Long, translucent tubes sticking out of a piece of wood, two of them entwined around each other.

The molluscs called giant feathery shipworms use their long siphons (pictured) to wrestle for the chance to mate. Credit: Dr Reuben Shipway/University of Portsmouth

Animal behaviour

The ferocious sex lives of giant shipworms: rivalry and wrestling matches

First footage of ‘pseudocopulation’ shows the lengths certain molluscs go to to mate.

Researchers have captured videos of acrobatic styles of sex in shipworms, molluscs that colonize ships, piers and driftwood as larvae and then spend their lives burrowing into and eating the wood around them.

The only part of a shipworm’s long, soft body that is visible outside its wooden hideout is a retractable ‘siphon’ — a tube used to bring in food and oxygen and expel waste. Faced with the constant danger of literally eating themselves out of house and home, the various species of shipworm have developed a smorgasbord of sexual strategies, from males releasing a huge amount of sperm into the sea to females keeping miniature males in a side pocket. 

Reuben Shipway at the University of Portsmouth, UK, and his colleagues recorded giant feathery shipworms (Bankia setacea) using their siphons to deposit sperm directly into their neighbours — in probably the first ever films of what is known as pseudocopulation. The astonished team also saw competing shipworms wrestling with their siphons over the opportunity to deposit sperm, and pulling the siphons of potential mates out of rivals’ reach.