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The Marine Mammal Center

Zoo in California, United States

  • 11 min read
  • 5 chapters

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Through Environmental chemistry, Ocean and Medication

Research

The research team consists of veterinarians and biologists who conduct not only medical diagnosis and intervention, but also publish scientific reports on marine animal health in relation to the Pacific Ocean’s environmental chemistry. They collaborate with other institutions to provide vital information on disease, immunological systems and environmental effects. Some patients are fitted with radio or satellite tags before release, to further specific research goals. The center collaborates with counterparts around the world (most notably from England, Canada, Mexico, Brazil, Australia, Scotland, the Netherlands, France and Germany) in working on complex cases, and also researches the interactions of ocean-dwelling mammals with the marine environment in collaboration with other institutions.

Researchers at TMMC 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, but mammals are. California sea lions are disproportionately affected because they feed closer to shore, where more of these diatoms are present. When consumed by marine mammals, DA activates neural pathways in the brain, specifically, the hippocampus. This neural activation is unregulated and results in seizures. Repeated exposure will cause repeated activation, ultimately burning out these neural pathways and causing permanent brain damage — specifically, atrophy of the hippocampus. Domoic acid is the same biotoxin that causes amnesic shellfish poisoning in humans.

Another discovery by TMMC, in collaboration with the University of Florida, is that seal pox is distinct from pox viruses isolated from other species. It is unrelated to chicken pox or smallpox. Also being investigated is the increased incidence of leptospirosis, a bacterial pathogen that can acutely damage the kidneys of marine mammals.

The Marine Mammal Center has made advances in the use of general anesthesia on marine mammals, used during surgical procedures. To a certain extent, marine mammals are voluntary breathers. Pinnipeds (seals, sea lions and fur seals) can reduce their respiratory rate in order to conserve oxygen and remain underwater for extended periods. This makes the use of general anesthesia and tranquilizing darts more problematic.

Any animal that dies in treatment, or is euthanized while at the center, will undergo a necropsy to further research. At the center, there is a viewing area where the public can observe the procedure. Animals are only euthanized if their illness or injury is beyond treatment and would lead to the animal's death, or unabated suffering. Considering that animals in need are only identified when their distress is significant enough to be observable by the public, it is not unusual for some of these animals to be beyond rehabilitation.

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