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. 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

the life of a Krill

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

Male Jonah Crab

Female Jonah Crab

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!