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4th Edition of
World Aquaculture and Fisheries Conference

June 24-26, 2024 | Paris, France
WAC 2024

Tamar Lotan

Tamar Lotan, Speaker at Aquaculture Conferences
University of Haifa, Israel
Title : Myxozoans simple but sophisticated parasites


With over 2200 species, myxozoans are microscopic obligate spore-forming parasites affecting marine and freshwater fish worldwide. They have complex life cycles requiring alternate vertebrate (mostly fish) and invertebrate (mostly worms) hosts. Myxozoans can cause emerging diseases in many commercial fish species, including tilapia, catfish, carp, trout and salmonids, inflicting economic and environmental damage. Myxozoans belong to the phylum Cnidaria, alongside free-living corals, sea anemones and jellyfish. Although they are highly reduced compared to free-living cnidarians, myxozoans have retained the phylum-defining stinging organelles, known as nematocysts, which are essential for initiating fish infection. To explore the adaptation of myxozoan nematocysts to parasitic life and their role in host infection, we studied their structure, firing process and protein content. High-speed imaging revealed that activation of myxozoan nematocyst results in anchoring to the host body and injection of parasite content. To understand fish-parasite interaction, we used the newly discovered myxozoan Myxobolus bejeranoi, which infects gills of hybrid tilapia at more than 80% prevalence, leading to high mortality rates. We characterized the temporal progression of M. bejeranoi infection and the immune response of the host fish by performing transcriptomic analyses of both the sporulation site and the immune organs. We found that the parasite employs an immune evasion strategy of a thorough shutdown of the immune response, including deactivation of secreted cytokines and of a transcription factor responsible for T helper cell differentiation. The consequence is an immune-deprived fish, which is expected to be highly susceptible to other opportunistic pathogens. These findings suggest that M. bejeranoi is a highly efficient parasite that can disable the defense mechanisms of its fish host. Lastly, I will discuss the specificity of myxozoans as well as their global distribution, including concerns about fish stock import and the efficiency of health testing of imported livestock.


Prof. Lotan is a co-founder of The Marine Biology Department, at the Leon Charney School of Marine Sciences, University of Haifa, serving as Head of the department at 2018-2022. Within the field of fish parasitology, her main interests are parasite-host interaction, focusing on myxozoan development, evolution and adaption to the changing environment. She founded two companies in the fields of health care and drug delivery, both based on cnidarian biology. In 2009, she joined the Leon H. Charney School of Marine Sciences to lay the foundations of the evolving Marine Biology Department. Between 2008 and 2020, she was a board member at the Kinneret College on the Sea of Galilee and, currently, she serves as a member of the General Assembly of the College. In 2011-2015, she was a board member at The Israeli Association of Aquatic Studies (IAAS) and in 2015-2022, she was a board member at The Interuniversity Institute for Marine Sciences in Eilat (IUI). She holds a BSc and an MSc in biology from the Hebrew University of Jerusalem, and a PhD in genetics from the Weizmann Institute of Science, Israel.