Calcium

Abstract

Calcium in tissues of crustaceans exists in two states namely diffusible and non-diffusible. Diffusible calcium is also referred to as dialysable and ultra filterable calcium, which includes free calcium ions and calcium complexed with carbonate, citrate, phosphate and free acidic amino acids. Non-diffusible calcium is referred to as non-dialysable calcium and non-ultra filterable calcium. It is also commonly called as bound-calcium. In this state, calcium may be bound to proteins, lipids and acidic mucosubstances. Bound calcium is precipitable with 80% ethanol. The supernatant will contain dialysable fraction. Complete precipitation of bound calcium is achieved by diluting the tissues twenty times with ethanol (Kannan & Ravindranath, 1980).