Hello my name is Gerry Gastropoda and I'm here to tell you about my very big Class. I am a member of the class scientists call Gastropoda. In Latin, this means stomach foot. My class is further divided into three very important subclasses representing over 40,000 known species living today. My large class of molluscs holds approximately 75 to 80 percent of all the known living molluscs.
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My
three subclasses are as follows:
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The Prosobranchia: This is the biggest of the subclasses and contains most of the mollusc seashells that people recognize and pick up along our beaches. Most of the members here are marine inhabitants, or in other words, they live only in salt water. However, many of the members can also live in freshwater or even on land (terrestrial). Every member of this big subclass has a coiled shell. Their soft bodies have a head complete with two eyes located on the tops of two tentacles. These cousins of mine all breath by means of gills. They have a big flat foot, which they use for locomotion and on the back end of this foot is a structure called an operculum, which acts as a trap door. When a prosobranch is threatened by an enemy or he is afraid of getting dried-out (all molluscs must keep moist to stay alive), they pull all their soft, moist body into their shell then they close the operculum behind them just as you close the door to your house.
Most of the seashells you people collect along beaches or lakes are from the members of this subclass. Some of the families in this subclass are known by names such: conchs (Strombidae), whelks (Buccinidae), limpets (Fissurellidae), periwinkles (Littorinidae), cones (Conidae), murex (Muricidae), volutes (Volutidae), and cowries (Cypraeidae).
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Opisthobranchia: All of the members of this subclass are marine inhabitants.
Most members in this sub-class only have a very small, fragile shell and
it is often contained right inside their soft bodies or they may not have
a shell at all. Most of these cousins of mine breathe through their gills;
however, some absorb oxygen from the water directly through a specialized
membrane (something like the thin skin lining the insides of your cheeks)
lining their mantle cavity.
Many of these molluscs have very colorful bodies. We know some of the Opisthobranches as: sea hares, sea butterflies (Thecostoma), sea slugs (saccoglossans and nudibranchs), and canoe (Scaphandridae) and bubble shells (several families).
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The Pulmonates: These are my woodland and garden dwelling snail and slug cousins. Most of these molluscs live on land or in freshwater lakes and streams; however a few are marine dwellers. They all breathe by means of pulmonary sacs not gills.
Some have coiled shells, but many do not have a shell at all. One very interesting fact about most pulmonates is, the members of this subclass are both male and female (hermaphrodites) at the same time.
This comes in very handy as these snails are very slow moving and don t like moving around too much. If they had to go looking for a boyfriend or girlfriend, it could take them a very, very long time to have babies. Being both male and female solves this problem. When they come across another snail of their kind, they just exchange sperm packets with each other and then they both go off and lay eggs. Baby molluscs hatch out some time later and they too are born as both boy and girl within the same slug or snail body.
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Here
are some very interesting gastropod facts:
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