• It is a molluscan larva found in the development of Bivalvia or Pelecypoda.

• It is a microscopic bivalve larva consisting of conical shell containing incurved hooks ventrally and mantle. Mantle is produced into sensory brush like hairs. Shell valves are operated by a large adductor muscle situated at the base.

• A byssus gland is present near adductor muscle through which a long filament like structure arises called as byssus.

• Glochidium larva attaches itself to fish skin and leads an ectoparasitic life during which it absorbs food from fish and changes into adult form. Later Glochidium detaches from the fish when adult leads free life.