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    Phylum Mollusca

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    rakingbulugbe194
    Phylum Mollusca is highly diverse with over 80,000 species found in both marine and freshwater environments. They have soft, unsegmented bodies and include snails, clams, squids, and octopuses. Key characteristics include a mantle cavity containing gills and other organs, a radula used for feeding, and a life cycle involving a trochophore larva and often a veliger larva. The phylum contains 6 classes - Aplacophora, Monoplacophora, Polyplacophora, Bivalvia, Gastropoda, and Cephalopoda. Molluscs have economic importance as food sources, sources of pearls and shells,

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    Phylum Mollusca

    Uploaded by

    rakingbulugbe194
    51 views12 pages
    Phylum Mollusca is highly diverse with over 80,000 species found in both marine and freshwater environments. They have soft, unsegmented bodies and include snails, clams, squids, and octopuses. Key characteristics include a mantle cavity containing gills and other organs, a radula used for feeding, and a life cycle involving a trochophore larva and often a veliger larva. The phylum contains 6 classes - Aplacophora, Monoplacophora, Polyplacophora, Bivalvia, Gastropoda, and Cephalopoda. Molluscs have economic importance as food sources, sources of pearls and shells,

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    Phylum Mollusca is highly diverse with over 80,000 species found in both marine and freshwater environments. They have soft, unsegmented bodies and include snails, clams, squids, and octopuses. Key characteristics include a mantle cavity containing gills and other organs, a radula used for feeding, and a life cycle involving a trochophore larva and often a veliger larva. The phylum contains 6 classes - Aplacophora, Monoplacophora, Polyplacophora, Bivalvia, Gastropoda, and Cephalopoda. Molluscs have economic importance as food sources, sources of pearls and shells,

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    © All Rights Reserved
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    Download as pptx, pdf, or txt
    51 views12 pages

    Phylum Mollusca

    Uploaded by

    rakingbulugbe194
    Phylum Mollusca is highly diverse with over 80,000 species found in both marine and freshwater environments. They have soft, unsegmented bodies and include snails, clams, squids, and octopuses. Key characteristics include a mantle cavity containing gills and other organs, a radula used for feeding, and a life cycle involving a trochophore larva and often a veliger larva. The phylum contains 6 classes - Aplacophora, Monoplacophora, Polyplacophora, Bivalvia, Gastropoda, and Cephalopoda. Molluscs have economic importance as food sources, sources of pearls and shells,

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    Phylum : Molusca

    K. O. K. Popoola
    Introduction
    • The name ”Mollusc” is from Latin word
    meaning soft body
    • They are the largest phylum with 80,000
    sps living and 15 fossil sps
    • Highly diverse with wide varieties like ;
    snails, calms. Squids and octopus
    • Biologically successful; found in fresh
    water, sea and land
    • They of high economic values; food,
    defoliators vectors, jewellery and currency
    Characteristics features of Mollusca
    • Triploblastic,

    • bilaterally symetrical,

    . non-metamerically symetrical
    coelomates
    Characteristics features cntd’
    • Body consist of Head, foot, visceral mass and
    shell
    Characteristics features cntd’
    • The mantle cavity consists of : 2 gills or
    ctenidia, the hypobranchial gland,
    anus, the kidney opening and oesphradium

    (is an olfactory organ in certain molluscs, it


    is a chemoreceptor)
    • Buccal cavity with unique radula, a toothed
    belt used for feeding
    • Coelom reduced to cavity of gonad, kidney
    and perivisceral
    Biology of Mollusca
    • Circulatory system: Made up of heart and blood vessels
    with 2 auricles and 1 ventricles
    • Excretory system: molluscs, have slightly-more-evolved
    excretory structures called nephridia. They are tubular or
    branched structures in contact with the internal body .
    • Nervous system: Circum-pharyngeal ring
    Buccal ganglia
    Cerebral ganglia
    Pleural ganglia
    Pedal ganglia
    Parietal ganglia
    Visceral ganglia
    Biology of Mollusca contd’
    • Lococmotion; it is highly diverse and it is by;
    Gliding, jumping using foot muscles wave
    contraction

    Gliding Jumping

    Swimming in
    Sea angel
    • Swimming in cephalopod through jet proportions
    • Use of lateral fins by cuttlefish
    • Reproduction : They undergo sexual
    reproduction (simple or complex)
    - Fertilized egg gave Trochophore larva and
    developed to give veliger lavar
    - The two larvae forms are typical of Mollusca

    Apical tuft (cilia

    Prototroch (cilia)

    Mouth
    Metatroch (cilia)
    Mesoderm
    Anus
    Veliger larva
    Trochophore larva
    • Feeding: Use radula to scrape
    rocks at sea to collect microscopic
    algae and diatoms
    • Scrapped particles are molded
    together using mucus and
    send to stomach
    • In stomach partial digestion
    occurs, which is extracellular
    • Intracellular digestion occurs in
    Digestive Diverticular
    Tubules (DDT) Radula in Snail
    Clasification
    • The phylum Mollusca consists of 6 classes:
    (i) Class Aplacophora (“bearing no plates”) worm-like
    (ii) Class Monoplacophora (“bearing one plate”)
    primarily, benthic marine habitats.
    (iii) Class Polyplacophora (“bearing many plates”) are
    commonly known as “chitons”
    (iv) Class Bivalvia is a class of marine and freshwater
    (v) Class Gastropoda (“stomach foot”) E,g snails, slugs,
    nudibranchi and pteropod
    (vi) Class Cephalopoda (“head foot” animals) E.g
    octopus, squids, cuttlefish, and nautilus.
    Economic Importance of Mollusca
    • As food to both man and animals
    • For pearls and native currencies
    • Index of aquatic pollution
    • Toxic and can cause food
    poisoning
    • Sting is fatal and some are
    venomous
    Thank you

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