Even More Trivia: August 2015

Today's trivia looks at some of the most interesting adaptations in the Gastropod family.

As a species, Gastropoda are incredibly diverse. Only insects represent a more diverse species. This trivia hopes to cover more adaptations that some species of Gastropod have evolved to allow them to live where they do.

The familiar garden snail has evolved all the adaptations needed to live on land.

The following are some examples of the wonderful variation found in the Gastropod family.

Raft Building

This first example is known as the common purple snail Janthina janthina. This snail floats on the surface of the water by building a 'raft'. The raft is made up of air bubbles trapped in a thin layer of chitin. This allows the snail to stay afloat in the sea and feed on its preferred food, jelly fish.

A common purple snail washed ashore. Note the raft remains intact.

Common purple snail floating in water.

Net-Hunting

Perhaps even stranger is a species of Cone snail called Conus tulipa which uses its very modified mouth parts to find and envelope small fish that stay too close to it. Once captured, the snail draws in the catch and slowly digests it.

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Harpoons

All members of the Conus family are predators, and another fascinating adaptation is a combination of harpoons and neurotoxin venoms. The mouthparts of the Cone snail are again highly specialised. The harpoon is held in a long tentacle like extension of its mouth which it uses to catch and paralyse small fish.

The colour patterns are a surprising camouflage - Full Size

Some species of Cone snail can have up to 100 different neurotoxins which allow the snail detect and sting the fish it wants to eat. This also makes them significant for medical research.

Image sequence showing hunting behaviour of the Cone snail

The venom of a Cone snail is exceptionally dangerous. Many species contain a complex mix of different toxins. The risk to humans handling live specimens is high. A sting from a small species might be no worse than a hornet sting. However a sting from a larger species like Conus geographus can cause fatalities with a lethal dose of 0.001-0.003mg/kg making it the most venomous creature on the planet.

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Spikes

The Venus comb murex uses spines as protection against predation. This can be particularly striking and we can imagine quite a hindrance to any passing fish.

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Another example of a curious spiny snail are those of the Alviniconcha genus which live in the deepest parts of the ocean by the deep sea vents.

Alviniconcha strummeri: “Because they look like punk rockers in the 70s and 80s and have purple blood and live in such an extreme environment, we decided to name one new species after a punk rock icon.”

Glow in the Dark

Cluster-wink snails like Hinea brasiliana have an adaptation which allows them to bioluminece. When something disturbs them they give off a rapid pulse of bright flashes of green/blueish light. This light is so bright that it is thought to dazzle attacking creatures like crabs.

It may also act like a burglar alarm in that it will draw the attention of larger predators which might then eat the thing bothering the snails.

This image shows examples of the clusterwink snail H. brasiliana emitting bioluminescent light

The way the shell diffuses the specific wavelength of light is surprising as it is more efficient than any commercial light diffuser.

Research: "It's rare for any bottom-dwelling snails to produce bioluminescence," Wilson said. "So its even more amazing that this snail has a shell that maximizes the signal so efficiently."

Iron Coating

The scaly foot gastropod Crysomallon squamiferum#https://en.wikipedia.org/wiki/Scaly-foot_gastropod) is an example of a snail that also lives deep in the ocean by the deep sea vents. The snail's foot is very unusual in that it is armored with iron-mineralised sclerites, composed of iron sulphides greigite and pyrite. No other animal is known to use iron sulfides in this way.

The sclerites of Kairei population is strongly magnetic due to the greigite (sulfur equivalent of magnetite) content and stick to magnets.

The snail's shell is also unusual in that is is made of three layers. Each layer is of a different material (including more iron suflide). The composition of the shell protects the snail from predators. The impact of the force of a crabs claw for example is dissipated around the shell preventing the crab from cracking open the shell.

Researcher: http://www.zoo.ox.ac.uk/group/oceans/people/CC.html

Today's trivia is all about a remarkable ability of cats to land on their feet.

This ability is know as the Cat Righting Reflex, and is a remarkable to see in action. It has also been fairly extensively tested. By tested I mean scientists spend time dropping cats and seeing what they do.

The ability is a combination of the cats highly developed reflexes and its flexible body. The backbone is surprisingly flexible, and they have no functioning collarbone which allows further flexibility.

1) The cat can detect which way is up, either via vision or by its sense of balance. (works when blindfolded).

2) The cat then draws in its front legs and extends its hind legs. It starts a large body twist with the front half of its body, which produces a smaller turn in the rear section.

3) Then the cat extends its front paws, and draws in its rear paws, performing the complimentary turn with its rear half.

4) When both halves are aligned, it extends its paws and braces for impact.

Images of a falling cat which appeared in the journal Nature in 1894, captured in a chronophotography by Étienne-Jules Marey.

NASA

Some researchers where investigating this effect and describing it in a mathematical model. This caught NASA's attention so they funded the research which lead to the publication of "A Dynamic Explanation of the Falling Cat Phenomenon" in 1969.

NASA's interest lay in the fact that they could use this research to develop maneuvers that would help astronauts orient their bodies in the weightless conditions of space, during a spacewalk for example.

Kane worked with NASA and used his equations to develop moves which were tested by a gymnast on a trampoline. The gymnast is able to use a combination of his hips and arms to orient himself midair.