BACKGROUND:
The marine environment has many different environments
where organisms can live. There are consumers as well as producers,
including carnivores, omnivores, and herbivores.
The marine environment has physical conditions that change like
those in the terrestrial environment. The conditions, however, are
different and include water temperature, salinity, ocean currents, depth,
and nutrient supply. Plants can only live in the upper 200 meters
of water, because light cannot penetrate any further. The farther
you go down in water depth, the more you will only find consumers.
The ocean environment is very complex.
The gastropods are a very large group within the
Phylum Mollusca.
The group includes the conches, periwinkles, limpets, garden snails, and
slugs. Most gastropods have shells, generally in the shape of a spiral
with numerous turns. Virtually every type of feeding habit is exhibited
by gastropods. Larger bottom dwelling carnivore gastropods burrow
into the sand to reach their prey including volutes, bonnets, helmets,
olive shells, harp shells, and whelks. Some species in these groups
smother the victims with their feet. Some may grip the bivalve with
the foot, pulling, or wedging the two valves apart with the edge of the
shell. Some are adapted to drill holes in the shells.
The living gastropod has a distinct head with a mouth, eyes and
tentacles. Most have an organ in their mouth area called a radula,
a series of rows of minute teeth on a flexible piece of flesh with which
they scrape up food, tear the flesh of prey, or bore holes in the shells
of clams. Gastropods may be plant-eaters, carnivores, scavengers,
deposit-feeders (obtaining food particles from sediment) or suspension-feeders
(straining suspended food particles from the water. It is very difficult
to determine if a snail is a herbivore or carnivore by looking at its shell.
Gastropod shells display an infinite variety of colors, patterns, shapes
and sculpturing. There is one clue that works most of the time when
trying to determine if a snail is a herbivore or carnivore, by looking
at the siphonal notch area of the shell.
