For marine life, the Hawaiian Archipelago is an oasis in the middle of the Great Pacific Desert. Farther from a major land mass than any other island chain on earth, the tall volcanic sea mounts rise 19,000 feet (5,800 meters) before they break the surface of the ocean. In that rise, their slopes provide a multitude of habitats and light conditions for complex communities of sea life. Shellfish (marine mollusks) are important members of the marine communities.
Because their larvae disperse in the ocean currents, closely related shellfish can be found spread across vast stretches of ocean. Hawaiʻi shares many species with other islands in the Indo-West Pacific, which reaches from our islands in the northeast to the Marquesas and Society Islands in the southeast, and across the tropical Pacific and Indian Oceans to east Africa. And yet, because of its isolation, some species have settled here and their offspring remained long enough to create unique creatures found nowhere else on earth. The talented artists who create the famed Niʻihau shell lei can tell not only which island, but which beach certain shells are from.
The shells of most mollusks provide protection from predators. But the shells also provide a skeletal framework to which the animal’s muscles are attached.
Snails on land move by contracting their foot muscles in waves which ripple across the bottom surface. Marine snails do the same. And just like their landlubber counterparts, marine snails secrete slime or mucus to reduce friction between their foot and whatever they are moving over. Sea snails also often have a trap door, called an operculum, which they can close when they retract into their shells. Not only can this help keep predators from eating them, for the snails which live in the intertidal zone, it seals in precious moisture so that they do not dry out during low tide.
The Hawaiian Terebridae mostly eat marine worms. They attack their prey with a venomous barb similar to that of the cone snails. While they are not generally considered dangerous to humans, it’s a good idea to leave shellfish where they live and not disturb them – for your safety, as well as theirs!
Tonna generally eat sea cucumbers, sea urchins, starfish, fish, and other shellfish. Their saliva contains from 2% to 5% sulphuric acid, which they use to kill their prey. They will squirt it out if disturbed!
Lambis are herbivores, and like to graze on the fine red algae which grows in shallow water.
Hippopus are filter feeders, helping to keep our oceans clean!
When the animals die, their shells are washed back and forth by the waves, eventually breaking down and being crushed into sand.
Seashells were an important source of meat protein in ancient times, and many Hawaiian people still find this resource to be significant. Shoreline development, water pollution, over harvesting, and increasing ocean temperatures and acidity are damaging these animals and their habitat. Many Hawaiian people are participating in various activities to help our shellfish come back to healthy population levels.
Shellfish not only were important for food, they also provided tools, musical instruments, and ornaments.
The pū (Charonia tritonis) is the largest marine snail in Hawaiian waters. It is one of the shells use to make the famous trumpet often seen at the beginning of Hawaiian ceremonies. Cassis cornuta also is used as a trumpet.
The leho (cowry, Cypraea maculifera) was popularized as a musical instrument by kupuna Nona Beamer, and is used in her hula, Pūpū Hinuhinu.
Shells were worn as ornamentation, and continue to be prized by all of Hawaiʻi’s people.