1. 6. Arthropods: Armored Achievers Crabs, Lobster, Shrimp, Barnacles

2. Arthropods Largest phylum (3/4 of all species on earth)
Insects – largest group
Majority of marine arthropods are crustaceans (subphlyum Crustacea)
Flexible, segmented, bilateral symmetry
Jointed appendages moved by sets of attached muscles

3. Arthropods exhibit bilateral symmetry and a chitinous exoskeleton
Arthropods exhibit bilateral symmetry and a chitinous exoskeleton. Provides support, protection, and increased surface area for muscle attachment.
To grow they must molt the exoskeleton and absorb water to expand
before the new exoskeleton hardens.

4. Arthropods: Subphylum Crustacea
Most marine with gills for gas exchange
Appendages specialized for swimming, crawling, attaching to other animals, mating, and feeding
Two pairs of antennae involved in sensing surrounding.

5. Arthropods: Subphylum Crustacea
Small Crustaceans
Copepods (cope-a-pod)
Planktonic, use mouthparts to filter feed, some may swim, many are parasitic
Barnacles
Filter feeders that usually live attached to surfaces, even living organisms
Cirri (sear-I) (feathery legs) sweep water for food
Crustacean larvae that swim and attach before metamorphosing into adults

6. Barnacles

7. Arthropods: Subphylum Crustacea
Small Crustaceans
Amphipods
Curved, flattened bodies (sideways)
Beach hopers, common in shore debris, seaweed, burrowing in whales, or planktonic
Isopods
Parasitic fish lice that are dorsoventrally flattened
Marine pill bug

8. Amphipods and Isopods Orchestoidea, a beach hopper
are often found on marine
mammals.
Sea louse: a marine pill bug

9. Arthropods: Subphylum Crustacea
Small Crustaceans
Euphausiids (yoo-fa-ze-id) (Krill)
Planktonic, shrimp-like, filter feeders
Common in polar waters in giant schools
Most exclusive food source for whales, penguins and fish

10. Arthropods: Subphylum Crustacea
Shrimps, Lobsters, and Crabs
Decapods (10 legs)
Largest in size, great commercial importance
5 pairs of legs w/ first pair being claws used for feeding and defense
Well developed carapace encloses cephalothorax
Rest of body called abdomen

11. Arthropods: Subphylum Crustacea
Shrimps and Lobsters
Laterally compressed
Shrimp - scavengers feeding on detritus
Some may remove parasites from skin of fish
Lobsters – Marine scavengers and predators that crush molluscs and sea urchins
Hermit crabs – not true crabs that hide soft body in empty shells

13. Arthropods: Subphylum Crustacea
Crabs
Abdomen small and tucked under large cephalothorax
V shaped abdomen = male
U shaped abdomen = female
Highly mobile and walk sideways

14. Arthropods: Subphylum Crustacea
Crabs
Scavengers/predators
Some have specialized diets of seaweeds, organic matter, or coral mucus
Live along rocky shores or sandy beaches
Land crabs live most of life on land but may return to ocean to release eggs

15. Biology of Crustaceans
Feeding and Digestion
Filter feeding common among small crustaceans
Bristles on some appendages used to gather food
Other appendages move food from bristles to mouth
Some may use appendages to pierce or suck (parasitic)
Bristles sift, chitinous teeth in stomach grinds

16. Biology of Crustaceans
Feeding and Digestion
Decapods have 2 chambered stomach connected to digestive gland that secretes enzymes and absorbs nutrients (extracellular)
Intestine ends in an anus
Open circulatory system distributes nutrients

17. Biology of Crustaceans
Nervous System and Behavior
Small, simple brains but well-developed sensory organs
Compound eyes
Keen sense of smell (chemical sensitivity)
Have statocysts for balance
Most behaviorally complex of all invertebrates
Have special body posture and movement of legs and antennae
Helps settle disputes between neighbors and courtship

18. Biology of Crustaceans
Reproduction and Life History
Separate sexes in most crustaceans
Males use specialized appendages to transfer sperm directly to female
Decapods - takes place after molting and females can store sperm to use on different batch of eggs
Most have planktonic larvae type and number of larval stages vary widely

20. Other Marine Arthropods
Horseshoe Crabs (class Merostomata)
Only surviving members
Widely represented by fossil records
5 living species and not true crabs
Live on soft bottoms of shallow waters on Atlantic and Gulf coasts of North America and Southeast Asia
Emerge on beaches to reproduce

21. Other Marine Arthropods
Sea Spiders (class Pycnogonida) Pic – no – ga- ni- da
Superficially resemble spiders
Four or more pairs of legs
Large proboscis with mouth at tip used to feed on soft invertebrates such as sea anemones and hydrozoans
More common in cold water but do not occur throughout oceans

23. Other Marine Arthropods
Insects (class Insecta)
3 pairs of legs as adults
Rare in the sea
Live at waters edge scavenging for seaweeds, barnacles, and rocks
Inhabit decaying seaweed that accumulates at high tide