Lily Miller So, do starfish have eyes? In this article, we’ll talk all about that but let’s start with a quick answer:
Starfish do have eyes, but they are located at the tips of each of their arms. They can have a total of about 50 eyes installed on their limbs.
But it’s clear that’s not the complete picture. More details about the starfish eyes, their location, and what they can see are provided below. I’ll also go over why starfish have eyes, if they do in fact have them, and how they grow new ones. Read on!
Table of Contents
Where Are Starfish Eyes Located?
Even though arthropod compound eyes lack true optics, starfish have eyes that are located at the very tip of each arm. A red or black dot on the end of their arms is the eye, if you ever get a chance to look very closely.
Sea stars have a full field of vision because their eyes are on their arms, which allow for some arm bends. These animals have the ability to raise their arms and bend their elbows between 80 and 120 degrees upwards, which also raises their eyes.
A small, flexible appendage called a modified tube foot supports each eye. Like other Echinoderms, starfish also use their tube feet, which are located on the underside of their bodies, to move about the seafloor and, like sand dollars, to transfer food to their mouths.
Two rows of altered tube feed help to define the visual field. They encircle the eye and likely block light coming from both above and below. When the sea star is active, its tube feet spread out; when startled, the animal can retract and cover its eye.
The size of starfish eyes varies by species and size of the animal. The biggest discovered eye measured 25 micrometers (0.025 mm) in width and 60 micrometers (0.06 mm) in depth. About 120 photoreceptors and a comparable number of pigment cells were present in this eye, which was composed of seven to eight layers along its long axis.
The number of arms and species of sea star affect how many eyes are present. The most widespread species have five arms, but some can have as many as forty! Thus, the sunflower sea star, which has 24 arms, also has 24 eyes.
How Do Starfish See?
The body of a starfish lacks both blood and a brain. Even their nervous system is lacking.
They do, however, have mouths, eyespots, and stomachs. A number of light-detecting cells make up these eyespots, which function as eyes. The lens that covers the eyes of humans and other animals does not cover these cells. This restricts what and how a starfish can perceive its surroundings.
Starfish lack this ability, whereas humans and the majority of other animals can see the world in vibrant colors and distinct tones. Starfish eyes are compound eyes that only have the ability to distinguish between light and dark.
The eyespots of sea stars can detect large structures around them, according to recent research by scientists. The cells move slowly, so they cannot detect an object moving too quickly.
How Many Eyes Do Starfish Have?
The eyes or eyespots of sea stars are not centrally located, which is an intriguing fact about them. A mouth and eyes are frequently depicted in the middle of a starfish in cartoons. It’s not accurate, though.
A starfish’s eyespots are found on each of its arms. Each starfish eye is made up of a collection of light-collecting cells that are housed in one of the many hundreds of tiny, tube-like feet on each arm. The sea star can move and swim in the ocean thanks to a tube foot. In each of the starfish’s arms, there are hundreds of these. The starfish’s arms function as legs and the fish moves when the water in its arms is filled up with the assistance of these tube-like feet.
When someone holds a starfish in their hands, they can see the eyespot. There is a red dot at the tiny, rounded corner of each arm. The eyespot is represented by this red dot. A five-armed starfish will have five eyespots, and a starfish will have more eyespots the more arms it has.
How Do Starfish Detect Light Changes?
Starfish can detect objects around them thanks to the photosensitivity of their eyespots. A sea star’s compound eye is made up of several lenses, or ommatidia. The entire image that an animal sees is made up of one pixel by these lenses.
Some researchers have discovered that despite the extreme darkness all around it, the deep-sea starfish, a species of sea star that stays so deep in the water that not even sunlight can reach it, can still see. Some people believe that these starfish have better vision than tropical starfish that are found in shallower waters.
A few of these species are also bioluminescent, according to some additional studies. This implies that they produce brief light bursts that illuminate their skin. These flashes are thought to serve as glowing signals for these deep-sea creatures to approach potential mates in addition to aiding in clear vision.
Human vision is distinct from that of stars. They are not color-blind like humans are. Starfish eyes function in a very simple way, with barely enough sense to distinguish between light and dark. Due to the difference in how their eyes are developed from human eyes, they are unable to see objects moving quickly. Starfish have a nearly 360° visual field thanks to the unusual placement of their eyespots. When none of its eyespots are obscured, this is possible.
The eyespots of this species enable them to see coral reefs and other nearby objects while navigating the ocean. The sight of this organism may not be as developed as that of humans, but it still helps them to see somewhat in the dark ocean and survive.
Why Do Starfish Have Eyes?
Finding food is one of the most obvious and straightforward reasons. Starfish primarily consume shellfish such as mussels, clams, and oysters, but they also consume algae and bacteria. It’s interesting that some animals can glow at night, which allows starfish to find them by spotting the light.
To find their way to and through their habitat, coral reefs, starfish need eyes. Starfish can recognize large immovable structures despite having poor vision. They are able to identify reefs, which serve as both a vital food source and form of defense.
Sea stars’ use of vision was studied by Garm and Nilsson. They blinded a number of sea stars, then placed them one meter from the reef and watched their movements to compare their behavior with that of unblinded ones. They learned that blinded sea stars moved erratically and were completely unable to locate the reef. In less than thirty minutes, those who could use their eyes easily located the reef.
Remember that Garm and Nilsson noted that sea stars could only navigate back when the reef occupies more than 30 degrees vertically. As a result of their behavior, which is only effective at close ranges, their vision may serve the purpose of preventing them from leaving the reef rather than looking for new reefs or managing significant displacements.
Some species of starfish, like Diplopteraster multipes, are bioluminescent and can communicate with other starfish by sending out glowing signals, which is another reason why they have eyes. This could imply that they share information about their reproductive status with other starfish, for instance.
Starfish Can Regenerate Their Eyes
Starfish, which are members of the phylum Echinodermata, have the ability to regenerate lost limbs and, in some cases, entire bodies. My other blog post on sand dollars cloning themselves might also be of interest to you.
The way starfish avoid perishing is by growing new limbs. As a result, the animal can escape and swim freely even when predators eat some of their arms or when it is trapped under a fallen rock. Later, the lost arm, along with tube feet and an eye, can grow back.
Starfish are capable of autotomizing limbs and reproducing, even though regeneration is typically used to replace limbs that have been eaten or removed by predators. When starfish shed their arms, the central disk still has a portion of it attached. The arm can then grow back into a starfish that is completely identical to the first one.
Last, Do All Starfish Have Eyes?
There are about 2000 different species of sea stars, and they all have unique adaptations. Some are found even in the chilly Arctic Ocean, while others are found in deep sea habitats or shallow tropical waters.
To adapt to and survive in their environments, all animals, including humans, have developed unique physical characteristics. This is a clue that not all species of sea stars have eyes, which is the correct response to the question of whether all starfish have eyes. The simple answer is that they don’t require them in order to survive.
The sea star C was one of the ones under investigation and lacked eyes. crispatus. According to scientists, this species’ lack of eyes is probably not related to depth but rather to its way of life. Similar to a sand dollar, the sea star Ctenodiscus crispatus is known for living underground to protect itself from predators, which may be why this particular sea star lacks eyes.
