Cnidarians of the Class Myxozoa parasitizing Rhaphiodon vulpinus: evolution, parasite-host interaction and nematocyst toxins

• Grant number: 23/06420-3
• Support Opportunities: Scholarships in Brazil - Doctorate
• Start date: December 01, 2023
• End date: February 28, 2027
• Field of knowledge: Agronomical Sciences - Fishery Resources and Fishery Engineering - Inland Water Fishery Resources
• Principal Investigator: Edson Aparecido Adriano
• Grantee: Rayline Thaimenne Alves Figueredo
• Host Institution: Instituto de Biologia (IB). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil
• Associated research grant: 18/24980-8 - Myxozoa - cnidarians adapted to parasitismo: integrating different tools to investigate diversity, evolutionary history, development, and host-parasite interactions, AP.BTA.TEM

Abstract

Myxozoa is a class of the phylum Cnidaria has diverged into the obligate endoparasitic life system, having adopted mainly fish as vertebrate hosts. Cnidaria are considered the oldest lineage of venomous animals, and their toxic compounds are used to immobilize, subdue, and digest prey, as well as deter and repel predators and competitors. Their toxins are produced by the Golgi apparatus of special cells called cnidocytes and stored in nematocysts, which are small capsules containing a coiled and eversible tubuleresponsible for releasing the poison. Unlike free-living cnidaria, myxozoans do not use their nematocysts (polar capsules) for food or defense, but rather to anchor the infective myxospore to the host during the infection process. However, little is known about the characteristics, functions and evolution of the cnidocytes of these parasites. Recent studies have shown that in addition to anchoring the myxospore in the host, nematocyst tubules may also serve as a delivery device, releasing the contents of the nematocyst, which may facilitate adhesion and/or penetration in the infection process. Omics technologies - genomics, transcriptome and proteome, have been enabling advances in understanding the components of toxins in free-living Cnidaria, but results are still incipient and controversial in Myxozoa. South America is the continent with the largest freshwater ichthyofauna, and among this diversity stands out the species Rhaphiodon vulpinus, family Cynodontidae, a predatory species that is present in several hydrographic basins of the continent. This project aims to inventory the Myxozoa diversity that infect R. vulpinus in four South American hydrographic basins, as well as to address aspects of the parasite-host interaction and phylogeny of these cnidarian parasites. For these purposes will be usedmorphological, sanger sequencing and ultrastructural approaches. Furthermore, aiming to contribute to the advancement of knowledge about the toxins produced by Myxozoa cnidocytes, we will use the Ceratomyxa barbata species, recently found in high prevalence and intensities in the gallbladder of R. vulpinus specimens from the Amazon and Paraná basins, to characterize the structures and functions of the organelles responsible for the production and release of substances present in nematocysts, as well as to identify the genetic machinery involved in the synthesis of these substances and their evolutionary patterns.