Exploring the Diversity of Mollusks and Arthropods in Marine Biology

1. Chapter 7- Part 2 Marine Biology

2. Phylum Mollusca Mollusks

3. Greatest # of species • Body covered by mantle made of calcium carbonate • Bilateral symmetry • Foot used for locomotion • Radula used to feed

4. Gastropods: • Snails • Mostly eat algae from rocks- ex. Periwinkles

5. Continued…… • Some snails such as mud snails are deposit feeders

6. Continued……. • Snails such as whelks can be carnivorous preying on clams, worms, or small fish

7. Continued…… • Sea slugs are snails without shells. Often have noxious chemicals or nematocysts for protection

8. Bivalves: • Clams, mussels, oysters • Body enclosed in shell • Gills filter food and used for breathing • Mantle lines the inside of shell

9. Continued…… • Clams use foot to burrow in sand- water enters and leaves shell through siphon

10. Continued……. • Mussels attach themselves by using byssal threads

11. Continued…… • Oysters cement their left shell to a hard surface- often other oysters • Pearl oysters are the source of most valuable pearls.

13. How a pearl is made: • Particles merge in between mantle cavity and shell • Oyster secretes shiny layers of calcium carbonate to coat irritating particle

14. Oysters can be forced to make pearls by inserting an irritant in shell (cultured pearl)

15. Cephalopods: • Octopus, squid, cuttlefish • Good swimmer • Complex nervous system • No shell

16. Arms with suckers to capture prey • Eyes on side of head • Move by forcing water out of their siphon, or funnel

17. Octopus • 8 arms (2 in to 9 ft in size) • bottom dwellers • Efficient hunters- crabs, lobsters, and shrimp • Radula scrapes away flesh

18. Some are toxic and their bite can paralyze • Live in crevices and even discarded bottles • Distract predators by spraying ink

22. Squid • Better adapted for swimming • Ten arms • Two of the arms are longer and wider for catching prey • Sizes range up to 66ft in the giant squid

25. Cuttlefish • Similar to squid except the body is flattened

26. Biology of Mollusks

27. Digestion: • Separate mouth and anus • Radula can be modified from scraping or drilling through flesh • Amount and strength of digestive enzymes range depending on matter being digested

28. Circulatory system: • Most mollusks have a open circulatory system- blood flows out of vessels into open space • Cephalopods have a closed circulatory system-blood always remains in vessels

29. Nervous System: • Most mollusks have a ganglia • Cephalopods have a more advanced brain, similar to humans • Intelligent and remarkable learners- some cuttlefish can even change colors

30. Reproduction: • Usually separate sexes • Some hermaphrodites • In bivalves and some snails-external fertilization • Cephalopods and most snails- internal fertilization

31. Cephalopods do not have larvae- young born from and egg. Mother usually dies after egg hatches due to lack of food while guarding egg.

32. Phylum Arthropoda Arthropods

33. Barnacles, shrimp, lobster, crab, etc. • Segmented • Bilateral symmetry • Jointed appendages • Exoskeleton

34. Molt to grow-old skeleton discarded, animal takes in water to expand itself, grows a new skeleton

35. Crustaceans: • Called the insects of the sea • Gills • Appendages used to swim, crawl, feed, and mate • Two pair of antennae (sensory organs)

36. Small Crustaceans • Copepods- planktonic, some parasitic

37. Barnacles-filter feeders; live attached to surfaces

38. Beach hoppers (amphipods)-tail and head curve down, strong jumpers

39. Isopods- marine version of a roly-poly

40. Krill- shrimp-like, filter feeders, main food source for many whales, penguins, and fish

41. Large Crustaceans • Decapods- shrimp, lobster, crab (10 legs) • Commercial importance • 5 pair of walking legs • First pair larger for obtaining food and in defense

42. Shrimps typically scavengers • Lobsters tend to be nocturnal (hide during day)- scavenge and catch prey • Crabs are scavengers as well • Female crab-U shaped abdomen for carrying eggs • Male- V shaped abdomen

43. Digestion: • Small teeth or ridges are found in stomach for grinding • Digestive glands help digest and absorb nutrients

44. Nervous System: • Small brain • Compound eyes- In decapods at the end of stalks • Body posture used for communication: mating, disputes, hunting, etc.

45. Reproduction: • Mostly separate sexes • Males directly penetrate females to reproduce • Reproduction in decapods takes place directly after molting • Can store sperm

46. Phylum Echinodermata: Echinoderms

47. Sea stars, sea urchins, sea cucumbers, etc. • Larvae –bilateral symmetry • Adults-radial symmetry • Lack a head

48. Oral surface/aboral surface • Water vascular system • Tube feet and ampullae’s are part of this system • Madreporite connects internal to the external

49. *Sea Stars • Tube feet (with suckers) found in ambulacral groove • Pedicellariae help keep surface clean • Eat bivalves, snails, barnacles, etc.

50. *Brittle Star • Long arms • Tube feet lack suckers-feeding • Organic matter, small animals