Monomyxum ligophori n. sp. in a ParasiteBlitz: a monopisthocotylan as a myxozoan host in South Carolina and monophyly of a cosmopolitan hyperparasitic clade

A ParasiteBlitz event offers a brief, intense opportunity to discover diverse parasite species and to reveal life cycles of heteroxenous parasite taxa. In this study, we describe Monomyxum ligophori n. sp., a hyperparasitic myxozoan (Monomyxidae) proliferating in a dactylogyrid monopisthocotylan flatworm (Ligophorus mugilinus) infecting mugilid fishes (Mugil cephalus, Mugil curema) on the Atlantic coast of North America. Furthermore, we used DNA barcoding, to infer the parasite’s complex life cycle, matching its hyperparasitic myxospore stages with actinospore stages infecting the polychaete Streblospio benedicti found in the same locality during the ParasiteBlitz and also reported previously from the same region. Thus we provide evidence inferring the first life cycle of a myxozoan that does not require a vertebrate host. Hyperparasitic myxozoans are rare with only five species reported worldwide to infect flatworms. This study provides more evidence of the previously debated high-host specificity towards monopisthocotylan hosts of these monomyxid myxozoan hyperaparasites. Notably, Monomyxum ligophori n. sp. was detected only in L. mugilinus, and not in the other species of monopisthocotylan parasitic flatworms (Ligophorus cf. uruguayense and Metamicrocotyla macracantha) found infecting the same fish individuals during the ParasiteBlitz. Our molecular data and phylogenetic analysis support the previously suggested common origin of Monomyxum species infecting monopisthocotylan flatworms, and contribute to understanding the life cycle and host interactions of this unique hyperparasitic myxozoan lineage.

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https://doi.org/10.1017/S0022149X25100904