Núñez-Pons L et al. (2018), Exploring the pathology of an epidermal disease...

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Sci Rep 2018 Jul 27;81:11353. doi: 10.1038/s41598-018-29684-0.

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

Núñez-Pons L , Work TM , Angulo-Preckler C , Moles J , Avila C .

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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.

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Genes referenced: LOC100887844 LOC115919910

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	Figure 1. Antarctic sea star Odontaster validus: Normal (upper left) and diseased (remainder) specimens. Note epidermal lesions characterized by multifocal to locally extensive punctate to amorphous distinct to indistinct areas of discoloration on the dorsum. Stars on bottom row manifest partial loss of arms.
	Figure 2. Prevalence of Odontaster validus sea stars affected by visually evident lesions in populations within Port Fosterâ€™s bay, Deception Island, South Shetland Archipelago (Antarctica).
	Figure 3. Higher magnification under stereoscope of epidermal lesions in Odontaster validus showing depigmentation (white arrow), and erosion of paxillae and epidermal ulceration (black arrow). Arrowhead pointing to the madreporite.
	Figure 4. Histological sections of Odontaster validus epidermal lesions: (left) note inflammatory cell infiltrate lifting off epidermis from underlying ossicle (big black arrow) with diffuse ulceration (small black arrow); (right): note marked subepithelial infiltrates of inflammatory cells with cleft formation (arrow).
	Figure 5. Proportional Venn Diagrams depicting represented OTUs by tissue type for the bacterial (A) and fungal (B) communities associated with Odontaster validus sea stars. Healthy (in red): tissues from healthy sea stars; NON_Affected (in green): apparently healthy tissues from diseased specimens; and Affected (in blue): diseased tissues from diseased specimens.
	Figure 6. Principal Components Analysis (PCoA) plots based on Bray-Curtis distances of Odontaster validus associated bacterial (A) and fungal (B) communities composition across three tissue types: healthy tissues from healthy sea stars (Healthy; green triangles), apparently healthy tissues from diseased sea stars (NON_Affected; yellow circles), and affected tissues from diseased sea stars (Affected; red circles). The proximity of samples on the PCoA illustrates the similarity of bacterial or fungal communities.
	Figure 7. Class-level taxonomic diversity profiling of bacterial communities associated with tissues from healthy sea stars (Healthy), with apparently healthy (NON_Affected) and diseased (Affected) tissues from diseased specimens of Odontaster validus. â€œNAâ€: non-determined taxa.
	Figure 8. Class-level taxonomic diversity profiling of fungal (B) communities associated with tissues from healthy sea stars (Healthy), with apparently healthy (NON_Affected) and diseased (Affected) tissues from diseased specimens of Odontaster validus. â€œNAâ€: non-determined taxa.

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Abarenkov, The UNITE database for molecular identification of fungi--recent updates and future perspectives. 2010, Pubmed