Mollusks and Annelids. Chapter 23+

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1 Mollusks and Annelids Chapter 23+ 1

2 Annelids and Mollusks Coelomates Trochophore larvae Bilateral symmetry More complex organ systems 2

3 Moving On Up 3

4 Coelom Coelomates Evolutionary milestone True body cavity Forms within mesoderm Internal body organs cushioned by fluids in cavity 4

5 Trochophore Larva Larval stage Most Mollusks and Annelids Suggests related? Develops from fertilized egg Ciliated In some species free-swimming 5

6 The Mollusks Second largest animal phylum Widespread More species of terrestrial mollusks than all terrestrial vertebrates 7 classes 6

7 Mollusk Characteristics Body cavity True coelom Small area around heart Bilateral symmetry Three part body plan Foot Muscular Locomotion Visceral mass Contains organs Mantle Fold of tissue Outer layer of body Cape-like 7

8 Characteristics- Continued More organ systems Excretion, circulation, respiration, digestion, and reproduction Shell Many mollusks One or two Protein + CaCO 3 Protection Radula All, except bivalves Tongue-like Rasping Feeding 8

9 Mollusk Classification Domain = Eukarya Kingdom = Animalia Phylum = Molluska Three major classes: Gastropoda Bivalvia Cephalopoda Nemo Mollusk joke 1:15 9

10 Mollusks Only coelomates w/out segmented body 10

11 Mollusk Digestion Complete digestive system One-way Two openings Varies in mollusk groups More complex than roundworms 11

12 Mollusk Excretion Removal of metabolic wastes Wastes in body fluids collect in coelom Fluid pulled into nephridia by cilia Tiny tubes Recover water, sugars, and salts 12

13 Excretion Useful molecules reabsorbed Waste fluid leaves through pore in mantle cavity All coelomates have nephridia except Arthropods Chordates 13

14 Mollusk Circulation Circulatory system! Diffusion won t work Most: 3 chambered heart Open system Blood sloshes in hemocoel Exception: Octopi and squid 14

15 Mollusk Respiration Most have gills: In mantle cavity Cilia beat and move water Gills extract >50% of dissolved O 2 15

16 Mollusk Respiration Terrestrial snails Membrane lines mantle cavity Primitive lung Must be moist Active at night and after rain Sea snails No gills Gas exchange thru skin 16

17 Mollusk Reproduction Most = distinct sexes Some snails and slugs are hermaphrodites Some sea slugs and oysters can change back and forth between sexes! 17

18 Reproduction Larval forms Many marine mollusks have trochophore Ciliated and moves Squid, octopi, and freshwater snails and some freshwater mussels No free swimming larva Larva form within egg 18

19 Just to really keep your interest! Celtic Mollusk presentation 3:30 19

20 Gastropods 20

21 Gastropods Largest mollusk class 40,000 species Snails, nudibranches, and slugs Single or no shell 21

22 Gastropoda Muscular foot - locomotion Mostly marine Size Microscopic to 1 meter Nudibranch clip - 27 sec Nudibranchs California Academy of Sciences (Low) 4 min.mp4 22

23 Gastropod Feeding Habits Some herbivores Radula Scrape algae off rocks Some are predators Radula Drill into other mollusks Ex: Cone shell Uses poison Swallow prey 23

24 Gastropods and Humans Can be pests Garden and agricultural Can be eaten Genus Helix raised on snail farms Conchs are considered delicacies 24

25 Bivalvia 25

26 Bivalves All aquatic Most marine Two hinged shells Secreted by mantle Ligaments and muscles hold shells together Adductor muscles 26

27 Bivalves Head is reduced Radula absent Most are filter feeders Most are sessile 27

28 Bivalve Nervous System Nerve ganglion Simple brain Simple sense organs Sense organs on edge of mantle Sensitive to light and touch Giant Clam 6:47 28

29 Bivalve Reproductive System Most have distinct sexes Few hermaphrodites Reproduce sexually Release gametes into water 29

30 Bivalve Reproductive System Fertilized egg develops into free swimming trochophore larva Few brooded in pouches Then complete life cycle as parasite on fish gills 30

31 Bivalve Filter Feeding Slow moving creatures Cilia on gills Create water flow Siphons Hollow tubes Inlet and outlet Gills Mucus covered Trap microorganisms Cilia move mucus to mouth 31

32 Bivalve and Humans Human food resource Oysters, clams, scallops, mussels Over 6.5 billion lbs/yr Demand increasing 32

33 Bivalve and Pearls Many bivalves produce pearls: Foreign object trapped between shell and mantle Coat irritant with sheets of nacre Mother-of pearl Like the inner layer of shell 33

34 Bivalve and Pearls Only a few species Gem-quality pearls Pearls Thin sheets of nacre Over-lapping mineral crystals Act-like prisms Makes pearls iridescent Cultured pearls 34

35 Clam Structure 35

36 Clam Structure 36

37 Cephalopods 37

38 Cephalopods Shell is reduced or absent Nautilus is the only living cephalopod with an external shell Small internal shell of cuttlefish Bird cages for calcium Active marine predators Closed circulatory system Beak-like jaws Large head Foot divided into tentacles Suckers or hooks 38

39 Shark vs Octopus showdown 39

40 Cephalopods Most advanced group of mollusks Most intelligent of all invertebrates Complex nervous system Well developed brain Eye structure similar to vertebrate eye Exhibit complex behaviors Cephalopod character 3:40 40

41 Cephalopod Movement Jet propelled Draw water into mantle cavity When threatened Close mantle cavity quickly Force water out of siphon 41

42 Cephalopod Escape Squids and octopuses Release dark fluid Clouds water Confuses predators Conceals escape route Cuttlefish ink Sepia Used by artists Many famous paintings Cephalopod Defense 2:30 42

43 Cephalopod Feeding Marine predators Eat Fish Crustaceans Worms Use: Tentacles Beak-like jaws Radula pulls in food Feeding video 2 min 43

44 Moving On Up 44

45 The Segmented Worms Phylum annelida Anellus Latin - Little rings Segmented bodies Also known as metamerism All coelomate animals except mollusks Evolutionary milestone 45

46 Body Segments Series of ring-like structures Each segment contains organs: Digestive, excretory, circulatory, muscular Some segments modified Special function: Reproduction, feeding, sensation Septa Internal body walls that separate segments 46

47 General Characteristics 1) Coelom Larger than mollusks 2) Most have bristles Setae - external bristles Parapodia - fleshy appendages 3) Organ Systems Highly specialized Closed circulatory system Nephridia Digestive system Primitive brain = cerebral ganglion 47

48 Annelid Classification Domain Eukarya Kingdom Animalia Phylum Annelida Classes: 1) Polychaeta 2) Oligochaeta 3) Hirudinea Differ in # of setae/segment Presence/absence of parapodia 48

49 Class Polychaeta Poly = many Chaeta = seta Marine worms Largest group of annelids Live in all oceans Often have setae Feather duster worm 49

50 Class Polychaeta Unusual forms and colors Pair of parapodia on most segments Swim, crawl, burrow Increase surface area Gas exchange 50

51 Class Polychaeta Tube worms Form Protective tubes Secretions and sand Ex: Feather duster Filterfeeder 51

52 Class Polychaeta Nereis Predataor Free swimming 52

53 Class Oligochaeta Oligo = few Chaeta = seta Earthworms & freshwater worms No parapodia Few setae/segment Size varies mm to 3 meters 53

54 Earthworms Lack distinct head region Specialized scavengers Eat their weight in soil each day Thousands of earthworms per acre No eyes Have light sensitive organs Hydrostatic skeleton 54

55 Earthworm Humor 55

56 Earthworm Gas Exchange No respiratory system Gas exchange through its skin Diffuses into blood capillaries Skin must be moist Covered in a watery mucus 56

57 Earthworm Digestive System Complete digestive tract One way street Mouth Pharynx Esophagus Crop Thin walled storage chamber Gizzard Muscular grinding chamber Intestine Anus Castings 57

58 Earthworm Circulatory System Closed circulatory system Blood stays in vessels Dorsal blood vessel Aortic arches (hearts) Ventral blood vessel 58

59 Earthworm Nervous System Primitive brain Cerebral ganglion Ventral nerve cord Segmental nerves 59

60 Earthworm Reproduction All hermaphrodites Two worms mate Each exchanges sperm Clitellum Enlarged band-like structure Secretes the cocoon (w/ fertilized eggs) Deposited in soil 60

61 Internal Structure 61

62 Internal Structure 62

63 Ventral Surface 63

64 Earthworm Basic Structure 64

65 Cross-Section of Earthworm 65

66 Cross-Section of Earthworm 66

67 67

68 Review Anatomy 68

69 Dissection Overview 69

70 Earthworm Dissection Pharynx Esophagus Crop Gizzard Intestine Dorsal BV Septa Mouth 70

71 Earthworm Dissection 71

72 72

73 Class Hirudinea Leeches No setae No parapodia Flattened bodies Segments not separated internally Most predators or scavengers Some are parasites 73

74 Class Hirudinea (Leeches) Suckers on both ends Used in medical field Medicinal Leaches 2:00 74

Chapter 28 Mollusks & Annelids. BIOLOGY II Miss. Loulousis

Chapter 28 Mollusks & Annelids BIOLOGY II Miss. Loulousis Mollusks have a true coelom Snails, slugs, oysters, clams, scallops, octopuses, and squids are all mollusks Annelid earthworm next section Mollusks