One of the biggest challenges for marine biologists is understanding how marine animals reproduce. For many species, these are rare events that require very specific circumstances. This problem is compounded for species that are too shy—or too particular—to mate in captivity. A new paper co-authored by Reuben Shipway (University of Portsmouth, UK) and OGL’s Director Dan Distel shows that when it comes to sex, shipworms are definitely not the shy and retiring type!

In this paper, researchers describe catching never-before-seen mating behaviors on video for the giant feathery shipworm (Bankia setacea). Shipworms are a type of bivalve that spend their life boring into and feeding on wood, and they have been observed to use a wide variety of reproductive methods. Among the most fascinating of these methods is pseudocopulation, which has now been recorded on video for the first time in shipworms. 

While most bivalves are broadcast spawners that simply release eggs and sperm into the water column, leaving them on their own to find each other, these shipworms have found another way. Shipworms live their whole lives inside wooden burrows with only their tube-shaped excurrent and incurrent siphons exposed to the outside world. Like most shipworms, Bankia setacea uses these siphons to breathe in oxygen-rich water and expel the oxygen-stripped water as waste. But B. setacea has found another use for these siphons: It uses its excurrent siphon to insert its sperm into another shipworm’s incurrent siphon in a process known as pseudocopulation.

During this study, researchers observed shipworms simultaneously giving and receiving sperm at the same time, even in groups of up to six individuals! Even more surprisingly, this shipworm species exhibits competitive mating behaviors that have never been seen before, such as using their siphons to wrestle away rivals by bringing another shipworm’s incurrent siphon out of reach of its competitors. This type of mating competition is rare, and may help scientists understand the unusual mating behaviors that shape the evolution of marine species.  

Want to learn more about shipworm reproduction? Click here to read about this important discovery!

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