Predator deterrence and 2,4-dibromophenol conservation by the enteropneusts Saccoglossus bromophenolosus and Protoglossus graveolens

Abstract

Saccoglossus Dromophenolosc~s I n g et al., 1994 and Protoglossus graveolens Giray & Klng, 1996 contain high concentratlons of 2,4-dibromophenol (DBP), the functlon of whlch is uncertain. Mature enteropneusts that were collected from the field and maintamed in v~tro without bromide retained DBP, which is inconsistent wlth actlve DBP secretion into the burrow env~ronment. DBP was also conserved during field manipulations that decreased food availability in situ. Further, DBP did not deter predation in feeding experiments 1~1th the anomuran crab Pagurus longicarpus and the polychaetes Glycera dibranchiata, Nereis virens and Nephtysincisa. The hermit crabs fed on S. brornophenolosus readily, and in preference to shrimp, in the field and in laboratory aquaria. Elevated DBP levels were measured in crabs that had recently consumed S. bromophenolosus, and ingested DBP was degraded to 4-bromophenol. Elevated levels of DBP in polychaetes were associated with the disappearance of enteropneusts during in vitro feeding experiments. Control incubations with DBP-containing agar plugs indicated that the polychaetes did not accumulate DBP passively. These results suggest that DBP is not an effective anti-predatory agent against hermit crabs or some predatory polychaetes. A definitive role for DBP in enteropneusts remains to be shown.