1 Unit 6.1 Phylum Mollusca

2 Mollusks 50, ,000 living species 35,000 extinct species Largest = 1000 pounds 80% less than 5 cm Soft body Most have a shell Most marine Snails terrestrial –Most habitat

Phylum Mollusca Ventral Foot –Locomotion Mantle –Encloses body cavity Shell – created by mantle Coelom (eucoelomate) Visceral mass contains contains organs of digestion, circulation, excretion, & reproduction 3

Phylum Mollusca Radula – rows of posteriorly oriented teeth. Basically a tongue with teeth Open circulatory system –Closed in cephalopods Mantle cavity – opens to the outside and functions in gas exchange 4

5 Economically Important Pearls Burrowing shipworms Snails & slugs –Garden pests –Food –Intermediate hosts for parasites

6 Trochophore Larva Same type as Phylum Annelida Shows phylogenetic relationship to higher taxa

7 MyxozoaMyxozoa ArthropodaArthropoda AnnelidaAnnelida MolluscaMollusca LophophoresLophophores HemichordataHemichordata VertebrataVertebrata OtherpseudocoelomatesOtherpseudocoelomates NematodaNematoda PoriferaPorifera CtenophoraCtenophora CnidariaCnidaria PlacozoaPlacozoa PlatyhelminthesPlatyhelminthes NemerteaNemertea CiliophoraCiliophora SarcomastigophoraSarcomastigophora MicrosporaMicrospora ApicomplexaApicomplexa MesozoaMesozoa EchinodermataEchinodermata CrustaceaCrustacea ChelicerataChelicerata UniramiaUniramia Other Chordata

8 Generalized Mollusk

9 Body Plan Mantle cavity CtenidiumCtenidium Pericardial cavity MetanephridiumMetanephridium RadulaRadula GonadGonad Stomach and digestive gland FootFoot

10 Dorsal mantle covers the visceral mass.

11 Secretes the shell

12 Ctenidium (Respiration)

13 Complete digestive system

14 Paired ventral nerve cords

15 Radula

16 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Source: From A Life of Invertebrates, Copyright © 1979 W. D. Russell-Hunter. Radular Structure

17 Coelom - metanephridia

18 Class Polyplacophora Chitons

19 Class Polyplacophora Eight dorsal plates Fishy flavor & tough to chew Reduced head Radula reinforced with iron –Scrape algae from rocks

20 Class Polyplacophora Mantle cavity MouthMouth CtenidiumCtenidium FootFoot AnusAnus

21 Class Polyplacophora MouthMouth DigestiveglandDigestivegland StomachStomachGonadGonad Pericardial cavity NephridiumNephridium AnusAnus

22 Class Bivalvia Clams, Oysters, Mussels, & Scallops

23 Class Bivalvia Two shells actually form as a single structure Most are filter feeders – helpful in removing bacteria from polluted waters No head or radula Burrowing animals –Sand, wood, rocks

24

25

26 Giant Clam & Burrowing Clam Muscular Foot

27 Zebra Mussel Environmental Pest Ballast water of ships from Europe in 1986 Attach by secreting adhesive byssal threads –Each other –Other mussels –Man made objects Pipes, plumbing

28 Zebra Mussel Live in high densities Feed on phytoplankton Reproduce rapidly Attach to native mussels Killed all native mussels in Lake Erie

29 Distribution of Zebra Mussel

30 Bivalve structures IncurrentsiphonIncurrentsiphon CtenidiumCtenidium ExcurrentsiphonExcurrentsiphon HingeHinge FootFoot Labial palp

31 Clam anatomy Pericardial cavity HeartHeart GonadGonadIntestineIntestine StomachStomach IncurrentIncurrent ExcurrentExcurrent IntestineIntestine MetanephridiumMetanephridium

32 Clam anatomy GonadGonadIntestineIntestine StomachStomach IncurrentIncurrent ExcurrentExcurrent DigestiveglandDigestivegland

33 Clam anatomy Pericardial cavity HeartHeart IncurrentIncurrent ExcurrentExcurrent IntestineIntestine

34 Clam anatomy Pericardial cavity HeartHeart GonadGonad IncurrentIncurrent ExcurrentExcurrent IntestineIntestine MetanephridiumMetanephridium

Oysters 35 Able to form pearls – the color depends on prevalent minerals in water Only eat oysters during cold months – less bacteria in filtrate Can cause severe wounds and Vibrio infections Use extreme caution when exiting boats in oyster infested waters

Vibrio vulnificus 36

37 Pearl formation Developing pearl EpitheliumEpithelium ShellShell An irritant, usually sand, becomes lodged between the shell and mantle. Layers of shell are then secreted by the mantle around the foreign material. The mineral content of the water determines the color of the resulting pearl.

38 Scallops Good swimmers – the only migratory bivalve Movement achieved by rapidly opening and closing shell Mostly free-living Highly regular and geometrically symmetrical shells

39 Shipworms Highly reduced shells. Known as termites of the sea. Burrow into any submerged wooden structure including ships, docks, & piers. Special gland called Deshayes gland contains bacteria that allow shipworms to digest cellulose

Shipworms 40

41 Class Gastropoda Snails, Slugs, Conchs, Abalones, & Limpets

42 Class Gastropoda One shell (if present) Torsion of body – allows head to retract before tail, allows clean water to enter mantle cavity, and orients sensory organs in direction of forward movement. Largest & most varied molluscan class

Torsion 43

Snails Terrestrial is most encountered type but marine varieties are much more numerous. Mantle cavity functions as lung in terrestrial snails. Herbivores, omnivores, and carnivores. All land snails are hermaphrodites. 44

45 Snails Tentacle (Eye stalks) TentacleTentacle PneumostomePneumostome AnusAnus FootFoot MouthMouth Genital pore ShellShell

46 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Internal Structure of a Generalized Gastropod

Nudibranchs No shell – commonly called sea slugs Dorsal projections aid in respiration and protection – they eat hydroid cnidarians, conserve the nematocysts, and move them to the dorsal projections 47

Nudibranchs Some of the most colorful creatures on earth. Unlike most other gastropods, they are bilaterally symmetrical. One species of nudibranch is the only animal that can photosynthesize. However, it must also eat to satisfy all of its energy needs. 48

Nudibranchs 49

Abalones Several holes in top of shell –Excrete waste –Used for respiration Shell is incredibly strong. It is made of microscopic calcium carbonate tiles stacked like bricks. Live primarily on cooler waters. 50

Abalones Source of food and decoration – the inner part of the shell is highly iridescent and used for mother-of- pearl inlays. Cling to rocks in subtidal zone and feed on primarily red algae. 51

52 Slugs No shell Garden pests Bodies are prone to desiccation – confined to moist environments Secrete mucous to help prevent desiccation and to protect themselves against predation.

Limpets 53 Gastropods with conical shaped shells Attach to rocks or other hard substrates in intertidal zones. Contain gills and lungs to survive in intertidal zone. May be eaten in certain parts of the world.

54 Conchs Large shell with highly spiraled character All species are marine Conchs are found in the Indian & Pacific oceans as well as in the Caribbean sea. Their meat is used as food and their shells are highly prized as decorations.

55 Class Cephalopoda Squids, Octopi, Nautiluses

Class Cephalopoda Shell in squid and octopus absent or vestigial. Present in nautilus. Movement via jet propulsion Ink sac used for defense Foot modified into arms and tentacles All marine and predatory. 56

57 Squid Dorsal Ventral Posterior surface Right Left

Squid Have 8 arms and two tentacles. Siphon allows jet propulsion in both directions along the axis of the animal. Swimming fins located on either side of the mantle. Giant axon is the largest neuron in the animal kingdom 58

59 Squid FinFin ArmArm Funnel (siphon) EyeEye TentacleTentacle CollarCollar

60 Squid Shell (Pen) CtenidiumCtenidium FunnelFunnel SystemicheartSystemicheart Branchial heart

61 Squid Male TestisTestis Hectocotylous arm PenisPenis

62 Squid Female Ovary with eggs Nidamental glands Oviducal gland Oviducal opening

63 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cephalopod Eye

Octopus Eight arms with suckers Crawl or eject water from siphon Change skin color –chromatophores Most intelligent invertebrate 64

Chromatophores 65

66 Nautilus Up to 94 tentacles –No suckers Shell with many chambers – lives in outermost chamber. Considered to be a living fossil. Can alter the amount of gasses in shell chambers thus controlling its position in the water column.

Nautilus 67

68 Class Scaphopoda Tooth shells Shell opens on both ends Burrow into mud No gills –Mantle for gas exchange Feed on detritus and protozoa

69 Class Scaphopoda

70 The End