Geography Cone Snail

Various shells that used to belong to Geograph

Although you wouldn’t think it, these seemingly innocuous shells belong to one of the most dangerously venomous creatures on the planet, and they are called Geography Cone Snails. I saw the little shells at the Secret Cities of the Sea exhibition at the Natural History Museum amongst various (less dangerous) animals. These animals, named for the mountain-like patterns on their red-white shells, are the most venomous animals on Earth, capable of delivering a fatal sting through a barbed harpoon that is actually a modified tooth. There is no known cure for such a sting the only method of survival being to last until the venom in your blood wears off. Bizarrely, this predatory snail only hunts on small fish, which it stuns with a poison soup before spearing and ingesting through its proboscis. We can, for this reason, assume that the venomous barb is for mainly defensive purposes, since using this kind of poison on small fish would be the largest recorded case of overkill ever seen.

Around 10cm in length, not only is this snail hard to spot in passing, but it is also scarily common, found fairly regularly in reefs around the Red Sea and the east African coast. 0.001 mg of the venom used would be enough to kill half of the population if every person were given a dose of that size, and even 0.0002 mg can seriously paralyse someone. Ironically, the venom has recently been discovered to contain a type of insulin, previously unseen, that can also be used as a highly effective painkiller, several thousand times more powerful than morphine without any of the addictive side effects that normal morphine gives. The problem remains of how to produce large quantities of these proteins for public use. How do you milk a Geography Cone? Very carefully. The answer to this may lie in implanting bacteria with plasmids containing the appropriate DNA for this proteins production, similarly to the way that Factor 8 and human insulin are produced for hospitals. Research is on going.

While this creature is extremely interesting (the most venomous animal on Earth, after all) and actual cases of snail attacks are very low, I hope that I never run into one of these unseeming killers while it’s having a bad day.

Mushroom Coral

An example of a mushroom coral at the Natural History Museum.

This unusual coral is a Ctenactis Echinata, a species of mushroom coral, so named due to their similarity to the cap of a mushroom and I saw it at the Secret Cities of the Sea exhibition. Most mushroom corals are free-living rather than colonial and sit by themselves in crevasses and on the edge of kelp forests. Many mushroom corals also looked bleached due to a lack of zooxanthelles, symbiotic algae, in their bodies which is unusual for a coral and as such many people mistake them for dead. Luckily, unlike the coral reefs we are used too, bleaching in many species of mushroom coral is perfectly healthy.

The specimen above is particularly round in shape, ctenactis echinata normally being more of an oval pattern around 20-30cm long and roughly half that in width. Like most mushroom coral, this coral has a single mouth opening on the top of its body, through which polyps will emerge at night in order to feed. The edged plates that make up the radius of the coral are sharply edged with tiny teeth, that can badly cut attackers although, other than specialised coral eaters, this species doesn’t have much to fear except from attacks by other coral. This species does not appear bleached, instead having a dark brown colour while alive, that makes it look similar to the rocks it nestles amongst.

The Ctenactis Echinata can both reproduce with the use of spawning, in which all corals simultaneously release eggs and sperm into water, or by sprouting off smaller versions of itself to create genetically identical clone corals. Asexual reproduction like this is often done when the current coral is to badly injured to continue living for long, and such a measure is required to ensure the corals genes continue to exist. Fortunately for the coral, its genetics do not seem under threat, being rated as one of the least concerning species in terms of its rarity. This is perhaps due both to its enormous distribution, across most of the Pacific from China to the Red Sea to Australia, and the lengths to which it will go in order to survive.

It is almost impossible to go diving in the Pacific ocean without coming across on of these corals or one of its mushroom coral cousins. If I am able to pursue diving in those areas I’m sure I will see it.

Australian Trumpet

The shell of a (deceased) Australian Trumpet.

One of the more eye-catching exhibits at the Secret Cities of the Sea exhibition at the Natural History Museum was this shell of the Australian Trumpet or Syrinx Aruanus. This spectacular shell belongs to the largest shelled mollusc in the world, and one of the biggest gastropods, extinct animals not included. Measuring in at around 90cm at its largest length and nearly 20kg in weight this monster is known mainly for its tremendous size and is often hunted both for the amazing shell and the flesh, which is edible and used for food and fish bait. The shell is typically a faded yellow colour, but on a living specimen a thin skin will cover the majority of the shell, making it look more of a brown muddy colour, much in the same way that land snails have greyish shells while alive, but empty shells soon become a magnolia colour. The proboscis, a sucking mouthpiece used by many invertebrate predators to drain fluids from their prey, is a full inch long and is used to catch its extremely large food.

Living, as the Trumpet’s name suggests, in the northern parts of Australia and areas above it such as southern Indonesia and much of Oceania, it is fairly common along the sandy sea bottom around 20-30m underwater. In some areas it is fished heavily and far less common, but generally it is a common animal and not unusual to see while diving. Using its large proboscis the Trumpet reaches under sandy banks and into rocky crevasse in search of gigantic tubular worms that can measure over a metre long, making the perfect enormous meal for another enormous predator. It will suck up its prey whole through its mouthpiece, rather than rasping against its food like non-predatory snails that we are used to in Britain.

This is a very interesting snail, and if I get the chance to go diving in the waters of Oceania (which would be truly amazing) I hope that I will have a chance to see this behemoth in the flesh.

Sea Fan

A preserved sea fan on display at the museum.

In the Secret Cities of the Sea exhibition at the Natural History Museum in London, which I discovered while listening to an Inside Science program, there were various displays about the inhabitants of the reefs. One such example was this stunningly preserved sea fan. The sea fan is a type of coral that grows out of the continental shelves at the edge of tropical and subtropical reefs. They build out into large fan-like structures that help them to catch plankton and other tiny organisms that are brought up from the deep waters of the Twilight Zone by strong currents. These same currents are what feed the reef and keep a large supply of nutrients available to the creatures that live there, and the sea fan is simply seating itself closer to the source.

Like other corals, often contain zooxanthellae, tiny algae that are allows to grow inside and around the coral giving them protection in return for photosynthesising for the coral. This symbiotic relationship is essential for keeping reefs alive, since most reefs are fairly near the surface. These algae are also what give the coral its colour, which is why coral bleaching occurs when a reef is sick, since the stress of illness makes the coral jettison its cargo of zooxanthellae. With changes in acidity and temperature in coral reefs across the globe (mainly due to what humans are doing to the ocean) more and more reefs are beginning to bleach and turn white, which will eventually kill them. Some sea fans, that live deeper down in the shelf wall do not have zooxanthellae, since it is no longer beneficial due to the lack of light, and so they must rely entirely on capturing enough plankton to eat.

Many species live in the winding mazes that sea fans create, jutting out of the shelf walls, including starfish, kinds of pipefish, and colonies of bryozoan, which are actually several zooids living together. Bargibant’s Pygmy Seahorse and Denise’s Pygmy Seahorse are two species of the tiny pygmy seahorse that live especially on sea fans and their relatives. They are perfectly camouflaged to the coral, coloured and with bumps and knobs in lighter colours over them. Large groups of these seahorses can be found over a sea fan, where they eat the plankton that filter through from the deeps. The Bargibant’s Seahorse will likely never leave the coral that they were born on, leading to large families of seahorses living in the same place for generations.

These sea fans are extremely interesting, now being looked into by the medical industry for the chemicals they produce, and I am glad that I saw them here at the museum.