yes, planarians have one opening in their digestive system
A digestive system with only one opening is called an incomplete digestive tract. Organisms with this type of digestive system ingest food and eject waste through their mouth.
if i got this right snakes are the only one opening animals and have to puke their food after digestion while two opening animals like us just get rid of the waste the way we do.
They cannot eat continuously (there mouth and anus are present in the same opening)
Parasites such as tapeworm, planarian and live fluke have digestive systems that are saclike. Their digestive tracts have one opening and they live inside a host animal.
A digestive chamber with one opening is called a "gastrovascular cavity." This structure serves both digestive and circulatory functions, allowing food to enter and waste to exit through the same opening. Organisms with this type of digestive system, such as jellyfish and flatworms, typically have a simple body plan and rely on diffusion for nutrient distribution.
Oysters have a two way digestive system. This means that they only have on opening for both food to go in and to come out.
An open digestive system is one where there is an entrance "mouth" in one end of the organism and an "exit" or anus of some sort in the other end of the organism. (think of worms or people). A closed digestive system is in something like a hydra or anemone where there is just one cavity and one opening that acts as both mouth and anus.
The stomach
No bats have a one way digestive system. Food goes in the mouth, is digested, and comes out the other end. In two way digestive systems food is taken in and waste is excreted through the same opening.
Having a single opening for both ingestion and elimination can increase the risk of contamination and infection from waste material. It can also limit the efficiency of digestion and nutrient absorption, as food may not be fully broken down before being expelled. Additionally, this type of digestive system may restrict the size and complexity of organisms that can be sustained due to the limitations in processing food.
An incomplete gut only has 1 opening. Basically if something has an incomplete gut, it has no anus, and all food that it takes in must either be completely digested, or re-excreted through the mouth.
Organisms that have only one opening in their digestive tract through which food enters and waste exits are known as having an incomplete digestive system. Some organisms with incomplete digestive systems are jellyfish, sea anemones, flatworms, and corals.