BIO 2135 Lecture Notes - Lecture 9: Ink Sac, Ovotestis, Pneumostome
8 Feb 2017
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Prevent being top heavy by compacting the shell. Original will pull the middle in first, but really wants to protect the head first. Pull in head and tail first then the middle. Torsion causes the anal opening on the head. Sometimes you do slightly to the right or left. In young larval stages it is a way for protection. For adults, they use the ctenidium to sense water. Torsion puts the sensory structures at the front. Also, when water comes in, may have grains of sand that can clog the ctenidium. Only class that is actually asymmetric despite being pretty symmetric outside. Because of coiling, there is not much space. Used to have two ctenidium, but then during coiling only one works. Can lower and raise floor of mantle cavity. Now the pneumostome is slightly to the side. So air, gametic, excretory are all at the front. Next to food ducts, albumin gland, like a yolk gland.
