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Worms 27-1, 27-2,27-3 BIO 1004 Flatworms Soft and flattened Have tissues and internal organ systems Known as “acoelomates” – means without coelom Coelom – fluid filled body cavity Contain “flukes” which are parasitic and tapeworms Characteristics of Flatworms Carnivores/decomposers/parasites Single opening through which food and waste pass (like cnidarians) Most have NO circulatory system – rely on diffusion to move materials Have “flame cells” that help remove excess water from the body Cont. Flatworms No true brain, but a connection of ganglia cells Nerve cells Have an eyespot Most are hermaphrodites Usually two worms will deliver sperm to each other and eggs are laid and hatch a few weeks later Also can reproduce by fission Roundworms (27-2) Un-segmented with tapering ends Contain “pseudocoeloms” – false coelom Have two openings – mouth and anus No circulatory/respiration system – diffusion Sexual reproduction – internal fertilization Ex: hookworms, filarial worms,etc. Annelids (27-3) Derived from the latin word “annellus” – means little ring Body divided into segments called “septa” Segments can carry specialized features such as eyes, antennas, sense organs, etc. Have a true coelum Mouth and anus Cont. annelids Closed circulatory system Possess a crop and gizzard Aquatic annelids have gills and terrestrial annelids exchange gases through their skin Sexual reproduction Clitellum secretes a mucus in which the sperm and eggs are released into Groups of Annelids Oligochaetes – earthworms – few setae Leeches Polychaetes worms – blood worms and sand
