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The Sea Shells of the Bahamas

The phylum Mollusca  (Mollusks in the USA) have been around for some 500 million years. In that time they have diversified to all habitats and range in size from the tiniest snail to the giant squids of the deepest oceans. They are have been used by mankind as food, for decoration and adornment, to make trumpets and for much more. The molluscs with snail-like shells belong to a group called the gastropoda, the largest of which is the Florida Horse Conch - seldom seen in the central or southern Bahamas.

There are however,  some very large species in the shallow waters of the Bahamas, that may be seen by the tourist, the snorkeller and the diver. 

Trumpet Triton

The Triton's Trumpet is one of largest, growing to some 18 inches (45 cms) in length. In parts of the Pacific they are actually used as trumpets, the shell producing a fine resonance and a very loud note when blown through from a hole made at the tip.

Triton's Trumpet is found in crevices on coral reefs or on adjacent sea grass beds where it may be searching for its prey the Starfish.

The Flame Helmet, Cassis flammea  is the smallest of the Bahamian species of Cassis or Helmet shell. The closely related 'Cameo shell' of the Indo-Pacific has been historically, and still is used to carve cameos for brooches. Cameos can however be carved from any of these shells.

Flame Helmet

The largest species of Helmet shell in the islands are the King Helmet, Cassis tuberosa  and the Emperor or 'Queen' Helmet, Cassis madagascariensis.  The former has a triangular shell base, and the latter a more rounded appearance - see below.

These molluscs have an interesting way of feeding on sea urchins. They slowly creeps up to their prey, raise the heavy shell  high, then quickly drop the shell so that the urchin is completely covered. Sea Urchin spines contain a poison, so the helmet snail releases a paralytic enzyme from its salivary gland, then it secretes sulphuric acid which dissolves the sea urchin shell in about 10 minutes after which it can then eat the contents of the Urchin.

The King Helmet - Cassis tuberosa

King Helmet - largest of the Helmets and easily identified when mature by its triangular base

The Queen or Emperor helmet - Cassis madagascariensis

Emperor (Queen) Helmet

By far the commonest and most well known of the large Bahamian sea shells is of course the Queen or Pink Conch, Strombus gigas. For details of its life cycle, go to my Conch page. Below is a juvenile Conch or 'Roller' and a mature Conch with a wide lip. The Conch is an important part of the Bahamian diet - served as 'Crack' Conch, Conch Chowder or Conch Salad. The Conch is a herbivore, feeding primarily upon Sea grass on the shallow banks and in the lagoons inside fringing coral reefs.

Conch - a mature wide lipped specimen

Adult wide-lipped Queen Conch

A juvenile 'Roller' Conch

Juvenile 'Roller' Conch

Conch are becoming uncommon in many parts of the Caribbean - especially those with limited shallow waters. They are also becoming less common in those parts of the Bahamas near large centres of population. Legislation will soon be needed if the populations of Conch are to stabilise.

The West Indian Chank - this big shell has a velvety covering or periostracum when alive. This dries and peels off after the shell is removed from the water. The Chank is recorded as having been used as a trumpet by ancient peoples. In Bhutan, a sacred Chank appears on the 10 chhertum coin. The Sinistral (left handed) sacred Chank is found in the waters off Sri Lanka. In India the Chank is used to make Bangles. It seems to have had no such use in the Bahamas.

West Indian Chank - Turbinella angulata

Tulip shell

Banded Tulip Shell

The much smaller Tulip shells are predatory, feeding on smaller bivalve molluscs. As are the Tun shells below. These have been recorded feeding on Holothurians (Sea Cucumbers) which they ingest whole with their large distended proboscis.

Live Tun shell

The Tun shells have an enormous foot which cannot be withdrawn into the shell. A live Tun shell  is shown above with its proboscis extended to the front.

Tun shell

Atlantic Partridge Tun

 

There are hundreds of shell species in the Bahamas, many of them small and relatively insignificant. A close examination of the beach sand just above the water line will reveal many of these, while many more will be seen close to low tide level on rocks or around the edges of rock pools. These include the Bleeding Tooth Nerite - seen on the right.

Sunrise Tellin shells

On the beach also will be the shells of dead bivalves. These are filter feeders for the most part and are usually buried in the sand when they are alive.  On the left is the beautiful Sunrise Tellin, one of the most colourful of the Bahamian bivalves. The famous pink sands at Harbour Island off Eleuthera gain their colour from shell fragments and the remains of coraline algae mixed with the sand.

There are no really large bivalves in the Bahamas. There is no Giant Clam in the Coral reefs as in Pacific reefs, nor do the muddy creeks support a giant like the northern Pacific Geoduck Clam.

The largest bivalve in the islands is probably the Pen shell which grows to some seven inches in length. This shell is sometimes found on the beach where the Sea grass beds are close to shore. I have found it on Montagu beach in Nassau.

Pen shells

Spiny Oyster

Atlantic Thorny Oyster

The scuba diver will see shells that the casual tourist will never see. One of these is the Atlantic Spiny Oyster which may be found attached to both hard and soft Corals  in water from 50 - 150 feet deep.

 As this species is found beyond the fringing reef, it is never found washed up on the beach after death like many of the shells that inhabit the shallow lagoons inside the reef.

 
Divers will also see the strange little Flamingo Tongue shell, Cyphoma gibbosum which feeds exclusively on sea fans. The colourful spotted mantle of the mollusc is usually extended over the shell (on right). The cleaned shell is a pinkish colour (on left).

All tourists and scuba divers should ensure the future of these species by leaving live molluscs in the sea, collecting only dead shells, for too many shell species around the world  are now threatened as a result of over zealous collection.

Note: Some observant persons may see that images have been reversed - this is for purely aesthetic reasons - they do not represent sinistral or left-handed shells.

A live Flamingo Tongue (right) and the cleaned shell (left)