LB 13-126 - Physiological effects of kainic acid on Asterias forbesi and potential ties to sea star wasting

Along the west coast of North America starting in 2013, one of the largest marine disease events, known as sea star wasting (SSW), resulted in the deaths of billions of sea stars across 20+ species. Despite numerous studies, we do not yet have a definitive cause of SSW. We hypothesized that domoic acid (DA), an algal neurotoxin from a diatom called Pseudo-nitzschia, may contribute to an irreversible destiffening response in the mutable collagenous tissues of sea stars which thus may give rise to signs of SSW. The mutable collagenous tissues are vital for the structural integrity of sea stars and are controlled by neurotransmitters. Consequently, a large influx of excitatory neurotransmitters like DA, and its agonist substitute kainic acid, may overwhelm glutamatergic and kainate receptors causing paralysis to the mutable collagenous tissue. Hence, we predicted this toxin-induced disruption in neural and connective function in stars may be a contributing factor leading to SSW, and if not, may still reproduce similar signs to SSW unrelated to disease.We performed an experiment injecting phosphate buffer saline (control), 3 ppb and 30 ppb of kainic acid into the arms of the Asterias forbesi. Kainic acid was used as a substitute for DA due to a supply-chain bottleneck. Measurements of righting time and arm circumference of each star over the course of 7 days were used as proxy for the stars’ wellbeing and turgor. We used generalized linear mixed effects models for analysis. We found that the stars dosed with 30 ppb kainic acid took 23 times longer than their pre-treatment times to right themselves suggesting the stars may have been paralyzed by the dose, but the effect declined over time. We found that the standardized arm circumference for the 30 ppb treatment saw a significant lower arm circumference suggesting these arms lack structural integrity as a result of the kainic acid. There was not a strong effect of a 3 ppb dose of kainic acid on either measure.These findings provide evidence that kainic acid (and possibly domoic acid) affect sea stars physiologically and harmful algal toxins may be relevant to the 2013 SSW epizootic. With the rise of harmful algal blooms across the world’s oceans, the risk of DA intoxication not only is becoming more prevalent, but also presents a health risk for diverse marine faunas across different trophic levels including sea stars.