Marine mammal Marine mammal Marine mammals are aquatic mammals that rely on the ocean and other marine ecosystems for their existence. They include animals such as seals, whales, manatees, sea otters and polar bears. They do not represent a distinct taxon or systematic grouping, but rather have a polyphyletic relation due to convergent evolution, as in they do not have an immediate common ancestor. They are also unified by their reliance on the marine environment for feeding. Marine mammal adaptation to an aquatic lifestyle varies considerably between species. Both cetaceans and sirenians are fully aquatic and therefore are obligate water dwellers. Seals
The Marine Mammal Center Researchers at the Marine Mammal Center have discovered that domoic acid (DA) is the causative agent responsible for illness in a great many California sea lions. DA is naturally produced by the diatom "Pseudo-nitzschia". DA passes up the food chain as the diatoms are consumed by zooplankton. These zooplankton are then consumed by fish where the toxin accumulates. Fish are unharmed by it. California sea lions are disproportionate affected because they feed closer to shore, where more of these diatoms are present. When consumed by (marine) mammals, it activates neural pathways in the brain, specifically, the hippocampus. This neural activation