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

Lessons Learned from the Sea Star Wasting Disease Investigation

Marine invertebrate mass mortality events (MMEs) threaten biodiversity and have the potential to catastrophically alter ecosystem structure. A proximal question around acute MMEs is their etiologies and/or environmental drivers. Establishing a robust cause of mortality is challenging in marine habitats due to the complexity of the interactions among species and the free dispersal of microorganisms from surrounding waters to metazoan microbiomes. The 2013-2014 sea star wasting disease (SSWD) MME in the northeast Pacific Ocean highlights the difficulty in establishing responsible agents. In less than a year of scientific investigation, investigators identified a candidate agent and provided at the time convincing data of pathogenic and transmissible disease. However, later investigation failed to support the initial results, and critical retrospective analyses of experimental procedures and reinterpretation of early findings disbanded any candidate agent. Despite the circuitous path that the investigation and understanding of SSWD have taken, lessons learned from the initial investigation-improving on approaches that led to misinterpretation-have been successfully applied to the 2022 Diadema antillarum investigation. In this review, we outline the history of the initial SSWD investigation, examine how early exploration led to spurious interpretations, summarize the lessons learned, provide recommendations for future work in other systems, and examine potential links between the SSWD event and the Diadema antillarum MME.

Ichthyosporea: a window into the origin of animals

Ichthyosporea is an underexplored group of unicellular eukaryotes closely related to animals. Thanks to their phylogenetic position, genomic content, and development through a multinucleate coenocyte reminiscent of some animal embryos, the members of Ichthyosporea are being increasingly recognized as pivotal to the study of animal origins. We delve into the existing knowledge of Ichthyosporea, identify existing gaps and discuss their life cycles, genomic insights, development, and potential to be model organisms. We also discuss the underestimated diversity of ichthyosporeans, based on new environmental data analyses. This review will be an essential resource for researchers venturing into the study of ichthyosporeans.

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

Coelomic fluid surrounds the internal organs of asteroid echinoderms (asteroids, otherwise known as sea stars or starfish) and plays an essential role in the immune system, as well as in the transport of respiratory gases, nutrients, waste products, and reproductive mediators. Due to its importance in physiology and accessibility for nonlethal diagnostic sampling, coelomic fluid of asteroids provides an excellent sample matrix for health evaluations and can be particularly useful in disease and mortality investigations. This is especially important in light of recent increases in the number of affected individuals and species, larger geographic scope, and increased observed frequency of sea star wasting events compared with historic accounts of wasting. This review summarizes the current knowledge about coelomocytes, the effector cell of the asteroid immune system; coelomic fluid electrolytes, osmolality, acid-base status and respiratory gases, and microbiota; and genomic, transcriptomic, and proteomic investigations of coelomic fluid. The utility of coelomic fluid analysis for assessing stressor responses, diseases, and mortality investigations is considered with knowledge gaps and future directions identified. This complex body fluid provides an exciting opportunity to increase our understanding of this unique and ecologically important group of animals.

A National Catalogue of Viruses Associated with Indigenous Species Reveals High-Throughput Sequencing as a Driver of Indigenous Virus Discovery

Viruses are important constituents of ecosystems, with the capacity to alter host phenotype and performance. However, virus discovery cued by disease symptoms overlooks latent or beneficial viruses, which are best detected using targeted virus detection or discovered by non-targeted methods, e.g., high-throughput sequencing (HTS). To date, in 64 publications, 701 viruses have been described associated with indigenous species of Aotearoa New Zealand. Viruses were identified in indigenous birds (189 viruses), bats (13 viruses), starfish (4 viruses), insects (280 viruses), and plants (126 viruses). HTS gave rise to a 21.9-fold increase in virus discovery rate over the targeted methods, and 72.7-fold over symptom-based methods. The average number of viruses reported per publication has also increased proportionally over time. The use of HTS has driven the described national virome recently by 549 new-to-science viruses; all are indigenous. This report represents the first catalogue of viruses associated with indigenous species of a country. We provide evidence that the application of HTS to samples of Aotearoa New Zealand's unique fauna and flora has driven indigenous virus discovery, a key step in the process to understand the role of viruses in the biological diversity and ecology of the land, sea, and air environments of a country.

A Review of Asteroid Biology in the Context of Sea Star Wasting: Possible Causes and Consequences

AbstractSea star wasting-marked in a variety of sea star species as varying degrees of skin lesions followed by disintegration-recently caused one of the largest marine die-offs ever recorded on the west coast of North America, killing billions of sea stars. Despite the important ramifications this mortality had for coastal benthic ecosystems, such as increased abundance of prey, little is known about the causes of the disease or the mechanisms of its progression. Although there have been studies indicating a range of causal mechanisms, including viruses and environmental effects, the broad spatial and depth range of affected populations leaves many questions remaining about either infectious or non-infectious mechanisms. Wasting appears to start with degradation of mutable connective tissue in the body wall, leading to disintegration of the epidermis. Here, we briefly review basic sea star biology in the context of sea star wasting and present our current knowledge and hypotheses related to the symptoms, the microbiome, the viruses, and the associated environmental stressors. We also highlight throughout the article knowledge gaps and the data needed to better understand sea star wasting mechanistically, its causes, and potential management.