How do predatory deep-sea bivalves capture small crustaceans?

Predatory deep-sea bivalves have evolved specialized mechanisms to capture small crustaceans and other prey, departing from the typical filter-feeding habits of most bivalves.12

In the genus Propeamussium, the ctenidia (gills) are incapable of filtering. Instead, these bivalves detect prey and suck them into the mantle cavity through an inrush of water created when the valves open. Once inside, the prey is pushed into the mouth using the foot.1

Many deepwater species within the subclass Anomalodesmata utilize a modified ctenidium known as a "septibranch" ctenidium. This structure creates pressure changes within the mantle cavity, producing sudden inrushes of water that carry prey into a funnellike inhalant siphon. Some of these bivalves, such as Cuspidaria, use this siphon to draw prey in, while others, like Poromya and Lyonsiella, can rapidly evert their inhalant siphon to act like a hood, trapping small crustaceans beneath it before drawing them into the mantle cavity. In these cases, the food is subsequently pushed into the mouth by the palps and the foot.12