Mollusk

=__ Mollusks __= =__ Phylogenetic tree __= = =

__ classes of mollusks __
__1.__ Gastropoda __2.__ Monoplacophores __3.__ Polyplacophores __4.__ Scaphopods __5.__ Bivalves __6.__ Cephalopods

==__ Basic Structures __ All mollusks have a soft body and three main structures in common. A mantle, a head-foot and a visceral mass. The head-foot contains the sensory organs and enables movement. The visceral mass contains the digestion excretion and reproductive organs. Last the mantle which is a fleshy tissue that protects the organs and in some mollusks secretes the shell. ==

= **__ Geographic Distribution __** = Mollusks can be found all over the world in any environment. Whether it be a high mountain, a calm lake or a vast ocean, Mollusks can be found. There are about 100,000 identified species of Mollusk in the world today, so finding one would be rather an easy task. New species of Mollusk are being found in ocean depths and tropical rainforests, so the number of species are slowly rising.

=**__ Reproductive Mechanisms in Mollusks __**=
 * Reproduction in mollusks is very unique. There are many variations in their methods as well. Many types of snails and two-shelled mollusks reproduce using external fertilization. This is a process where they release large amounts of eggs and sperm cells into the water and they become fertilized and turn into free swimming larvae.
 * In reproduction in tentacled mollusks and certain snails, reproduction occurs in the body of the female. However, most mollusks are hermaphrodites (meaning they have both male and female reproductive organs) and typically reproduce with another individual – even though they can reproduce alone if they chose to do so.
 * Mating within the mollusk phylum generally occurs during the late spring or early summer. One of the snails will stab the other snails skin, known as a “love dart”, which will stimulate the snail sexually and allow them to mate. It takes approximately 1 month for the snail to lay eggs, 14 days for it to hatch, and two years for the baby to become mature.

**__Feeding Mechanisms: __** - The Mollusks feeding mechanisms are very interesting and unique. Mollusks have many important features that help them eat their food. One being that they have a very muscular mouth that has a radula or “tongue”. The radulae have many rows of chitinous teeth and which are eventually replaced after they wear out. - The radulae are mainly used to scrape bacteria and algae off rocks and to tear food into chunks. The mollusks have glands in their mouths that produce and discharge a sticky slimy mucus to which their food sticks. Tiny “hairs” or also called cilia, which helps lead the mucus to the stomach, which allows the mucus to make a long string. - At the rear end of the stomach and also thrust slightly into the hindgut is the prostyle. A prostyle is a cone that is a backward pointing cone of mucus and feces. The cone acts as a bobbin because the cone is rotated because of other cilia and then like a regular bobbin winds the mucus string unto it. - The mucus string is much less sticky before they reach the prostyle because of the acidity of the stomach. The particles that were freed from the mucus string because of the acidity of the stomach are then sorted by more cilia. The smaller particles (mainly minerals) are then sent to prostyle so they will eventually be excreted. While this is happening the larger particles which are mainly food are sent to the stomach cecum which is a pouch with no exit so it can be digested. Though this sounds like this process is perfect, it still has flaws. From time to time a piece of the prostyle is excreted because of circular motions at the hindguts entrance pinch off. This keeps the prostyle from becoming too large. - Bivalve Mollusks have no head so therefore use a different type of feeding method which is filter-feeding particles or more specifically phytoplankton from the water through their gills. This traps the food particles which are then moved to the mouth. =**__ Unique Facts About Mollusks __**=
 * There are only 8 groups of mollusks alive today
 * The body of most mollusks consists of two parts: a head-foot and a visceral mass
 * Mollusks have a mantle that secretes a hard shell that covers and protects the visceral mass
 * Mollusks exhibit bilateral symmetry
 * Most of the mollusks have an open circulatory system
 * Mollusks are more closely related to annelids than they are to arthropods
 * T here are approximately 110,000 species of mollusks
 * Some mollusks don’t have a shell
 * Some mollusks don’t have a head
 * The giant squid and the giant clam are among the worlds largest mollusks
 * There are over 160,000 species of mollusks known, and of which about 128,000 are living and 35,000 are fossil records
 * Mollusks can be found almost everywhere! They live from the deepest ocean floor up to the intertidal zone. They can also be found in freshwater and everywhere on land
 * Cephalopods are shy and avoid humans
 * Cephalopods can move backwards quickly and move slowly in any direction
 * Cephalopods don’t respond to sound but to very low frequencies
 * Many land snails can lift 10 times their own weight up a vertical surface
 * T he common garden snail travels about 2 feet in 3 minutes



// Notordius minor //

// Tridacna maxima //

// Lima //// scabra //

// Lolliguncula brevis //

// Helix aspersa // __** Ecological Niche **__ Compared to the meat of other animals, the food prepared from mollusks has high nutritious value, as it contains high protein content and many amino acids, and they are relatively in low fat content. Mollusks produce a wide range of biotoxins and metabolites that are used in medical research. They are sensitive to changes in their environments, and therefore could provide an early warning of habitat deterioration.land snails, freshwater snails, mussels, clams, and slugs, are vital to healthy ecosystems. Land snails, for example, not only provide food for a host of small mammals and birds, but they play vital roles in recycling forest nutrients. Freshwater snails also provide food for fish, including native trout and salmon, and are also important recyclers of plant and animal waste, essentially keeping water clean and healthy. Mollusks are also considered excellent ecological indictors, their status providing a window into the health of entire ecosystems.

-"gastropod." //Encyclopædia Britannica. Encyclopædia Britannica Online //. Encyclopædia Britannica, 2011. Web. 16 Feb. 2011. < [|**http://www.britannica.com/EBchecked/topic/226777/gastropod**] >.
 * __ References __**

-"bivalve." //Encyclopædia Britannica. Encyclopædia Britannica Online //. Encyclopædia Britannica, 2011. Web. 16 Feb. 2011. < [|**http://www.britannica.com/EBchecked/topic/67293/bivalve**] >.

"Mollusks." //Acadia Oceanside Meadows Historic Inn, Downeast Maine Bed and Breakfast//. Web. 17 Feb. 2011. .

"Phylum Mollusca." //Infusion// . Web. 17 Feb. 2011. .

six classes of mollusks []

-"Monoplacophora" Web. 19 Feb. 2011. []

<span style="background-color: transparent; color: #000000; font-family: Arial; font-size: 11pt; font-style: normal; font-weight: normal; text-decoration: none; vertical-align: baseline;">-"Decline of Mollusks" Web. 19 Feb. 2011. []