The Mollusca Introduction
This system is one of the most diverse group of species (animals) in this planet. The Mollusca system contains around 50,000-200,000 species. Molluscs are a group of organisms that have a soft body, usually classified with head and foot regions. The Mollusca system most commonly includes snails, squids and oysters.
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Mollusca Phylum
This phylum contains species where their bodies are covered by a hard exoskeleton such as shells of snails and clams or even the plates of Chitons. Their system contains this hard skeleton shell that protects the soft body inside. It also has the muscular foot region that is used for movement.
They are a part of almost every community of living species in the world, molluscs are part of a very important portion in ecological associations. They range in living environments from earthly mountains to hot vents and cold seeps of the deep blue sea, and ranges in size from a 20 meter long giant squid to microscopic aplacophorans, a millimeter or less in length, that usually lives between common sand grains.
These species have been important to humans throughout history as a source of food, jewelry, tools, and sometimes even pets. Species whose members once numbered in the millions, now teeter on the verge of extinction. For instance, fewer than a hundred white abalones remain after several million individuals were captured and sold as meat in the 1970s. Besides having yummy soft parts, molluscs often have some desirable hard parts. The shells of some molluscs are considered quite beautiful and valuable. Molluscs can also be nuisances, such as the common garden snail; and molluscs make up a major component of fouling communities both on docks and on the hulls of ships.
Morphology(structure)
-Despite their large diversity, all molluscs share a few unique characteristics that define their body structure. The body has a head, a foot and a visceral mass. They are normally referred to as the head, foot and visceral region. The visceral region being the part that contains most of the organs. These are all covered with a mantle (or Pallium) that typically separates everything from the shell. In some groups, like slugs and octopuses, the mantle may have another function such as used for other activities, respiration.
Snails (Gastropoda branch)
Of the Mollusca system, Snails is by far the largest portion of Molluscs. There are a guarantee of more than 62,000 living species in this branch of Molluscs. Their body type is diverse in size, shell structure, body and habits. Their action of occupying the widest range of niches from all molluscs are the only group that actually invaded the land. Their first appearance on the earth was during the Early Cambrian Age.
Most snails move around by gliding along on their muscularfoot, which is lubricated withmucus. This movement is powered by strong waves of muscle contraction that moves down the bottom of the foot. This muscle movement action is visible and clear when a snail crawls on glass or a window of an aquarium. Snails move at a very low speed around: (1 mm/s). They make mucus in order to help locomotion and this ends up reducing friction, and the mucus also helps reduce the snail's risk of mechanical injury from sharp objects that are on the glass.
Most snails move around by gliding along on their muscularfoot, which is lubricated withmucus. This movement is powered by strong waves of muscle contraction that moves down the bottom of the foot. This muscle movement action is visible and clear when a snail crawls on glass or a window of an aquarium. Snails move at a very low speed around: (1 mm/s). They make mucus in order to help locomotion and this ends up reducing friction, and the mucus also helps reduce the snail's risk of mechanical injury from sharp objects that are on the glass.
Squids (Cephalopoda branch)
Cephalopoda Molluscs are the largest among all type of species in a molluscs system. They are also the most mobile and smartest. Some examples beside a squid can be cuttlefish, octopuses, the chambered nautilus, and other similar relatives. They display extreme diversity in size and lifestyle with adaptations for disguise and communication. These intelligent invertebrates have evolved suckling tentacles, camera like eyes, color changing skin, and intense learning behaviors. Their lengthy history spans show an impressive 500 million years. Today, paleontologists and biologists continue to captivate the human mind and imagination with details of these type of mollusc behavior, their natural history, and their spectacular evolution.
Oysters (Bivalve Branch)
The Bivalve branch contains Oysters, Clams, Mussels and more similar species. The Bivalve branch is the second most diverse group of the Molluscs system. They have over 10,000 type of species that are found in deep bottom of oceans to places like the little streams that flow by your backyard. Always recognized by two-halved shelves, they can be found on the ocean bottom floor or buried in sediment. Not all bivalves have shelves but the ones that do can swim by opening and shutting their shelves. Bivalve system with the outer, hard, two-halved shell as it's system to protect the inner soft body have been used as jewelry, food, decoration and sometimes money.
Relationship with Cnidaria
Mollusca and Cnidaria are the top two most diverse type of phylums. They have the most possible species but they also share one unique characteristics. These two contain species that can protect themselves with their outer "shell" Mollusca have a hard shell that protects their inner soft body while Cnidaria are armed with stinging cells.
-Jesse Fung (Xavier Hs)
-Jesse Fung (Xavier Hs)