Exploring the pathology of an epidermal disease affecting a circum-Antarctic sea star

Abstract

Over the past decade, unusual mortality outbreaks have decimated echinoderm populations over broad geographic regions, raising awareness globally of the importance of investigating such events. Echinoderms are key components of marine benthos for top-down and bottom-up regulations of plants and animals; population declines of these individuals can have significant ecosystem-wide effects. Here we describe the first case study of an outbreak affecting Antarctic echinoderms and consisting of an ulcerative epidermal disease affecting ~10% of the population of the keystone asteroid predator Odontaster validus at Deception Island, Antarctica. This event was first detected in the Austral summer 2012–2013, coinciding with unprecedented high seawater temperatures and increased seismicity. Histological analyses revealed epidermal ulceration, inflammation, and necrosis in diseased animals. Bacterial and fungal alpha diversity was consistently lower and of different composition in lesioned versus unaffected tissues (32.87% and 16.94% shared bacterial and fungal operational taxonomic units OTUs respectively). The microbiome of healthy stars was more consistent across individuals than in diseased specimens suggesting microbial dysbiosis, especially in the lesion fronts. Because these microbes were not associated with tissue damage at the microscopic level, their contribution to the development of epidermal lesions remains unclear. Our study reveals that disease events are reaching echinoderms as far as the polar regions thereby highlighting the need to develop a greater understanding of the microbiology and physiology of marine diseases and ecosystems health, especially in the era of global warming.

Perspective: Something Old, Something New? Review of Wasting and Other Mortality in Asteroidea (Echinodermata)

“…An epidermal disease was reported in the circum-Antarctic asteroid Odontaster validus near the volcanic Deception Island (South Shetland Islands, near Antarctica) from 2012 to 2013 and again in 2016 (Núñez-Pons et al, 2018). The disease presented as focal epidermal dispigmentation, anorexia, and limb autotomy, affecting ∼10% of the population.…”

“…Fungal communities, however, were not different between lesions and clinically normal tissues. No etiological agent could be identified from analysis of the disease (Núñez-Pons et al, 2018).…”

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

“…Modified primer design to exclude metazoan partners, using primers distinct to expected taxonomic groups (e.g. fungal ITS; [13]), and the use of blocking PCR primers [14, 15] may alleviate this burden, but demand a priori knowledge of native protistan diversity. The study of viral diversity associated with metazoan hosts has been approached by two methods.…”

Virome Temporal Variation During Sea Star Wasting Disease Progression in Pisaster ochraceus (Asteroidea, Echinodermata)

“…Other proposed mechanisms of wasting, including repeated [9] and monotonic [10] temperature excursion, high pCO2 conditions [11], and low precipitation [5] have been hypothesized to influence SSWD. SSWD is not associated with any eukaryotic microorganism nor bacterium [4,5,[12][13][14]. Microbiome studies during wasting progression suggest a progressive enrichment of copiotrophic bacteria on surfaces and within tissues [8,12,14] but none appear distinct only to affected specimens.…”

“…SSWD is not associated with any eukaryotic microorganism nor bacterium [4,5,[12][13][14]. Microbiome studies during wasting progression suggest a progressive enrichment of copiotrophic bacteria on surfaces and within tissues [8,12,14] but none appear distinct only to affected specimens.…”