Phylum Arthropoda Major arthropod features Major arthropod features Body segementation/specialization of regions Body segementation/specialization of regions Paired, jointed appendages Paired, jointed appendages Exoskeleton Exoskeleton

Steps of molting Cuticle separates from epidermal layer Cuticle separates from epidermal layer Space fills with molting fluid Space fills with molting fluid New exoskeleton New exoskeleton Enzymes digest most of old procuticle Enzymes digest most of old procuticle Old cuticle splits, animal crawls out Old cuticle splits, animal crawls out Gut fills with water, stretching new exoskeleton Gut fills with water, stretching new exoskeleton

Phylum Arthropoda Subphylum Crustacea features Two pair of antennae, followed by three pairs of mouthparts Two pair of antennae, followed by three pairs of mouthparts Compound eyes, sometimes on stalks Compound eyes, sometimes on stalks Head and thorax combined into a “cephalothorax” Head and thorax combined into a “cephalothorax” Biramous (“double-branched”) appendages Biramous (“double-branched”) appendages Often with calcium carbonate cuticle Often with calcium carbonate cuticle Many have gills Many have gills

Order Amphipoda (Beach hopper)

Order Isopoda Idotea sp. Ligia pallasii

Order Decapoda Carapace completely covers head and thorax Carapace completely covers head and thorax Eight pairs of thoracic appendages Eight pairs of thoracic appendages 3 as modified mouthparts (maxillopeds) 3 as modified mouthparts (maxillopeds) 5 pairs as walking legs 5 pairs as walking legs

Order Decapoda Pagurus sp. Petrolisthes cinctipes

Shore crabs Pachygrapsus crassipes Hemigrapsus oregonensis Hemigrapsus nudus

Cancer sp. crabs C. antennariusC. productus C. magister Not shown: C. oregonensis

Pugettia producta: kelp crab

Order Cirripedia: the barnacles Balanus sp. Chthamalus sp. Pollicipes polymerus