Finally, a critter with a purse…
Yes, you read the subtitle correctly. A purse. A pocket. A bursicle.
The common Black Turban Snail is an interesting little critter with an interesting organ in its pocket.
They are one of the most abundant snail species along the Pacific Coast and inhabit most of the North American Pacific Coast from Canada to Baja California, Mexico.
This rocky shore snail is commonly found between high and low tides in protected areas near boulders, tide pools, and close to shore.
The snail is pretty easy to identify, and so is the age of the snail. Juvenile snails live in more shallow water compared to adults. As the snail ages, it also migrates to higher waters. A fully grown Black Turban shell may be just over an inch long (30 mm) and 30-years-old.
The name sake for the snail is not the shell but the head and foot which are also black. The shell is smooth, whorled and pyramidal shaped.
The Black turban snail has many predators including humans, crabs, stars, otters, birds, other snails, and more.
There is evidence that some humans also harvested the snail as part of their diet about 12,000 years ago. If the snail were the only food consumed, the average human would need to eat around 400 of them each day to survive. When they are easy to harvest, this is possible and the snail continues to be collected today.
But wait, what is IN that shell?
Don’t be too surprised to find something other than a snail living inside the Black Turban shell. Hermit crabs will frequently adopt empty Black turban snail shells as their new home.
The black distinctively smooth shell helps protect the snail. The Black Turban can withdraw its entire body into it for protection.
Black Turbans shred alga using a rasp-like (like a file) structure full of teeth. These teeth are constantly breaking and wearing. Thus, replacement teeth are produced continually, much like a shark must do.
What’s ON that shell?
The shell of the Black Turban is covered with red algae. Limpets graze the shell eating the algae. Slipper shells (Crepidula adunca) also live on the Black Turban Snail’s shell. The Slipper shell is a filter feeder and eats phytoplankton, bacteria, and diatoms that are on the shells.
Tegula funebralis feed on algae such as Macrocystis sp., Nereocystis sp., Gigartina sp., and Mastocarpus sp..
So what’s up with the purse?
Black Turbans have a special organ that they carry in a pouch or purse like structure called more scientifically as a bursicle. This chemoreceptor will sense chemical changes that emanate from predators such as crabs and seastars.
Once detected, the snail can take defensive actions and attempt to escape. However, snails are not known to be speedy. Yes, they may flee, but not quickly.
They may move to higher, potentially safer ground, potentially out of the water, to try and avoid contact. They may also simply float away to esacpe.
And of course, they always take their purse.
–Merriam-Webster dictionary, bursicle (https://www.merriam-webster.com/dictionary/bursicle)
–SIMoN Species database (https://sanctuarysimon.org/dbtools/species-database/id/131/tegula/funebralis/black-turban-snail/ and photos from their gallery)
–iNaturalist, Black tegula (https://www.inaturalist.org/taxa/460365-Tegula-funebralis)
–Prezi, Black Turban Snail (https://prezi.com/0ac53jzexytf/black-turban-snail/)
–Biodiversity of the Central Coast (https://www.centralcoastbiodiversity.org/black-turban-snail-bull-tegula-funebralis.html)
–Wikipedia, several (https://en.wikipedia.org/wiki/Crepidula_adunca, … Microalgae, and chemoreceptors)