It flutters a pair of purple-speckled “wings,” moving underneath the water as gracefully as a flamenco dancer. So gracefully, in fact, it’s hard to believe it is a slug. Aplysia californica, also called the California sea hare because the two tentacles on its head look like ears, is a marine mollusk that typically lives in the cool waters of the Pacific Ocean. But at any given moment there are thousands of them frolicking in water from Miami’s balmy Biscayne Bay, cooled down to a brisk 55 degrees Fahrenheit and pumped into tanks at the Rosenstiel School of Marine and Atmospheric Science.

Millions of Aplysia have been born and raised at the Rosenstiel School since 1989, when the nation’s first Aplysia rearing facility moved here from the Woods Hole Oceanographic Institution in Massachusetts. For almost 40 years, scientists have been studying Aplysia as an ideal model for research on the human brain because of its easily mapped neural network. There are a mere 20,000 relatively large neurons in its brain, compared with nearly a trillion tiny neurons in the human brain, explains Lynne Fieber, M.S. ’83, Ph.D. ’89, associate professor of marine biology and fisheries at the Rosenstiel School. The animal’s one-year life span also makes it convenient for studying the aging process.

“Many times there is only one neuron or maybe two neurons involved in a behavior,” says Fieber. “This means we can actually observe physical and biochemical changes in the neural circuit when the animal learns something.”

The example Fieber offers is the siphon withdrawal reflex. The Aplysia’s siphon is a very sensitive muscular tube that draws water over its gills to breathe. If you touch the siphon, the Aplysia will pull it back. But if you continue to touch the siphon repeatedly, the animal will eventually stop reacting, having learned that your touch is not harmful. Stimulation of the siphon causes levels of a molecule called cyclic AMP (cAMP) in the animal’s brain to change throughout the learning process. Understanding the role of molecules like cAMP in Aplysia can help scientists understand the mechanisms of learning and memory in humans.

“The siphon withdrawal reflex is the same kind of short-term learning that humans have,” Fieber says. “If your car needs work, for example, and you drive to the body shop multiple times in a week, by the third time you won’t need directions. But if your car runs great until a fan belt breaks two years later, you’ll probably need directions again.”

Fieber’s lab also is investigating the role of an amino acid called D-aspartate. Her team of scientists has shown that in Aplysia, D-aspartate prompts certain neurons to fire. This is important because D-aspartate is the precursor to a neurotransmitter that has been implicated in the development of Alzheimer’s disease in humans.

“Aplysia is often looked down upon by people who study higher organisms,” Fieber says. “But this is the kind of basic science research that could lead to a cure for Alzheimer’s.”

An early advocate of Aplysia as a neurological model is Eric Kandel, a Columbia University professor who won the Nobel Prize in Physiology or Medicine in 2000 for demonstrating how nerve cells respond to chemical signals to produce behavioral changes. His research employed Aplysia californica supplied by the National Resource for Aplysia at the Rosenstiel School. Kandel is also the first person to conceive of a laboratory for rearing Aplysia. In the late 1970s he recruited Tom Capo, now senior resource manager at the Rosenstiel School facility. The pair opened a lab at Woods Hole in 1977, then moved it to Miami in 1989 because ample light and warm temperatures here enable year-round growth of red algae, the Aplysia’s main food source.

In 1995 the facility officially became the National Resource for Aplysia under a five-year, $450,000-per-year renewable grant from the National Center for Research Resources of the National Institutes of Health.

Michael Schmale, M.S. ’80, Ph.D. ’85, professor of marine biology and fisheries at the Rosenstiel School, is principal investigator of the NIH grant. He also coordinates several research projects, including studies of gene expression associated with development and sen­escence. Every fall semester he and Fieber teach Aplysia lab classes for freshman marine and atmospheric science majors. “The students really love seeing these animals for the first time and working with them,” Schmale says. “These are great animals for teaching.”

Each year the facility supplies more than 30,000 Aplysia californica to scientists all over the world for important research and teaching, but Capo remembers one order in particular. “We once shipped Aplysia to a scientist who was going to put them on the space shuttle—slugs in space!”

If Eric Kandel and Tom Capo are the founding fathers of the National Resource for Aplysia, Ana Bardales, head culturist since 1989, is the den mother. She nurtures and feeds each animal, the proud guardian of its growth—from microscopic embryo to tiny larva to juvenile to adult.

“I’ve raised everybody who has been born here,” she says, noting her fondness of these little invertebrates. “They are the most beautiful right before they metamorphose. That’s when you can see their purple ink glands and digestive glands.”

In addition to the team of faculty and staff, students help keep the National Resource for Aplysia running smoothly. “Students get involved in every aspect, and they do 30 to 40 percent of the actual care of the animals,” Capo says. “The key thing is that they graduate with not only academic knowledge but also hands-on knowledge of how to raise animals.”

Those in Florida or other East Coast regions might catch sight of an Aplysia in the wild. It’s most likely not the californica but perhaps the Aplysia brasiliana or Aplysia morio. Its flamenco dance or the purple plume of ink it expels when startled will give it away. If you do get the chance to study its gentle movement, consider tipping your snorkel in gratitude. After all, this magical mollusk is helping scientists wade through the dense cloud of mystery surrounding the human brain.

MEREDITH DANTON is an editor at the University of Miami.