. nov., Cryptomycota and Microsporidia. We discuss here all aspects of aphelid investigations: history of our knowledge, life cycle peculiarities, the morphology (including the ultrastructure), molecular phylogeny, ecology, and provide a taxonomic revision of the phylum supplied with a list of species. We compare the aphelids with their nearest relatives, the species of Rozella, and improve the diagnosis of the phylum Cryptomycota.
Despite increasingly sophisticated microbiological techniques, and long after the first discovery of microbes, basic knowledge is still lacking to fully appreciate the ecological importance of microbial parasites in fish. This is likely due to the nature of their habitats as many species of fish suffer from living beneath turbid water away from easy recording. However, fishes represent key ecosystem services for millions of people around the world and the absence of a functional ecological understanding of viruses, prokaryotes, and small eukaryotes in the maintenance of fish populations and of their diversity represents an inherent barrier to aquatic conservation and food security. Among recent emerging infectious diseases responsible for severe population declines in plant and animal taxa, fungal and fungal-like microbes have emerged as significant contributors. Here, we review the current knowledge gaps of fungal and fungal-like parasites and pathogens in fish and put them into an ecological perspective with direct implications for the monitoring of fungal fish pathogens in the wild, their phylogeography as well as their associated ecological impact on fish populations. With increasing fish movement around the world for farming, releases into the wild for sport fishing and human-driven habitat changes, it is expected, along with improved environmental monitoring of fungal and fungal-like infections, that the full extent of the impact of these pathogens on wild fish populations will soon emerge as a major threat to freshwater biodiversity.
Although many species of zoosporic true fungi have been frequently observed and studied in freshwater and soil ecosystems, only three species have been properly identified and partially characterised from brackish and marine ecosystems, namely Rhizophydium littoreum Amon, Thalassochytrium gracilariopsis Nyvall, Pedersén et Longcore and Chytridium polysiphoniae Cohn. These species are either facultative or obligate parasites of marine macroalgae and invertebrates. Also, some species of Olpidium and Rhizophydium are parasites of small marine green algae and diatoms. Although the physiological effects of these pathogens on the growth and metabolism of their hosts are poorly understood, parasitism by C. polysiphoniae possibly affects the rates of photosynthesis and patterns of growth in infected communities of brown algae. Saprobic ecotypes of R. littoreum can also colonise dead-plant and animal substrates. Zoospores from zoosporic true fungi and other groups of microbes possibly provide important food resources for grazing and filter-feeding zooplankton and metazoans in marine ecosystems where the prevalence of disease is high or where accumulated detritus enhances biodiversity in food webs. However, quantitative studies have not yet been attempted. Recently, environmental sampling with molecular techniques has revealed unknown clades of zoosporic true fungi in extreme marine ecosystems. These fungi have been grossly under-sampled and under-studied in marine environments.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.