University:
Manchester University
Course:
BIOL 101 | General Biology
Academic year:

2023
Views:

58

Pages:

10
Author:

larbiwxcvbn

Gastropods Gastropoda • Largest and most diverse class of mollusks – Most have shells • Snails • Abalones • Conchs – Others are shell less • Slugs • nudibranchs Gastropods • The only mollusks to undergo Torsion – During development the Visceral Mass twists 180 degrees – Mantle cavity, gills, and anus are now at the front • They can withdraw their head into the mantle cavity when threatened Gastropods • They use the foot to move – Wavelike muscular contractions – Can only be seen by looking at the bottom of the foot during movement – http://www.youtube.com/watch?v=vGYbG7HchD 8&feature=related Gastropods • Have an open circulatory system – Circulatory fluid hemolymph does not remain entirely within the vessels – They form blood cavities called hemocoel – The gills and lungs are used to pump the hemolymph back to the heart from the hemocoel Snails • Land, fresh water, and the ocean • Eyes at the end of the tentacles to locate food • Can retreat into their shell for protection – From predators – Or the elements Snails • Water dwelling snails use gills to respire • Land dwellers use modified lungs – The membrane lining the mantle cavity must be kept moist in order to allow diffusion of the gasses – Snails are more active in moist conditions – They can survive dry spells by coiling back into the shell, and secreting a mucous plug Slugs • Look like snails without shells • Breath in the same manner • Must avoid drying out Nudibranchs • Marine gastropods that lack shells – “naked gill” – The entire body surface acts as a gill for gas exchange – Many extensions to the body help with gas exchange Cone • Use powerful venom to capture prey – Worms – Mollusks – Small fish • The venom is injected through the harpoon like radula – http://www.youtube.com/watch? v=OK3NiK9Pu5Q