Single and multi-gene phylogeny ofHepatospora(Microsporidia) – a generalist pathogen of farmed and wild crustacean hosts

Abstract

SUMMARYAlmost half of all known microsporidian taxa infect aquatic animals. Of these, many cause disease in arthropods.Hepatospora, a recently erected genus, infects epithelial cells of the hepatopancreas of wild and farmed decapod crustaceans. We isolatedHepatosporaspp. from three different crustacean hosts, inhabiting different habitats and niches; marine edible crab (Cancer pagurus), estuarine and freshwater Chinese mitten crab (Eriocheir sinensis) and the marine mussel symbiont pea crab (Pinnotheres pisum). Isolates were initially compared using histology and electron microscopy revealing variation in size, polar filament arrangement and nuclear development. However, sequence analysis of the partial SSU rDNA gene could not distinguish between the isolates (~99% similarity). In an attempt to resolve the relationship betweenHepatosporaisolated fromE. sinensisandC. pagurus, six additional gene sequences were mined from on-going unpublished genome projects (RNA polymerase, arginyl tRNA synthetase, prolyl tRNA synthetase, chitin synthase, beta tubulin and heat shock protein 70). Primers were designed based on the above gene sequences to analyseHepatosporaisolated from pea crab. Despite application of gene sequences to concatenated phylogenies, we were unable to discriminateHepatosporaisolates obtained from these hosts and concluded that they likely represent a single species or, at least subspecies thereof. In this instance, concatenated phylogenetic analysis supported the SSU-based phylogeny, and further, demonstrated that microsporidian taxonomies based upon morphology alone are unreliable, even at the level of the species. Our data, together with description ofH. eriocheirin Asian crab farms, reveal a preponderance for microvariants of this parasite to infect the gut of a wide array of decapods crustacean hosts and the potential forHepatosporato exist as a cline across wide geographies and habitats.