![]() ![]() ![]() ![]() “We have long wondered about how the somatosensory systems of sea lions and seals are organized, as they have such remarkable abilities to use touch and their whiskers to explore and feed in deep water,” Kaas said. The researchers focused on the sea lion’s somatosensory system because they were particularly curious about the animal’s sense of touch. Or it could just be a random outcome of evolution.” But it may also be related to other factors, such as the weightlessness of the marine environment or coping with cold water temperatures. Animals with larger bodies are expected to have larger brains. “It is at least partially explained by their large body size. “It is striking that both cetaceans and pinnipeds tend to have large and convoluted brains, but there is no single accepted explanation for this observation,” said Sawyer. Jon Kaas (Steve Green / Vanderbilt University) Although they have some features in common with the brains of their closest relatives – dogs, cats, bears and weasels – their brains are also intensely folded in a fashion similar to that of whales and dolphins. Sea lion brains are about the same size as chimpanzee brains. Due to our inherent interest in our own evolution and the importance of the large human brain to our identity, it is worthwhile looking at these independent examples of how brains become large, Sawyer pointed out. Humans, elephants, cetaceans and pinnipeds each evolved large brains independently, so the way that their brains are organized is quite different, particularly the cortex. “We know a lot about how some brains are organized and function, mice and primate brains for example, but mammals are highly varied, and we know almost nothing about the brains of most mammals, including pinnipeds,” said Kaas. Doctoral students Emily Turner, left, and Eva Sawyer examining a replica of a sea lion skull. Fellow doctoral student Emily Turner collaborated in the study under the supervision of Jon Kaas, Gertrude Conaway Vanderbilt Professor in Social and Natural Sciences. “It was amazing to see the sea lion brain for the first time because, after spending years studying brains, it was shocking to see something so large and so different from any other brain I had ever worked with,” said first author Eva Sawyer, a doctoral student in neuroscience at Vanderbilt. The results of their study are described in the paper “ Somatosensory brain stem, thalamus and cortex of the California sea lion ( Zalophus californianus)” published online in the early view of the Journal of Comparative Neurology. (Sea lions, like all marine mammals, are protected by the federal government under the Marine Mammal Protection Act of 1972.) Last year, the dramatic upsurge of juvenile California sea lion deaths due to strandings throughout central and southern California made it possible for Sawyer to obtain two juvenile sea lion brains for study. Juvenile California sea lion brain (Courtesy of Eva Sawyer) However, a team of neuroscientists at Vanderbilt University has taken an important step toward rectifying this lack of knowledge by conducting the first comprehensive study of the California sea lion’s central nervous system, concentrating on the somatosensory system, which is concerned with conscious perception of touch, pressure, pain, temperature, position and vibration. The other large-brained groups are humans, elephants and cetaceans (whales and dolphins).ĭespite considerable evidence of their cerebral skills, very little is known about pinniped brains. Along with seals and walruses, she is part of a group of fin-footed, semiaquatic marine mammals called pinnipeds. Rio’s display of intelligence is less surprising when you consider the fact that she is a member of one of only four groups of animals that have evolved extremely large brains (weighing more than 1.5 pounds). In fact, she is so smart that scientists at the Long Marine Lab at the University of California, Santa Cruz designed a series of tests that prove she is the first animal besides humans that can use basic logic (If A=B and B=C then A=C). Rio is a California sea lion who can solve IQ tests that many people have trouble passing. ![]()
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