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IDENTIFICATION OF MOLLUSKS

 

Introduction

 

Mollusca are one of the "phylum" of the animal kingdom; they can be distinguished  from other animals because are invertrebate and have a soft body, the mantle (epidermic layer producing material for the shell, but not all of the Mollusca have a shell, sometime it is very small or missing) and a foot (muscular organ for locomotion). Generally respiration is brachial (in aquatic species) or pulmonary (in terrestrial species). They have a heart and circulation. Generally they are oviparous and hermaphrotide. Most of them are subject to the process of metamorphosis.

 

Here it is the list of most common Italian mollusk classes. The name of classes is the Latin one and, when available, there is also the link to the photos.

 

 

Bivalvia


Bivalvia can be distinguished from other Mollusca because they have a shell made of two moving parts. They are also called Lamellibranchiata because their typical lamellar gills. All of them are aquatic animals.

 

See also Bivalvia photos

 

Cephalopoda


Cephalopoda foot is transformed in tentacles attached to the head, this character explains their name. The shell, when it is not missing, generally is internal (i.e. cuttle-fish bone). Cephalopoda are sea animals and have a special gland secreting a black substance that is ejected when the animal is in a dangerous situation to benumb the water; furthermore their mantle has a special pigment that change colour to camouflage the animal.

 

Cephalopoda: cuttle-fish, calamary, octopus.

 

Gastropoda


Gastropods have only one shell, sometimes it may be very little or missing. On the head there are one or two pairs of tentacles with sensorial organs such as eyes. There are both aquatic and terrestrial species. Some of the most common terrestrial families are: Agriolimacidae (foot keeled only in its dorsal tip, pneumostome located in the hind half of the mantle, without a visible shell), Arionidae (foot not keeled, pneumostome located in front half of the mantle, without a visible shell), Clausiliidae (whit a coiled shell longer - at least 0,7 cm -  than wider), Helicidae (with shell, umbilicus may be open or closed), Hygromiidae (with shell, cylindrical umbilicus, diameter up to 2,5 cm), Limacidae (foot keeled only in its dorsal tip, pneumostome located in the hind half of the mantle, without a visible shell), Milacidae (dorsal side of foot entirely keeled, pneumostome located in the hind half of the mantle, without a visible shell) and Pomatiasidae (conical and large shell with 4-5 whorls); all of these families are in the order Stylommatophora (eyes located at tentacle apex).

 

See also Gastropoda photos

 

Glossary

 

Pneumostome: breathing opening. FIG.1

Umbilicus: hole or depression in the back of the shell.  FIG.2

 

Bibliography

 

 

Alessandro Strano