Abstract
BackgroundMyxozoa represents a diverse group of microscopic endoparasites whose life cycle involves two hosts: a vertebrate (usually a fish) and an invertebrate (usually an annelid worm). Despite lacking nearly all distinguishing animal characteristics, given that each life cycle stage consists of no more than a few cells, molecular phylogenetic studies have revealed that myxozoans belong to the phylum Cnidaria, which includes corals, sea anemones, and jellyfish. Myxozoa, however, do possess a polar capsule; an organelle that is homologous to the stinging structure unique to Cnidaria: the nematocyst. Previous studies have identified in Myxozoa a number of protein-coding genes that are specific to nematocytes (the cells producing nematocysts) and thus restricted to Cnidaria. Determining which other genes are also homologous with the myxozoan polar capsule genes could provide insight into both the conservation and changes that occurred during nematocyst evolution in the transition to endoparasitism.ResultsPrevious studies have examined the phylogeny of two cnidarian-restricted gene families: minicollagens and nematogalectins. Here we identify and characterize seven additional cnidarian-restricted genes in myxozoan genomes using a phylogenetic approach. Four of the seven had never previously been identified as cnidarian-specific and none have been studied in a phylogenetic context. A majority of the proteins appear to be involved in the structure of the nematocyst capsule and tubule. No venom proteins were identified among the cnidarian-restricted genes shared by myxozoans.ConclusionsGiven the highly divergent forms that comprise Cnidaria, obtaining insight into the processes underlying their ancient diversification remains challenging. In their evolutionary transition to microscopic endoparasites, myxozoans lost nearly all traces of their cnidarian ancestry, with the one prominent exception being their nematocysts (or polar capsules). Thus nematocysts, and the genes that code for their structure, serve as rich sources of information to support the cnidarian origin of Myxozoa.
Highlights
Myxozoa represents a diverse group of microscopic endoparasites whose life cycle involves two hosts: a vertebrate and an invertebrate
Comparative investigations of the molecular components underlying nematocysts, and the genes restricted to Cnidaria, could contribute to better understanding the evolution of this diverse phylum [12], including its transition from a free-living cnidarian to a microscopic endoparasite
Identification of nematocyst-specific cnidarian-restricted proteins shared between cnidarians and Myxozoa Reciprocal BLAST (Basic Local Alignment Search Tool) searches [20] were initially performed using Hydra vulgaris
Summary
Myxozoa represents a diverse group of microscopic endoparasites whose life cycle involves two hosts: a vertebrate (usually a fish) and an invertebrate (usually an annelid worm). Myxozoa are microscopic parasites that principally infect fish, annelids, and Bryozoa [1] Their spores are characterized by the presence of complex organelles, called polar capsules, which are triggered during host infection and are thought to assist in attachment to the host tissue. Shpirer et al [11] demonstrated that the nematocyst-restricted structural protein families, minicollagen and nematogalectin, are present in Myxozoa. This finding strengthened the hypothesis that myxozoans are cnidarians and that the polar capsule is the nematocyst. Comparative investigations of the molecular components underlying nematocysts, and the genes restricted to Cnidaria, could contribute to better understanding the evolution of this diverse phylum [12], including its transition from a free-living cnidarian to a microscopic endoparasite
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
