Phylum Arthropoda aka: Arthropods Literally means “Jointed foot” animals Includes crabs, shrimps, barnacles, spiders, insects, horseshoe crabs, etc…

Common Characteristics of all Arthropods Exoskeleton-tough outer covering made of chitin-carbohydrate. Some chitin may contain calcium to strengthen the skeleton. Protection and muscle attachment. Jointed appendages that are specialized for feeding, movement, protection, and reproduction.

Class Crustacea a.k.a. Crustaceans Bilateral Symmetry 2 main segments-cephalothorax and abdomen Cephalothorax-head and chest region; covered with carapace Abdomen-posterior region often including a tail. Decapods (lobster, crabs, shrimps) 5 pr of legs under carapace. (not barnacle) 1st pair= claws for food getting; 2nd-5th pr walking Head-two eyes, 2 pr. Antennae, special mouth parts for feeding. Thorax-chilipeds (claws), and walking legs. Abdomen-swimmerets (paddle-like appendages for swimming).

Anatomy of Crayfish

Molting Shedding of the exoskeleton Occurs once or more per year Soft-shelled crabs are newly molted crabs

Lobsters Northern lobster (Homarus americanus)- American or Maine lobster w/ 2 large claws Spiny lobster (Planularis aragas)- no large claws; CA, FL, and Gulf of Mexico

Feeding and Digestion Predators that eat mussels and sea urchins; scavengers One-way digestive tract-mouth, esophagus, stomach, intestines, and anus

Respiration Uses gills-featherlike structures located in the water-filled chamber under the carapace. Each gill is attached to the upper end of a walking leg. Rapid beating of mouth parts sends currents of water over the gills. O2 diffuses in and CO2 out.

Circulation Open circulatory system (no capillaries so blood just passes through tissue spaces) Blood is blue b/c of pigment called hemocyanin (contains copper) Blood is pumped through the body by a one-chambered heart.

Nervous System Have a brain and ventral nerve cord to carry impulses and messages from the eyes and antennae.

Reproductive System Sexually Internal fertilization External development Male deposits sperm cells into the female’s abdomen in the seminal receptacle As the eggs are released, they are fertilized by the sperm. Holds eggs on her swimmerets for nearly one year. Plankton when they hatch.

Lobsters One in a million lobsters are blue. Mutant of the brown lobster DNA codes for a special protein that mixes with the red pigment to create blue.

Crabs Mole Crab (Emertia) Lives in turbulent surf zone along sunny beaches. Has smooth body to burrow w/ its swimmerets. Feathery antennae to catch microscopic organisms in the sand.

Fiddler Crab (Uca) Digs tunnels in sand along shores of bays and inlets. Males have one large claw and one small. Females have 2 small claws.

Hermit Crab (Pagarus longicarpus) Lives in shallow coastal waters. Has soft abdomen w/o exoskeleton so it finds an empty shell to live in. Changes shells as it grows.

Spider Crabs (Libinia emarginata) Slow moving due to lack of paddle-like appendages So slow that algae and barnacles grow on it. Giant spider crab of Japan can grow up to 4m long from leg to tip.

Life Activities Similar to lobster Abdomen folded up between walking legs. V-shaped abdomen is a male; U-shaped abdomen female. Mostly eat dead plant and animal matter.

Shrimp: Common Species Pink Gulf Shrimp (Penaeus duorarum)- popular seafood; 17cm in length Common Shore Shrimp (Palaemonetes vulgaris)- smaller; scavenges in marshes Mantis Shrimp (Spuilla empusa)- largest shrimp (25 cm in length); eat worms and small fish; found from Cape Cod to Brazil. Cleaner Shrimp (Periclimenes)- lives on coral reefs and rides tropical fish in Caribbean and Gulf waters and eats parasites that are found on their skin.

Examples of Shrimp Mantis Shrimp  Cleaner Shrimp (below)

Copepods Copepods (Calanus)- 1000’s of species. Less that ½ cm long; eats diatoms; important part of zooplankton community; abundant in spring and winter

Krill Krill (Euphasia)-cold water (Antarctica) relative of copepod; grow 5 cm in length; principal food source for filter-feeding (baleen) whales

Amphipods and Isopods Amphipods- crustaceans that look like tiny shrimp that have flattened sides; scuds and beach fleas Isopods- small crustaceans with flattened bodies (dorsoventrally) and seven pairs of legs; sea roach.

Giant Isopod

Barnacles Acorn Barnacle (Balanus)- have overlapping, sharp calcium carbonate plates; live in uppertidal zone, attached to rocks and other hard surfaces Filter Feeders- Have cirri to feed-six pairs of feathery appendages extend to catch phytoplankton and other food particles. No gills- O2 in water diffuses into skin Hermaphrodite- contains both testes and ovaries; internal fertilization- penis from one barnacle is inserted into another barnacle. Internal development- fertilized eggs develop into larvae and enter the plankton population.

Example of Barnacle Gooseberry barnacle

Class Merostomata- Horseshoe Crabs (Limulus polyphemus) Most closely related to spiders and scorpions Lack antennae and mouthparts; have 2 compound eyes and 2 simple eyes Have 6 prs of appendages; 1st pr are pinching claws (cheliceras); and the other 5 are for walking

Horseshoe Crab cont. Scavenge and feeds on dead matter Book Gills- used for breathing and locomotion Telson (tail)- helps it right itself if it is tossed over by a wave.

Life Cycle Late Spring high tide, female HS crabs w/ smaller males clutched to their backs come to shore Females dig holes and lay eggs; males fertilize them externally while still attached to their backs. In two weeks, the eggs hatch into juvenile HS crabs (no larval phase) Can live 20 yrs. Living fossil. (no change in 400 million years!)

Horseshoe Crab Mating Eggs (below)

Marine Insects- Class Insecta Live in bays and marshes; have chitinous exoskeleton and jointed appendages but only have 3prs of legs and have 3 body segments (head, thorax and abdomen) Marsh Mosquito- use proboscis to draw blood from host; (only female bite) Sand Fly- “no-see-um” very tiny!