SYSTEMATICS GRP 3: PHYLUM MOLLUSCA

mollusca

most common phylum in aquatic environments, with at least 50,000 living species

soft body; exoskeleton

the name mollusca refers to a ___, and their bodies are covered by a hard ___

mantle

body wall, secretes shell

visceral mass

houses body organs

radula

tongue of mollusks; shredding and scraping food

muscular foot

locomotion and anchoring

sexually; mantle

mollusks mate ___, gametes are released into the ___

internal or external

fertilization can be ___ depending on the species

larvae

fertilized eggs turn into ___

trochophore

mollusks have a distinct larval stage called ___, a ciliated free-swimming larva

Aplacophora

- body is cylindrical and bilaterally symmetrical, lacking head, shell, mantle, nephridia, foot and digestive ceca
- covered by a spicule-bearing cuticle with a dorsal longitudinal keel
- ex. neomenia, chaetoderma

Monoplacophora

- body is bilaterally symmetrical with no eyes or tentacles on the head
- respiration occurs via external fills, and nephridia excrete nitrogenous waste
- ex. neopilina

Polyplacophora

- body is dorsoventrally flattened and bilaterally symmetrical, with a shell of 8 plates and a well-developed radula
- flat ventral foot
- ex. chiton, cryptochiton

Bivalvia/Pelecypoda

- aquatic, bilaterally symmetrical body compressed laterally, lacking a distinct head
- typically burrow in mud or sand
- ex. clams, oysters, mussels

Gastropoda

- found on land, freshwater, or marine
- head with tentacles, eyes and mouth
- spiral shell
- flat, large foot
- ex. haliotis, pila

Cephalopoda

- marine, with an external, internal or absent shell
- sexes are separate, with direct development
- ex. octopi, squids, cuttlefish

Scaphopoda

- marine, bilaterally symmetrical
- lacking eyes and tentacles
- reduced foot
- ex. dentalium, dentaliidae

aculiferan phylogenetic mdel

divides mollusks into two subphyle: conchifera and titular aculifera

conchifer

"shell-bearing" mollusks

aculifera

"spiny" mollusks