Sea Cucumbers Can Puke Up Their Guts and Grow New Ones, and Scientists Are Figuring Out How

Though it may not look the part, this holothuroid -- or sea cucumber -- is a relatively close cousin of vertebrates, and a prized delicacy in Asian seafood markets. It also has the unique ability to discard its viscera and grow them back in a few weeks. Qiang Xu

Never threaten a sea cucumber—it may poop out its guts on you.

Sea cucumbers, members of the class Holothuroidea, are weird animals. They aren't related to cucumbers, which are plants. The spineless marine animals are echinoderms, like starfish and sea urchins. Unlike those animals though, which mostly have hardened calcium exoskeletons, sea cucumbers are soft and squishy. There are several species, which look like colorful, sometimes prickly, logs.

One particularly strange adaptation is their ability to eject their viscera when they feel threatened. Even more bizarre is that they can regrow their intestines within a couple of weeks.

New research aims to use genetics to understand how they are able to do this, and whether this can affect the future of regenerative medicine. However, the primary focus of the research is to better understand the animals that are bred for human consumption.

Scientists at the Institute of Oceanography and the Chinese Academy of Sciences have now sequenced most of the genome of one species of sea cucumber, Apostichopus japonicus. The study, published today in PLOS Biology, fills in some gaps in their storied past.

Sea cucumbers, the analysis shows, must have evolutionarily split off from their cousins, the sea stars and urchins, about 479 million years ago. They have fewer genes for biomineralization, or creating bony structures, and those genes are less expressed than in other echinoderms. Animals may contain genes for a characteristic, but if it's not expressed, or expressed less, then they may not show that characteristic in their phenotype.

Furthermore, two sets of genes could account for their amazing regenerative abilities. One set of genes was duplicated in A. japonicus, but not in other echinoderms, suggesting that sea cucumbers owe some of their uniqueness to these genes. They were also highly expressed specifically in the regenerating intestines of the animals, meaning that they have an important function in that area. The other set of genes were also activated during regeneration.

The potential benefits of this research are two-fold. First, it can help us understand an animal that sells. A. japonicus , which is bred in commercial fisheries, is popular in markets for sale for its suspected medical benefits, and for sale as food. Chinese dishes sometimes include sea cucumbers, either dried, chopped, drizzled in sauce, or deep-fried.

Secondly, understanding the creature's ability to re-grow body parts, a super power reminiscent of Marvel's Wolverine, could shed light on regenerative medicine and ultimately help human healing.

The science is a long way from having practical medical implications, though, so don't go expelling your guts just yet.