Bubble Shells

By Alex Scott

The snail and the slug often get a bad reputation in the animal world for being slow or slimy or just ugly. But the class of invertebrates known as Gastropoda, which contains snails, slugs, and limpets, is second only to insects in its number and diversity of species in the animal kingdom. Coming in a myriad of shapes, sizes, and colors, gastropods are a vast group of animals that fulfill a variety of important roles in almost every ecosystem around the world. And one bright pink gastropod in particular, given the scientific name Hydatina amplustre, also fulfills another critical purpose: adding to the collection of avid beachcombers.

Widely distributed throughout the tropical Pacific and Indian oceans (from Hawaii to Africa), H. amplustre is most often found in coastal, rocky tide pools. This species is a member of the family Amplustridae, which is a type of heterobranch sea snail. “Like nearly all heterobranchs, they are simultaneous hermaphrodites, meaning each snail is both male and female at the same time,” says Cory Pittman from Sea Slugs of Hawaii. “The animals are nocturnal, burying themselves in sand during the day.” These tiny animals usually live no longer than a year and eat mostly polychaete worms living on the seafloor.

Species in the family Amplustridae are known for their thin bulbous shells that give them the name “bubble shell.” H. amplustre is also called Royal Paper Bubble, Pink Bubble, Ship’s Flag Bubble, or Swollen Bubble Shell. This thin and colorful pink, white, and black shell does offer some protection from predators, but the snail also relies on distasteful chemicals obtained from its food to deter them. Two tiny black eye spots detect light and help the animals navigate.

Although marine biologists would say that the snail within the shell is the most interesting part of the animal, for beachcombers, it’s all about the outside. “These delicate and hard-to-find seashells are just as breathtaking as the translucent, dreamy, and pretty cute snail that resides within,” says Becky Reinbold, a beachcomber who has a beautiful collection of bubble shells she has found in Maui, Hawaii.

Tiny, vacant shells can be found at the highest tide line in the sand, mingled with other rubble and debris. Occasionally, the empty shells can be found in tide pools, floating on top of the water. Becky adds, “The shell itself is quite fragile and paper thin and can be difficult to find intact, making them a fun and rare beachcombing find!”

This article appeared in the Beachcombing Magazine March/April 2020 issue.

Update: We just had to share this adorable video of a hermit crab that made its home inside a bubble shell! Thanks to Autumn and Adriana R. for sharing it! Don’t worry — Adriana returned this little cutie to the water after she filmed it.

Learn more about seashells

Learn more about identifying shells, the history of seashell collecting, great shelling beaches, and the lives of the animals who make the shells we find on the beach. Articles ›

No live shelling: Be sure shells are empty of the animals that made them or the animals now living in them, and sand dollars, sea stars, and sea urchins are no longer alive before you bring them home.