Marine scientists from the German federal state Bremen discover new giant clam - A hitherto unknown species shows signs of overfishing that already began 125.000 years ago

Researchers of the Center for Tropical Marine Ecology (ZMT), the University of Bremen and the Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association have, in cooperation with Jordan and Philippine colleagues, discovered a hitherto unknown giant clam. Tridacna costata lives in the coral reefs of the Red Sea and grows to a length of 40 centimetres. It also exists in fossilized form and had in former times a proportion of about 80% of all giant clam species in the research area. Today, only less than one per cent of all clams belong to this species. Its decline about 125.000 years ago is seen by the researchers as the first incidence of overfishing in the history of mankind. Following the criteria of the IUCN Red List (International Union for Conservation of Nature), the new species – scarcely discovered - is already threatened with extinction.

Confusion about the identity of the giant clam
“We have collected giant clams for cultivation experiments when we were struck by the animals' particularities”, reports Prof. Dr. Claudio Richter, who worked at that time for the ZMT and is now a member of staff at the Alfred Wegener Institute with a professorship at the University of Bremen. His team has been looking for possibilities to breed the giant clam Tridacna maxima within the framework of a German-Jordan cooperative project. This clam is very popular among Aquarians, and successful breeding could not only satisfy growing demand within this sector, but also increase the decimated stock in the Red Sea. Dr. Hilly Roa-Quiaoit of the Xavier University (Philippines), at that time doctoral candidate at the ZMT, found a giant clam during her research in this project which exhibited features of two species living in the Red Sea, but which also exhibited some very particular features. “We were astonished that so far nobody has stumbled over these clear particularities like the serrated edge of the shell”, continues Richter.

Confirmation of a new species
To finally clarify the identity of the clam they contacted the molecular geneticist Dr. Marc Kochzius of the University of Bremen. Roa-Quiaoit and Kochzius carried out a genetic genealogical analysis which clearly shows that Tridacna costata is a unique species. This is the first new description of a giant clam for more than twenty years. Further investigations show that Tridacna costata, in contrast to its sister species Tridacna maxima and Tridacna squamosa, only lives on the roof of tropical reefs in the Red Sea and breeds differently.

Fossilized clam findings show historical overfishing
While they were only trying to find a possibility to make a new organism usable for aquaculture, they thereupon examined fossilized findings in the Red Sea. They discovered that 125.000 years ago up to about 80% of the clams in the region belong to the newly described species Tridacna costata. “The giant clams were probably highly diminished by an extensive use of early modern men”, explains Richter.” Tridacna costata lives sessile in shallow waters and therefore was easy prey for our predecessors who were spreading out from Africa into the Mediterranean.” Giant clams are still used as food along their area of circulation, and they are also collected for their shells. All in all, the direction which this research project took shows how important it is that scientists of different disciplines like palaeoecology and molecular biology work together. “Even in an easily accessible investigation area like the shallow water zones of the Red Sea, not even clearly visible species are completely identified. This is why fundamental research has to be furthered”, concludes Richter.

The results of the latest research are presented in the current online issue of the periodical “Current Biology” (www.current-biology.com)

Notes for Editors:

Your contact persons at the Alfred Wegener Institute is Prof. Claudio Richter (phone: +49/471/4831-1304; email: Claudio.Richter@awi.de).

Your contact person in the public relations department are Folke Mehrtens (phone: +49/471/4831-2007; email: Folke.Mehrtens@awi.de) and Magdalena Hamm (phone: +49/471/4831-1376; email: Magdalena.Hamm@awi.de).

The Alfred Wegener Institute carries out research in the Arctic and Antarctic as well as in the high and mid latitude oceans. The institute coordinates German polar research and makes available to international science important infrastructure, e.g. the research icebreaker “Polarstern” and research stations in the Arctic and Antarctic. AWI is one of 15 research centres within the Helmholtz Association, Germany’s largest scientific organization.