Phylum Arthropoda animals with jointed

appendages

• includes insects, crustaceans, centipedes, millipedes, and arachnids

• exoskeleton made of chitin• must shed shell to grow

Chelicerates

• Includes spiders, ticks, scorpions, horseshoe crabs, and sea spiders– Six pairs of appendages– One pair of chelicerae (for feeding)

Horseshoe crabs

Sea spiders

Mandibulates

• Crustaceans– Decapods

• Crabs, lobsters, shrimp

Durban Dancing Schrimp

Crustaceans• The crustaceans are a large group

of arthopods–Lobsters–Crabs–Shrimp–Crawfish–Barnacles–copepods– The majority are aquatic, living in

either freshwater or marine environments,

– Some are terrestrial

Crustaceans Continued

• The majority move about independently• a few are parasitic and live attached to

their hosts– Sea lice, fish lice, whale lice (crustacean lice)

• adult barnacles live a sessile life — they are attached head-first to the substrate and cannot move independently.

Sea lice are parasitic

Structure of crustaceans • Crustaceans have three distinct body

parts: – head, thorax and abdomen

• the head and thorax may fuse to form a cephalothorax

Structure continued

• The head has two pairs of antennae, one pair of compound eyes and mouthparts– Mandibles– maxillae

• Each body part usually has a pair of appendages– chelipeds– Walking legs– swimmerets

Molting

• Like other arthropods, crustaceans have a stiff exoskeleton which must be shed to allow the animal to grow or molt.

Reproduction

• crustaceans all have a larval form known as the nauplius

• most crustaceans have separate sexes, in many decapods, the eggs are retained by the females until they hatch into free-swimming larvae.

Crustaceans of the Gulf of Mexico

• Decapods – Shrimp– Crabs – Lobsters and

Lobsterettes– Hermit crabs – Squat crabs and Porcelain crabs

Common Name of some species

American Spider Crab Sentinel Crab

Pebble Crab