Blow Lugworms

At low tide in Washington state one recent afternoon, I discovered the shoreline dotted with little mounds of coiled sand. They were everywhere – a beach dotted with mini sandcastles! I’d never seen such a thing and was instantly wondering who made them. I later discovered they were made by creatures called blow lugworms which can grow to be nearly 8 inches long.

Before getting into the natural history of a blow lugworm, let’s start with the fact that the tiny, coiled mounds that captured my attention are essentially worm poo. Ha! More scientifically, they are called casts. The worms ingest sandy sediment within their burrow. They feed on the microorganisms in the sand and the indigestible material is cast off above the surface into coiled mounds.

Blow lugworms play an important role in the coastal ecosystem. Like their terrestrial cousins, earthworms, their burrowing aerates the sand! They also recycle nutrients that other organisms thrive on and break down decaying matter. Of course they are also an important food source.

While their burrows may be 8-16 inches below the surface, the lugworms are vulnerable when expelling the indigestible material because their tails are close to the surface. Savvy crabs, birds, and animals nip at their tails. Lucky for the lugworm, the tails are fragile and will break off. Thus the predator gets a bite and the lugworm lives to create another cast. I never cease to be amazed at the intricate workings of Mother Nature!