BIS 2C Lecture Notes - Lecture 30: Clitellata, Polychaete, Clitellum
27 Apr 2018
School
Department
Course
Annelid Overview: Bilaterally Symmetrical Protostomes
Protostome with schizocoely - mesoderm splits to make coelom
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Segmented with segments marked external and internally with repeated body structures
at each segment
External rings and internal septa
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Setae hairs made of chitin to anchor annelid
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Each segment has paired appendages called parapodia that have muscles for
respiration
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Body wall has inner long and outer circular muscles
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Hydrostatic skeleton: fluid cavity surrounded by muscles
Contracting circular muscles to elongate body segment
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Contracting longitudinal muscles shortens segments
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Setae anchor the segments
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Cephalized with 3 segment head
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Closed circulatory system with cutaneous respiration (gas diffuse across cuticle)
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Complete gut/regions
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Excretory and nervous systems well developed
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Annelida Reproduction
Typically dioecious with extern fertilization and trochophore larva
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Some monecious (Clitellata) with internal fertilization and direct development
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Asexual reproduction is the cause of regeneration from body fragments
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Annelid Groups
Both marine, freshwater and terrestrial (most aquatic)
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Two groups Polychaeta (not a clade, paraphyletic) and Clitellata
Polychaeta
Marine worms such as sandworms and tubeworms
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Example: beard worms - gutless worms that live in tubes at great depths in
the seas with chemoautotrophic symbiotic bacteria
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Clitellata
Freshwater and terrestrial without parapodia and tentacles
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Clitellum: thickened band, secretes cocoon for young
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Example: oligochaetes (earthworms):
deposit feeders (ingest soil and extract nutrients then put out soil), cross
fertilizing hermaphrodites that hold together to swap perm in mucus
in clitellum
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Example: leeches
Predator/blood sucking parasites
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Lack setae with anterior and posterior suckers
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Produce painkillers and anticoagulant and a vasodilator
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Annelida (30)
Tuesday, March 6, 2018
6:05 PM
Document Summary
Protostome with schizocoely - mesoderm splits to make coelom. Segmented with segments marked external and internally with repeated body structures at each segment. Setae hairs made of chitin to anchor annelid. Each segment has paired appendages called parapodia that have muscles for respiration. Body wall has inner long and outer circular muscles. Closed circulatory system with cutaneous respiration (gas diffuse across cuticle) Typically dioecious with extern fertilization and trochophore larva. Some monecious (clitellata) with internal fertilization and direct development. Asexual reproduction is the cause of regeneration from body fragments. Two groups polychaeta (not a clade, paraphyletic) and clitellata. Example: beard worms - gutless worms that live in tubes at great depths in the seas with chemoautotrophic symbiotic bacteria. Example: oligochaetes (earthworms): deposit feeders (ingest soil and extract nutrients then put out soil), cross fertilizing hermaphrodites that hold together to swap perm in mucus in clitellum.
