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Coelomates: Mollusks and Annelids

Coelomates: Mollusks and Annelids. Coelomates (Eucoelomates). Have body cavity Peritoneum present: from mesoderm. Phylum Mollusca (mollusks). Large: 110,000 described species (#2 behind arthropods!) Bilateral symmetry, _____________ Body usually has calcareous shell, muscular foot, head.

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Coelomates: Mollusks and Annelids

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  1. Coelomates: Mollusks and Annelids

  2. Coelomates (Eucoelomates) • Have body cavity • Peritoneum present: from mesoderm

  3. Phylum Mollusca (mollusks) • Large: 110,000 described species (#2 behind arthropods!) • Bilateral symmetry, _____________ • Body usually has calcareous shell, muscular foot, head.

  4. Phylum Mollusca (mollusks) • Mantle: fold of tissue that wraps around body. • Secretes shell • Gills are specialized mantle portion to extract oxygen from water • Organs: stomach, heart, gills, etc.

  5. Phylum Mollusca (mollusks) • Often have radula in mouth • Usually ____________ Radula

  6. Phylum Mollusca (mollusks) • Circulatory system open. Heart 3 chambers (2 collect blood from gills, one pumps to body) • Coelom is cavity around heart.

  7. Phylum Mollusca (mollusks) • Excretory system: ____________ gather nitrogenous wastes from coelom, discharge them into mantle cavity. Can reabsorb valuable solutes so they aren’t lost

  8. Phylum Mollusca (mollusks) • Class Bivalvia (bivalves) • Class Gastropoda (gastropods) • Class Polyplacophora (chitons) • Class Cephalopoda (cephalopods)

  9. Class Bivalvia (bivalves) • Body contained between 2 hinged shells (valves) • Foot hatchet-like, modified for burrowing in sand/mud • Little cephalization: no head, no ___________

  10. Class Bivalvia (bivalves) • Adductor muscles (2 in most bivalves) close _____________ • Cilia on gills pull water into and out of shell through siphons. Brings oxygen, food particles

  11. Class Bivalvia (bivalves) • Importance: • 1) biodiversity • Ex, freshwater mussels. Many Alabama species endangered, some extinct • Used to be harvested to make buttons from shells

  12. Class Bivalvia (bivalves) • Importance: • Larvae parasitic on host fish gills or fins as glochidia • How get fish to come close to receive glochidia?

  13. Class Bivalvia (bivalves) • Importance: • Lure them in! • Mantle of female mussel mimics fish.

  14. Class Bivalvia (bivalves) • Importance: • 2) pollution monitors • Aquatic filter feeders (mussels) process large quantities of water during feeding • Concentrate metals, pesticides, PCBs. • Sample tissues periodically to detect pollution • California Mussel Watch Program, National Mussel Watch Program.

  15. Class Bivalvia (bivalves) • Importance: • 3) human food (clams, oysters, scallops, mussels) oysters clams mussels

  16. Class Bivalvia (bivalves) • Importance: • 3) human food (clams, oysters, scallops, mussels) Scallops have one large (edible) adductor muscle

  17. Class Bivalvia (bivalves) • Importance: • 4) jewelry (pearls)

  18. Class Bivalvia (bivalves) • Importance: • 5) invasive species. Ex, zebra mussel from Caspian Sea • Colonies encrust exposed surfaces (mussels are filter feeders) • Can kill freshwater clams (wiped them out in Lake Erie)

  19. Class Bivalvia (bivalves) • Importance: • 5) invasive species. • Cleaning water intake pipes will cost $3.1 billion over next 10 yr.

  20. Class Polyplacophora (chitons) • Small group: 600 species • Marine, rocky intertidal zone • Graze algae from rocks • Have 8 overlapping valves • Cling to rocks with foot. Gumboot chiton: largest in world

  21. Class Gastropoda (snails/slugs/limpets) • Single shell present (usually coiled in snails) or lacking (slugs) • Foot flattened, modified for crawling • Head with eyes, tentacles • Radula modified as _________ (many herbivores, some predators)

  22. Rare snails • Land snails diverse group • On islands, have radiated into many species • Ex, Partulid snails from S. Pacific.

  23. Rare snails • 120 species in family Partulidae • Moorea, small S. Pacific island.

  24. Rare snails • Moorea had 7 species of Partulid snails found nowhere else on Earth.

  25. Rare snails • Problem: Giant African snail introduced to island • Damaged agriculture.

  26. Rare snails • Solution (new Problem): Introduce predatory Euglandina snail • Wasn’t supposed to invade areas containing Partulid snails and eat them • But it did.

  27. Rare snails • By 1987 all Partulid snails on Moorea were extinct in wild • But 6 of 7 species are being maintained in captivity by several zoos.

  28. Rare snails • Ex, white abalone • Marine snail, coast S. California. lives on submerged rocks, eats algae. Has large foot which is delicious. Shells of red abalone

  29. Rare snails • Ex, white abalone • Fishery developed in 1970s, when populations were 1,000-5,000/acre • Quickly overharvested them • Now <1 abalone/acre left (maybe 1,600 total) • Listed endangered 2001

  30. Rare snails • Ex, white abalone • Problem: Don’t move about much. Depend on water to mix sperm and eggs. Males/females must be about 3 feet apart for fertilization to occur! • Density now too low for reproduction in wild • Captive breeding program underway. Female releasing eggs (can make 3 million!

  31. Other uses of snail shells • Seashell collectors This rare specimen is for sale: $7,000

  32. Other uses of snail shells • Shell money: early form of currency (before coins) S. Pacific shell money Sumerian shell ring money: Syria 3000BC

  33. Class Gastropoda (snails/slugs) • Nudibranchs (naked gills) • ____________. Some can eat cnidarians and transfer nematocysts to their gills to defend them from enemies!

  34. Class Cephalopoda • Foot divided into arms/tentacles • Squids: 10 tentacles. Octopuses and cuttlefish: 8. Nautiluses: 80-90. • Tentacles with suckers

  35. Class Cephalopoda (octopuses, squids, nautilus) • Have ______________ • Have extreme cephalization • Shell absent (octopus, squid), internal (cuttlefish: cuttlebone), or present (nautilus) • Swim by taking water into mantle cavity and expelling it through siphon (jet propulsion)

  36. Class Cephalopoda • Excellent vision • Intelligent • Have both long-term and short-term memory • Ex, one aquarium octopus helps clean its aquarium by handing debris to staff Common octopus

  37. Class Cephalopoda • Deadly (Octopussy) • Blue-ringed octopus: bite deadly due to tetrodotoxin (neurotoxin) • No known antidote • Fashionable pet in Thailand.

  38. Phylum Annelida (segmented worms) • 11,000 species (2/3 marine) • Bilaterial symmetry, triploblastic • Protostomes • Eucoelomates: Coelom fluid-filled and pressurized. Provides hydrostatic skeleton

  39. Phylum Annelida (segmented worms) • Note circular and longitudinal muscles • Cephalization, complete digestive tract

  40. Phylum Annelida (segmented worms) • Closed circulation system (arteries, veins, capillaries). Note dorsal and ventral blood vessels. Dorsal moves blood to head, ventral toward tail. Multiple ____________.

  41. Phylum Annelida (segmented worms) • Excretory system: metanephridia • Bristles (setae) on body. Sensory or aid in locomotion

  42. Phylum Annelida (segmented worms) • Monoecious. Gonads: where sperms and eggs made • Worms mate by passing sperm to each other Mating Earthworms

  43. Phylum Annelida (segmented worms) • Clitellum located near reproductive organs • Clitellum secretes ___________. • Sheath collects eggs/sperm as it slides off worm to form cocoon • Young worms develop in cocoon. Earthworm cocoons and head of pin

  44. Phylum Annelida (segmented worms) • Segmented body: Key characteristic. Body series of compartments with similar systems in each • Advantages • 1) Allows adjacent segments to operate independently, give precise control of body movement (expand and contract segments) • 2) System redundancy: if one segment injured, others contain muscles, nerves, excretory, circulatory systems that can continue to function.

  45. Class Oligochaeta (earthworms) • Most familiar group • Few setae, head poorly developed • Cuticle outside epidermis • Detritivores: Feed on organic matter in soil. Castings rich in minerals. • Burrowing causes soil aeration • Flooding rains can drown them Large Australian earthworm

  46. Class Polychaeta (polychaetes) • Marine. Most species in this class. Important members of marine ecosystems. • Parapodia (paddle-like appendages) present with setae on them • Head well-developed. Usually dioecious, ____________ external

  47. Class Polychaeta (polychaetes) • Examples in lab: plume worm, clam worm Clam worm Plume worm (lives in tube) Filters water for food with tentacles

  48. Class Hirudinea (leeches) • 1 or 2 suckers present: anterior (head end) and posterior (tail end) • No setae or _______________ • No septa between segments (superficial segmentation: not segmented within body)

  49. Class Hirudinea (leeches) • Parasites or predators. Mostly freshwater. • Parasites: Asian ones terrestrial (tropics). Detect heat and vibrations • Others aquatic.

  50. Class Hirudinea (leeches) • Parasites: have anticoagulant (so blood doesn’t clot) and anesthetic (so leech not noticed) in saliva • Medical use: can relieve inflammation and swelling better than medication

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