Ben Brandao remembers his first official introduction to comb jellies vividly. It was 2017 and he was running kayaking tours in Cape Canaveral, Florida, taking people to see bioluminescence—a phenomenon in which some creatures emit light. In late October that year, two buses full of geneticists pulled up at the shore to join his tour. Having come from Europe for a genetics conference in Orlando, they rode an hour and a half to Cocoa Beach and were clearly excited. “Are we going to see comb jellies?” they kept asking. “We really want to see comb jellies!”
Comb jellies (whose many species make up the phylum Ctenophora) are some of the creatures that can emit bioluminescence, particularly when agitated in water splashed by paddles or even hands. But other organisms here glow in the same manner, so Brandao was curious why two busloads of scientists were so thrilled about them.
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, says George Matsumoto, senior education and research specialist at Monterey Bay Aquarium Research Institute. But about a year prior to Brandao’s geneticists visit, the creatures made a splash in the scientific world for an entirely different reason: their unexpected pooping process.
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,” because it made eating more efficient and more hygienic. Before comb jellies evolved the extra waste-expelling outlet, all known organisms were eating and excreting through the same orifice. That makes comb jellies the proud owners of the world’s oldest asshole.
This finding propelled the creature to evolutionary stardom—and brought two busloads of geneticists to Brandao’s tour. He, too, was hooked and became comb jellies’ ardent fan, completely fascinated by them.
“Developing an asshole makes comb jellies score high on the evolutionary race,” he says affectionately, adding that having an excreting orifice may have also allowed them to spend more time eating. “And they are voracious eaters; they literally eat nonstop, anything they can find, including other comb jellies,” he says.
Afterward, every time he led a tour, whether to see bioluminescence or not, he began looking for their oblong, glass-like bodies in the water. That trained eye led him to a previously unknown natural phenomenon.
In 2020, when the COVID-19 pandemic hit, Brandao was back in his hometown of St. Augustine. He had formed his own company, GeoTrippin, and was running kayak tours on Guana Lake, a tidal estuary between St. Augustine and Jacksonville, when he made a discovery.
While on a sunset tour, he spotted walnut comb jellies (Mnemiopsis leidyi) after dark, twinkling in the water as he paddled. This was unusual for September, but he didn’t think much of it, figuring it was an isolated occurrence. Generally, organisms produce bioluminescence only at certain times of the year, when the salinity and temperature are right. “I think if my eyes weren’t trained, I wouldn’t have seen it,” he says. But as he kept conducting the sunset tours, he started seeing the comb jellies glow every time. Finally, after months of seeing them flickering regularly, he realized this phenomenon was happening in the lake year-round.
Brandao’s findings attracted local researchers from the University of Florida, who came to join his tours to investigate this unusual occurrence. While they’re still studying the causes of this year-round phenomenon, they know it has something to do with the lake’s specific conditions.
A very shallow body of water, Guana Lake is an impounded creek, formed by an earthen dam that was constructed across Guana River in 1957. Thriving in that sheltered environment, comb jellies eat, grow, and breed actively, so they’re always there in large numbers.
“I’ve seen it disappear after heavy rains because the salinity drops and they die, because there’s not enough salt in the water,” Brandao says of their bioluminescence. “But then a couple of weeks later, it’s back.”
As strange as it may sound, humans and comb jellies share many genes. One recent study found that comb jellies are distantly related to all other animals on Earth and described them as “sisters” to all other creatures. Scientists are therefore studying them to understand what roles different genes play in an organism. Essentially, if a gene persisted through a million of years of evolution, it likely carries an important function, explains Matsumoto. “You get a better idea of how important a gene might be, because it has been around for a longer period of time,” he says.
Do humans have comb jellies to thank for our own through-gut and anus genes? It’s hard to tell for sure, because we may have evolved them independently. But we certainly share that capability with them. Scientists hope to find out more, as well as why this particular group in Florida sparkles so regularly. Meanwhile, the fact that comb jellies possess the world’s most ancient anus makes Brandao’s twilight tours a popular attraction. “Who doesn’t want to meet the world’s oldest asshole?” he quips. Especially the one that twinkles in the dark.
Article by:Source: Lina Zeldovich
