7. Platyhelminthes, Nemertia, Pseudocoelomates

7. Platyhelminthes, Nemertia, Pseudocoelomates - 1 Phylum...

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Unformatted text preview: 1 Phylum Platyhelminthes Platyhelminthes flatworms - Free living or Parasitic Ectoparasitic - Outside Endoparasitic - Inside Triploblastic Triploblastic Organ Grade Organ Grade Bilateral Bilateral Symmetry Cephalized Acoelomate Acoelomate Organ Grade Flame cell No circulatory system Protostomes Spiralian Development Locomotion : Muscles- circular and longitudinal Dorsoventral - keep flat but not used in locomotion Cilia - glide across surfaces ciliated outer body Observe this in the lab with the live flatworms and in the slide material Do they use both at the same time? When is one more impt. than the other type? Nervous system conc. Anteriorly - has a brain = cerebral ganglia Nerve cords (2), commisures connect cords across body Sensory structures: Light Chemical stimuli Touch Will see sectioned material in lab Look at nervous system, brain, eyes, other receptors Digestive system Mouth - mid body Pharynx Pharynx- muscular Blind gut (= not complete) 2 Excretory system- Flame cell = Protonephridia Discrete excretory/ osmoregulatory structures Be sure to see these in lab - understand how they work! They are believed to be the evolutionary precursor to most other excretory and osmoregulatory systems in animals Reproductive System : Hermaphroditic - simultaneous Internal fertilization - hypodermic Complex reproductive systems Asexual fission very good at regeneration NEOBLASTS mesenchyme, totipotent Reproductive systems vary in Reproductive systems vary in Turbellaria Turbellaria - some with female ducts, some some with female ducts, some without, some with with single penis, some with pairs, some without, some with with single penis, some with pairs, some mutually copulate, some do not mutually copulate, some do not See video on penis fencing See video on penis fencing - Shape of Life Shape of Life - The first hunters The first hunters http://www. http://www. pbs pbs .org/ .org/ kcet kcet /shapeoflife shapeoflife /episodes/hunt_ /episodes/hunt_ explo2 explo2 .html .html Link on BB Link on BB Details of repro. system define some suborders of Turbellaria Acoel flatworms traditionally thought to be primitive Turbellaria Some recent work suggests they may not be flatworms - Jury still out - can read about this Herv et al. 2007 PLoS ONE pdf posted on BB Parasitic Flatworms Parasitic Flatworms Show many adaptations seen in all parasite groups Show many adaptations seen in all parasite groups What traits would you expect to be important What traits would you expect to be important for a parasitic lifestyle? for a parasitic lifestyle? Ectoparasitic Ectoparasitic ? Endoparasitic Endoparasitic ? Simple life history? Simple life history? Complex life history? Complex life history? 3 General Internal Parasite Adaptations Adhesive organs- hooks, suckers Not gut- absorbs through body wall Tegument - Neodermis (syncytial) Large reproductive capacity Reduced sense organs Complex life cycle Mobile larvae Induce behavioral changes in host increase trans....
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7. Platyhelminthes, Nemertia, Pseudocoelomates - 1 Phylum...

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