1. Shelby Lynch, Gillian Johnstone Anik Obomsawin, Chantalle Byron
Gastropoda
Shelby Lynch, Gillian Johnstone
Anik Obomsawin, Chantalle Byron

2. Introduction Snails and Slugs
Class consisting of around ~ species
~ ocean living
~ land on living
~5 000 fresh water living
Herbivores, carnivores (ex. Moon snail) and scavengers

3. 4 defining characteristic
Developed head – tentacles
Foot used for motion
Coiled shell
Asymmetrical organism
*organs twisted in figure 8
*coils to right or left
*torsion in larval stage

4. Characteristics

5. Developed head
Tentacles
Pigment eyes
Central nervous system

6. Torsion & Development During Veliger stage
180o turn and upward twist of the posterior- reposition it over the head
Anus, mantle cavity, and gills above head

7. Specialized Shell Asymmetric helical coiling Helps with protection
Sealed off with operculum

8. Specialized Respiration
thin skin permeable for water- breathe through skin
originally breathe by gills situated in the pallial cavity

9. Specialized Respiration
Loss of gills, and developed a vascularised lung from the mantle cavity
Varied gill arrangement and respiration method

10. Life Cycle

11. Life Cycle Mating Fertilization Development Hermaphroditic species
Trochophore Larval Stage
Veliger Larval Stage

12. Evolution Basic Trends: Changes in radula and shell morphology
Loss of organs
Changes in diet (herbivorous to carnivorous)
Changes in habitat (seawater – freshwater – terrestrial life)
Adoption of slug-like form
*changes occurred independently, at several times in gastropod history

13. evolution PROSOBRANCH
Diotocardia: this species has two sets of mantle organs; most similar to generalised gastropod structure
Trochacea & Neritacea: gradual loss of set of mantle organs on the right side of the body occur
Monotocardia: only has one set of mantle organs; has fewer radula teeth; shift in diet, from algae and fungi to consumption of larger sessile organisms.
Neogastropoda: peak of prosobranch evolution; marine predators with modified radular teeth, poison glands to aid catching prey, and reduction and loss of right mantle organs, more efficient respiration.

14. Evolution OPISTHOBRANCH
Arose from an unknown primitive prosobranch group
Show reduction of visceral hump and shell
In some forms: an external cerata develops to provides a respiratory surface
This replaces lost mantle-cavity surface and ctenidia

15. Evolution
PULMONATES
Varying degrees of adjustments to freshwater and landlife
Union of male and female gonoducts (more prevalent in advanced groups)
More sophisticated means of water consumption
Some pulmonates are predators of snails or earthworms

16. Facts On average they have a speed of 8cm per minute
Radula- ribbon of teeth helping with food consumption
Can store digested food in its liver for use during inactive times
Warning coloration (bright shells) is present in carnivore snails which produce poisons when catching prey
Range from 600mm to 0.5mm in size

17. Sources
J. Mollus. Stud. (1988) 54 (4): doi:  /mollus/
bstract
sca/gastropoda.php
777/gastropod/35728/Evolution-and-paleontology

18. SOURCES
Solem , G. A. (2012, April 17). gastropod. Retrieved from opod/35728/Evolution-and-paleontology
(n.d.). Retrieved from
Nordsieck, R. (n.d.). Retrieved from a/morphology/respiration.html
Myers, P., & Burch, J. B. (n.d.). Retrieved from da/
(n.d.). Retrieved from da/Pulmonates.html