CLASSIFICATION OF UNIO (FRESH WATER MUSSEL)
KINGDOM :- ANIMALIA (Multicellular eukaryotic organisms)
PHYLUM :- MOLLUSCA (Unsegmented bilaterally symmetrical and provided with visceral mass, foot and mantle.)
CLASS :- PELECYPODA OR BIVALVIA (Bivalve shell.)
ORDER :- UNIONIDA (Gill filaments united by inter-filament and inter-lamellar junctions.)
FAMILY :- UNIONIDAE
GENUS :- Unio (The Fresh water Mussel or Clam)
It is commonly found in India, Europe, Atlantic slope and U.S.A.
HABIT AND HABITAT
Unio is the most familiar and very favourite pelecypod, found in ponds, lakes, rivers and streams. The animal is usually buried in the mud.
GENERAL CHARACTERSTICS OF UNIO (FRESH WATER MUSSEL)
- Commonly called as fresh water mussel or clam.
- Body is dark brown, unsegmented, bilaterally symmetrical and flattened from side to side measuring 5 to 10 cm in length.
- Animal is completely enclosed in equal bivalve shells. The periostracum is generally smooth and without rays.
- Two valves are united together along the dorsal side in a straight hinge-line by hinge-ligament. Anteriorly, in front of the hinge, there is a whitish, knob-like swelling on each valve, called as umbo. Outer surface of each shell contains various lines of growth. Hinge is without teeth.
- Posteriorly, on lateral margins there are two openings; smaller one is exhalent siphon, while the larger one is inhalent siphon.
- Mantle consists of two lobes, corresponding to two valves of the shell. Ctenidia are W-shaped and eulamellibranch.
- Foot is large, muscular and wedge-shaped and is used for burrowing.
- Adductor muscles are of same size, i.e. isomyarian.
- Sexes are separate but the male and female shells are alike. Development includes glochidium larva.
The shells are used in making buttons and animals are largely dissected for understanding nervous system and invertebrate anatomy.
The animal contains Umbo, hinge and all above characters, hence it is Unio.