A promising new anti-cancer drug found in a sea creature may be much harder to harvest than expected. A new report shows that the drug only occurs in a small number of the creatures.

The drug, bryostatin-1, is being tested in the US on leukaemias, lymphomas, melanomas and solid tumours.

It is made from a widely-distributed marine invertebrate, Bugula neritina, found worldwide in temperate waters. But research to be published in the June issue of the Biological Bulletin shows that only one place in which the animal is found produces bugula that contain bryostatin-1.

The research was carried out by two scientists from the Scripps Institution of Oceanography, Seana Davidson and Professor Margo Haygood.

Bugula, whose stringy brown colonies are sometimes mistaken for algae, often fouls boats' hulls. The authors are convinced that there are two distinct species.

The one which produces bryostatin-1 lives only in fairly deep water along the coast of southern California.

Chemically distinct

The other, producing 17 bryostatins that appear to have no medical potential, lives in most other parts of the world.

Davidson and Haygood sampled Bugula populations from 13 places along the Californian coast, and also from one Atlantic site, in North Carolina. They found there was a chemical difference between those from deeper water in southern California and all the rest.

Bugula neritina - unprepossessing, but potent

And they also found that the deepwater Californian Bugulas contained a different strain of the bacterium Candidatus endobugula sertula.

The authors suggest it may be an environmental factor, such as water temperature, that accounts for the different Bugula species. But although the amount of Bugula available for making bryostatin-1 is obviously much smaller than had seemed likely, there are two promising routes for developing the drug.

One is aquaculture, growing the Bugula on plastic panels placed well below the sea surface. Dominic Mendola, a Scripps graduate who now runs CalBioMarine, an aquaculture company, says that could satisfy the US demand for bryostatin-1.

"We estimate we should need 50,000 kg of Bugula a year", he says. "It would be difficult. But we could do it".

The other route is to try to synthesise bryostatin-1 directly from the sertula bacterium.