Zebra Mussel

(Image Source)

Phylum : Mollusca
Class : Bivalvia
Subclass : Heterodonta
Order : Veneroida
Family : Dreissenidae
Genus : Dreissena
Species : polymorpha

Length : .25-2in (.6-5cm)

IUCN Status : Not listed

Zebra Mussels were originally located in Southwest and Central Asia, in the Black and Caspian Sea regions. By the 1800s however, these little guys were invading waterways throughout Europe, making it as far as England and Ireland. In 1988, they were first discovered in the American Great Lakes, and are now considered an invasive species.

Zebra Mussels aren't particularly large, as a adults they rarely grow above two inches. They have a "D" shaped shell with an opening. Out of this opening comes a threadlike external organ called a Byssus, which allows them to attach to just about anything. They even attach themselves to other living organisms. Zebra Mussels are filter feeders; they go through about a quart of water each day and consume algae and phytoplankton.

So why are Zebra Mussels so bad? Well first off, they are prolific breeders. Females produce between 30,000 and 1,000,000 eggs every year, and adults can live as long as 6-8 years. The larvae are small and free-swimming, which makes it very easy for them to get into new water supplies and cause contamination. Because they attach to most surfaces and filter so much water, they threaten the food supplies of native species. They have also caused the decline of other Mussel species, since they will attach themselves to those as well.

(Image Source)

Zebra Mussels also have a very expensive impact on humans. They clog up the pipes of power plants and water treatment centers, and it costs over $500 million dollars per year to control them. Special metals and coatings can be used to deter them from attaching themselves, but so far there is no single, completely effective method of controlling them.

Strangely, Zebra Mussels have a positive effect on some species. Because they filter so much detritus, water is clearer in certain areas, which prompts growth in underwater plants. This in turn feeds fish and other aquatic animals. Zebra Mussels are also a food source for several species. However, there are so many of them that even with rapid consumption their numbers are not put in check.

Big Fin Squid

(Image Source)

Phylum : Mollusca
Class : Cephalopoda
Order : Teuthida
Family : Magnapinnidae
Genus : Magnapinna

Length : 5-23ft (1.5-7m)
Weight : Unknown

IUCN Status : Not listed

I'm afraid that this entry might be a short one, simply because these Squid are still so unknown to us. There are five identified species, but two are still unnammed, and all five still hang in a bit of taxonomic limbo, subject to change with any sort of breakthrough.

Big Fin Squid have been found in the deep waters of the Atlantic and Pacific Oceans. As their name denotes, they have large fins that extend outward from the mantle (their main body segment.) Big Fin Squids also have ten arms, all of about equal length and thickness. Many other squid species, in contrast, have eight shorter arms with two longer tentacles.The arms of Big Fin Squids are also typically hung at right angles, as if they have elbows.

Only larval and juvenile Big Fin Squids have actually been physically studied. Videos and images of adults have been picked up by underwater cameras and ROV's (Remotely Operated Vehicle), but because these are just images it is difficult to properly study them and even establish them as specific species. A few years ago, in 2007, an ROV owned by the Shell oil company in the Gulf of Mexico picked up an image of one of these Magnapinna species.

Cone Snail

Conus textile
(Image Source)

There are around 500 species of Cone Snail, marine gastropods that belong to the genus Conus. They live in tropical and subtropical waters around the world and vary in size depending on the species, with the largest measuring over 20cm in length. Cone Snails also look quite pretty. They have long, attractive shells that tend to have nice little patterns and designs on them, no wonder they are popularly used as jewelry!

But beware! Cone Snails have a extremely potent toxin (called Conotoxin), and they have to. They are tiny little guys who don't move very fast. Their toxin needs to paralyze their prey quickly, otherwise it'll get away. The toxin in these Snails has the ability to kill a human being, and there is no known antivenom. They attack via a barb that shoots out from their shell, and the type of paralysis is dependent on the species. When their prey is immobilized, they draw it back in to their shell, still attached to the barb. Cone Snails are carnivorous and predatory, and feed off of fish, worms, and other mollusks, depending on the specific species.

Interestingly, when some of the components of the toxins are isolated, they make an extremely potent painkiller. The drug Prialt is made from the toxin of Conus magnus, and new uses for the toxins are still being researched.

Common Octopus

Image from New York Daily News

The 2010 World Cup ended yesterday, and while the world is abuzz with Spain's first win, there has also been a great deal of talk about Paul. Who is Paul? Paul is the Common Octopus "Oracle" who correctly picked the outcomes of all 7 of Germany's games, plus the World Cup Final. Treats were placed in boxes adorned with national flags. The treat eaten first was the winning team. Paul went 8 for 8. (Though he did make some blunders during the 2008 Euro) Anyway, Paul is retiring now, but in celebration of his strange cephalopod superpowers, enjoy some facts on the Common Octopus (Octopus vulgaris)!

Common Octopuses (Octopi is actually an incorrect plural term) are found in temperate and tropical coastal waters across a great deal of the planet. They live at depths shallower than 500 feet. Octopuses are carnivorous, and are active predators during the daytime. They feed primarily on crustaceans and mollusks, and they will actually stockpile their food to eat at a later time. They hunt by a variety of methods, including stalking, luring, and simply groping around for their prey. After consuming a meal, they will leave the shell in a heap known as a midden pile. These piles help scientists to study not only what Octopuses eat, but also what kinda of organisms live in the area.

Image from Animal Picture Archive

Octopuses have some pretty amazing senses. They have the largest brains of any invertebrate and have both long and short term memories. They are also capable of some pretty advanced problem solving. The Common Octopus has wonderful eyesight, and they are able to distinguish between other creatures and objects, both by sight and by touch.they also have extremely flexible bodies, and can squeeze through spaces that are only a fraction of their overall body size.

Common Octopuses also have an amazing array of defense mechanisms. They are able to change both the color, and the texture of their skin. This allows them to hide virtually in plain sight. Skin color is also able to reflect the mood of the Octopus. Another defense they have is their ink. If the camouflage fails, the Octopus will shoot a jet of ink at its attacker, which disorients them and gives the Octopus time to escape. This ink also contains a substance that affects the attackers' sense of smell, further allowing the Octopus to flee in safety.

Roman Snail

Also known as the Burgundy Snail and the Edible Snail, Helix pomatia is probably most commonly known by its culinary moniker... Escargot. Now, these snails are not the only species that can become Escargot, but they are certainly one of the most traditional. Roman Snails have been picked up and eaten since well, Roman times, if not earlier. While they are found in all of continental Europe, it was the Romans who first brought the snails with them to England, were they can still be found, albeit rarely. These snails now have legal protection in the U.K.

Courtship image from The Living World of Molluscs

They are quite large, with body lengths of 4 inches and shells up to 2 inches in diameter. They are the largest land snails found in Europe. Roman Snails are hermaphroditic, meaning they are both male and female at the same time, and their courtship rituals are quite extensive. The process can last for hours as the snails circle around each other before touching their soles against one another. The young that hatch from the eggs look like miniature versions of their parents, but only a few will actually live to reach maturity at about two years. Roman Snails have the ability to hibernate, which allows them to live 10-15 years.

Roman Snails also have a substantial impact on decomposition within an ecosystem. They are able to assimilate high percentages of their food, and consume it very quickly, which assists in the aforementioned decomposition and break down.

Image from Wikimedia Commons

As previously mentioned, Roman Snails are rare and have legal protection in the United Kingdom. They are also scarce and protected in other areas as well, including France. Ever since snail consumption became fashionable in the 19th century the population has reached endangered levels. The culinary tradition is only able to continue due to established Snail farms and importation from countries where the numbers are higher.

Cuttlefish

Did you know that a cuttlefish is not actually a fish? It's a mollusk! They are actually more closely related to snails then they are to fish. Like squids, octopi, and nauteluses, the cuttlefish is a cephalopod. Members of class cephalopoda have been dated back 500 million years!

There are currently 120 species of cuttlefish recognized, all of which live in shallow tropical and temperate waters around Europe, Asia, Africa and Australia. Cuttlefish have a pretty interesting mechanism built in to their bodies: the cuttlebone. Made primarily of aragonite, these structures act as buoyancy mechanisms, enabling the cuttlefish to float at a steady, desirable level. The existence of this bone is also what prevents the cuttlefish from surviving at deep depths, as they will implode when there is too much pressure. Cuttlebones are very rich in calcium, and are often given to caged pets like parakeets and reptiles as supplements.

Cuttlefish have the ability to change their skin color in order to blend in with their surroundings. They do this with help from three special types of skin cells: chromatophores, iridophores, and leucophores, all of which reflect light in different ways to cause the camouflaged effect. With their stealthy camouflage in place they are  able to ambush their prey, which is caught using their eight arms and two tentacles, all of which possess a pad at the end which is covered in powerful suckers.Their diets consist of fish, crustaceans, and even other cuttlefish. They also make use of their color changing skills in mating displays and to hide from predators. Cuttlefish have one of the largest body size to brain ratios among invertebrates, and are considered to be one of the most intelligent of all invertebrates. Their cleverness and thinking skills are pretty astounding when you realize that many of their mollusk relatives don't even possess brains!