Scientists are studying its bowel movements, its dazzling sparkle, and its relation to us.

It turns out geneticists study these organisms because they are among the oldest living beings on Earth and thus carry some of the oldest genes on the planet. Comb jellies have been around for about 600 to 700 million years.

The transparent, oblong jellies shocked scientists with their “number two” tricks in 2016, when evolutionary biologist William Browne showed videos of them defecating at a conference in St. Augustine, Florida. Until then, scientists believed that comb jellies ate and excreted through the same opening, similarly to other simple organisms. But Browne’s videos showed that they had a mouth in addition to an anus, which meant that they had evolved the so-called “through-gut,” in which food comes in through the mouth—and then comes out the other end.

That revelation was such a big deal that it merited publication in the journal Science, which stated that “the butthole is one of the finest innovations in the past 540 million years of animal evolution,”