Teacher Logbook:
Wednesday, July 5, 2000 1900 hrs.

Our mooring elevator came up from the bottom full of specimens this morning. The biologists were anxiously awaiting the OK from the crew that it was safe to take their samples from the milk-crate looking platform. In the large bio-boxes were thousands of limpets and more interestingly, lots of tube worms.

Tube worms are the best known animal in vent communities because of their endosymbiotic relationship with bacteria. With no mouth, gut, or anus, scientists were puzzled how these worms acquire food. The answer came in 1981 from a graduate student, Colleen Cavanaugh. She showed that tube worms contain a feeding sac, the trophosome. Bacteria live inside the cells of this structure in unbelievably large quantities and produce food by chemosynthesizing hydrogen sulfide into organic carbon. This, in turn, feeds the worm. The bacteria benefit in two ways. The worm provides a place of residence and the hydrogen sulfide necessary to produce food. On top of the worm's white chitin tube is a red feathery cap. The worm waves the cap in vent water, collects hydrogen sulfide, and binds it to a special hemoglobin in its blood, (similar to hemoglobin in human blood) which transports the nutrient to the trophosome. Symbiosis at its best!

On board our ship we have a world authority on tubeworms, Verena Tunicliffe. Today, with the help of her graduate student, Jean Marcus, she sorted, dissected and preserved the worm samples for reproductive studies back on shore. Their lab smelled like rotten eggs (hydrogen sulfide) so I made my photographic visits brief. Verena's worms from Axial are all one species while other venting areas, such as the East Pacific Rise, contain four. The Northeast Pacific's low number might be due to the Gorda, Juan de Fuca, and Explorer plate's isolation from the 40,000 km seam of oceanic ridges that encircles our planet.

Signing off from 45ø56' N 130ø00' W.
Jeff

Tube worm colonies at the Ashes vent field.