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21 Cards in this Set
- Front
- Back
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3 types of molluscs |
Cephalopoda - octopus Bivalvia - mussels Gastropoda - snails |
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Bivalves |
Bilaterally symmetrical No segmentation Foot, mantle & head Muscular foot - locomotion Mantle: - enclosed mantel cavity - gills or a lung - secretes shell Metanephridia Filter feeders Marine and FW |
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Polyplacophora |
Polyplacophora - earliest and most widespread chiton: lepidochitona cinerea |
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Polyplacophora reproduction |
Gonochoristic - make and females Eggs - singly or in a string Sperm - cloud release Fertilisation external In water or in mantle cavity of female Trochophore larvae Metamorphoses into adult |
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Burrowing Bivalve |
Burrowing: Added protection Siphones - most 2 Pallial sinus - infolding of mantle allowing siphons to be drawn back in Shells laterally compressed 2 valves left and right joined at dorsal side by hinge. Muscles - pedal retractors - shell adductors Use foot to dig, requires to adductor muscles. If one large one small then surface bivalve Similar sized ones - burrower Rapid burrowers- smooth streamlined elongated Shallow burrowers - ridges spines etc Deep burrowers - very long siphons, can't fully retract |
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Byssal threads |
Strong fibres grown by a gland in the foot, protrude through and opening between the valves. Swimming or floating larvae use these to settle on the ground |
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Mantle |
Lobes - space within called the mantle cavity - partly grown together 3 openings, 2 in which water enter and leaves and then 1 for the foot. 3 fold to the mantle: Outside - calciferous cells attach CaCO3 in rings producing she'll Middle - sensory Inside - fold regulate the water flow |
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Bivalves Filter feeding Digestive system Circulatory system |
More folds increased surface area in gills Palps carry food to mouth form fills Digestive system contains structures for processing food Crystalline style, rotates via cilia in stomach to help grind food Blood oxygenation occurs across, gills, mantle and foot. |
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Bivalves shell composition (periostracum, ostracum, hypostracum) |
Main shell made of aragonite, CaCO3 crystals prism-shaped Hard but susceptible to chemical corrosion Hard layer - periostracum Shell layer below the ostracum - hydrostacum Foreign objects caught between the mantle and the shell - a pearl - hypostracum |
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Bivalve reproduction |
Gonochoristic normally, occasionally hermaphrodite External fertilisation Eggs hatch into trocophore Trocophore --> veliger larvae --> metamorphosis Some brood and some go through larval stages |
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FW mussels |
FW pearl mussel, glochidia on a trouts gills. Male produces sperm Female produces eggs Produce glochidia Mussel traps trout and glochidia lock into the gills |
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Gastropoda - single shells, reduced shells, no shells
3 types |
Prosobranchia - whelks, periwinkles, sea snails Pulmonata - terrestrial snails Opisthobranchia - nudibranchs, sea slugs |
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Torsion |
veliger larval stage after trochophore 2 phases: Quick 90 twist driven by muscles Slow 90 continuation by differential growth of right side versus left Nervous system forms figure of 8 Mantle cavity now over head Provides more space for head withdrawal Anterior gills and sensory organs Especially important is the olfactory organs
But Anus now over head, so solid waste disposal issue, so anus places close to beginning of exhaled water flow
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Gastropoda shell |
Translation rate vs curve enlargement rate
Not all whirls occupied by all spp.
Columnar muscle attached shell to body
Shell handidness: Sinistral (left) or dextral (right) |
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Opisthobranchia - sea bunnies |
Detorsion 90 Reduction or loss mantle cavity, ctenidia, shell Secondary development of bilateral symmetry Anal gills Internal copulation & fertilisation Hermaphroditism |
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Aeloid- Opisthobranchia |
Recyclers: ingest nematocysts from cnidarians and deposit into cnidosac in the cerata |
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3 developmental stages |
Direct - hatch from large eggs, hatch as juveniles Planktotrophic - veliger larvae hatch from small eggs, spend along time feeding and growing Lecithotrophic larvae - free swimming larvae, settle and metamorphosis |
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Pulmonata - terrestrial adaptions |
Terrestrial adaptations: Desiccation, low Ca environment
Solutions: Regulate activity during dry, hot times - aestivate during winter Nocturnal Burrow into soil Excrete very little water, produce instead conc. Uric acid accumulates in nephridia as crystals Can stay submerged in water
Mainly FW and terrestrial Kings on right side |
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Pulmonata - simultaneous hermaphrodites |
Copulation leads to exchange of sperm Love dart 0.025% sperm survives Love dart - contains mucus that temporarily contracts a part of the female reproductive system in a way that allows a greater number of sperm to reach the storage area and survive |
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Pulmonata - reproductive organs |
Ovotestis Hermaphrodite duct Sperm duct Spermatophore Flagellum Penis Mucus glands Dart sac Spermatheca Oviduct Albumen gland Oviposited |
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Cephalopoda - octopus, squid |
Head footed arms/tentacles Subclasses: Nautiloidea - external shell Coleoidea Prehensile tentacles Muscular mantle - jet propulsion Fats and intelligent predators Closed circulatory system Cilia reduced in importance Muscles developed more Reduction in shell |
