Underwater Cannibalism: Baby Sea Stars Eat Each Other When Hungry

New research recently showed underwater cannibalism occurring specifically involving baby sea stars that eat each other when hungry.

According to a Live Science report, baby stars may seem innocent and charming, but they are teensy little animals and they are eating their own siblings for their own survival.

Two researchers found this behavior among Asterias forbesi or baby Forbes' sea stars by accident. Originally, they were attempting to understand how baby sea stars were reacting when they were introduced to ferocious crab killers in the laboratory.

However, associate professor Jon Allen from William & Marry's Department of Biology said they all started to eat each other before they were even introduced to the crabs. So, they had to scrap that particular experiment.

Consequently, Allen, together with his team, switched gears to study this previously unidentified phenomenon among the baby sea stars.

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The Forbes' Sea Stars

A National Geographic report specified that the Forbes' sea stars, commonly found on the East Coast of the United States can reach from 4.7 to 9.4 inches long as adults.

Juvenile sea stars are basically pinhead-size versions of their parents, Allen said. These sea stars undergo a process called metamorphosis in which they transform from an immature form to an adult form just as caterpillars transform into butterflies.

These sea stars, according to doctoral student Karina Brocco French, from the University of California, Irvine, while in their immature, young larval form, look similar to weird tiny spaceships that fly through the water.

In a statement, Brocco French, who's also an undergraduate student working in the lab of Allen during the study added, the sea stars stay in this weird-little-spaceship stage for about one month prior to their metamorphosizing into juvenile sea stars and settle on the seafloor.

Cannibalistic Behavior

Researchers already knew that juveniles on the seafloor would consume the much-tinier larval forms that sink in to the bottom, although they did not realize that juveniles would consume each other.

Still, even though these baby sea stars, as described in the Gulf of Main are approximately the same size as one another, the lightly larger ones are always ending up eating the smaller ones, the statement specified.

Both Allen and French discovered that the juveniles in this cannibalistic behavior as early as four days from metamorphosing.

The baby sea stars did so through the use of one of their multiple stomachs also identified as their cardiac stomach, which they are pushing out to consume and break down their food.

As indicated in the report from the science information site, sibling cannibalism might give the individual stars an adaptive benefit, specifically since adult female sea stars are generating five million to 10 million eggs every year, explained Allen.

While this particular behavior was unidentified in this species, cannibalism is not unusual in the animal kingdom with over 1,3000 species which include humans documented to present it, the statement specified.

The study authors added, they think that cannibalism is likely to be even more widespread among tiny animals which include juveniles. The findings of this study were published in the Ecology journal.

Related information about Forges' sea star is shown on New England Aquarium's YouTube video below: