Barnacles are arthropods of the subclass Cirripedia in the subphylum Crustacea. They are related to crabs and lobsters, with similar nauplius larvae. Barnacles are exclusively marine invertebrates; many species live in shallow and tidal waters. Some 2,100 species have been described.
Barnacle
Whale barnacles on a humpback whale
Nauplius larva of Elminius modestus
Cypris larva of Amphibalanus improvisus
Arthropods are invertebrates in the phylum Arthropoda. They possess an exoskeleton with a cuticle made of chitin, often mineralised with calcium carbonate, a body with differentiated (metameric) segments, and paired jointed appendages. In order to keep growing, they must go through stages of moulting, a process by which they shed their exoskeleton to reveal a new one. They are an extremely diverse group, with up to 10 million species.
Protaetia cuprea (copper chafer). Beetles are the most diverse order of arthropods.
Cicada climbing out of its exuviae while attached to tree
Long bristles (setae) of a Tliltocatl albopilosus tarantula
Head of a wasp with three ocelli (center), and compound eyes at the left and right