Sea lions as a natural model for charting the developmental course following in utero exposure to domoic acid.

Abstract

Domoic acid-producing algal blooms are increasing in size, frequency, and duration along the eastern Pacific coastline resulting in regular and repeated exposure of marine mammals to the toxin. Because of their prolonged gestation, large numbers of marine mammals are now encountering this excitotoxin in utero, with potential long-term developmental effects. Evidence of developmental neurotoxic effects is accumulating in California sea lions particularly, which serve as an accessible sentinel species for studying the effects of domoic acid exposure in mammals. In biomedical settings, rodent models have revealed some developmental aspects of early domoic acid exposure, including a tendency for gross neurobehavioral changes to emerge after puberty. However, rodents are altricial and have a truncated developmental course. In contrast, marine mammals are precocial and mature slowly. Further, neurobehavioral responses to domoic acid have notable differences between those in adult rodents exposed in vivariums and in free-ranging wildlife. Primate models address some of these gaps, but are limited by practical constraints. There is a clear need to establish an ecologically valid model of brain development and clinical progression of developmental domoic acid exposure in long-lived and precocial mammals. Here we present California sea lions born in wildlife rehabilitation facilities to mothers with documented domoic acid toxicosis as a promising and accessible disease model, and we provide a framework for future research. Hundreds of adult sea lions in rehabilitation centers have already taken part in veterinary assessments and experimental assays of brain and behavior, demonstrating the plausibility of careful and scalable science with these animals. We discuss preliminary work with a juvenile sea lion enrolled in a longitudinal study with repeated clinical, behavioral, and neurobiological assessment, and advocate for cohort-based studies of maternally exposed sea lions.