Arthropods

1. Arthropods The Armored Achievers: Numerically the largest Phyla and literally means jointed foot.

2. Sub Phylum - Crustacea – Crab, shrimp, barnacle, and lobster • Segmented body and displays bilateral symmetry. • Jointed appendages have a variety of specialized functions • The body is covered by an exoskeleton made of chiton • Advantage: good protection, muscles attach to it for strength • Disadvantage: heavy, does not grow: must molt becomes vulnerable to prey

3. Body has 2 segments – cephalothorax covered by the carapace and the abdomen • Meroplanktonic larvae do not compete with adults for food: metamorphosis provides a gradual change to adult • Open circulatory system contains a blue pigment called hemocyanin to transport oxygen from gills to the body • Blood carries copper instead of iron • Excellent medium for long-term lab tests because it will not support bacterial growth • Ventral nerve chord with a well-developed brain and compound eyes. • Neurosecretory cells control molting, color changes, food storage and hormones.

4. The Small Crustaceans • Copepods • Barnacles • Beach Hoppers • Isopods • Krill

5. Barnacles

6. Decapods – ten legged • Five pairs of walking legs – first pair usually heavier and has a claw • Shrimp, lobster and crabs

7. Horseshoe crab • Only living member of Merostomata • Living fossil • Not a true crab

8. Molting • Like many animals with hard shells, a horseshoe crab must molt or shed its shell as it grows. Before molting, a new shell begins to form. When this new shell is ready, the horseshoe crab absorbs water through its gills, making itself bigger. • The old, hard shell cannot expand and splits in the front where the top and bottom join. The horseshoe crab crawls out the front, leaving the old shell behind. It takes about 24 hours for the new soft shell to harden. With each molt, the horseshoe crab increases in size by an estimated 25-30%.

9. Sea Spider • Feeds on soft invertebrates • Common in cold waters

10. Hermit Crabs • Not a true crab • Scavenger • Hide abdomen in empty gastropod shells • Sometimes cover shells with sea anemones .

11. True Crabs • Abdomen is small and tucked under the compact cephalothorax • V shaped abdomen in males, U shaped in females. • Most are scavengers and predators.

12. Biology of the Crustaceans • Feeding and Digestion • In general, digestion is extracellular and absorbed nutrients are distributed in an open circulatory system • Nervous system • Small simple brain • Most have compound eyes • Sensitive to chemicals • Pair of statocycst for balance

13. Behavior • Complex • Body postures and movements for communication • Disputes in territory and courtship • Elaborate courtship behavior.

14. Reproduction • Mostly separate sexes • Males use special appendages to transfer sperm to females • Mating in decapods usually takes place within a few a hours of the female molting. • Females in many species can save and store sperm for different broods of eggs. • Decapods carry eggs using pleopods.

15. Marine Crustaceans Growth Chart

16. Weird but True? • Do you know that horseshoe crabs are not really crabs at all? They're actually the only four living species of a group, class Merostomata, that are largely represented by fossils. Horseshoe crabs are in fact living fossils, resembling creatures that went extinct thousands of years ago! • Crabs don’t have ears. Still, they can detect sound which seems a bit of a conundrum. Basically, the hollow hairs on the outside of the crab’s body pick up vibrations created by sounds and vibrations in the water. These hairs are also used for feeling, tasting and smelling. How’s that for multi-tasking. • If a crab loses a claw, it grows back. Don’t you wish you had that quality? • Crab legs and swimming. All crabs have legs. In fact, those are generally the tastiest parts of the crab. Although they live in the water, and have all of those legs, most can’t swim. The Blue and Lady crabs have specialized legs for swimming. These swimming legs are flattened out and act more like paddles. Other than that, the legs are used for walking. These paddle legs move at 20 to 40 revolutions per minute.

17. Crustaceans turn red when exposed to heat, so while you may see the live ones with a nice blue color, the cooking process will change the color. Similarly, a dead crab on a beach will turn red just because of its exposure to the sun’s rays. • A male crab is called a Jimmy. • The female crab can only mate during the molting process. She emits a powerful aroma to attract the male crab. The problem is, she may not be in the molting process quite yet, so the male crab literally stakes his claim by carrying the female crab around underneath his own body until conditions are just right. • The female blue crab lays her eggs from 2 to 9 months after mating, depending upon when the mating took place. • The oldest crab industry in the United States is the blue crab industry of the Chesapeake Bay area, dating back almost to the early 1600s. • The ghost crab is on record as having the fastest crawling speeds. On firm sand, they have been clocked at 4 miles per hour, and 5 miles per hour on a solid, wooden deck. • A single Alaskan King Crab can yield over six pounds of meat. They can measure up to a 6-foot leg span.

18. Crustacean Humor