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phylum annelida

Adapted from Lesser Known Protostome Phyla. SICB 2001. J.R. Garey. . . Possess trochophore larvae. Mollusca and Annelida are closely allied phyla . Phylum Annelida: 12,500 spp: 3 classes = Class Polychaeta (8000 spp)Class Clitellata; subclass Oligochaeta (3500 spp)subclass Hirudinea (630 spp).

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phylum annelida

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    2. This cladogram is adapted from one presented by J.R. Garey at a special symposium on the Lesser Known Protostome Phyla held at the 2001 meetings of the Society for Integrative and Comparative Biology held in Chicago January 2001.This cladogram is adapted from one presented by J.R. Garey at a special symposium on the Lesser Known Protostome Phyla held at the 2001 meetings of the Society for Integrative and Comparative Biology held in Chicago January 2001.

    4. Annelid characteristics Trochophore larvae Closed circulatory system True coelom Annuli refer to segmented, metameric body plan Each segment has metanephridia, branches of nerves and blood vessels, chitinous setae / chaetae Segments partially divided by septa ? efficient hydrostatic skeleton ? Pre-adapted for regional specialization and tagmatization

    5. Metamerism

    7. Polychaeta Mostly marine Errant and sedentary spp Possess parapodia:

    8. Cephalization

    9. Tube worms: The sedentary polychaetes

    10. Giant tube worms Discovered in 1977 Ocean floor 8000 ft deep 4 ft tall No mouth. Get food from endosymbiotic bacteria that feed on sulphur released at deep sea vents

    11. Polychaete reproduction Separate sexes 1. Conventional sexual reproduction: Sperm + egg released into water ? trochophore larva 2. Epitoky: Epitokous individual forms an epitoke by a. Transformation of posterior portion b. Asexual budding Mature indiv = atoke Gamete-bearing part = epitoke capable of swimming about in search of mates (timed w lunar cycle)

    12. Class Clitellata Possess cylindrical ring used in reproduction Formation of a cocoon for the embryos Permanent gonads Two subclasses: 1. Oligochaeta 2. Hirudinea

    13. Oligochaeta Mostly fossorial, some aquatic little cephalization No specialized organs for gas exchange Feed on detritus, organic debris Hermaphroditic Sperm exchanged between two mating individuals

    15. Eggs and sperm from other worm released into forming cocoon Many terrestrial forms can be parthenogenic

    16. Hirudinea Occur in freshwater or moist terrestrial habitats Highly streamlined No special organs for gas exchange, sensory except ocelli Have 2 suckers for feeding, locomotion 3-toothed jaws Ectoparasitic, but many are predaceous or scavenge

    17. Leech reproduction Reproduction similar to oligochaetes (use of clitellum to form cocoons)

    18. Class(?) Echiura: spoon worms Have trochophore larva but lack segments or any indication of metamerism as adults Briefly segmented period as embryos Molecular data links Echiura to Annelida Reproduction similar to polychaeta

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