1. Crabs, Lobsters, Shrimp, Barnacles, Horseshoe Crabs and More!
Arthropods
Crabs, Lobsters, Shrimp, Barnacles, Horseshoe Crabs and More!

2. Arthropod Characteristics
Phylum: Arthropoda (Arthro = jointed, Pod = foot)
Invertebrate with an external skeleton, jointed appendages, and a segmented body
Over 80% of all animal species are Arthropods!
Estimate: 1,000,000 spp. arthropods ,190,000 spp. animals
~ 84% of all animal species are arthropods

3. Arthropod Characteristics
The arthropod body plan consists of repeated segments, each with a pair of appendages
Open circulatory system
External Skeleton (exoskeleton)
Skeleton does not grow with them, so they must molt

4. Open Circulatory System
Blood is not contained in vessels
All the organs are constantly bathed in hemolymph, a combination of blood and lymph
Blood is drawn in to the heart through holes called ostia, then pumped out again to circulate through the tissues and return again to the heart.

5. Molting
Exoskeleton cannot grow, so they replace their exoskeletons by molting, or shedding the old exoskeleton after growing a new one that is not yet hardened.
Molting Time Lapse

6. Secretion of "molting fluid" to dissolve old endocuticle.
Molting (Step 1)
Secretion of "molting fluid" to dissolve old endocuticle.

7. Molting (Step 2) New cuticle formed under old exocuticle.
Break out of old cuticle
Old cuticle breaks at line of weakness

8. Molting (Step 3)
Inflate with water/air to increase size while skeleton soft,
but soft skeleton & gravity limit size;
Hardening of new exocuticle.
Vulnerable until new skeleton hardens

9. 1 2 3 4

11. Growth Stages Arthropod passes thru 3-20+ growth stages in life cycle.
Some stop molting as adults (insects, most spiders)
Some continue to molt (crayfish, tarantulas)

12. Reproduction in marine arthropods
Sexes are typically separate
Some species are hermaphroditic (barnacles)
Internal fertilization: males have specialized appendages to transfer sperm to females

13. Chelicerates (arachnids)
Crustaceans
Marine Arthropods

14. Chelicerata (Arachnids)
Includes spiders, mites, scorpions, ticks and horseshoe crabs—4 pairs of legs (8 legs total)

15. cHELICERATA
Sea Scorpion
(extinct)
Sea Spider

16. Horseshoe crabs Horseshoe Crab Facts
Common off of the Atlantic and Gulf coasts
Large dorsal carapace bearing compound eyes
Abdomen terminates in a long tail called the telson; used to turn the animal right side up
Possess a series of gill plates called book gills
Horseshoe Crab Facts

17. Crustaceans
Includes lobsters, crabs, crayfish, barnacles, and shrimp Most are aquatic 5 pairs of walking legs

18. Copepods (Small Crustaceans)
The smallest & most abundant crustacean
Marine zooplankton
Elongated antennae
Filter feeding mouth

19. barnacles
Usually live attached to a surface, including crabs and whales
Surrounded by thick calcium plates
Lie on their backs and use feathery appendages called cirri (attached to legs) to filter feed

20. Barnacles and Whales Symbiotic Relationship
Barnacles get a place to live, protection from predators, and feed on plankton as the whale swims
Whales are typically not bothered, and the barnacle “suit of armor” often protects them

21. decapods 5 pairs of legs (10 total), first pair are claws
Lobsters, Crabs, Shrimp
Largest groups of crustaceans (and very delicious!)

22. Japanese spider crab Largest crustacean in the world!
Up to 12 feet wide from claw to claw

23. Mantis Shrimp Highly advanced eyes
Modified claws to pack a deadly punch!
True Facts about the Mantis Shrimp

24. Deep Sea Shrimp
Spews a Bioluminescent Mucus Cloud!

25. How do you know this is a crab and not a spider?
Arrow Crab
How do you know this is a crab and not a spider?
Fiddler Crab
Fiddler Crab Waving

26. Crayfish dissection
External Anatomy (Start at 4:00)
Internal Anatomy