The digestive system of Linckia laevigata, commonly known as the blue sea star, is characterized by its specialized stomachs, particularly the eversible cardiac stomach used for external digestion.
Key Components of the Digestive System
The digestive tract of the blue sea star is relatively straightforward, designed for its unique feeding strategy.
- Mouth: The digestive process begins at the mouth, located on the underside (oral surface) of the sea star.
- Esophagus: A short tube, the esophagus, connects the mouth to the primary digestive organs.
- Cardiac Stomach: This is a large and highly significant part of the blue sea star's digestive system. Its most remarkable feature is its ability to be everted, or pushed out, of the body.
- Pyloric Stomach: Following the cardiac stomach, a smaller pyloric stomach receives partially digested food.
Functionality and Feeding Strategy
The unique structure of the Linckia laevigata's digestive system facilitates an effective method of obtaining nutrients:
- Extraoral Feeding: The most distinctive aspect of the blue sea star's digestion is its extraoral feeding capability. When feeding, the large cardiac stomach is pushed out through the mouth and surrounds the prey externally. This allows the sea star to secrete digestive enzymes directly onto the prey, beginning the breakdown process outside its body.
- Prey Digestion: Once the prey is partially digested externally by the everted cardiac stomach, the liquefied or semi-digested material is then drawn back into the body.
- Further Processing: The partially digested food then moves from the cardiac stomach into the smaller pyloric stomach, where further digestion and absorption likely occur.
This eversible cardiac stomach is a key adaptation that allows Linckia laevigata to consume prey larger than its mouth opening, making it an efficient predator in its marine environment.
