Molluscs are a diverse group of invertebrate animals with over 110,000 species, including clams, oysters, snails, and octopuses. They have a muscular foot and a mantle cavity used for various functions. Molluscs have been important to humans for food and decoration, and their shells provide evidence of prehistoric lifestyles. They range in size from less than 1mm to the colossal squid, which can kill sperm whales.
Molluscs (British spelling: molluscs) are a large and diverse phyla of invertebrate animals, numbering over 110,000 species. Their phylum name, Mollusca, means “thin-shelled,” although many species lack shells entirely. Molluscs include clams, oysters, scallops, mussels, snails, squid, octopuses, slugs, nudibranchs, sea hares, and several classes of deep-sea worm-like creatures. Some molluscs – snails and slugs – have even adapted to life on land. Mollusca is one of the “Big Nine” animal phyla, along with Porifera, Cnidaria, Platyhelminthes, Nematoda, Annelida, Arthropoda, Echinodermata and Chordata.
For thousands of years, molluscs have been one of mankind’s favorite marine creatures alongside fish and crustaceans, providing us with their meat and decorative shells. Shell mounds, huge piles of shells left behind by prehistoric peoples, line many coastal areas of the world, providing important evidence about the migration patterns and lifestyles of our ancestors. Some mounds are tens of thousands of years old.
Molluscs include a variety of record holders and unusual animals. There is the colossal squid (Mesonychoteuthis hamiltoni), the largest of all modern invertebrates, which is at least 14 m (46) feet long, the vampire squid (Vampyroteuthis infernalis, literally “vampire squid from hell”), a relict phylogenetic with characteristics of both squids and octopuses, and nudibranchs (suborder Nudibranchia), some of the most beautiful and colorful marine animals that exist. Molluscs range in size from less than 1mm, in the case of some micromolluscs, to the colossal squid, which is capable of killing sperm whales for prey.
The distinguishing features of molluscs are a muscular foot, especially evident in the case of snails, and the mantle, a protective dorsal wall that covers the main body from the outside. Between the mantle and the main body is a mantle cavity, containing the gills, anus and other organs of the mollusk. The mantle cavity may be used as a feeding structure (bivalves), a respiratory chamber (all molluscs), a brood chamber (several), or a locomotor organ (squid and some clams).
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