Today we finished our discussion on gastropods, by describing the diversity and defining anatomical characters of the opistobranchs (mainly the presence of rhinophores, cerata or gill plumes, complete detorsion, and reduction or loss of shell, ctenidia, and mantle cavity).
We then turned our attention to pulmonates, gastropods that have colonized terrestrial and freshwater environments, mainly through the loss of ctenidia and gills, and the development of a highly vascularized mantle cavity which acts as if it were a lung (hence the name 'pulmonates'). Some have also lost the shell.
We started the discussion of the class Bivalvia, the group comprising oysters, scallops, clams, and mussels. We discussed their general body plan and did overview of their life cycle, including a special mention of the modified veliger state of Unionoidea: The parasitic glochidium larva.
We mentioned that we will divide the Bivalvia into the traditional groupings of Protobranchia and Lamellibranchia (with no current taxonomic validity), and explained how the lamellibranchs can use their gills to filter food.
(entry in progress)
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