When you imagine marine predators from the vast ocean, you probably envision apex predators like sharks and killer whales, but some deadly predators hail from more humble backgrounds. Sea snails might not look all that threatening to the untrained eye, but they have evolved to travel, feed, and hunt in some weird and wonderful ways.
The sea snail Olivella semistriata is a suspension-feeding, swash-surfing snail that can be found on the tropical sandy beaches of the East Pacific. They spend much of their time in the intertidal zone, where the changing tide flushes and withdraws from the shoreline. Their habitat here has inspired an ingenious passive feeding strategy whereby the snails extend two wing-like appendages lavished in mucous from the snail’s foot. Once extended, they create two gooey nets that filter tiny food from the ebbing and flowing water of the ocean tide. What’s more appetizing than taking your goo-net for a filter, hey?
While the intertidal zone offers some great filter feeding opportunities, it also puts a little snail at considerable risk from predators so to avoid getting monched O. semistriata has engineered some effective escape strategies. As excellent burrowers, these snails can submerge themselves fully in the wet sand using two metapodial flaps to pull themselves under. They also like to burrow when busting out the goo nets.
If the snails want to get a bit more distance, they can also make a speedy exit back into the ocean by putting these flaps to work in a different way. By extending them as well as their foot, they can essentially surf the waves and pump these flaps to gather more momentum until they reach a good spot.
One of O. semistriata’s most fearsome foes is actually another kind of sea snail, Aragonia propatula. These killer snails are investigative hunters that depend on coming into contact with their prey in order to identify it. They’re opportunistic too and will essentially try to ingest anything that moves in its path. They can detect prey by sensing chemical changes as well as making physical contact, and once prey is identified their true skill is revealed.
O semistriata is one of A. propatula’s most common meals, though they will also eat crustaceans including hermit crabs. When prey is identified, the snail launches itself on whatever it’s caught and essentially wraps its body into a sealed ball. Inside this unfortunate looking ball, the snail will release digestive enzymes which break down the prey trapped inside. As this happens, A. propatula begins burrowing into the sand, sealing its victim’s fate by encasing it in the sand as well as its mucous-laden flaps.
So, it seems sea snails are more agile than their above-ground counterparts. Find out about one of the world’s most dangerous here.