1. Photo credits: www.wikipedia.org
Phylum Arthropoda
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2. Arthropod Characteristics
More than 1 million species known, mostly marine
Most marine species are subphylum Crustacea (shrimp, lobster, crab, barnacles, etc)
Coral crustaceans
California crustaceans
About 75% of all animals on earth are arthropods
Chitin exoskeleton - hard, but light and moderately flexible
Must molt to grow (Video: molting)

3. Arthropod Characteristics
Jointed appendages
Many divided into sections called head, thorax and abdomen
Specialized segmentation- segments combined for specific functions
Simple brain but specialized eye & sensory organs
Specialized respiratory structures, gills, used for gas exchange
Some are filter feeders, some scavengers, others carnivores

4. Arthropod Reproduction
Male transfers sperm directly to female to ensure reproductive success
In some species, female will house eggs for a time until they are further developed
Females can store sperm for fertilization at a later time
Many arthropods have complex behaviors including mating rituals (lobsters); mating rituals (crabs)
Baby Crabs
6th show videos

5. Planktonic larvae to Adult organism

6. Subphylum Crustacea 68,000 species 2 pairs antennae
Gills for respiration
Head and thorax fused into a single unit called a cephalothorax; entire external body is called the carapace
Large array of appendages specialized for different functions; ex: pinchers on crabs, swimmerettes on the underside of shrimp hold developing eggs, etc.
Types of crustaceans – copepods, barnacles, amphipods, isopods, crabs, shrimp, lobsters, etc.

7. Copeopod Amphipod Isopod Curved and flattened sideways, ~2cm.
Orchestoidea – beach hopper
First antennae –
Specialized for swimming
Curved and flattened sideways, ~2cm.
Planktonic, extremely abundant.
Isopod
Ligia oceanica – sea louse
Dorsoventrally flattened, commonly parasites, ~2cm.

8. Cirri are modified legs
Barnacles
Cirri are modified legs
Reproduction

9. Decopods Largest group of crustaceans with ~10,000 species
Largest crustaceans
10 legs
Shrimp, lobster, and crabs
Carcinus maenas

10. American Lobster
Homarus americanus

11. Caribbean Spiny Lobster Panulirus argus

13. Class Merostomata Horseshoe crabs-
5 pairs of legs, first pair modified in males for reproduction
Females larger than males
Mating pairs come onto beaches each spring to breed and lay their eggs in wet sand
Among the oldest creatures on earth – they have remained virtually unchanged for millions of years
They live and borrow in soft sediments, normally near shore where they feed on other invertebrates and scavenge.
Valuable blood

14. Class Pycnogonida Sea Spiders: Four of more pairs of jointed legs
Not insects or true spiders
Possess a mouth and proboscis for feeding
Mainly feed on sea anemones and hydrozoans (they are voracious predators!)
More common in cold waters, but can be found worldwide

15. Sea spiders

16. Class Insecta Insects: Very few marine insects exist
Many insects feed in the intertidal zone at low tide, but these are just temporary visitors

17. Phylum Chordata Characteristics:
Notochord – flexible support rod between nerve cord and gut
Tubular nerve cord
Muscular pharynx (gut)
Gill slits
Post-Anal Tail
Ventral heart
Note: no backbone. In vertebrates, notochord is surrounded or replaced by the vertebral column.

18. Invertebrate Chordates Tunicates – Subphylum Urochordata, Class Ascidiacea
Characteristics:
Commonly called “sea squirts” because most filter feed via an incurrent siphon and “squirt” water out an excurrent siphon after the water has been filtered (Exception: Predatory tunicate)
Larvae has chordate characteristics that are not seen in adults- only pharynx remains
Called tunicates because of thick outer covering called a tunic
Larvae are free swimming after fertilization occurs in open water- mass reproduction - see Fig. 7.51
Adults normally live attached to boats, docks, reefs, or other hard substrate
All 3000 known species are marine

19. Tunicates A A B
Figure 7.51 A. Clavelina picta, colonial ascidian. B. tadpole larva of ascidians exhibits all the distinguishing characteristics of chordates.

20. B A
Figure 7.52 A. Cliona intestinalis, shallow water sea squirt. B. Adult tunicate