Mussels- Pteriomorpha
Mussels are filter feeders. They suck in water through their incurrent siphon. They feed on microscopic sea creatures and plankton that are floating in the ocean. Once food particles enter their incurrent siphon the food passes through the esophagus into the stomach where a combination of mechanical and chemical digestion breaks them into smaller particles. The stomach is a thin-walled sac, lined with a gastric shield around which the crystalline style revolves. In all bivalves, the style is a gelatinous rod-like body that contains starch-digesting enzymes and is continually being used up and renewed. The breakdown of food particles is aided by these enzymes and the mixing of the stomach contents by the rotation of the crystalline style against the gastric shield. The digestive gland secretes digestive enzymes that aide chemical digestion. The remainder of the stomach is extensively lined with cilia, with many ridges and folds that sort the material that was eaten. When the particles are broken down sufficiently, they are carried on ciliary tracts in the stomach to the digestive diverticulum for intracellular digestion. Digestive cells in the digestive diverticulum take up small food particles into food vacuoles within the cells where nutrients can be used by the cells. The intestine carries both undigested particles and waste products to the rectum, where they are stored prior to evacuation from the anus through the exhalant siphon.
This is a picture of the zebra mussel that was originally discovered in 1796 in Russia.