Spionid polychaetes expand their distribution by accompanying oyster shells during transportation

Spionid polychaetes which associate with oysters are suggested to have been increasing their populations as the result of host oyster increase by (1) constructing artificial structures along the seashore to enhance their opportunity to settle and increase their populations and (2) growing oyster commercially for food sources. They also have been spreading all over the world to become unintentional invasive species by accompanying oyster shells which have been transported from their native range quicker and easier than ever.