Annelida Phylum handout
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Transcript of Annelida Phylum handout
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Phylum AnnelidaPhylum AnnelidaThe Segmented WormsThe Segmented Worms
• Annelids are to be found in marine, freshwater, and terrestrial habitats
• The body is vermiform, bilaterally symmetrical, and segmented
• The body is triploblastic with a well developed coelom
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Classes of Annelida
• Class Polychaeta (fanworms, clam worms)• Class Oligochaeta (earthworms)• Class Hirudinea (Leeches)
• Classes not covered– Class Branchiobdellida– Class Acanthobdellida
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General Characteristics
• Each segment is separated from contiguous ones by a transverse septum
• The body is covered with a flexible non-chitinous cuticle• Respiratory gas exchange through skin, gills, or
parapodia• Most forms have chaeta, hard, bristle-like chitinous
structures• Excretory system typically consists of a pair of
metanephridia per segment
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Class - PolychaetaFeather Duster worms, Clam worms, Christmas Tree worms
• Mostly marine and free-living• Many chaeta, on fleshy lateral outgrowths of the
body wall known as parapodia• Well developed head bearing appendages• Sexes separate, with a free-swimming
trochophore larva• No clitellum
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Figure 17.03d
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Class OligochaetaEarthworms and Freshwater Worms
• Are terrestrial with a few freshwater species• Have few chaeta• No parapodia• No distinct head appendages• Clitellum present• Hermaphrodites, with copulation required• Eggs are deposited in a cocoon and development is
direct
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Earthworm Dissection
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Figure 17.12c
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Figure 17.15
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Class Hirudinea
• Ectoparasites, not all - many feed on organic debris• Usually dorso-ventrally flattened with fixed number
of body segments (34) • No chaeta or parapodia• Clitellum present only during reproduction• Reproduction similar to earth worms/direct
development• Two suckers – anterior and posterior
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Figure 17.20• Coelom reduced by invasion of connective tissue