Evolutionary biologists were thrown for a loop recently, all because of one of the most common jellies we have here in Long Island Sound.
At the center of all the fuss are comb jellies, which are like the gelatinous creatures you think of when you think of jellies – for example, moon jellies and lion’s mane jellies. But comb jellies actually not related to those jellies at all. (They’re in a whole different classification phylum. Comb jellies are ctenophores – pronounced TEEN-o-fours. Moon jellies and lion’s manes, and also corals and sea anemones, are cnidarians – pronounced nye-DARE-ee-ans.)
One of the primary things that sets comb jellies apart from other jellies is that they don’t sting. They lack the stinging cells that cnidarians have.
Comb jellies – a sort of walnut-shaped creature – also move through the water differently. They have eight rows of hair-like structures called cilia, lined from front to back, and these cilia beat rapidly in moving pulses. That motion propels the comb jelly.
Here’s what’s cool about the cilia: they refract light, so the movement of the cilia results in a rainbow of colors flowing across the comb jelly like a movie marque.
It’s easier to see than to explain, and the Monterey Bay Aquarium offers a nice segment: www.youtube.com/watch?v=bW3sqB7RTIc
Comb jellies are in the news because researchers doing genome work recently announced that comb jellies may have preceded sponges, which have long been thought to be the first multicellular animal. In other words, comb jellies may bump sponges from the base of the “Tree of Life.”
That’s surprising enough. But what really throws the scientists is that comb jellies are more complex animals than sponges. If sponges came after comb jellies, why didn’t comb jellies pass their molecular features on to sponges? After all, the general rule is that animals don’t evolve to become simpler.
One possibility is that comb jellies may have come first, but they didn’t have the complex systems at first. Instead, they may have evolved their features independently of other early life forms, which would have been quite the trick. Or could it be that sponges indeed simplified over time? (We’re talking some 550 million years ago. Squishy things didn’t leave much of a fossil record.)
Research on comb jellies will continue, with lots of interesting possibilities. The current issue of Science News magazine explains it all: http://tinyurl.com/cj2vcwj
Meanwhile, the crew of The Maritime Aquarium’s research vessel, Oceanic, is bringing up comb jellies on every outing onto Long Island Sound. See them for yourself by coming aboard one of our public study cruises, offered at 1 p.m. Saturdays through June 29. We’ll go out daily at 1 p.m. in July & August. Get all the details at www.maritimeaquarium.org.
Photo: © Fredrik Pjeijel