Sea star wasting disease demography and etiology in the brooding sea star Leptasterias spp.

Abstract

Sea star wasting disease (SSWD) describes a suite of disease signs believed to have led to catastrophic die-offs in many asteroid species, beginning in 2013. While most studies have focused on large, easily visible sea stars with widely-dispersing larvae, less information is available on the effect of this disease outbreak on smaller sea star species, such as the six-armed sea star Leptasterias spp. Unlike many larger sea stars, Leptasterias brood non-feeding young instead of broadcast-spawning planktonic larvae. Limited dispersal and thus limited gene flow may make these sea stars more vulnerable to local selective pressures, such as disease outbreaks. Here, we examined Leptasterias populations at sites along the California coast and documented abundance changes coincident with recent Pacific coast SSWD in 2014. Detection of Leptasterias in central California declined, and Leptasterias were not detected at multiple sites clustered around the San Francisco Bay outflow in the most recent surveys. Additionally, we categorized disease signs in Leptasterias in the field and laboratory, which mirrored those seen in larger sea stars in both settings. Finally, we found that magnesium chloride (MgCl2) slowed the progression of physical deterioration related to SSWD when applied to sea stars in the laboratory, suggesting that MgCl2 may prolong the survival of diseased individuals.

Evidence That Microorganisms at the Animal-Water Interface Drive Sea Star Wasting Disease

“…The relative rugosity between SSW-affected and less SSW-affected asteroid species was examined by calculating the ratio of 3D (determined by computed tomography) to 2D (as calculated below) for each asteroid specimen and comparing between species. Asteroid species were categorized based on prevalence of SSW (less or not affected = Dermasterias imbricata , Henricia leviuscula , Patiria miniata ; SSW affected = Pisaster ochraceus , Solaster stimpsoni , Pycnopodia helianthoides , Leptasterias sp., Asterias forbesi , Orthasterias kohleri , Pisaster giganteus , and Pisaster brevispinus ) as reported elsewhere ( Montecino-Latorre et al, 2016 ; Bucci et al, 2017 ; Miner et al, 2018 ; Jaffe et al, 2019 ; Konar et al, 2019 ). These were likewise compared between animal volume, surface area:volume and 2D area.…”

“…Sea star wasting (SSW) disease gained prominence in 2013 when it caused mass mortality of > 20 asteroid species in the Northeastern Pacific ( Hewson et al, 2014 ) with continuous observations since ( Miner et al, 2018 ; Jaffe et al, 2019 ). SSW in field populations is reported to comprise a wide suite of disease signs, including loss of turgor (deflation), discoloration, puffiness, arm twisting/curling, limb autotomy, body wall lesions and erosions and protrusion of pyloric caeca and gonads ( Hewson et al, 2014 ).…”

Evidence that non-pathogenic microorganisms drive sea star wasting disease through boundary layer oxygen diffusion limitation

“…The relative rugosity between wasting-affected and less wasting-affected asteroid species was examined by calculating the ratio of 3D (determined by computed tomography) to 2D (as calculated below) for each asteroid specimen and comparing between species. Asteroid species were categorized based on prevalence of wasting (less or not affected = Dermasterias imbricata, Henricia leviuscula, Patiria miniata; wasting affected = Pisaster ochraceus, Solaster stimpsoni, Pycnopodia helianthoides, Leptasterias sp., Asterias forbesi, Orthasterias kohleri, Pisaster giganteus and Pisaster brevispinus) as reported elsewhere (Montecino-Latorre et al, 2016;Bucci et al, 2017;Miner et al, 2018;Jaffe et al, 2019;Konar et al, 2019). These were likewise compared between animal volume, surface area:volume and 2D area.…”

“…Sea star wasting (SSW) disease describes a suite of clinical signs in asteroids including loss of turgor, arm twisting, epidermal ulceration, limb autotomy, and death. The condition gained prominence in 2013 when it caused mass mortality of >20 asteroid species in the Northeastern Pacific (Hewson et al, 2014) with continuous observations since (Miner et al, 2018;Jaffe et al, 2019). However, lesions compatible with SSW in various asteroid species have been reported since at least 1896 in the Eastern US (Mead, 1898), and at many locations globally (reviewed in Hewson et al, 2019).…”

Temporal and spatial variation in population structure among brooding sea stars in the genus Leptasterias

“…SSWD impacts on sea star genera, including Pisaster and Pycnopodia, were first noted in central California in 2013 (Eisenlord et al, 2016). Collections for this study were completed in 2014, before major impacts of SSWD were evident in Leptasterias (Eberl et al, 2017;Eisenlord et al, 2016;Jaffe et al, 2019;MARINe, 2015).…”