Powers Marine Science Crusteceans

• Phylum Arthropoda is the largest phylum

and includes crustaceans (subphylum
crustacea).

• Arthropod means “jointed feet.”

• Some features that arthropods share

include:

• Bilateral symmetry.
• Segmented body plan with paired and

jointed appendages.

• Arthropods have a non-living

chitinous exoskeleton that molts.

•Molting is the process in which

arthropods shed their old exoskeleton
in order to grow a new one. New
shells grow underneath the old one
and then harden once the old shell is
discarded. This is the reason
arthropods are usually small in size.

• Crustaceans are part of the subphylum

Crustacea and consist of mostly marine
species including barnacles, copepods,
and decapods.

• Many of them possess gills and a

chitinous exoskeleton made of calcium
carbonate.

• They also have mandibles for chewing

and appendages attached to each body
segment.

• Two pairs of antennae with receptors are

used for sensing surroundings.

• Crustaceans have appendages for obtaining

food and bringing it towards the mouth. A
two-chambered stomach connects to digestive
glands that secrete enzymes.

• Crustaceans have a simple brain and compound

eyes which consist of a bundle of photoreceptor
units. Sensory organs are well-developed.

• Most crustaceans have separate sexes. Males use

specialized appendages to transfer sperm to
females. Many females can store sperm for a
long time to fertilize eggs separately. Larvae are
planktonic.

• Barnacles are in class Cirripedia.
• Stay anchored to one spot.
• Have a carapace which is a hard, dorsal

shell that covers the body.

• Have free-swimming larvae that attach to

surfaces before they reach the adult
stage.

• Eat by extending its

feathery-like legs to
capture food.

• Some species

are parasitic.

• Class Copepoda includes the small

crustaceans, most are less than a mm long
and shaped like a tear drop.

• Largestclass found in the ocean.
• Very important to the marine ecosystem

and the food chain because of their large
numbers in the plankton.

• Many live in deeper ocean during the day

and rise towards the surface at night.

• Many species are parasitic.
• Eat microscopic phytoplankton

• Decapods are the biggest of the

crustaceans and include lobsters, shrimps
and crabs.

• Decapod means “10 legs.” They have

four pairs of walking legs and one pair of
claws.

• Three pairs of maxillipeds are used for

sorting food and bringing them towards
the mouth.

• The carapace covers the cephalothorax

which is a fused head and thorax. This also
contains the gills. The rest of the body is
referred to as the abdomen.

• Crabs and lobsters are benthic organisms.

Crabs can travel quickly and are either
predators or scavengers.

• Most females and males display differences

that help them be identified. Males have an
oversized claw used for attracting mates and
fighting. Females can use both of their claws
for feeding.

• Hermit crabs use empty snail shells for their

habitats.

• Japanese Spider Crabs are the largest

arthropods.

Lobster

Crab

Shrimp

• Shrimp are scavengers near surface or deep water.
• Krill are primary consumers that swim in the open

ocean. Many are filter feeders and are a food
source for large animals like whales.

• Lobsters prey on live organisms such as mollusks,

crushing them with claws before consuming them.

○ They are benthic and are mostly nocturnal. They

tend to hide in rocks or crevices, even burrowing
in the sand to create their own tunnels.

○ Humans are lobster’s biggest predator as they

are commercially fished and eaten by us.

Hermit Crab

Lobster

krill