Supported by USGS, Collaborator: Thierry Work

Sea star wasting disease (SSWD) comprises a suite of gross morphological abnormalities, including ray twisting, loss of turgor, limb autotomy, formation of lesions, tissue loss and death that affects asteroids (Echinodermata) in several locations worldwide (Hewson et al. 2014, Hewson et al. 2018, Hewson et al. 2019). Since 2013, SSWD has been reported in ~ 20 species on the North American Pacific coast, leading in some locations to >95% reduction in overall biomass of key species (e.g. Pycnopodia helianthoides) (Montecino-Latorre et al. 2016, Harvell et al. 2019). The etiology of SSWD is unknown (Hewson et al. 2018) and there is currently no case definition for any species affected. Comparative histology of clinically normal and wasting individuals in North America (Bucci et al. 2017) and elsewhere (Nuñez-Pons et al. 2018) revealed vacuolized and necrotic outer epidermis and cuticle, and edema and cleft formation between outer epidermis and mutable collagenous tissue.  Microbiome (bacterial/archaeal and viral) analyses revealed no consistent associated microorganisms to this condition (Hewson et al. 2018, Jackson et al. 2018). However, shifts in subcuticular microbiome structure from predominately aerobic to obligate anaerobic taxa occur during disease progression (Lloyd & Pespeni 2018), and perhaps global warming and acidification play a role (Harvell et al. 2019).

There is also a lack of data on morphology of SSWD in the wild at the gross and microscopic level.  To rectify this, we aim to: 1) Compare normal and diseased wild stars from the Pacific Northwest using careful gross and microscopic examination of lesions; 2) perform experiments to elicit compromised epidermis/cuticle by pCO₂/temperature variation and monitor changes histologically to see how they compare to wild animals.

Work completed on this project:

Bodega Bay Marine Labs Organic Matter Amendment Experiments Summer 2019

Publications from this work:

 Hewson I (2021) “Microbial respiration in the asteroid diffusive boundary layer influenced sea star wasting disease during the 2013–2014 northeast Pacific Ocean mass mortality event” Marine Ecology Progress Series DOI: https://doi.org/10.3354/meps13735

Work TM, Weatherby TM, DeRito CM, Besemer RM, Hewson I (2021) “Pathology of experimental sea star wasting disease in the ochre sea star Pisaster ochraceus shows a bottom-up process affecting color phenotypes differently” Diseases of Aquatic Organisms DOI: https://doi.org/10.3354/dao03598

Aquino CA, Besemer RM, DeRito CM, Kocian J, Porter IR, Raimondi P, Rede JE, Schiebelhut LM, Sparks JP, Wares JP, Hewson I (2021) “Evidence that microorganisms at the animal-water interface drive sea star wasting disease” Frontiers in Microbiology. DOI: https://www.frontiersin.org/articles/10.3389/fmicb.2020.610009/