When people think of sea squirts, they might picture an image from one of those viral Internet memes. But these unassuming, potato-shaped creatures are quite fascinating, and they have plenty to teach us about life.
Ault sea squirts are members of the tunicate group, which is the first evolutionary step toward vertebrates (including fish, amphibians, reptiles, and humans). They live in saltwater bodies all over the world. These animals have a handful of unusual characteristics that set them apart from other aquatic organisms: They filter feed, they are capable of regenerating lost parts of their body, and they have a sedentary lifestyle. They also have a remarkable ability to survive in a range of salinities, making them useful for studying the effects of climate change on marine ecosystems.
As you might have guessed from their Internet fame, sea squirts can do some pretty weird things. These include posing for viral photos, regenerating lost organs, and even “eating their own brains.” The latter isn’t nearly as gross as it sounds. All adult sea squirts are simultaneous hermaphrodites, meaning they have both male and female reproductive organs. When they spawn, their eggs are fertilized by sperm that is released into the water. The resulting tadpole-like larvae can swim around freely, but they cannot feed because their tail and notochord are absorbed when they settle down to mature.
What do these tadpole-like larvae do to find food? They secrete a thick liquid that looks like a biological lava flow. The sticky mucus grabs plankton, and it slides down into the stomach, where it is digested. The result is that sea squirts are constantly releasing nutrients into their surroundings. This may not be a good thing for some aquatic environments, as sea squirts can remove too much of the valuable plankton from the ecosystem. However, this behavior can also help coral reefs by removing excess bacteria that hinder their growth.
Researchers have been studying the innards of sea squirts for years, and they have found that these simple creatures are capable of doing some very sophisticated things. For example, a USF microbiologist named Larry Dishaw is using a type of sea squirt called Ciona intestinalis to study how the innate immune system works in a human’s gut.
He discovered that sea squirts exhibit some of the same behaviors as our own innate immune systems, which respond to foreign material that may be dangerous to our cells. This is important because our innate immune systems can sometimes overreact and attack our own healthy tissue, which leads to illness and disease.
Another interesting finding from his work with sea squirts is that they have cells similar to natural killer cells. These cells are responsible for destroying cancerous or otherwise unwanted cells, and they share a few similarities with the natural killer cells in sea squirts.
If that wasn’t enough, another team of scientists has recently published research on the benefits of plasmalogens, a substance derived from the body of a sea squirt. In a series of experiments on mice, the researchers discovered that the mice who were fed a plasmalogen supplement had healthier synapses in their brains. This is particularly significant, as the brain’s synapses are susceptible to deterioration over time, which can lead to cognitive impairment in old age. The researchers believe that their findings suggest that a plasmalogen supplement might be able to improve cognitive function in humans by slowing down the progression of neurodegenerative diseases.