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Many questions come to mind when you think of fishes and how they move even at night. Sometimes we wonder how they can swim at night and even ask, ”can fish see in the dark? Does it have a special night vision?
Fish can see at night due to the particular function of their retina. There’s a unique organ in the eyes of fish known as a cone cell. The development of this organ makes it possible for this creature to see in the dark.
But, the ability of fish to move in the dark does not depend solely on its eyes. This creature also possesses a unique organ (Lateral Line) on both sides of its body. The presence of a lateral line enables it to sense pressure changes, particularly from other animals and objects.
As you read, you’ll find some detailed information about the night vision of fish. Also, we’ve addressed some critical facts about fish’s eyes and more. Keep reading to learn more.
Facts About Fish Eyes
The eyes of fishes work uniquely. But knowing what fish see helps to understand the mechanism of its eyes. Here are a few facts about the fish eye you should know about.
The Mechanism of Fish Eyes
The eyes of fish and terrestrial vertebrates work similarly. First, sunlight reflected by water enters the eyes of the fish. This usually occurs through an organ called the cornea. The light then gets to the retina through the pupil.
When this happens, the cells (cone or/and rod) in the eyes change the light into electrical signals. These electrical signals are then sent to the brain through optic nerves. Once the signals reach the brain, it converts them to an image.
Aside from the mechanism, there are still some differences between them and those of terrestrial vertebrates. This is particular to how they process vision and the construction of the eyes.
The Different Visions of Fish Species
The visual cues of fish are quite different from that of humans. The eyes of every human work in the same manner, regardless of our location and identity. The same cannot be said about fish. All fish species don’t have the same visual cues, given that they reside in different habitats.
These creatures could be surrounded by opaque or very clear waters. Some live more on the brilliant surface of the water. Others feel very comfortable in the inky depth of the sea. Certain species dwell in the bright sand and others in the coral reefs. These habitats just highlight why these creatures don’t have similar visual capacities.
Moreover, each of these habitats requires a unique vision for the inhabitants to dwell comfortably.
Far Vision of Fish
The vision of fish covers a reasonable distance compared to that of humans. For humans, our retina shape has to change when we focus on objects at different distances. The change in the shape of the retina is usually initiated by the muscles in our eyes.
This is not the mechanism of the fish eyes since they lack such an ability. So, they move their lenses back and forth to focus on objects at varying locations. This is possible, given that their lenses are more spherical than ours.
Most times, fish keep their lenses backward when targeting their prey. This is necessary as it helps them get a more precise distant vision. They use a process known as accommodation when the prey is much closer. At this point, the lenses move from back to front.
Color Vision of Fish
When it comes to visioning colors, fish eyes work similarly to those of humans. They process images using the rod or cone cells in their eyes. These cells are responsible for their ability to differentiate colors. However, certain fish species possess little or no cone cells. On the other hand, some other species have these cells in surplus.
This means that not every fish specie has the ability to differentiate colors. The majority of such fish species dwell deep down on the seabed. Humans are trichromatic, and so are fish. However, certain species have a fourth color vision.
A visual illustration of this topic can help simplify things. Refer to the following YouTube video for a better understanding of fish vision.
The Night Vision Of Fish, Can Fish See In The Dark?
Most creatures living in the water possess the ability to navigate at night., So, can fish see in the dark? Can it move around in low-light conditions?
Fish possess two photoreceptor cells in their retina, just like every other vertebrate. They’re the cone and rod cells. Each of these cells has a specific function for varying levels of light. The cone cells are more effective during the day due to their low-light sensitivity.
On the other hand, the rod receptors struggle during the day but operate better at night. At this time, the fish can sense even the tiniest of photons.
However, not all fish species have the ability to see in the dark. Meaning it takes more than just the eyes of fish to navigate at night. So, what organs are responsible for this ability?
For fish, colors don’t matter in low light. This is because, in the dark, it’s always difficult for this creature to distinguish between colors. At this point, it only depends on the rod cells in its eyes for vision and easy navigation. How?
The rod cells in the eyes of fish enable it to identify contrast. Additionally, it can detect movements still depending on these cells.
In the dark, fish prefer to vision white color. The reason is that this color creates the best contrast for them in such low light conditions.
Generally, lateral lines are some sense organs found on both sides of these vertebral creatures. They’re usually seen as visible lines. Fish use these sense organs to identify vibration, pressure gradients, and movement in the water.
While these organs don’t provide a vision for fish, they’re quite essential for moving in the dark. The mechanism of these organs occurs through some cells called hair cells, which are modified epithelial cells. Typically, these cells react to motion displacement, sending some electric impulses to the brain via an excitatory synapse.
Lateral lines for fish are quite useful for hunting, learning, and orientation. With these organs, fish can track their prey by following the vortices they generate while fleeing from them.
In some fish species, these organs operate more uniquely. For these species, lateral lines act as electroreceptors. This means that this set of fish can use these organs to sense electrical signals.
Fish have several unique abilities. But the question is can fish see in the dark? What makes the vision of these creatures different from humans? Well, fish possess two photoreceptor cells called cones and rods. This is quite similar to those of most vertebrates.
While the cone cells are quite useful during the day, the rod cells make night vision possible for these creatures. Additionally, fish can use one of its unique organs, lateral lines, to navigate in water at night.