What Are the Functions of the Ampulla in a Starfish?

Starfish have a unique water vascular system that connects to their feet and allows them to move. Known as “tube feet,” these structures in the water vascular system use what is called an ampulla to push water through them, expanding and contracting the foot.

The ampulla is an important structure in the water vascular system of starfish. The water vascular system is a network of fluid-filled tubes that starfish use to move around, manipulate objects, and perform other functions. The ampulla is a key component of the hydraulic system found in starfish and other echinoderms, which include other animals such as sea urchins, sand dollars, and sea cucumbers.

What Are Ampulla?

Ampulla is the name of one of the tube feet on a starfish. Such tube feet are common to all echinoderms, which are sea creatures that also include urchins, sand dollars, and sea cucumbers. They are used for locomotion and for attaching to surfaces. Starfish use ampulla for both purposes. It is responsible for pumping water into and out of the tube feet, which then causes them to expand or contract. Expanding the tube foot makes it longer, while contracting it makes it shorter.

Ampulla is small, tube-shaped pocket located along the arms of a starfish. They are particularly prominent on the tips of the starfish’s arms and along their length. The ampulla helps starfish adhere to surfaces and move from one place to another. They also assist with reproduction.


The ampulla is a small, sac-like structure filled with fluid. The fluid controls the suction of the tube feet, which helps them attach to surfaces. This allows the starfish to crawl along surfaces or hunt for food, such as oysters and clams.

The ampullae are connected to the coelomic fluid surrounding the gut by a hydraulic system that is controlled by a ring canal that runs around the outside of each arm. The coelomic fluid circulates through each arm and can be moved into or out of an ampulla by moving muscles in its wall.


The ampulla can be found at the end of each arm. It is connected to its own bulbous, muscular sac called the madreporite through its own tube called a pedicel. The madreporite is located on the top surface of the starfish and functions as a sieve for food and water.

The ampulla is located at the very base of each starfish arm, where it meets the animal’s central disc. This makes it easy for the ampulla to pump fluid throughout the entire length of each arm. While it does not have any special function, it is an important sensory organ for the starfish. So Ampullae are located on the tip of each arm and are within a shallow pit.

What is the ampulla part of?

The ampulla is a part of the nervous system of starfish. Ampulla is a structure located underneath the body of a starfish. It is made up of neurons and can be found at the center of each arm, where it serves as a central hub for information from the arm’s tube feet. The arms themselves are also home to more neurons, which combine with those in the ampulla to make up the starfish’s entire nervous system.

Ampulla Structure

The ampulla is part of the starfish’s water vascular system, which helps it move and eat. It functions as a hydraulic pump to move water through the starfish’s tube feet, according to the “Encyclopedia of Life.” The ampulla is located in each arm of the starfish’s body. Water fills the ampulla, causing it to become rigid. This pushes outward on the tube feet and creates suction, helping the starfish grip the surface with its tube feet.

What Are the Functions of the Ampulla on a Starfish?

The ampulla is one of the five arms of a starfish. It has many functions that enable the starfish to move, eat, and reproduce. The ampulla is round, like a ball, and helps the starfish survive by moving, transporting sperm, and capturing food.

The ampulla is the bulbous end of a starfish’s arm. It contains water that is ejected and retracted by two muscles. The ampulla, also called the tube foot, has a number of functions, including locomotion and feeding. Some of the main functions of the ampulla are:

Starfish Use Ampulla For Locomotion

Every species of starfish has five arms extending from its central disc, but the internal anatomy of these arms varies greatly between species. In addition to muscle, nervous and vascular tissue, starfish arms contain an organ called the ampulla. The ampulla is a unique structure that allows starfish to move across the seafloor in search of food.

The main function of the ampulla is to use for locomotion. When a starfish needs to move, it will extend its arms in front of itself and latch onto the substrate. It will then retract its tube feet, pulling its body forward with each contraction. As the starfish moves along, it alternates arms to maintain constant motion. The ability to move in this manner, as well as its lack of eyes or hearing organs, makes a starfish very dependent on its sense of touch.

Pink sea star (Pisaster Brevispinus)

Feeding & Food Transport

Another function of the ampulla is feeding. When it encounters food, a starfish extends its tube feet along the surface of the food and forms an oral disc around itself. It then moves its stomach out through its mouth into the disc to digest the food externally before absorbing it back into its body cavity. This process is called extracellular digestion because digestion takes place outside of cells rather than inside them.

Ampullae are used to carry food to the mouth of a starfish after it has been captured by the tube feet and oral surface. The ampullae contract and push food to the mouth. The functions of the ampulla are primarily related to reproduction and to food transport. The ampulla carries food from the mouth to the stomach, where it is digested. Food that is not digested or needed by the starfish is passed through the starfish’s digestive system and passes out through an anus located within another arm called an anal papilla.

Trapping Prey

Ampullae are used to trap prey. The ampullae have the ability to create a suction force that pulls prey into its mouth. This suction is created by the ampullae contracting and expanding at a rapid rate.

When a starfish uses its arm to capture food it curls its arm around the food, trapping it against its body. It then uses its ampullae to suck water out of the tube feet, creating a vacuum that holds the food in place against the body wall of the starfish, which is where its mouth is located.

This suction action also serves another purpose for starfish. It allows them to attach themselves to rocks or other surfaces so they do not get swept away by currents in the ocean.


The ampulla aids in respiration by pumping water from the surrounding environment through the starfish’s body cavity for gas exchange between blood vessels and organ systems. Tube feet also help maintain homeostasis by pumping water into gills for oxygen absorption and waste removal. Water is pumped from the outside environment into the body cavity via a sieve plate, then to a ring canal around the mouth, and finally to each of the five arms. The ring canal is a system of internal hydraulic canals that branch out with tube feet at each end.


The ampulla pumps blood through the radial canals, which transport nutrients throughout the starfish’s body. Starfish do not have a central nervous system, but nerve cells running parallel to radial canals allow communication throughout their body systems. Sieving plates are used as filters to remove debris and excrete wastes. The ampulla also has a receptor that allows organisms to detect light, which is why most species prefer hiding under rocks or sand during daylight hours.

Reproductive Transport

Starfish rely on their ampulla for both reproductive activities and moving from place to place. When swimming, starfish transport sperm using their ampulla, and they use them to attach eggs onto coral reefs and other hard surfaces where they are less likely to be swept away by currents.

The ampulla also serves as a transport system for gametes (reproductive cells) during reproduction. Because starfish can reproduce sexually or asexually, their reproductive process varies greatly depending on whether they spawn eggs or grow offspring within their bodies. However, regardless of how they reproduce, their offspring will use the ampulla as a means of transport until they reach maturity.

Defense Mechanism

The ampullae contain toxins that can be released into the water as a defensive mechanism against predators such as sea otters, which feed on starfish. This defense system is called autotomy or self-amputation and occurs when a predator bites off part of one arm or leg from a starfish, allowing the rest of the animal to escape.

Propulsion System

The ampullae release water to propel the starfish through the water in a process called jet propulsion. The ampullae also help with respiration by pumping oxygen toward the starfish’s central disc and by removing carbon dioxide from its body. In addition, they help regulate internal pressure in the starfish’s body.

Adhesive Uses

The ampulla on a starfish contains suction cups that can be extended out of their tubes when needed. These suction cups allow the starfish to adhere to rocks and other surfaces, making it easier for them to crawl along the seafloor or remain in one spot without being washed away by currents.

The ampulla also contains sensory receptors that help detect changes in light and temperature. The ampulla responds to these changes by either increasing or decreasing contractions to move faster or slower. Tube feet also serve other purposes for echinoderms such as respiration and gas exchange. Additionally, they secrete mucus that helps keep them moist in dry environments.

When the starfish feels threatened or needs to move, it forces water into the ampullae, making them expand. This causes the starfish’s body to become stiffer, and also extends the suction cups at the ends of the ampullae. The starfish then crawls along the seafloor by alternately releasing water from its ampullae, pulling itself along, and then attaching to another spot with its suction cups.

Some Exceptions

There are only two species of starfish that do not have any ampullae in their body, namely the Hymenaster pellucidus and Hymenocera picta, belonging to the Hymenaster family. These two species, however, do not feed on sedentary animals like most other starfishes; they mainly feed upon crustaceans. They grab these crustaceans with their limb, move towards them and swallow them whole using a specialized jaw mechanism located at the center of their body.

There are some exceptions when it comes to an ampullae carrying food, such as when a starfish has been fed too much food, which can cause its stomach to become distended. In this case, an ampullae will actually carry away excess food from the stomach so that it does not burst.

There are also some exceptions where they do not catch prey with their feet but instead use them as suction cups to suck out body fluids from the prey like sea urchins, sea cucumbers, or mussels etcetera! They are also known as predators of clams which they open up using their powerful muscles.

Importance of the Ampulla

The importance of the ampulla on a starfish is not fully understood. The ampulla is a sac-like structure that acts as a water reservoir within the starfish’s body. It is used to help absorb oxygen and nutrients while excreting waste products like carbon dioxide and ammonia. The ampulla also acts as a trap for prey, by luring them into its cavity with secreted chemicals. Once inside, it begins to close and the starfish uses its water-powered suction system to draw it in.

While the ampulla has several functions, it is generally not considered vital for survival. In some species, researchers have removed this organ from starfish with little effect on their lives.

So the ampulla is very important for starfish because it helps them to move over surfaces, maintain their equilibrium, and also aids in feeding. Without it, they would not be able to move, feed or remain upright on hard surfaces like rocks. It is important to know the function of ampulla in a starfish. We can say that it contains the ink which is used by the starfish to protect itself when it feels threatened.

The ampulla is the fleshy interior part of the aboral portion of sea urchins and starfish that acts as their main source of gonads. The ampulla is an important structure in the development of echinoderms, in which it plays a key role in the development of their ordinary body plans. When you know the structure of a starfish, you will really understand how amazing it is.


In conclusion, we can see that the ampulla serves as a connection between the blood and the tube feet of a starfish. It comes into play when feeding, moving, or even stinging or releasing the ink. The ampulla is crucial to the starfish’s survival because death would almost certainly result from its removal. The ampulla is a filtering device located in the coelom or body cavity. It is proximal to the water vascular system. Its role is to remove large undigested particles from the coelomic fluid and debris from the tube feet. So the ampulla has many important functions for a starfish and impacts the animal greatly.

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