Barnacles are sessile: they attach their shells permanently to rocks or other surfaces. From their shells, their feathery legs...Read More >>Barnacles are sessile: they attach their shells permanently to rocks or other surfaces. From their shells, their feathery legs reach out into the water to gather in plankton and other particles of food to eat. When they are exposed to the air at low tide, the barnacles slide plates across the openings to their shells, preventing them from drying out—and from predators getting in. Invertebrates are animals that do not have backbones. Many are only found in the sea. Marine invertebrates are a extremely large and diverse group that includes corals, sea anemones, sea urchins, starfish and many crustaceans, molluscs and worms. Crustaceans and molluscs are sometimes grouped together and called “shellfish”. Among the marine invertebrates are some of the largest animals on Earth (the colossal squid may measure up to 14 metres / 46 feet long) as well as some of the deadliest (the box jellyfish).
Crustaceans are a group of arthropods—animals that have jointed legs and an external skeleton. As they grow, they moult their external skeleton (exoskeleton) and grow a new one. Crustaceans include crabs, lobsters, shrimp and barnacles. They all have two pairs of sense receptors called antennae on their heads.
Shrimp are stalk-eyed crustaceans with long, narrow abdomens, long antennae and slender, fragile legs. They swim using legs called swimmerets attached to their abdomens.
The octopus has the largest brain of any invertebrate.
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