Heather Farren Marine and Estuarine Science Program Department of Biology MSc. completed 2002 BSc. Biology and B.A. Spanish, Central Washington University, 1995. Teaching Credential (Biology, Spanish, and Earth Science endorsements), Central Washington University, 1997.

Project

Title: Protections conferred by sponge epibionts on the scallop Chlamys hastata:  Effects on barnacle encrustation and sea star predation.

Abstract: The spiny scallop Chlamys hastata frequently carries epibionts such as sponges and barnacles.  Past research has suggested that the sponges protect the scallops by preventing tube foot adhesion by sea star predators, and has shown that barnacles impede the swimming ability of the scallop while sponges do not.  My research determined whether sponges provide other advantages for their scallop hosts.  I investigated whether the sea star Pycnopodia helianthoides shows a preference for scallops with one type of epibiont over others.  In this study, P. helianthoides ate significantly more barnacle-encrusted scallops than either type of sponge-encrusted scallop.  I then used scallop and sponge homogenates to investigate whether the two sponges that commonly live on scallops in Puget Sound, Mycale adhaerens and Myxilla incrustans, have a chemical defense that deters sea star predation. Sea stars reacted positively to scallop puree, and negatively to sponge puree, indicating that sponges may have chemical defenses that benefit their scallop host.   The last phase of my research determined whether sponge on the scallop prevents barnacles from settling.  Field experiments indicated that barnacle larvae settled more frequently on epibiont-free scallops than on those with sponge.  These results demonstrate that sponge epibionts benefit scallops by preventing predation by P. helianthoides and settlement by barnacles.