1. Mollusks and Annelids Chapter 45
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2. Body cavity lined with mesoderm cells
Coelomates
Coelomate
Body cavity lined with mesoderm cells
Allows the development of complex tissues and organs.
Allows wider array of body architectures and increased body size.
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3. Characterized by a coelom. Great economic significance Pearls
Coelomates
Mollusks (Mollusca)
Extremely diverse.
Characterized by a coelom.
Great economic significance
Pearls
Mother of Pearl
Economic / Environmental Costs
Zebra Mussel Invasion
Intermediate hosts for parasites.
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4. Body Plan of the Mollusks
Distinct bilateral symmetry.
Digestive, excretory, and reproductive organs all concentrated in a visceral mass and a muscular foot.
May have differentiated head.
Folds constituting a mantle.
Gills - Increased surface area for gas exchange.
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5. Body Plan of the Mollusks
Shells serve primarily for protection.
Radula - Rasping tongue-like organ used for feeding.
Circulatory system (except cephalopods) consists of a heart and an open circulatory system.
Nitrogenous wasted removed by nephridia.
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6. Body Plan of the Mollusks
Reproduction in Mollusks
Most have distinct male and female individuals.
Most engage in external fertilization.
Many have free-swimming larvae (trochophores) which closely resemble larval stage of many marine annelids.
Veliger stage follows trochophore stage.
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7. Polyplacophora: The Chitons
Classes of Mollusks
Polyplacophora: The Chitons
Oval bodies with eight overlapping calcareous plates.
Gastropoda: Snails and Slugs
Heads of most have pair of tentacles with eyes at the ends.
Undergo torsion during embryological development.
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8. Bivalvia: The Bivalves Clams, scallops, mussels and oysters.
Classes of Mollusks
Bivalvia: The Bivalves
Clams, scallops, mussels and oysters.
Have two lateral shells hinged together dorsally.
Mantle secretes shell and ligaments.
Most are sessile filter-feeders.
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9. Cephalopoda: Octopuses, Squids, Nautilus
Classes of Mollusks
Cephalopoda: Octopuses, Squids, Nautilus
Most intelligent of the invertebrates.
Active marine predators.
Foot evolved into a series of tentacles equipped with structures to capture prey.
Highly developed nervous systems.
Closed circulatory system
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10. Building of body from series of similar segments.
Segmented Animals
Building of body from series of similar segments.
Small change in existing segment can produce new kind of segment with different function.
Phylum Annelida
Three characteristics:
Repeated Segments
Specialized Segments
Connections
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11. Segmented Animals Body Plan of the Annelid Tube within a tube.
Internal digestive tract within the coelom.
Specialized for different functions.
Hydrostatic skeleton for locomotion.
Each segment typically possesses setae, that help anchor during locomotion.
Most have closed circulatory system.
Nephridia collect and transport wastes.
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12. Classes of Annelids Polychaeta: The Polychaetes
Well developed head with specialized sense organs.
Parapodia on most segments.
Usually lack permanent gonads.
Oligochaeta: The Earthworms
Hermaphroditic
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13. Hirudinea: The Leeches Occur mostly in fresh water. Hermaphroditic
Classes of Annelids
Hirudinea: The Leeches
Occur mostly in fresh water.
Hermaphroditic
Develop clitellum during breeding season.
Unable to self-fertilize.
Secrete anticoagulant into wounds.
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14. Polychaeta: The Polychaetes
Classes of Annelids
Polychaeta: The Polychaetes
Well developed head with specialized sense organs.
Parapodia on most segments.
Usually lack permanent gonads.
Oligochaeta: The Earthworms
Hermaphroditic
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15. Lophophorates Phylum Phoronida: The Phoronids
Lophophore - Circular or U-shaped ridge around the mouth bearing one or two rows of ciliated, hollow tentacles.
Functions as surface for gas exchange and as food-collection organs.
Use cilia to capture food.
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16. Phylum Ectoprocta: The Bryozoans
Lophophorates
Phylum Ectoprocta: The Bryozoans
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17. Phylum Brachiopoda: The Brachiopods
Lophophorates
Phylum Brachiopoda: The Brachiopods
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