Most mollusk species develop a hard shell for safety, but their shell grows in only a couple of pieces. It does not have joints like the exoskeletons of crustaceans and insects.
You can find almost 100,000 species of mollusks all over the world and many thousands more undiscovered. Most mollusk species only live in the sea, but some live in freshwater or on land. In Michigan you can find about 300 species of mollusks recognized, with more to be found.
You can find three primary groups of mollusks. Snails (Gastropoda) are the most varied group, you can find tens of thousands of species. Almost all snails grow a spiral shell which is all one piece. Several snail groups have stopped growing shells; they are called slugs.
The term, mollusk signifies soft and mollusks are just that. They do not have exoskeletons or skeletons. Some have shells made from calcium. Can you guess what animals might be mollusks? If you guessed snails and slugs, you are right. Mussels, Clams, squids and octopus are also mollusks. Consider it. None of these animals have bones. None of them have outer skeletons such as beetles. They all are soft.
Octopuses have incredible defenses. They can modify their coloring to mix in with their environment. They can squirt out ink to distract a predator. They can even lose an arm if a predator grabs them.
Ultimately, octopuses can give a nasty bite using their beaks if necessary. Donít mess with an octopus.
Many squids are small, however the giant squid is massive. It can develop to 55 feet long. Most are rround 33 feet long. Their eyes are the size of beach balls, which allows them see in the dark ocean.
Snails and slugs are known as gastropods. You can find over 80,000 species of gastropods on earth. Some people like to eat snails.
Clams and mussels live in the ocean and rivers.
Mollusks are a phylum of soft bodied invertebrate creatures. Numerous mollusks have a tough external shell, however others do not. You can find several various classes of mollusk. The most frequent mollusks are the gastropods (e.g., snails and slugs), the bivalve (e.g., clam, muscle, oyster and scallop) and the cephalopod (e.g., octopus, squid and cuttlefish). The Giant Squid and the Colossal Squid are the biggest animals with no backbone.
Gastropods constitute 80% of the mollusk species with 60,000 to 80,000 species. They are the 2nd most populous animals following the insects.
You can find about 800 types of cephalopod and are located only in seas of the world. None are present in freshwater or on land. Cephalopods have a huge head and a series of tentacles or arms.
You can find about 30,000 species of bivalves such as muscles, clams, scallops and oysters. Bivalves possess a shell composed of two halves, known as valves, attached together at one edge by a flexible ligament referred to as the hinge.