Marine and synthetic glutamatergic neurotoxins accumulate in and immobilize intertidal sea stars.

Domoic acid (DA) is a naturally occurring amino acid structurally analogous to kainic acid (KA). DA, a neurotoxin commonly associated with toxigenic Pseudo-nitzschia species, enters the food chain via filter feeders and poses a potential threat to predators such as sea stars. To assess the presence of DA, wild-collected sea stars (Pisaster ochraceus and Asterias spp.) were analyzed for DA. Although there were no signs of a recent Pseudo-nitzschia bloom prior to collection, both species had low levels of detectable DA, primarily concentrated in the pyloric caeca. DA concentrations in P. ochraceus tissues ranged from 0 to 1033 ng g-1 tissue, averaging (±SE) 614 ± 93 ng g-1 in pyloric caeca, and were negatively correlated with body mass. DA concentrations in Asterias spp. averaged 123 ± 34 ng g-1 in pyloric caeca. Subsequently, to assess neurotoxic impacts-behaviorally and physiologically-we challenged Asterias spp. with KA, as a stand-in for DA, using intraperitoneal injections of 0, 3, or 30 μg KA g-1 body mass. Immediately following exposure, 11 out of 12 sea stars injected with 30 μg KA g-1 failed to right themselves within 30 min and their arm circumference was reduced by 19.7 ± 3.5%. Righting time, but not arm circumference, recovered within 2 d. We hypothesize that these responses precipitated from KA binding to glutamate receptors in the mutable collagenous tissue. These findings reveal that DA accumulates in sea star tissues, and that KA can cause significant yet reversible behavioral changes, raising concerns about the impact of repeated, long-term, or higher-dose exposures of wild sea stars to these neurotoxins.