Unusually large mollusc discovered in Antarctic waters

A new species of ‘gigantic´ mollusc has been discovered in the Antarctic waters

October 2011. Spanish researchers have discovered a rare mollusc in Antarctic waters that looks the same as limpets but is bigger in size than all species known to date. The specimen appeared in waters very distant from where this type of species is normally found.

A new species of mollusc that shares the same morphology as the limpet (Fissurellidae) and is 14 millimetres in length has been found in Antarctic waters.

Cristian Aldea, co-author of the study, explains that "this genus belongs to a group which we know very little about. This group is made up of 14 species of which very few specimens have found."

Named Zeidora Antarctica, this 14 millimetre long specimen is much bigger than members of the same genus, who are not normally longer than 5 millimetres.

Discovered 600 metres down
It was discovered at a depth of more than 600 metres in the Bellingshausen Sea in Antarctica - a habitat with very different characteristics to that of other Zeidora species. Most specimens of this group live in tropical and warm waters. Of all of them, eight species have been discovered in the Northern Hemisphere in the Caribbean, Japan, Panama and the Red Sea, and six have been found in the Southern Hemisphere in places like the Galapagos Islands, Easter Island, Australia and New Zealand.

Surprise find
The specimen was found during the BENTART expedition of the Spanish National Antarctic Programme on board the Hespérides. Aldea recognises that he was not expecting "to find such a species on the trip since those that have already been discovered are known to be distributed from low (tropical) to medium latitudes with the closest becoming a species found in New Zealand."

Aldea states that "we carried out the description of the species based on the shell, given that no soft tissue could be found in the only caught specimen." These studies have allowed us to show, for instance, the number and size of ribs that the mollusc has. However, the morphology of its soft tissue was not revealed but "all of the characteristics taken from the shell indicate that it is a living species as opposed to a fossil species," according to the expert.

The discovered specimen is on display at the Madrid's National Natural History Museum (MNCN) and has been compared with other Zeidora naufraga Watson, Zeidora maoria Powell and Zeidora reticulata species that are on display at the London's Natural History Museum.

This discovery by a research team from the Ecology and Zoology Department of the University of Vigo, Spain has been published in The Nautilus and provides more information on the members of the Zeidora genus and their geographic distribution.