A University of Victoria scientist and her team of researchers has discovered a unique sea slug that harms itself in order to survive. When its back, lined by plate-like appendages called cerata (singular: ceras), is attacked by predators, the slug simply cuts them free and swims away. This self-cutting, or autotomy, used by Melibe leonine, also known as the hooded sea slug, helps the creature avoid further harm when they face dangers in the seagrass beds of the eastern Pacific Ocean.
"It's a remarkable animal, I'm happy to ride on its coattails," Louise Page, who participated in the research, said in a press release. "When they are handled roughly or pinched, the tissue at the base of the cerata seems to melt away, and they just pop off."
Page speculates that due to the vulnerability of the oral hood, these sea slugs may actually encourage predators to attack their backs instead in order to reduce the harm that comes to them, similar to the way that some lizards and amphibians shed their tails when caught by predators.
"I've often wondered if the cerata may be acting as a decoy, to attract the first attack from a fish or a crab, to deflect it away from the hood, because the oral hood is so vulnerable," she said. "Autotomy is a voluntary loss of an appendage, and animals must also have a way to seal off the wound so they don't bleed to death."
The team of researchers examined the base of the ceras, also referred to as the autotomy plane, and discovered several unique structures including a set of longitudinal muscles, two muscular sphincters and a set of granule-filled cells that are directly connected to nerve pathways, cells that are not found anywhere else in the animal.
"It looks suspiciously like these cells may be involved in releasing something that is breaking down connective tissue," Page said, allowing the tissue at the base of the ceras to come apart with ease. Page and her team of undergraduate researchers are continuing to examine the anatomy of the sea slugs and hopes that their findings will have broader implications.
"What Melibe has here is some mechanism to drastically reduce the tensile strength of connective tissues," she said. "Maybe this could be a platform for research into things that have medical applications."
The team is currently presenting their findings at the 2016 annual meeting of the Society for Comparative and Integrative Biology in Portland, Oregon until Jan. 7.
