Jake Vargas, Guest Author
Tegula Funebralis: One Tough Little Snail
The black turban snail (Tegula funebralis) is one of the most prolific marine gastropods – a fancy way of saying saltwater slugs, and/or snails – along the northern California coast. If you were to go to Trinidad, Baker, or most any beach during a good low tide, you could see hundreds of the black turban’s distinct black shells littering the rocky shore. Despite their abundance, Tegula’s small size often lends to them being overlooked. As small as they may be (often smaller than a pinky nail!), the harshness of their environment and the stress of predation have turned the black turban snail into one tough creature.
During low tide, turban snails can be found clinging onto the underside of rocks using their muscular black foot. These rocks provide a cool, shady place for the snails to wait for the incoming tide, while avoiding predators, and minimizing the potential of drying out. If frightened (perhaps from human footsteps or a hungry crab looking for its next meal) turban snails will release from their shady hideaways and go tumbling down into the water below, doing their best to avoid the perceived danger. When evasion fails, black turban snails have a backup strategy. Tegula also possess an incredibly tough shell, which can protect them from attackers. In the face of danger, turban snails may choose to retreat deep within their shells to wait out potential threats. In fact, if you look closely at a turban snail’s shell, you may see a triangle shaped scar, the relic of a long-ago crab attack!
Unfortunately for the turban snail, “jumping away” and hunkering down doesn’t always work. “Jumping” requires turban snails to visually identify a threat, but turban snails have very poor eyesight, making it difficult for them to identify danger in murky water. On top of that, large crabs have powerful pinchers that can crush even very large turban snail shells, so what’s a snail to do? Luckily, these gastropods have a powerful “hidden” tool.
Their secret? An amazing sense of smell! Using a small pouch-like structure called a bursicle (which we can think of like a human nose), Tegula detect chemicals within their tidepool homes. These chemicals, which may be derived from natural predators, alert the black turban snail when a crab or starfish might be near, even if the snail cannot see its attacker. Although we generally think of snails as being quite slow, when a turban snail senses danger nearby, it can double its crawling speed! If, for example, a black turban snail senses a starfish nearby, it will book it to the water’s surface, just out of reach of the starfish, which will not exit the water in pursuit of prey.
It is likely that turban snails have developed many defensive strategies due to the constant stress of predation, and these strategies have evolved very slowly, over thousands of years. While turban snails may be adapted to face natural predators, their future in the face of rapid climate change is uncertain. For this reason, it is incredibly important for both scientists and community members to keep an eye on how this ecologically important animal responds to an ever changing world. So, next time you visit a tide pool don’t forget to say hi to the snails and recognize that for a little tiny critter like Tegula, it’s a tough, tough world.