Crustaceans and molluscs

In short: Crustaceans such as crabs and shrimp carry a hard chitin shell and several pairs of legs, while molluscs such as mussels and snails have a soft body, often protected by a calcium shell.

In more detail: Both groups belong to the most species-rich animal phyla on Earth and inhabit oceans, fresh water, and land alike.

In detail

• Crustacean shell: The exoskeleton made of chitin must be regularly renewed by molting in order to grow.
• Leg pairs: Crustaceans usually have ten legs, some of which are transformed into claws.
• Mussels: Two-valved shells protect the soft body; many species filter water for plankton.
• Snails: They scrape food with a radula (rasping tongue); some species have no shell at all.
• Cephalopods: Highly developed octopuses and squid also belong to the molluscs (kraken-und-ihre-intelligenz).
• Habitat: From the deep sea to the garden bed, crustaceans and molluscs inhabit almost every habitat.
• Ecological role: Many species are important food for fish and birds and part of the food web (nahrungskette-und-oekosystem).