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GASTROPODA
Shelby Lynch, Gillian Johnstone
Anik Obomsawin, Chantalle Byron
• Snails and Slugs
INTRODUCTION
• Class consisting of around ~65 000 species
• ~30 000 ocean living
• ~30 000 land on living
• ~5 000 fresh water living
• Herbivores, carnivores (ex. Moon snail) and
scavengers
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
CHARACTERISTICS
• Tentacles
• Pigment eyes
• Central nervous system
DEVELOPED HEAD
• During Veliger stage
TORSION &
DEVELOPMENT
• 180o turn and upward twist of the posterior- reposition it
over the head
• Anus, mantle cavity, and gills above head
SPECIALIZED SHELL
• Asymmetric helical coiling
• Helps with protection
• Sealed off with operculum
SPECIALIZED
RESPIRATION
• thin skin permeable for water- breathe through skin
• originally breathe by gills situated in the pallial cavity
SPECIALIZED
RESPIRATION
• Loss of gills, and developed a vascularised lung from the
mantle cavity
• Varied gill arrangement and respiration method
LIFE CYCLE
LIFE CYCLE
• Mating
• Hermaphroditic species
• Fertilization
• Development
• Trochophore Larval Stage
• Veliger Larval Stage
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
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.
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
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
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
SOURCES
• J. Mollus. Stud. (1988) 54 (4):367441.doi: 10.1093/mollus/54.4.367
http://mollus.oxfordjournals.org/content/54/4/367.a
bstract
• http://www.ucmp.berkeley.edu/taxa/inverts/mollu
sca/gastropoda.php
• http://www.britannica.com/EBchecked/topic/226
777/gastropod/35728/Evolution-and-paleontology
• http://www.nhc.ed.ac.uk/index.php?page=24.25.
312.328.352
SOURCES
• Solem , G. A. (2012, April 17). gastropod. Retrieved from
http://www.britannica.com/EBchecked/topic/226777/gastr
opod/35728/Evolution-and-paleontology
• (n.d.). Retrieved from
http://www.ento.csiro.au/education/allies/gastropoda.html
• Nordsieck, R. (n.d.). Retrieved from
http://www.molluscs.at/gastropoda/index.html?/gastropod
a/morphology/respiration.html
• Myers, P., & Burch, J. B. (n.d.). Retrieved from
http://animaldiversity.ummz.umich.edu/accounts/Gastropo
da/
• (n.d.). Retrieved from
http://shells.tricity.wsu.edu/ArcherdShellCollection/Gastropo
da/Pulmonates.html