General Characteristics of
Phylum Molluscs
Habitat: Molluscs are highly adaptable and inhabit a wide range of environments, from tropical and Polar Regions to high altitudes, reaching up to 7000 meters. They are found in various aquatic ecosystems, from mountain lakes to the ocean's depths.
Body Symmetry and Development: Molluscs display bilateral symmetry, undergo protostome development, and have a coelomate (true body cavity).
Muscular Foot: A characteristic feature of molluscs is the muscular foot, which is primarily used for movement.
Mantle and Shell: The dorsal body wall forms a mantle, a specialized tissue that covers the internal organs. In many species, the mantle secretes a shell for protection, though in some molluscs, the shell may be absent.
Radula: Most molluscs possess a radula, a unique rasping organ used for feeding.
Circulatory System: Molluscs generally have an open circulatory system, where blood drains into sinuses. However, cephalopods (such as octopuses and squids) have a closed circulatory system, which is more efficient.
Respiration: Molluscs can respire through various means, including gills, lungs, or directly through the mantle cavity or skin.
Excretory System: They usually have one or two kidneys (metanephridia), which release waste into the mantle cavity.
Nervous System: Molluscs have a nervous system composed of paired cerebral ganglia, supporting complex behaviors.
Organ Systems: Their organ systems are well-developed, including specialized digestive, excretory, and reproductive organs.
Larval Stages: Many molluscs undergo two distinct larval stages: the trochophore and veliger, both playing key roles in their development.
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