BIS 2C Lecture Notes - Lecture 29: Nephridium, Gastrulation, Circulatory System
16 Mar 2018
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Characteristic features lies in lophotrochozoans (group of protostomes) Schizocoely (the body cavity is formed from blocks. Trochophore larva (free-swimming larva; band of of mesoderm around the gut that enlarge and hollow out) cilia; synapomorphy of lophotrochozoans) Reduced coelom (vestiges around the heart, gonads, and some other organs) Open circulatory system (hemocoel) with heart (3 chambered) and associated vessels. Closed circulatory system evolved in some subgroups. Body plan: mantle visceral mass and foot. Mouth with radula: rasping tongue-like organ for feeding (breaks up food) Well developed nervous system (especially in cephalopods) Body plan large ventral muscle mass (modified ventral body wall) Modified for burrowing in bivalves, and as. Mantle dorsal body wall: fold of tissue that covers the visceral mass and encloses the arms/ tentacles and siphon in cephalopods mantle cavity (containing gills) Shell (when present) is secreted by the mantle. Body proper, with digestive, circulatory, excretory, and reproductive organs. Gastropods: torsion (anus occurs above the mouth)
