Advantages of a coelom

1. CH 30 - More Invertebrates

2. Advantages of a coelom What are the advantages of the coelom? 2

3. Differentiated according to three major events in embryological development 1 Cleavage Spiral cleavage in protostomes Radial cleavage in deuterostomes 2 Fate of blastopore Mouth appears near blastopore in protostomes Anus appears near blastopore in deuterstomes 3 Coelom Formation Schizocoelom forms in protostomes Enterocoelom forms in deuterstomes Protostomes vs. deuterostomes

4. Protostomes Deuterostomes molluscs annelids arthropods echinoderms chordates 8-cell stage 8-cell stage top view side view top view side view cleavage mouth mouth anus blastopore blastopore primitive gut primitive gut anus fate of blastopore mesoderm schizocoelom enterocoelom mesoderm gut gut Coelom forms by a splitting of the mesoderm. Coelom forms by an out- pocketing of primitive gut. coelom formation

5. cleavage Protostomes Deuterostomes

6. molluscs annelids arthropods echinoderms chordates cleavage Protostomes Deuterostomes

7. molluscs annelids arthropods echinoderms chordates cleavage Protostomes Deuterostomes 8-cell stage 8-cell stage top view side view top view side view

8. fate of blastopore

9. mouth blastopore primitive gut anus fate of blastopore

10. mouth mouth anus blastopore blastopore primitive gut primitive gut anus fate of blastopore

11. coelom formation

12. mesoderm coelom formation

13. mesoderm schizocoelom gut coelom formation Coelom forms by a splitting of the mesoderm.

14. mesoderm schizocoelom mesoderm gut coelom formation Coelom forms by a splitting of the mesoderm.

15. mesoderm enterocoelom schizocoelom mesoderm gut gut coelom formation Coelom forms by a splitting of the mesoderm. Coelom forms by an out- pocketing of primitive gut.

16. Mollusks (phylum Mollusca) What animals do you think are in the phylum mollusca? Bivalves Clams, oysters, mussels, and scallops Cephalopds Octopodes, squid, chambered nautilus, cuttlefish Gastropods Land snails, nudibranchs, slugs, other weird stuff Mollusks

17. Mollusks Mollusks (phylum Mollusca) Have three-part body plan Visceral Mass Contains internal organs Mantle May secrete shell and/or contribute to development of gills or lungs Foot Muscle adapted for locomotion, attachment, or food capture 17

18. Body Plan of Mollusks

19. Mollusks (cont.) Nervous system consists of several ganglia connected by nerve cords Coelom is reduced, and largely limited to the region around the heart Heart pumps hemolymph through vessels into hemocoel Mollusks

20. The name "bivalve" is derived from the Latin bis, meaning "two", and valvae, meaning "leaves of a door". Clams, oysters, mussels, and scallops Bivalves

21. Bivalves Shell of two hinged parts, closed by powerful muscles No head, no radula Circulatory system open Sexes are separate Respiratory system - Ciliated gills hang down within mantle cavity on either side of visceral mass Beating of cilia causes water to enter cavity Filter Feeders – capture tiny food particles suspended in water 21

22. Bivalve Diversity

23. Cephalopods

24. Head Footed Force water out mantle cavity Tentacles and arms capture prey by adhesive secretions or suckers Beak used to tear prey apart Well-developed sense organs Closed circulatory system Spermatophore packets passed from males to females Cephalopods

25. Cephalopod Diversity Cephalopods are smart! Cephalopods are cool! Cephalopods are cool again!

26. Gastropods

27. Snails Terrestrial Marine (conchs) Limpets Slugs Terrestrial – Banana Slug Marine (nudibranchs) #2 Gastropods

28. Have elongated, flattened foot Well-developed head region Eyes and tentacles project from coiled shell Gills are found in mantle cavity in aquatic gastropods Mantle functions as lung in terrestrial gastropods Marine gastropods – mostly sexual Terrestrial gastropods – mostly hermaphrodites Gastropods

29. Gastropod Diversity

30. Gastropod Anatomy

31. Annelids

32. Phylum Annelida are Segmented partitions (septa) divide the well-developed, fluid-filled coelom, which acts as hydrostatic skeleton Specialized digestive tract Closed circulatory system Ventral solid nerve cord Most are marine Setae (bristles) help in movement Annelids

33. Do not have well-developed head or parapodia Setae protrude in pairs directly from surface of body Food drawn into mouth by action of muscular pharynx Digestion and absorption occur in long internal intestine Typhlosole increases surface for absorption Earthworms

34. Earthworm, Lumbricus terrestris

35. Segmentaion evidenced by: Body rings Coelom divided by septa Setae on most segments Gangli and lateral nerves in each segment Nephridia in most segments Branch blood vessels in each segment Earthworms

36. Reproduction Hermaphroditic Two worms lie in parallel to each other facing in opposite directions Fused midbody segment (clitellum) secretes mucus, protecting sperm from dessication Earthworms

37. Usually found in fresh water Same body plan as other annelids No setae Two additional suckers Some parasitic Why would leeches actually be useful in modern medicine? Keep blood flowing and prevent clotting by means of hirudin, a powerful anticoagulant Leeches

38. Medicinal Leeches, Hirudo medicinalis

39. Polychaete Diversity

40. Polychaete Diversity • Polychaeta or polychaetes • class of annelid worms, generally marine. • Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles • Sometimes referred to as bristle worms. • More than 10,000 species are described in this class. • Occur throughout the Earth's oceans at all depths • Only 2% of all polychaetes are from freshwaters.

41. Annelids & Molluscs

42. Arthropods (phylum Arthropoda) have freely movable jointed appendages Very successful due to many characteristics Rigid, jointed exoskeleton Must molt as they grow Segmented, but some segments are fused into regions Head, thorax, abdomen Well-developed nervous system Arthropods

43. Arthropod Skeleton and Eye

44. Variety of respiratory organs Occurrence of metamorphosis Three major arthropod subphyla Crustaceans Crayfish Uniramians Centipedes Chelicerates Spiders Arthropods

45. Crustacean Diversity

46. Decapods are the most familiar and numerous of crustaceans Shrimp, lobsters, crayfish, and crabs Thorax bears five pairs of walking legs Head and thorax fused into cephalothorax Covered by nonsegmented carapace Abdominal segments equipped with swimmerets Respiratory system consists of gills Crustaceans

47. Male crayfish, Cambarus

48. Include insects, millipedes, and centipedes Appendages attached to the thorax and abdomen only have one branch Head appendages include: Only one pair of antennae One pair of mandibles, and One or two pairs of maxillae Live on land and breathe by tracheae Uniramians

49. Insect Diversity

50. Two Types of Insect Mouthparts