phylum mollusca (lophotrochozoan)

mollusca

soft body

key characteristics

muscular foot (retract and extend), visceral mass and fold of tissue known as mantle

are gills present in mollusca

yes only aquatic ones

lungs

only in terrestrial types

radula

abrasive tounge like structure to shred food

mantle secretes

calcium carbonate hardened shell in most mollusks

dioecious

external fertilization

zygote

2 larval stages

2 larval stages

trochophore and in some the veliger larvae

cephalopods

no larvae

8 classes

likely all monophyletic

rudimentary NS

including sensory structures

class bivalves

2 shells

50% of molluscan species

in class gastropoda (snails, slugs)

torsion is a key aspect of embryonic dev of gastropods

how they retract into their shell; survival strategy

2 main classes

gastropoda, cephalopoda