Mollusca: Class Gastropoda (continued)

Question 1

Phylogeny

Answer 1

Patellogastropoda – true limpets
Vetigastropoda – shell perforations
Caenogastropoda – marine gastropods with shell
Heterobranchia – opisthobranchs & pulmonates. Terrestrial or reduction of shell
Heterobranchia & Caenogastropoda are sister groups

Question 2

Gastropoda traits (3)

Answer 2

Shell as a protective retreat
Torsion
Pronounced development of head

Question 3

Feeding Diversification

Answer 3

The primitive feeding method is herbivorous grazing using a radula
Vetigastropoda are mostly herbivorous grazers
Caenogastropoda have many herbivorous grazers, as well as predators and scavengers with proboscis

Question 4

Moon snails

Answer 4

Have an accessory boring organ
The organ is on the end of the proboscis
Secretes a calcium key alter to dissolve the shell
Mechanical action via radula as well
Bores a hole into bivalve shell

Question 5

Cone Snail

Answer 5

Predatory
Has harpoon-like radula that are filled with conotoxins
Buccal tube elongated to extend down length of proboscis
Radula at base of proboscis
Venom gland is an extension of the esophageal gland

Question 6

Marine Heterobranchia Defenses (4)

Answer 6

Chemical defense
Escape behaviour
Sequester nematocysts from cnidarian prey
Autotomy

Question 7

Terrestrial Heterobranchia Adaptations (3)

Answer 7

Mantle cavity forms internalized lung with pneumostome to exterior

Conversion of ammonia to uric acid

Aestivation – response to hot/dry conditions
Metabolic slow down, tolerance of desiccation and ability to rapidly rehydrate