Mechanisms and Drivers for the Establishment of Life Cycle Complexity in Myxozoan Parasites

Abstract

It is assumed that complex life cycles in cnidarian parasites belonging to the Myxozoa result from incorporation of vertebrates into simple life cycles exploiting aquatic invertebrates. However, nothing is known about the driving forces and implementation of this event, though it fostered massive diversification. We performed a comprehensive search for myxozoans in evolutionary ancient fishes (Chondrichthyes), and more than doubled existing 18S rDNA sequence data, discovering seven independent phylogenetic lineages. We performed cophylogenetic and character mapping methods in the largest monophyletic dataset and demonstrate that host and parasite phylogenies are strongly correlated, and that tectonic changes may explain phylogeographic clustering in recent skates and softnose skates, in the Atlantic. The most basal lineages of myxozoans inhabit the bile of chondrichthyans, an immunologically privileged site and protective niche, easily accessible from the gut via the bile duct. We hypothesize that feed-integration is a likely mechanism of host acquisition, an idea supported by feeding habits of chimaeras and ancient sharks and by multiple entries of different parasite lineages from invertebrates into the new host group. We provide exciting first insights into the early evolutionary history of ancient metazoan parasites in a host group that embodies more evolutionary distinctiveness than most other vertebrates.

Genetic Diversity of Serine Protease Inhibitors in Myxozoan (Cnidaria, Myxozoa) Fish Parasites

“…During a complex two-host life cycle, they infect both vertebrates (mostly fish) and invertebrates (mostly annelid worms) in freshwater and marine environments worldwide. The biodiversity of these parasites is remarkable and a result of host-associated cospeciation [ 2 , 3 , 4 ]. Developmental stages of myxozoans are motile during invasion, migration, and proliferation due to cellular processes that enable unique cell motility [ 5 , 6 , 7 , 8 ].…”

Broad but restricted detection of malacosporeans in a Neotropical cradle of diversification

“…Here we report the first case of a malacosporean infecting fish in the Southern Hemisphere. This is not unexpected given the observation of a Buddenbrockia species in freshwater bryozoans in São Paulo State (Marcus, 1941). Unexpectedly, however, our molecular phylogenetic analysis demonstrated that only a single species of Buddenbrockia , referred to here as Buddenbrockia sp.…”

“…These include kidney infections in 17 fish species in the family Cyprinidae (Bartošova-Sojková et al ., 2014; Hartikainen et al ., 2014; Naldoni et al ., 2019) and single species in the families Percidae (Bartošova-Sojková et al ., 2014) and Nemacheilidae (Naldoni et al ., 2019). Nearly all malacosporeans have been detected in Europe and North America, exceptions being the detection of a Buddenbrockia species in bryozoan hosts in Borneo (Hartikainen et al ., 2014) and an early observation of Buddenbrockia in a Brazilian bryozoan host (Marcus, 1941). Our knowledge of host species and of malacosporean diversities and distributions is thus highly biased and a hidden malacosporean diversity may await discovery.…”

Evaluation and optimization of an eDNA metabarcoding assay for detection of freshwater myxozoan communities

“…Myxozoa is one such parasitic group with a potentially highly underestimated diversity (Holland et al, 2011; Okamura et al, 2018). These endoparasitic cnidarians infect annelids and bryozoans as definitive hosts and fish, amphibians, rarely reptiles, and even birds and mammals as intermediate hosts (Aguiar et al, 2017; Bartholomew et al, 2008; Dyková et al, 2007; Fiala et al, 2015; Lisnerová, Fiala, et al, 2020). Myxozoan infections are often inconspicuous, but some cause severe damage to their hosts, including economically important fishes (Eszterbauer et al, 2015; Hartikainen & Okamura, 2015).…”