Myxozoa - cnidarians adapted to parasitismo: integrating different tools to investigate diversity, evolutionary history, development, and host-parasite interactions

Abstract

It is now known that a lineage of cnidarians diverged to become endoparasites, which compose the subphylum Myxozoa. This subphylum contains about 2,500 species, which are distributed in the classes Myxosporea and Malacosporea. Myxosporeans contain the vast majority of myxozoan species currently known, and their members infect various tissues and organs of vertebrates, mainly fish, but also amphibians, reptiles, birds and mammals. Annelids serve as the invertebrate hosts in the complex life cycle of myxosporeans. A wide range of species of myxosporeans are important fish pathogens and have a great economic impact on aquaculture and commercial fishing, even in Brazil. Malacosporeans, on the other hand, are restricted to a small fraction of myxozoan diversity, with only five species described. The complex malacosporean life cycle involves freshwater bryozoans as invertebrate hosts and fish. The species Tetracapsuloides bryosalmonae causes proliferative kidney disease in salmonids, and this disease decreases productivity and increases production costs in fish farms from Europe. In South America, however, there are no reports of malacosporids in fish to date. But in preliminary studies recently conducted in our laboratory, but not yet published, have for the first time documented malacosporean infections (Buddenbrockia) in South American fish, with infections being detected in the kidney of Brazilian fish from Amazonia. Also, in recent studies carried out by researchers of our group, have for the first time identified myxosporean infections in South America, with the description of two species parasitizing turtles in breeding systems. In this context, this project proposes to substantially strengthen and expand studies of myxozoan parasites of aquatic organisms of the Brazilian fauna. In particular, we propose to use, in an integrated way, a suite of tools to investigate the diversity, evolutionary history, development, distribution and host-parasite interactions of Myxozoa found in our country. Traditional taxonomy tools (light microscopy and morphometry), histopathological analysis, scanning, 3D (three-dimensional) and transmission electron microscopy, laser confocal microscopy, Sanger sequencing (SSU-rDNA) and Next-generation sequencing (NGS). The studies will be carried out from samples obtained from fish of commercial importance, reptiles (Testudines), and amphibians (Anura). Fishes will be collected from natural environment: in the municipalities of Manaus, in Amazonas State, Santarém, in Para State, Barão de Melgaço, in Mato Grosso State, and Porto Rico, in Paraná State; and from fish farms in Rondônia State and São Paulo State. The studies of Testudines and Anura will be done in specimens from the Amazon basin (Manaus and Santarém). The aim of this project is to inventory the diversity of Myxozoa in an unprecedented way in South America, focusing on both myxosporeans and malacosporeans. A major objective is to use NGS methods to develop markers for evolutionary studies and population genetic analyses of Myxozoa (e.g. Ultra-conserved Elements [UCEs], restriction site associated DNA [RAD] markers and single nucleotide polymorphisms [SNPs]). The establishment of protocols for marker development will also be useful for the study of other fish parasites. In addition to advancing our general knowledge of myxozoan parasites of fish and other aquatic animals, the proposed project will involve master's dissertations, doctoral theses, and postdoctoral internships, resulting in publications in specialized international journals. By bringing together researchers at different career stages and with complementary expertise the proposed work would encourage the development of highly qualified human resources that would promote important advances in research on pathogens of aquatic animals. (AU)