The sea walnuts or warty comb jelly (Mnemiopsis leidyi) are originally native to the western Atlantic coastal waters.
Vienna's Schönbrunn Zoo, considered the world's oldest zoo, was successful with breeding the fascinating jellyfish-like creatures and around 50 small sea walnuts have been born in the zoo's aquarium.
Zoo director Dagmar Schratter said: "Previously, the breeding of sea walnuts has succeeded only in the Monterey Bay Aquarium in California. Our animal care attendants have communicated with their American colleagues and received important information on breeding this species. And it has also worked for us."
The aquarium, which was specially built for the purpose, was crucial to their success.
The sea walnuts look like jellyfish but are actually a different type of animal altogether, called ctenophora.
Their body consists of transparent tissue, on which floating plates are situated which look a bit like ribs. As they swim around, these plates move in a wavelike motion and are illuminated.
The sea walnuts were originally found in subtropical waters on the American Atlantic coast. Due to ship traffic they succeeded in reaching the Baltic Sea.
They represent a big threat for the fish stock there, since they feed themselves with zoo plankton, which is also the preferred food of many fish species. The sea walnuts eat fish eggs and larvae as well.
The fragile sea dwellers can be seen at the aquarium in Vienna, with the zoo offering visitors a backstage tour to learn about how they breed.
Story courtesy of Central European News.