They are highly unusual for a fish

Mar 12, 2009 12:22 GMT  ·  By

Experts at the Natural History Museum in London, the UK, were puzzled to learn that they had had specimens of a new species of fish in custody for more than a year. Upon initial inspection, they thought that the animals belonged to a different family, and left them to go about their business in captivity. A year later, when the creatures began to die, scientists had the curiosity to put a preserved one under the microscope. And that was how the team was introduced to Danionella dracula, the vampire fish species.

These animals were caught in the waters of Myanmar, Burma, and those who captured them at the time had no idea that they had stumbled upon a new species of fish. They took them to England, where the creatures were briefly cataloged and then transferred to an aquarium. No one had any suspicion as to the true nature of the fish, until they started dying and thus drew attention to themselves. Upon inspection of their mouth, scientists found a pair of “fangs,” not unlike those you would expect to find in the mouth of a genuine vampire.

Ralf Britz, an expert at the museum, told the BBC News that “After a year or so in captivity, they started dying. When I preserved them and looked at them under the microscope, I thought, my God, what is this, they can't be teeth.” In fact, they were not teeth. In order to understand exactly the use of the formations and how they came to be, Britz stained the bones with a special substance, and then dissolved everything around. The microscope then showed the fact that the “teeth” were actually protuberances of the jaw.

This is in accord with what the experts first thought, seeing how the D. Dracula group of fish lost its teeth more than 50 million years ago. The existing formations, which the museum staff believes to play little to no part in the actual feeding process, have no pulp cavities or enamel caps, which are the indicators of true teeth.

“We did not study stomach contents, but we know that its close relatives live on small crustaceans… and other small invertebrates. In captivity it readily accepts brine shrimp, tiny nematodes, and even very fine flake food,” Britz adds in an e-mail to National Geographic News.