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Class gastropoda is the largest group of mollusks consisting of snails, sea slugs, limpets, and abalones. The name gastropoda means "belly-footed" or that their internal organs are positioned over their foot. Gastropods move by crawling this singular, muscular foot, often secreting a slime layer to aid their movement. Although recognized for their unique spiral shaped shelled and torsion (developmental twist that rotates the mantle and anus above the head), this shell is absent in sea slugs with a reduced mantle therefore losing the lead to undergo the torsion process.
Most gastropods utilize a radula for feeding on plants, other animals, or deposit feeding while some species utilize suspension feeding. In marine ecosystems, these organisms can be found in all oceans at all depths but are particularly common in shallow waters and intertidal zones.
Defining characteristics
Defining characteristics
"Belly-footed" body plan: muscular foot under viseral mass
Muscular foot used to crawl or glide across various surfaces
Typically possess a sprial shaped shell (absent in sea slugs)
Undergo torsion during development
Cephalization: defined head region with sensory organs
Radula for feeding present in most species
Open circulatory system
Complete digestive tract: separate openings for mouth and anus that allows for maximized digestive efficiency
Specialized respiratory systems adapted to environments
Marine and freshwater gastropods usually have gills for exchange
Well developed nervous system with a brain
Reproductive Adaptations
Reproductive Adaptations
Fertilization internal or external depending on species
Mostly dioecious (separate sexes)
Some hermaphroditic (both male and female reproductive organs)
Egg stage: Eggs often released in a protective gelatinous mass or within a capsule for protection
Trochophore larva: Tiny, ciliated larval stage produced by most species
Veliger larva: Gastropod develops a small shell (excluding sea slugs), muscular foot, and velum for swimming and feeding
Torison: 180 degree twist of the visceral mass
Metamorphosis: The larva settles and transforms into a juvenile gastropod
Adult stage: Reproductive system fully developed with the capability of mating
Where are they found?
Where are they found?
Large populations through marine, freshwater, and terrestrial habitats
Found in all oceans at all depths
Particularly common in shallow waters and intertidal zones
Often found in coral reefs
Some parasitic or symbiotic species
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