Comb Jellies Colonize My Fish Tank

Carlos Fraguela

Gemmation and tentacles hunting.

HAVANA TIMES — More than a year ago, I took on the challenge of building an aquarium at home. This has brought me no few surprises and many “discoveries” about the animal world.

I’d been observing and photographing small organisms without considerable difficulties until a micro-predator was introduced into my fish tank.

I am most interested in the invertebrates that swim freely across the water. When I started, I didn’t think a tiny organism could ruin my voyeuristic fun. As it turns out, however, this miniscule hunter feeds precisely on the organisms that interest me.

One bug is all it took: this organism has great reproductive capacity, an efficient hunting method and quite an appetite. It is a kind of ctenophore (comb jelly) that filters surrounding water in order to capture the plankton it feeds on.

These tiny animals are constantly on the lookout for nearby swimmers they can catch with their two, extremely long tentacles, which are equipped with hairlike protrusions they can sweep across the fish tank like a scanner. Sometimes, you see them stuck to the glass or to algae. Other times, they let themselves be carried by the current, in search of a better location.

I think I’ve discovered they have several reproductive methods. One of them is most probably gemmation, the other is through eggs. They reproduce exponentially and there appear to be no predators that check this growth. There are now hundreds of them in the fish tank and I am thinking of taking it apart.

These animals are particularly beautiful and tend to steal the show. Any animal or object that rubs against their tentacles gets stuck to them and is dragged to the place where it is ultimately devoured (few preys manage to escape after being caught). Sometimes, they employ pseudopods to encircle and trap its prey.

Cool, eh?

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