title: Diversification and repeated morphological transitions in endoparasitic cnidarians (Myxozoa: Malacosporea).
abstract: Malacosporeans are a poorly known myxozoan clade that uniquely demonstrates a tissue level of organisation. Thus, when exploiting their invertebrate hosts (freshwater bryozoans) they occur as non-motile sacs or vermiform stages capable of active swimming. We combine phylogenetic analyses of SSU and LSU rDNA with morphological observations to substantially enhance understanding of malacosporean diversification. The phylogenetic analyses incorporate the widest taxon sampling and geographic cover to date, reveal four novel malacosporean lineages and several putatively new species, one with a novel morphology of irregular, bulbous sacs and no musculature. This lineage currently forms the earliest branch of malacosporeans. Vermiform stages may have been lost or gained several times within the Malacosporea, even in cases where SSU sequence divergence is very low. Yet, sac and vermiform Buddenbrockia plumatellae appear to be separate species, an inference also supported by their utilisation of different bryozoan hosts. Cryptic speciation is also apparent with two novel, genetically divergent lineages (novel lineage 2 and Buddenbrockia sp. 4) being morphologically indistinguishable from known species. Finally, we provide evidence that fredericellid bryozoans are the main hosts for Tetracapsuloides bryosalmonae and are therefore most relevant for research on the ecology and management of Proliferative Kidney Disease of salmonid fish.
authors.affiliation: Department of Life Sciences, The Natural History Museum, Cromwell Road, London SW7 5BD, United Kingdom. Electronic address: Hanna.Hartikainen@eawag.ch.
authors.forename: Hanna
authors.initials: H
authors.lastname: Hartikainen
authors.affiliation: Department of Life Sciences, The Natural History Museum, Cromwell Road, London SW7 5BD, United Kingdom.
authors.forename: Alexander
authors.initials: A
authors.lastname: Gruhl
authors.affiliation: Department of Life Sciences, The Natural History Museum, Cromwell Road, London SW7 5BD, United Kingdom.
authors.forename: Beth
authors.initials: B
authors.lastname: Okamura
mesh_terms: D000818:Animals; D002013:Bryozoa / Q000469:parasitology*; D004275:DNA, Ribosomal / Q000235:genetics; D005393:Fish Diseases / Q000469:parasitology; D058507:Host Specificity; D007674:Kidney Diseases / Q000469:parasitology / Q000662:veterinary; D055764:Myxozoa / Q000033:anatomy & histology* / Q000145:classification* / Q000235:genetics / Q000254:growth & development; D010802:Phylogeny; D012474:Salmon / Q000469:parasitology; D017422:Sequence Analysis, DNA
chemical_list: D004275:DNA, Ribosomal
keywords: Buddenbrockia; Cryptic species; LSU; Phylactolaemata; SSU; Tetracapsuloides