CLASS: MEROSTOMATA CLASS: CRUSTACEA CLASS: PYCNOGONIDA PHYLUM ARTHROPODA CLASS: MEROSTOMATA CLASS: CRUSTACEA CLASS: PYCNOGONIDA

General Characteristics Jointed appendages – increases mobility Segmented body (2 or 3) Gills – gas exchange Feeding mechanism – filter feed, eat detritus Separate sexes Exoskeleton of chitin – protection, muscle attachment, support, reduce water loss. Must molt to grow Limits size of organism

Nervous system Compound eyes – a mosaic pattern for vision Smell – very sensitive, detects small amounts of chemical changes Communication behaviors – mating, defense & territorial displays (waving of claws to opponent) Well-developed nervous system

Class Merostomata “Middle stomach” - Horseshoe Crab Atlantic Ocean & Gulf of Mexico Horseshoe shaped carapace (exoskeleton-back) 5 pairs of legs Shallow water Collected off coast of Maine for chemical in blood that makes an antibacterial agent

Class Pycnogonida Sea spiders - Most have 4 pairs of legs and some may have 5 or 6 pairs Legs are twice as long as land spiders Live in cooler water

Sea Spiders Has proboscis (extension tube) with mouth on end to suck juices out of mollusks, cnidarians, sponges and worms Abdomen is reduced May have 2 pairs of eyes Most are separate sexes. Males care for eggs and young.

Class Crustacea Exoskeleton made of calcium carbonate 2 Pairs of antennae Appendages specialized for life habits: crawling, swimming, feeding & reproduction Small size Examples: Copepods, Barnacles & Krill

Crustacea Examples

Class Decapoda Larger size crustaceans & largest group Have 10 legs (deca) Chelipeds – 1st pair legs are large claws Maxillipeds (3 pairs) sort food & push in food Feeding - scavengers Body segments - 2 Cephalothorax – head & thorax covered by carapace Abdomen – walking legs attached

Class Decapoda

Examples Lobster: fanlike tail to move quickly 1 large claw for crushing, 1 small claw for biting Nocturnal scavengers Crabs: broad cephalothorax & reduced abdomen curved under body Males – V-shaped abdomen, Females – U-shaped abdomen Move sideways, burrow or swim for defense Largest decapod group

Examples Hermit Crab – live in abandoned shells Soft body twists to shape of shell Must relocate to larger shells for growth 1 claw is larger & is used to close off shell for defense

Hermit crab