Phylum Arthropoda

Phylum Arthropoda

Largest of all phyla (1,000,000+ species)

Segmented bodies

Jointed appendages

Tough exoskeleton made of chitin

Many have specialized appendages

One-way digestion, bilateral symmetry

Class Crustacea

Two body segments—cephalothorax and abdomen

Carapace: exoskeleton that covers cephalothorax

Also have calcium carbonate within exoskeletons, giving them a “crusty” texture (named for)

Cephalothorax

Abdomen

Order Decapoda—10 legs!

Most of the larger crustaceans

Five pairs of legs under carapace

1 pair claws—for feeding, 4 pairs walking legs

Head—two eyes, two pairs antennae

Thorax—legs

Abdomen—swimmerets

Examples: lobster, crab, shrimp

Lobsters

Aggressive predators

Regenerates appendages

Open circulatory system (hemocyanin)

Breathe with gills attached to walking legs

Well-developed nervous system

Lobster Anatomy

Lobster Reproduction

Internal fert., external develop.

Male stores sperm in female’s seminal receptacle

Eggs are fert. as released

Female carries eggs on abdomen up to 1 year

Hatch into planktonic larvae

Molt and grow into adult

American Lobster

Bottom-dweller, cold waters

Eats mollusks

Swimmerets not as useful as in shrimp, but can propel backwards using tail fan

Crabs

Two body segments, abdomen—small, flat, folded between walking legs

Shape of abdomen determines sex:

U shaped=female

V shaped=male

♀

♂

Crabs

Scavengers, algae eaters, predators

Claws to tear and shred food

Mouthparts to cut into smaller pieces

Large # of offspring—female carries between abdomen and thorax

Open circulation, well-developed nervous system

Mole (Sand) Crab

Follows tide

Burrows often

Feather-like antennae for feeding

Fiddler & Hermit Crabs

Fiddler—digs tunnels in sand, plugs up hole at low tide, claw for defense or show

Hermit—soft abdomen lacking exoskeleton, finds empty shell (gastropods), lives in shallow, coastal waters

https://www.youtube.com/watch?v=ExV4b77qfww

Spider Crab

Slow, no paddling appendages, algae and barnacles grow on shell

Shrimp

Planktonic swimmers

Cleaner: coral reefs, eats parasites

Mantis: Largest shrimp, burrow in sand or mud, spears prey with jackknife front legs

Pink-Gulf Shrimp: Carolinas and the Gulf of Mexico

Bycatch

Brown shrimp

Copepods and Krill

Copepods: less than 1 cm, most abundant crustacean, elongated antennae, single eye

Krill: less than 5 cm, cold water

Base of ocean food chain

Isopods

aka sea roach

Evolution to land?

Coastal waters, nocturnal

Some parasitic

Barnacles

Sessile crustaceans

Attach to substrates, “glue” secreted by gland

Body folded in shell

6 pairs of cirri protrude from shell, filter-feeders

Breathe by diffusion

Hermaphrodites

“Fouling”

Class Merostomata

Horseshoe crabs

Atlantic and Gulf coasts

4 eyes

1 pair of chelicerae (pinching claws)

5 pairs walking legs

Book gills—breathing and locomotion

Telson (tail) used for locomotion

Marine Insects (Class Insecta)

3 pairs legs, 3 body segments, 1 set antennae, 1 pair eyes

Rarely in open ocean

Common in marsh and bay areas

Examples: marsh mosquito, greenhead fly, sand fly