Phylum: ArthropodaInsects, crabs, lobsters, etc….

Diversity:◦ Over 85% of all known animals are arthropods◦ The most successful animals on the planet!

They live in the widest range of habitats and eat the greatest varieties of food

“Arthropod” – jointed legs (appendages)◦ Appendages are used for eating, moving, mating,

respiring, feeling, sensing, or defense

General Information

The word crustacean originates from the crusty exoskeleton produced by crustaceans◦ Chitin – the organic material produced by the

crustacean to form a hard exoskeleton this distinguishes them from mollusks whose shells

are made of calcium carbonate (CaCO3) “Insects of the sea” Live in all aquatic environments plus a few

land-dwellers

Group: Crustacea

Exoskeleton (outer shell) ◦ Hard, protective outer surface; this shell must be molted in order for the

arthropod to grow◦ Muscles attach to the inside of the skeleton

Cephalothorax ◦ the fused head and thorax section; literally means “head breastplate” (Fig 7-4)

Swimmerets ◦ the posterior pairs of jointed appendages (legs) that mostly function as

swimming legs

Walking Legs ◦ the middle pairs of legs that are used for most movement

Maxillae & Mandibles ◦ The anterior appendages that are used for food getting apparatuses

Antennae ◦ Anterior pairs of appendages that are used as sensory organs

Anatomy

Most crustaceans live in the ocean◦ Lobsters, shrimp, crabs…

Some live in freshwater◦ Crayfish & crabs

Few live on land◦ Isopods and pill bugs

Even fewer are extremophiles!◦ Kiwa hirsuta

Habitat

Freshwater Crab

Horseshoe Crab

Another freshwater crabKiwa hirsuta or the Yeti Crab

Lobsters & Crayfish ….◦ Sex is determined by (somewhat) easy to see

external structures Swimmerets –

Males: Large and point towards the front of the body Use the 1st pair to transfer sperm to the female

Females: Have hairs on the swimmerets that make them look like

feathers Used to hold fertilized eggs against the abdomen until

ready to hatch

Sexual Reproduction

Crabs◦ They have smaller abdomens with not so easy to

see reproductive structures Males:

Narrow abdomen that fits into a groove on the underside of the cephalothorax

Females: The abdominal flap is very broad and covers most of the

underside of the cephalothorax She can store sperm until her eggs are ready The female holds the fertilized eggs between the

abdominal flap and the body with a natural adhesive This is sometimes referred to as “berrying” or “berried”

Sexual Reproduction