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A Giant Triton (Charonia tritonis) on an Indonesian Reef

A Giant Triton (Charonia tritonis) on an Indonesian Reef

Yesterday this blog took us to the depths of space to explore the frozen ice-moon of Triton.  Today we atone for that cold voyage with a trip to the inviting tropical seas of the Indo-Pacific.  In these vibrant waters can be found one of the greatest living gastropods, a prince among predatory sea snails, the mighty Charonia tritonis, (commonly known as the giant triton or Triton’s trumpet).

A Giant Triton climbs over a pillow coral in Hawaii

A Giant Triton climbs over a pillow coral in Hawaii

Charonia tritonis grows to over half a meter (20 inches) in length: it is one of the largest living snails in the world (and it is not much smaller than the biggest extant snails). Equipped with a powerful muscular foot, acute senses (particularly smell), and an agile tentacle-like proboscis, the snails are formidable hunters.  Additionally they are protected from predators—even big fierce ones–by their beautiful spiral shells which are vibrantly colored orange, brown, yellow, and cream.  Of course such a shell would become a liability for the snail if an animal ever evolved which killed the snails in order to harvest the magnificent shells solely for their beauty (but what are the chances of that?).

A man sounds a blast on a triton shell--which has spiritual significance in Hawaii

A man sounds a blast on a triton shell–which has spiritual significance in Hawaii

Giant tritons hunt at night.  Their main prey are echinoderms—starfish, which can be large powerful and armored.  Fortunately the snails are not just equipped with powerful muscles and superior brains.  They also have salivary glands that produce sulfuric acid AND a chemical which paralyzes starfish.  The tritons find starfish—even big spiny poisonous starfish like the invasive and all-consuming crown-of-thorns which bedevils the reefs of the Indo-Pacific—then hold them down and inject saliva into them.  As the starfish dissolves from within, the snails rip them apart and feast!

A triton kills a crown of thorns

A triton kills a crown of thorns

Tritons have a specific gender—they are male or female.  They seek each other out for courtship and the female then lays a large clutch of eggs.  When the eggs hatch, the young snails become part of the oceanic plankton for a (poorly understood) time before developing into adults.  Triton shells are esteemed by many cultures as sacred musical instruments.  The shells themselves are collector’s items and are arguably better known then the formidable long-lived predators which make them.  Although the snails are not threatened with extinction as such, there are fewer and fewer really big adult ones (or even small ones) on today’s reefs. This is a real shame, since those same reefs are being devoured by the horrible crown-of-thorns. Hopefully a new generation of divers and wildlife enthusiasts will appreciate the triton on the reef and leave them to their invaluable hunting.  Resist the urge to buy the beautiful shells and help save the reefs of the Indo Pacific!

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Japanese Bonnet Snail (Phalium/Semicassis bisulcata)

Japanese Bonnet Snail (Phalium/Semicassis bisulcata)

The helmet and bonnet snails (Cassidae) are slow moving hunters which live along sandy coasts in the tropics and subtropics.  Depending on the species (of which tere are approximately 60), these sea snails live anywhere from the intertidal zone to a depth of 100 meters.  During the day they bury themselves in the sand and at night they emerge to hunt their favorite prey—echinoderms (particularly sea urchins).

A Horned Helmet (Cassis cornuta) from the Hawaii coast

A Horned Helmet (Cassis cornuta) from the Hawaii coast

Most of the Cassidae are large snails with big mantles and heavy, muscular foot. They see by means of two eyes located at the base of a single pair of head tentacles and they use an extensible tube for smelling.

A helmet snail closes in on a sea urchin (image from wannadivekona.com)

A helmet snail closes in on a sea urchin (image from wannadivekona.com)

When a helmet snail catches a tasty echinoderm, the snail immobilizes its prey by holding the smaller animal within its mighty foot and releasing a paralytic enzyme from its salivary gland (which prevents urchins from using their spikes in self-defense).  The snail has a sharpened radula (an organ which consists of a chitinous tongue-like strip covered with razor sharp teeth) and two proboscis glands which produce a secretion rich in sulfuric acid.  Using the combination of radula and acid, the helmet snail bores a hole in the echinoderm’s armored body and devours the creature from within!

Shells from the Cassidae family (from OuterBanksShells.com)

Shells from the Cassidae family (from OuterBanksShells.com)

The shells of helmet snails are frequently large and beautiful.  Shaped like a heavy helmet, these shells consist of dextral (right sided) coils which whorl outward from a tight spiral spire.  The snails are divided into males and females (unlike many mollusks which are hermaphrodites or swap genders) and the females lay large masses of hundreds of eggs which can either hatch into planktonic free swimmers or into miniature crawling snails—depending on the species.  Some Cassidae are prized by shell-hunters and artisans such as Cypraecassis rufa, a snail from the coast of Southeast Africa which is favored by cameo carvers.

Bullmouth Helmet Shell (Cypraecassis rufa) from the store "Evolution"

Bullmouth Helmet Shell (Cypraecassis rufa) from the store “Evolution”

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