Bellwork: 12/02/20131. The tube feet of echinoderms are very thin &

hollow. What are the benefits of this structure?

2. Why do urchins have relatively long tube feet?

3. Contrast the movement between sea stars & brittle stars:

Crustaceans

Crustaceans

• Kingdom – Animalia

• Phylum– ArthropodArthro = jointPod = foot

• Class– Crustaceans

Crustaceans• Class

– Crustaceans originally referred to the “crusty” exoskeleton made of chitin

– Often called the “Insects of the Sea”

– Most are marine, some fresh, and very few (pillbugs) isopods live on land

Crustaceans• Characterized by:

Jointed legged animals with an exoskeleton

Arthropods are considered the most successful type of animal on earth, making up 85% of all known species

Types of Crustaceans

• Many different types of crustaceans.– Hermit crabs– Crayfish– Shrimp– Lobster– Blue crabs– Sand crabs– Prawns– Barnacles

Crustacean - Appendages • Appendages have become specialized by evolving into a

wide variety of walking legs, mouthparts, swimmerets, etc. from modification of the basic biramous appendage.

Crustacean - Muscular System

• Striated muscles make up a major portion of crustacean body.

• Most muscles arranged as antagonistic groups.– Flexors draw a limb toward the body and extensors

straighten a limb out.

Crustacean - Muscular System

• Abdominal flexors of a crayfish/lobster/shrimp allow it to swim backward.

• Strong muscles located on each side of stomach control the mandibles.

Support System

• All crustaceans have an exoskeleton.

• They must molt (shed) to grow.

• Vulnerable during and right after molting because of soft exoskeleton.

• Contain muscle tissue in the joints to allow them to move.

Digestive System• Crustaceans are scavengers – eat dead material and they are also herbivores – plant eaters

• Mandibles help rip or crush food.

• Esophagus to connect mouth and stomach

• Stomach has grinding teeth inside to break apart food.

• Liver to produce digestive fluids.

• Intestines to absorb the food particles

• Anus to release wastes.

Respiratory System• Most

crustaceans breathe by absorbing oxygen from the water by the use of gills.

• Barnacles use feathery gills to take oxygen from the water.

Respiratory System

Circulatory System

• Crustaceans have a “heart” in which helps pump blood to gills and rest of body.

• Transports both oxygen and food nutrients to cells and takes wastes away from cells

Circulatory System• Open circulatory system• Dorsal heart - single-chambered sac

of striated muscle.• Valves in the arteries prevent

backflow of hemolymph.• Hemolymph conducted to gills, if

present, for oxygen and carbon dioxide exchange.

• Hemolymph may be colorless, reddish, or bluish.– Hemocyanin (blue) and/or

hemoglobin (red) are respiratory pigments.

– Contains ameboid cells that may help prevent clotting.

Nervous System

• Contain a brain, nerve cords and ganglia.

• The nerve cord runs along the dorsal side of the organism

• Ganglia are bunches of nerve cells in areas to help speed up responses.

• The have eyes to detect light/dark and movement.

• They have antennae to detect chemicals and movement in the water.

Nervous System

• Eyes and statocysts are the largest sensory organs.

• Tactile hairs occur on the body, especially on chelae (pincher claw), mouthparts and telson.

• Chemical sensing of taste and smell occurs in hairs on antennae and mouth.

• Statocyst opens at base of first antenna in crayfish.– Statocyst lined with

sensory hairs that detect position of grains of sand.

Nervous System

• Compound eyes are made of many units called ommatidia.

• Cornea focuses light down the columnar ommatidium.

• Distal retinal, proximal retinal, and reflecting pigment cells form a sleeve around each ommatidium.

Excretory System

• Antennal or maxillary glands are called green glands in decapods.

• End sac of antennal gland has a small vesicle and a spongy labyrinth

Reproductive System

• Crustaceans have two sexes and most have external fertilization

• Eggs are fertilized by the sperm that is released over them.

Reproductive System

• Easiest way to distinguish sexes between crustaceans with swimmerets:

– Female hair on the swimmerets

– Male hairless swimmerets

Limb Functions

Anatomy

Sand Crabs• Find these on the beaches of San Diego.

• They dig along the water line of the sandy beach and they will stick out filter mandibles that capture food particles

Swimming Crabs

• Many crabs have paddle-like last appendages that helps them swim for movement.

Krill

• Krill are small shrimp like crustaceans that many baleen whales will use as food. They will take in tons of water and force it out past their baleen and capture the krill.

Fresh Water Prawns

• Arizona is one of the leaders in the US in farming for Fresh Water Prawns right outside of Gila Bend.

• Similar to Shrimp – sweeter taste

Barnacles• A group of mostly

sessile crustaceans whose cuticle is hardened into a shell.

• Filter feeders

Using the Lobsters:1) Identify the sex of each sample.

Body Part Feeding Walking Swimming Escaping

Antennae

Antennules

Maxillae & Mandibles

Walking Legs

Abdomen and Telson

Swimmerets

Questions:1) How does the exoskeleton of an arthropod compare with that

of the endoskeleton of a fish?

2) Which appendages are attached to the cephalothorax? Which are attached to the abdomen?

3) Which sections of the body are most flexible?

4) How does the nerve cord of an arthropod compare with that of a human?

5) Arthropods are the first organisms that we have talked about that have a rounded eye. What do you think this will change about the visual information collected by this organ in comparison to eye spots from simpler organisms?

6) There are two arthropods, a hermit crab and a coral-banded shrimp, in the two salt tanks at the back of the classroom. Look at their structure & compare/contrast that to those of the lobster.