ZOO 115 Invertebrate Zoology Phylum Platyhelminthes Classes n

ZOO 115 Invertebrate Zoology Phylum Platyhelminthes

Classes n Turbellaria n n Mongenetic flukes - parasitic Trematoda n n Free-living flatworms Flukes- parasitic Cestoda n Tapeworms- parasitic

Phylum Platyhelminthes /gecko. gc. maricopa. edu/~lsola/bio 182/labreview/ www. pbs. org/kcet/shapeoflife/imganim/ © David Luquet Ed T. Schmidtmann, USDA/ARS. /gecko. gc. maricopa. edu/~lsola/bio 182/labreview/ www. islandream. com/wakatobi/flatworm 02. jpg /gecko. gc. maricopa. edu/~lsola/bio 182/labreview/

Phylum Platyhelminthes n n About 20, 000 sp. Substrate crawlers in both marine and freshwater Mostly small and soft-bodied Lack a circulatory system n n Diffusion limited Controversy about phylogeny

Platyhelminthes Class Turbellaria n n Virtually all are aquatic with most being marine Most are bottom dwellers but there are some pelagic forms www. seafriends. org. nz/enviro/habitat/f 017217 t. jpg

Body n Outer-layer is a ciliated epidermis n Skeleton – weblike sheet of actin filaments n Secrete Rhabdites n Thought to be important in locomotion, cocoon development and predator repellant

Body zoology. unh. edu/faculty/litvaitis/Flatworms/muscles. jpg Gland cells n n Mesenchyme – Hydraulic action on larger organisms Parenchyma – connective tissue compartment between body wall, musculature and gut. n n Neoblasts - wound repair and regeneration Chromatophores may be present and under control by brain. Gland cells zoology. unh. edu/faculty/litvaitis/Flatworms/muscles. jpg

Nervous system Bilaterial or Ring like brain Nerve net Longitudinal nerves

Nervous system - sensory Chemoreceptors over entire body Cilia mechanoreceptors Ocelli Some have statocysts in the head region

Musculature Also have diagonal muscles – not shown Longitudinal muscles Dorsoventral muscles Circular muscles zoology. unh. edu/faculty/litvaitis/Flatworms/muscles. jpg

How do they move? n n n Ciliary creeping Muscular creeping Swimming Peristalsis Twisting, turning, extension and retraction Somersaulting

Complete Bilateral gut Gut zoology. unh. edu/faculty/litvaitis/Flatworms/muscles. jpg www. emc. maricopa. edu/faculty/farabee/BIOBK/flatworm. gif

Feeding and digestion nn Food Most Sense Proteolytic are prey carnivores enzymes using chemreceptors and are scavengers injected into and n Gland cells in gut supply additional swallowed mechanoreceptors prey and pharynx is used to pump n Some Aoela have zooxanthellae enzymes. liquified pharynx contents. n by Capture prey n Digestive cells phagocytize remainder n or Gut types themselves around prey n Wrapping Acoela – syncytial mass nn Entangling it in slime enclosed by membrane Pinning prey with adhesive glands Simplehave unbranched sac nn Some toxicwww. emc. maricopa. edu/faculty/farabee/BIOBK/flatworm. gif mucus Multiple lateral nn Some use penisbranches n

Excretion www. lifesci. utexas. edu/faculty/sjasper/images/protonephridia. jpg

Reproduction n n Regeneration Clonal Reproduction – longitudinal fission

Reproduction n Sexual Reproduction n Most hermaphrodites Most copulation and internal fertilization Male n n 1 or more pairs of testis Ducts, storage area Penis – may have stylet Female n n I or more pairs of ovaries Copulatory bursa (vagina), seminal receptacle, uterus

Reproduction n Development n n Some freshwater species produce summer and winter eggs Usually egg->blastula->gastrula->juvenile>adult n n n Marine polyclads produce planktonic larvae Generation time: 16 -75 days Life span: 65 -140 days

Platyhelminthes – Dueling Penises Wounds Penis