Steady Supply of Simple-Brained Research Animals : Wild Sea Hares Spared by Lab Breeding Plan
Scientists studying the intricacies of the mind once combed the beaches of Southern California for a creature called the sea hare in order to conduct experiments on its simple brain.
Now, they need only pick up the telephone to order dozens of the snail-like animals from a Howard Hughes Medical Institute program based at the Woods Hole Oceanographic Institution in Massachusetts.
In an innovative program, specimens of the sea hare, Aplysia, are hand-raised from microscopic eggs in a warehouse of gurgling water tanks and refrigeration units.
“It took time to learn the best way to keep them alive and healthy,” said Thomas Capo, manager of the facility. “But, after many years we have come up with a very good survival rate.”
Raised for Laboratory Use
The program is indicative of a growing movement among scientists to raise the laboratory animals they need for research rather than collect them from the wild.
Scientists say hand-raised animals are better for experiments because they are available all year and come from a controlled environment.
“We are making the marine equivalent of the white rat,” Capo said. “They are all born the same way, fed the same food and kept in the same temperature water.”
There are other reasons for rearing the creatures. Scientists said wild populations may be unreliable and may be threatened if too many animals are taken from one area.
“During the El Nino a few years back, the population of Aplysia dropped in parts of California,” Capo said.
None for Scientists
If scientists had depended on collecting the creatures during the disruptive shift in normal weather patterns, they could have been forced to discontinue valuable experiments because of a lack of specimens, he said.
And, he said, it is difficult to predict what impact harvesting the already depleted animals would have had on future population growth.
Sea hares are unsightly marine animals that look like pudgy, slimy snails without shells. They can grow to the size of a basketball and weigh up to 15 pounds, but most used in experiments weigh around one pound and can fit in the palm of the hand.
Before their use as lab animals was discovered in the 1960s, sea hares were an oddity known for the sticky purple ink they emit when irritated.
Now they are treasured for their simple brains, which contain only 5,000 to 10,000 cells, compared to the millions of cells found in the brains of vertebrates, according to Jim Schwartz, who works with Aplysia at Columbia University in New York.
His colleague there, biologist Eric Kandel, was among the first to discover the excellent model that Aplysia provides to neuroscientists. He was able to map out the positions of cells and their interactions that make up the animal’s neural system.
Schwartz said in a recent report that scientists hope to isolate and characterize the enzymes and molecules in the sea hare brain that are responsible for specific behaviors.
According to Capo, Kandel first began raising sea hares in New York City in the 1970s, but he said most of the animals died while they were just microscopic larvae.
The scientists had better success when they moved their operation to Woods Hole, where they discovered that the animals need a certain type of algae in order to grow out of the early larval stage.
Through trial and error they learned to sustain microscopic Aplysia in bottles until they are large enough to be transferred to tanks, where they grow rapidly, consuming 15 to 40 times their body weight in algae.
The incentive to hand-raise Aplysia was intensified a few years ago when it was discovered that neural tissue from the animal grows well in laboratory cultures, Capo said.
“Scientists had tried to grow tissue cultures with a number of animals before they found how well Aplysia works,” he said. “The tissue cultures are an important tool in neurobiology.”
By the end of this year, the institute will have shipped 24,300 sea hares to 34 scientists around the world, Capo said, and demand for the animals is growing.
According to Doug Kutney, a technician at the institute, the sea hares are shipped airmail in water-filled plastic bags inside cardboard crates.
He feeds them several times a day with a specific type of sinewy algae either grown on the premises or harvested by local fishermen.
“You can tell when they are really getting hungry,” he said recently, dangling a choice bit of seaweed over a tank of apple-sized adolescents. The sea hares extended their antennae up out of the water in an effort to get to the food.
“We take very good care of the animals,” Capo said. “Maybe because of their importance to science, they get a lot of respect.”