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3454lablecture5 - Lecture 5 PHYLUM ANNELIDA Triploblastic...

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Lecture 5 PHYLUM ANNELIDA Triploblastic, coelomate (formed thru schizocoely), protostomous, bilateral, closed circulatory system Metameric segmentation – repeated segments with organs, muscles, ganglia In Polychaeta and Oligochaeta, each segment is divided by a septa and acts as an independent hydrostatic skeleton Circular muscles – get skinny, Longitudinal muscles – bulge (each segment is independent), allows for efficient burrowing and locomotion Setae – bristles that aid in locomotion and burrowing Metanephridia are kidneys (each segment passes waste to next segment) CLASS POLYCHAETA Mostly marine, highly variable, specialized head parts, many setae Parapodia act as pseudo limbs and may be precursors of true limbs, used in locomotion, feeding, and sometimes respiration CLASS OLIGOCHAETA (Earthworms) Few setae, head region not specialized, outer cuticle, many hearts Prostomium – most anterior segment Parastomium – 1 st segment with organs Hermaphroditic – but reproduce sexually No larval stage Typhlosole – structure in intestine that increases surface area (small loop in intestinal wall)
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