Transcript Gastropoda
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