Biology 3229F/G Study Guide - Final Guide: Colossal Squid, Flat Feet, Radula
9 Apr 2016
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Characteristics: parasitic or free living, unsegmented worms, triploblastic, acoelomate, bilaterally symmetrical, dorso-ventral flattened, spiral cleavage, complex gut (incomplete) absent in some diffusion for nutrients, cephalized cns. Longitudinal nerve cords connected by transverse commissures (ladder: protonephridia as excretory/osmoregulatory structures, hermaphroditic, complex reproductive systems. Some produce unusual mullers larva multiple arms. Few polyclads produce larvae: reproductive system. Complex and typically hermaphroditic: penis stylet. Some carnivorous turbellarians have penis supported by a stylet can be used as a weapon: asexual reproduction common. Fragmentation: regeneration two heads after split one. Neodermata: separate class of monogeneas, trematodes and cestodes, synapomorphy of tegument body covering. Budding at a rate of several per day. Each will mature into sexual structure: scolex. 4 sided knob suckers or hooks. No gut: behind scolex is the neck. Growth zone with stem cells: ns less well developed no eyes or complex sensory, excretory system is pair of flame cells, tapeworm is a simultaneous hermaphrodite.
