No Back Bone?
Snail Outline
Mollusk are boneless, in fact the closest thing they will ever have to bones is a shell. Being boneless as they are, Mollusk are classified as invertebrates, meaning they do not posses a back bone. However, considering that most of them do have shells, it is fair to say they posses exoskeletons.
- Mollusk are characterized by 3 main body-parts:
- The Head-Foot-Contains the sensory and motor organs
- The Mantle-Soft skin that encloses the visceral mass
(Excluding Nautilus)
Chiton-Class Polyplacophora
To the left you see a Chiton, which was not listed on the front page, as it is not a very well-known Mollusk, being the one and only of its class. The Chiton has a very interesting skeleton, consisting of 8 shells surrounded by spicules.
Spicules-described as needle-like or spike-like calcareous/siliceous bodies that serve as skeletal elements of various marine invertebrates.
Spicules-described as needle-like or spike-like calcareous/siliceous bodies that serve as skeletal elements of various marine invertebrates.
A very colorful Gastropod
Mollusk have bilateral symmetry. This means that they have two equal right and left sides.
Squid Tentacles
How do Mollusk move? I suppose that the most obvious answer would be tentacles, at least for class cephalopoda. Cephalopods use their tentacles to push themselves through the ocean, almost like jet propulsion. Snails use a wave-like movement which allows them to propel themselves forward. Snails also release slim upon the surface they are on to make movement easier on it. Clams usually just let the sea currents move them, however they do have the ability to burrow themselves under the sand.