A. Phylum Arthopoda “jointed feet”:

• Largest of all phyla

• Includes:

− Insects

− Arachnids

− Crustaceans

• 80% of animals species are arthropods

• Microscopic to several meters long

1. Subphyla

− Trilobites:

− Chelicerates:

− Myriapods:

− Hexapods:

− Crustaceans:

• Formerly numerous marine animals

• Died in the mass extinction at the end of the Permian

• 252 million years ago

• 96% of all marine life extinct

• 70% of all land animals extinct

• Possibly took 10 million years to recover

• Spiders/mites/scorpions

• Millipedes and centipedes

• Many body segments, each bearing one or more pairs of legs

• Insects: bees, ants, flies, …

• Lobsters, crabs shrimp

• Primarily marine

• Baramous (paired) appendages

2. Characteristics (general):

− Segmented body with jointed appendages on each segment (appendages 

− Dorsal heart and ventral nervous system

− Covered by a hard exoskeleton

move at the joins, giving more mobility)

• Less prone to dehydration

• Made of chitin

• Molts periodically to allow growth

3. Common Crustaceans (Hawaii):

− True Crabs:

• Five visible pairs of legs

• Abdomen folded under cephalothorax

• Females have a wide abdomen, males are narrow

http://www.featurepics.com/FI/Thumb300/20080614/Aama-Crab-769139.jpg

(‘A’ama crab)

http://1.bp.blogspot.com/-AsbY93HZegs/T-4-AsdoTLI/AAAAAAAACUI/Qyh-j4tWij8/s1600/7-

11+crab+B.jpg

(7-11 crab)

− Hermit Crabs:

• Last pair of walking legs are hidden in carapace (shell to protect their 

body)

• Salvage empty shell for homes

http://www.wax32.com/hermits/images/hermit8.jpg

(Hawaiian hermit crab)

− Lobsters:

http://images.fineartamerica.com/images-medium-large/hawaiian-lobster-dave-fleetham.jpg

(Hawaiian lobster)

http://reefguide.org/pix/bandedspinylobster1.jpg

(Banded spiny lobster)

− Shrimp:

http://www.tropicalreefstore.com/Coral_Banded_Shrimp.jpg

(Banded coral shrimp)

http://reefguide.org/pix/lysmataamboinensis1.jpg

(White-striped cleaner shrimp)

http://upload.wikimedia.org/wikipedia/commons/f/fe/Harlequin_Shrimp_1.jpg

(Harlequin shrimp)

− Barnacles:

• Abdomen with swimmerets (little feet)

• Similar to lobsters

• Infraclass Cirripedia

• “Curl footed”

• When larvae is ready to settle, it cements its head down

• Grow armor plates to protect body

• Hermaphroditic, altering male and female over time

• Use feathery legs to capture food

http://www.aecos.com/CPIE/barnacle.jpg

(Barnacles)