BIOLOGICAL ASPECTS OF THE DIGESTIVE SYSTEM OF CAELATURA TERETIUSCULA (BIVALVIA: UNIONIDAE)

The digestive system of the clam Caelatura lerelhtscvla consists of the mouth, oesophagus, complicated stomach, combined style sac and mid gut. intestine, rectum and digestive gland. The combined mid gut and style sac are differentiated into four regions. The crystalline style, is lodged inside the style sac and projected into the lumen of the stomach. There are three groups of digestive gland ducts that open into the stomach. The microscopic examination of the interior surface of the digestive tract is formed of a single layer of columnar cells provided with cilia, varying in their length and density. These cells have oval nuclei which occupy variable levels. There are some club-shaped secretory cells distributed between the columnar ones. They acquired deep magenta colour with PAS. The digestive gland tubules are lined with two main eel! types: the digestive and secretory cells. Its ducr is lined bv a laver of ciliated columnar cells. V If