|Cone Snails and Their Paralyzing Harpoons|
|Written by Gordon Wilson|
|Wednesday, 23 June 2010 08:42|
Beautiful, slow, and graceful, cone snails creep over the sands, rocks, and coral reefs of the tropical seas. The over 500 species in the genus Conus come in many sizes (small to half a cubit long) and sport a diverse array of colors and patterns (modest to ostentatious), yet they all share a very similar gestalt. Their elegant beauty is loved by shell collectors worldwide. Although a cone snail’s empty shell may be a nice touch to the décor of a beach cottage, these little mollusks are not a nice touch when alive.
Cones are deceptively dangerous and highly effective predators. When hunting they protrude a long flexible proboscis out of their mouth. This wormlike extension can be maneuvered toward a hapless fish pausing nearby. In Conus geographus the proboscis is brightly colored and is used as a lure to attract fish. Loaded within the proboscis is a tiny, hollow, barbed harpoon-like dart, called a radular tooth. The dart is loaded into the ‘muzzle’ of the proboscis from the radular sac (a kind of quiver holding several other darts in various stages of development). When the snail strikes certain muscles quickly thrust the business end of the dart into the prey.
An internal bulb gland propels venom through the poison duct which leads to the mouth cavity and up through the hollow harpoon. When the dart penetrates, this complex cocktail of toxins is injected into the fish (or other prey). In species that feed on fish and worms, the harpoon is tethered to the snail so it is of paramount importance that the venom paralyzes quickly so that the snail is not dragged unceremoniously over a coral reef by its panicked prey. The retrievable dart is then ‘reeled in’ pulling the paralyzed prey with it. The snail’s mouth widens and engulfs the prey whole. After it has digested its meal, the indigestible bits are regurgitated out of the mouth.
The venom is composed of about 200 different compounds. The mixture and quantity of the components differ from species to species thus the toxicity also varies ranging from bee sting intensity to paralyzing death. These so-called conotoxins are neurotoxins that target and quickly shut down the nervous system thus putting a quick stop to the struggles of fast swimming prey. Smaller cones tend to hunt marine worms and other mollusks but the larger species hunt fish. Since the latter can be deadly to humans, beachcombers, snorkelers, and scuba divers beware.
So God created the great sea creatures and every living creature that moves, with which the waters swarm, according to their kinds, ………... And God saw that it was good. Genesis 1:21
Here is the sea, great and wide,
|Last Updated on Wednesday, 23 June 2010 09:01|