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functions of different animal coeloms

functions of different animal coeloms. simple circulatory system increase in body size possible (follows from 1) storage area for organs, separates organs from gut independent growth of organs possible (e.g. coelomic space allows storage of gametes, seasonal reproduction enhanced)

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functions of different animal coeloms

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  1. functions of different animal coeloms • simple circulatory system • increase in body size possible (follows from 1) • storage area for organs, separates organs from gut • independent growth of organs possible (e.g. coelomic space allows storage of gametes, seasonal reproduction enhanced) • allows for developmental/physiological coordination via circulating hormones • hydrostatic skeleton - burrowing! • also allows for “eversible” mechanisms, such as annelid proboscis, and hence diverse feeding methods can evolve

  2. one recent Metazoan phylogeny (molecular data) (“worms” in red) NEMERTEA MOLLUSCA BRACHIOPODA BRYOZOA PHORONIDA ANNELIDA ECHIURA POGONOPHORA SIPUNCULA CHAETOGNATHA PLATYHELMINTHES from: Ruiz-Trillo et al. (1999) Science283: 1919.

  3. WHY WORM? body form adapted to crevices burrowing front and back specializations sensory information gathered in head region ("cephalization") coupled with regeneration, offers potential reproductive (budding) and survival advantages high surface area/volume ratio streamlined movement through environment (water, etc...)

  4. the parchment worm Chaetopterus variopedatus the sand worm Nereis vexillosa photo by Erling Svensen www.uwphoto.no http://www.lanecc.edu/science /Estuary/sandworm.htm Class Polychaeta THE THREE GROUPS OF ANNELIDS (the segmented worms) the earthworm Lumbricus terrestris leech (Erpobdella?) Class Clitellata http://www.swgc.mun.ca/ biology/envs1000/chaines/ http://www.scibridge.sdsu.edu/ coursemats/introsci/diversity/leeches.jpg Subclass Oligochaeta Subclass Hirudinoidea

  5. KEY ANNELID FEATURES segmentation, with segments clearly separated by septa complex circulatory, excretory, sensory systems live in a vast range of habitats, with a staggering diversity of lifestyles, reproductive strategies, etc. characterized by bristle-like appendages called "chaetae" or "setae" (this feature has been lost in the Hirudinoidea - the leeches) typical "protostome" development; spiral cleavage; usually with trocophore larva and metamorphosis Phragmatopoma trocophore unidentified trocophore Platynereis "setiger" from Shankland & Seaver (2000) PNAS, 97:4434-7 photos by Wim van Egmond http://www.microscopy-uk.org.uk/mag/artmar99/polych.html

  6. cross-section through an idealized polychaete worm From: Pechenik(2000) Fig. 13.3 Biology of theInvertebrates

  7. circulatory system 2 vessels (dorsal forward flow, ventral rear-word flow) with an interconnected network of veins no distinct heart photo by J. Hodin

  8. metanephridia - excretion in annelids …and what’s this similar strucure? from: K. Schmidt-Nielsen Animal Physiology (1997). from: Jan A. Pechenik (2000) Fig. 13.2 Biology of the Invertebrates

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