Teacher Logbook - NOAA Ship Ron Brown

This Ridgeia piscesae (tubeworm) larvae was captured in the plankton net tow during the Imagenex survey at CASM on dive R626. The ROV was towing the net through the water column, about 25 meters off the bottom.

Jeff Goodrich's Sealog:
Axial Volcano - 1998 lava flow
July 25, 2001

Last night Verena Tunnicliffe and Anna Metaxas made an important discovery. During our 12 hour Imagenex survey at the CASM vent field, a plankton net was towed by ROPOS at a height of 25 meters. After finishing the survey, the net caught a single tubeworm larvae (Ridgeia piscesae). This is the first time that the delicate larvae have ever been found in the water column along the Juan de Fuca Ridge. Previously, tubeworms have only been seen as adults or as recently settled juveniles on the bottom. Based on its size, about 2 mm long, this particular one is likely ready for settlement very soon.

This discovery could give some important insight into tubeworm feeding. Adult tubeworms have no functional feeding gut, meaning no mouth and no anus. How then, do they get their food? They survive because the trunk of the tubeworm is packed full of chemosynthetic bacteria. These bacteria use sulfide from the vent fluid as an energy source to fix inorganic carbon (from either the vent fluid or seawater). The tubeworm transports sulfide and carbon dioxide to the bacteria, and in turn receives organic molecules that it can use to feed itself. The question remains, how do the bacteria get into the tubeworm in the first place? Research to date indicates that the bacteria aren't passed from parents to eggs because gametes don't contain the bacteria. The bacteria must therefore, enter during the larval stage when there is a functional feeding gut. The working hypothesis right now states that larvae settle, and then must wait to ingest the correct bacteria before losing their functional gut. However, evidence for this hypothesis remains sparse. Having preserved the single sample, Verena will dissect the larvae back at her lab to find out whether it has a gut or has already acquired it's bacteria. This is one more piece of the puzzle towards a better understanding of tubeworms and their chemosynthetic symbionts.

The Imagenex data was crunched by geologist Bill Chadwick all day and a map of the CASM vent field was produced. It's use of colors reveals details not seen in lower resolution maps produced by the ship's SeaBeam mapping system. We are currently diving at the 1998 lava flow to recover and deploy MTR's (temperature recorders) and bacterial traps, take vent fluid samples, collect iron oxides, and sample more vent fauna. Busy, busy, busy.