MOLLUSCA: Diversity II (Mollusca study images; |
a) primitively were rasping grazers of epibenthos, but feeding modes are remarkably diverse & often reflected in radular form: simple rasping, shredding, piercing, drilling, harpooning; some even filter feed!
b) have a single, usually coiled shell; the body form is adapted for an epibenthic mode of life
c) have a large, creeping foot; a horny operculum functions like protective trap door (in marine snails & some sea slugs))
- Prosobranchia (marine snails) large shell, anterior mantle cavity, 1 or 2 ctenidia- some unipectinate, operculum, separate sexes
- Opisthobranchia (sea slugs) shell & mantle cavity reduced or absent; ctenidia & operculum absent in most; hermaphroditic
- Pulmonata (land snails & slugs) shell present or absent; mantle cavity is a lung; ctenidia & operculum absent in all; hermaphroditic; ancestor was likely marine, not freshwater
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Copyright © 2002 by A. Richard Palmer. All rights reserved.
(revised Mar. 6, 2002)