Digestive system of gastropods

The digestive system of gastropods has evolved to suit almost every kind of diet and feeding behavior. Gastropods (snails and slugs) as the largest taxonomic class of the mollusca are very diverse: the group includes carnivores, herbivores, scavengers, filter feeders, and even parasites.

In particular, the radula is often highly adapted to the specific diet of the various group of gastropods. Another distinctive feature of the digestive tract is that, along with the rest of the visceral mass, it has undergone torsion, twisting around through 180 degrees during the larval stage, so that the anus of the animal is located above its head.^[1]

A number of species have developed special adaptations to feeding, such as the "drill" of some limpets, or the harpoon of the neogastropod genus Conus. Filter feeders use the gills, mantle lining, or nets of mucus to trap their prey, which they then pull into the mouth with the radula. The highly modified parasitic genus Enteroxenos has no digestive tract at all, and simply absorbs the blood of its host through the body wall.^[1]

The digestive system usually has the following parts:

• buccal mass (including the mouth, pharynx, and retractor muscles of the pharynx) and salivary glands with salivary ducts
• oesophagus and oesophagal crop
• stomach, also known as the gastric pouch
• digestive gland, also known as the hepatopancreas
• intestine
• rectum and anus