1. Eukaryotic (an organized nucleus)
2. Multicellular (made of more than one cells)
3. Sexual reproduction- hermaphrodites or with separate sexes (male or female)
4. Heterotrophs
5. They all contain a certain type of covering called a “mantle”
6. Invertebrates (meaning they do not have a backbone)
7. They have 3 body regions: head (contains brain and sense organs), the “visceral mass” (contains internal organs) and the “foot” (muscular part of the body)

 

 

Some mollusks have separate sexes but others have both male and female reproductive organs (hermaphrodites) that may be active at the same time or may alternate through the organism’s lifetime. Mollusks that are more primitive do not exhibit courtship behaviour, but higher forms such as gastropods and cephalopods have highly complex courtship behaviour. Mollusks release eggs singly or in masses, and many are fertilized externally by sperm released into the water; however, gastropods and cephalopods are among those who have internal fertilization.

 

 

The organisms in the phylum mollusca are important in the fishing industry. Oysters, mussels, clams and scallops are collected my fishermen and sold.

Molllusks are eaten as food. Scallops, mussels, octopus, etc are eaten by humans and other animals.

Since some mollusks filter water for food, they also filter toxins out of water. Scientists use mollusk tissue to measure the amount of pollution in water.

Scientists also study mollusks to understand how muscles work.

The shells of some bivalves are used as a source of calcium that is taken as a pill.

 

 

Oysters are no the only creatures that make pearls. Snails and other bivalves can make them as well. A pearl is made when a tiny object such as a piece of sand gets stuck in the mantle of the mollusk. The creature then coats the object with a chemical that is used to make the inside of their shell. This chemical coats the objects, which makes it less painful for the mollusk. With more and more chemical added to the object, the object eventually becomes a pearl.

The difference between an octopus and a squid is that an octopus has eight legs and a squid has ten.

The correct plural form of octopus is actually “octopuses”, not “octopi” as many believe. Try to fool your teachers with that one.

There are about 100 000 living species of mollusks and about 50 000 fossil forms.

Oysters, a type of bivalve are rumoured to be aphrodisiacs. 

 

 

Shelled mollusks, like snails, move around by means of a foot that they extend from the shell. The foot is a muscular extension of the ventral, or lower, side of the animal, and in many species it can be completely withdrawn into the shell. Octopuses and squids, on the other hand, propel themselves by forcing water out of a funnel-shaped apparatus (siphon) located at the front end of the body. The mantle of squids is flattened into fins that are used to propel the animal slowly backward or forward. Bivalves move by clapping their shells together. Other mollusks spend their entire life attached to an object, they are sessile.

The methods of defense vary greatly in this phylum. The main method of defense for the class bivalvia is their byssus making it very difficult for a predator to remove the organism, much less, get past their hard outer shells Ex: Clam, mussel, and oyster. The class gastropoda also uses their hard outer shell for defense, some even have a trapdoor like structure called an operculum, making it possible for them to completely retreat into their shell. Some species in this class, however do not have a shell, and rely on their size and color to hide in small spaces, out of the reach of their predators. Ex: snail, slug, and whelk. Most species in the class Cephalopoda use a their speed to their advantage, they can take water in to their mantle cavity, and then expel it very quickly out their siphon, causing them to move quite rapidly.Ex: Squid, octopus

The digestive system of mollusks is filled with microscopic hairlike projections and contains several subdivisions for specialized digestive functions. The anterior section consists of the mouth and esophagus. A specialized, raspy, tounge-like radula in the mouth is used for feeding in the majority of mollusks and is found only in this phylum. Bivalve mollusks such as clams, oysters, and mussels are filter feeders and do not have the characteristic radula. The midsection of the digestive tract consists of the stomach and liver. In many mollusks (particularly in primitive gastropods and bivalves) a flexible rod composed of mucus and protein, found in the midsection of the digestive track, is important for secretion of digestive enzymes and also serves as a "stirring rod" for stomach contents. The last section of the digestive tract consists of the intestine and anus.

Mollusks can be herbivores, carnivores, scavengers or parasites.