Surveillance of densoviruses and mesomycetozoans inhabiting grossly normal tissues of three Aotearoa New Zealand asteroid species

Abstract

Asteroid wasting events and mass mortality have occurred for over a century. We currently lack a fundamental understanding of the microbial ecology of asteroid disease, with disease investigations hindered by sparse information about the microorganisms associated with grossly normal specimens. We surveilled viruses and protists associated with grossly normal specimens of three asteroid species (Patiriella regularis, Stichaster australis, Coscinasterias muricata) on the North Island / Te Ika-a-Māui, Aotearoa New Zealand, using metagenomes prepared from virus and ribosome-sized material. We discovered several densovirus-like genome fragments in our RNA and DNA metagenomic libraries. Subsequent survey of their prevalence within populations by quantitative PCR (qPCR) demonstrated their occurrence in only a few (13%) specimens (n = 36). Survey of large and small subunit rRNAs in metagenomes revealed the presence of a mesomycete (most closely matching Ichthyosporea sp.). Survey of large subunit prevalence and load by qPCR revealed that it is widely detectable (80%) and present predominately in body wall tissues across all 3 species of asteroid. Our results raise interesting questions about the roles of these microbiome constituents in host ecology and pathogenesis under changing ocean conditions.

Coelomic fluid of asteroid echinoderms: Current knowledge and future perspectives on its utility for disease and mortality investigations

“…Although early reports indicated a sea-star-associated densovirus may be implicated, 64 this virus has subsequently been found in tissues of clinically normal asteroids across the world and does not appear to play a role in SSW. 63,65 Interestingly, quantitative polymerase chain reaction and reverse transcriptase polymerase chain reaction have not detected sea star-associated densovirus or Asterias forbesi -associated densovirus in coelomic fluid, even when virus is detected in the body wall, gonads, and pyloric ceca. 75,76 The current understanding of SSW indicates that environmental stressors appear to play a central role in the pathogenesis, whether through direct effects or changes to body wall microbial communities.…”

Microbiomes of native Aotearoa New Zealand animals

“…While Asteroidea do appear to host tissue-specific microbes that are mostly distinct from those in surrounding seawater, any potential roles of these symbionts in nutrient acquisition, nitrogen fixation and as opportunistic pathogens, have so far only been speculated upon (Jackson et al 2018). Recently, an association of Asteroidea with densoviruses and mesomycetozoa has been reported (Hewson & Sewell 2021).…”