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Arthropods: The Marine Bio Version (chapter 5). Phylum Arthropoda. Largest and most successful phylum in the animal kingdom. 75% of all animals! Exoskeleton made of Chitin (light/hard polysaccharide). Must molt or shed exoskeleton to grow Jointed Appendages.
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Phylum Arthropoda • Largest and most successful phylum in the animal kingdom. 75% of all animals! • Exoskeleton made of Chitin (light/hard polysaccharide). • Must molt or shed exoskeleton to grow • Jointed Appendages. • Cephalization-compound eyes, ocelli (eyespots), antennae. • Segmented • Bilateral symmetry
Classification you should know (there is a LOT more) • Subphylum Mandibulata • Class crustacea • Order decapoda- lobsters • Subphylum Chelicerata • Class meristomata- horseshoe crabs • Subphylum Uniramia (not elaborating) • Insects, millipeds, and centipedes
SUBPHYLUM MANDIBULATATA • Antennae, Mandibles & Maxillae • Crustaceans-add some limestone to the chitinous exoskeleton. • Lobsters & crabs are the giants of this group-most are a few centimeters long.
Class Crustacea • Shrimps, crabs, lobsters • 2 pairs of antennae-sense surroundings • Dominant arthropods in sea (as insects are on land) • Appendages to swim, crawl, attach, mate, feed
Crustaceans • lobsters & crabs, shrimp, copepods and barnacles. • rigid exoskeleton, crustaceans must “molt” or shed their shell in order to grow. • use an enzyme to split their shell & then crawl out. • molting horseshoe crab!
1) Small Crustaceans • Copepods- extremely abundant, planktonic, filter feed • Barnacles- usually sessile, filter feed, body enclosed by calcareous plates • Krill- planktonic, shrimp-like, have carapace to cover anterior, filter feed
2) Larger Crustaceans-Decapods: shrimps, lobsters, and crabs • Five pairs of legs, first pair are claws • Carapace encloses cephalothorax (anterior region) • (posterior region) is abdomen
Shrimps and Lobsters • Long abdomens (tails we eat) • Scavengers for food • Lobsters prey on mollusks
Christmas Island Crab Migrations • History of the island • crabs vs. cars
Hermit Crabs • Not true crabs • Scavengers • Hide abdomens in empty shells
True Crabs • Small abdomen and tucked under cephalothorax • V-shape ab. in males • U-shape ab. in females • Largest and most diverse of decapods • Scavengers and predators
Feeding Observe feeding appendages at work! • Maxillipeds- appendages near mouth (decapods have 3 pairs) • Food passes to stomach w/ teeth for grinding • Digestive glands w/ enzymes • Intestine leads to anus • Nutrients distributed through open circulatory system
Response (nervous) • Well developed sense organs • Compound eyes (opposite of simple-14,000 sensitive units) • Keen sense of smell • Body postures/movements to communicate w/ each other • Simple brain
Compound Eyes- one way to respond to your environment- be able to see what is nearby!
Reproduction • Separate sexessexual reproduction • Males directly transfer sperm to females • Ex. Barnacle stretches out appendage to local females • Mating occurs after female molts
SUBPHYLUM CHELICERATA • Fang-like mouthparts (Chelicerae)-Pedipalps for sense. 2 Classes. • Class Merostomata-Horseshoe crabs. • Book gills on ventral surface • More closely related to spiders than crabs!
Horseshoe Crab • 1. Carapace • 2. Telson • 3. Compound eye • 4. Anterior spine • Five pair of legs
LAB WORK: • DISSECTING A CRAYFISH • Virtually same structure as a lobster or shrimp, but has a better size than shrimp, and a better price than lobster!