Generally, the vision of Betta Fish is slightly weak in darkness. The vision of Betta Fish is relatively poor because of slow iris functionality, consequently, they cannot adjust swiftly to changes in brightness. In order to aid this weakness, these fish use “lateral lines,” which run down their sides. To learn more in detail, read on…
Betta is a common and popular fish in the aquarium trade. It is highly territorial and belongs to the gourami family. Various research studies have found that male Bettas are highly aggressive in nature and will kill each other if housed in the same aquarium. In addition, it is known for its brilliant colors and flowing tails but it is not easy to maintain them as pets. Still, people love Betta fish for its beauty and good looks.
For most species of fish, vision is an important sense organ. Their eyes are similar in structure to the eyes of terrestrial vertebrates, birds, and mammals, but have a more rounded lens. Their retina contains sticks for monochrome vision and cones for color vision, so most species can distinguish colors. Some fish are able to see ultraviolet and even polarized light.
Can Betta fish see in the dark? This is one of the most important questions asked by aquarium lovers. In this article, we will try to answer this question in detail. You will come to know about the eyesight of Betta fish and how can you take care of them in the best possible way. Before answering the main question, let’s understand the day-night life cycle of Betta fish!
A Betta fish is usually playful and active at daytime. Due to the presence of light, they can easily eat and swim around in the aquarium. At night, when there is no light, these fishes will fall asleep. In fact, it is essential for them to fall asleep as it helps them relax their muscles and restore the energy.
It is not recommended to keep the Betta in a relatively dark room for more than eight to ten hours. Naturally, beta fish requires a minimum of 8-10 hours of light daily to upkeep their natural processes and bodily mechanisms. So, it is important for you to maintain a sufficient light in the room where you keep the aquarium. Another theory says that the Betta fish needs a sufficient amount of light in the darkness as well. If there is no light, these fishes will tend to be inactive. In contrast, a number of experts argue that there is no risk if you keep the fish in darkness. They can still remain active and healthy.
Generally, the vision of Betta fish is slightly weak in darkness. Some experts say that these fishes grow well in relatively murky water. They enjoy swimming in clean fresh water. Although Bettas have a monocular vision that allows them to see things in two different directions at the same time, these fishes lack depth perception. The vision of Betta fish is relatively poor because of slow iris functionality, consequently, they cannot adjust swiftly to changes in brightness. In order to aid this weakness, these fish use “lateral lines,” which run down their sides. The lateral line has small holes, which help them measure the pressure of water. In this way, they can approach the objects easily.
Studies show that the diurnal animal retina is made up of a greater number of cones than rods, which allows them to see a greater number of colors. On the contrary, in the nocturnal animals, the canes predominate, which allow them to see with greater clarity the nuances of the grey but in general perceive fewer colors. Based on this, we can say that although fishes do not perceive all colors if they see different ranges of color.
In fishes, the chromatic vision depends on the depth or turbulence of the waters they inhabit, there may be monochromatic, dichromatic (fish of turbid water) trichromatic (reef or coral) and tetrachromatic (fish of crystalline sweet water). We can affirm that the Betta fish does see different ranges of colors, although we do not know if it sees all if a large number of them because they are a diurnal animal and because they live in clear but stagnant waters. Therefore, in darkness, Bettas need special assistance for a reasonably better vision to identify objects of different colors.
Light enters the eye through the iris, passes the pupil, and reaches the lens. In most species, the pupil size is fixed and can adjust the diameter of the pupil. Depending on the species, its shape varies from round to slit. The lens usually has a spherical shape, but may be slightly elliptical. The refractive index of the aquatic environment is not very different from the refractive index of the iris and the surrounding fluid, so the lens makes the main contribution to the refraction of light. Due to the gradient of the refractive index inside the spherical lens, it can produce clear images without spherical aberration.
As soon as light penetrates the lens, it passes through a transparent liquid material and reaches the retina with photoreceptors. Like other vertebrates, photoreceptors are located on the inner layer, so the light needs to pass through the layers of other neurons before reaching the photoreceptors.
Inside the retina are sticks that provide visual sensitivity in low light conditions. Cones allow Bettas to see the image in high spatial and temporal resolution. They perceive the light of different lengths, and therefore also provide color vision. The ratio of rods and cones depends on the ecology of a particular type of fish. They are active during the day and have more cones than species that are active at night. Color vision is used in an environment with a full light spectrum, i.e. near the surface, and not at a depth where the spectral composition is poor.
The distribution of photoreceptors on the retina is not uniform. The fish may have two or three areas on the retina specialized in high sharpness (i.e. for catching prey) or sensitivity (i.e. from dim light coming from below). The distribution of photoreceptors may also vary throughout the life of the Betta. This happens when a Betta changes its habitat during its life cycle. Sometimes, most of the light entering the eye passes through the retina and only a small percentage of it causes the reaction of sensitive cells.
A Betta fish has a series of sensitive pressure sensors surrounded along the length of their bodies. You can observe a faint line, which makes gentle curves from the head all the way to the tail. Most often, these lines are a little shadier than the color of the skin. These lines are in fact a set of tiny pits that contain delicately tuned motion and pressure-sensitive cells for the detection of the minor changes in the pressure of the water. For instance, the lateral line creates a pressure wave when you drop in the food. The lateral line of Betta fishes can feel even a slight disturbance in the water.
Bettas establish and protect a small area around them in which they breed. Being able to locate food without depending on vision would be a big advantage. Small disturbances and chemical “smells” sensed by their lateral lines support them to find food in the dark. Large pulse waves or big disturbances from other fishes in the aquarium would help them avoid getting killed.
Moreover, when the lights are off, Bettas will always appear pale. However, this does not mean that they are not capable of seeing altogether. Bettas do not have eyelids, which imply that their eyes remain open during the night while they rest. What does this mean? Well, this clearly gives us the reason to believe that Bettas can see in the darkness even though the vision is poor.
So, how can you determine if Betta fish can see in the dark? Usually, most aquariums and tanks are designed with specialized lighting systems. In order to find out if the Betta fish can see in the darkness, you need to switch off the lights in the aquarium. This will allow them to settle down in the tank. You need to be very careful while observing the Bettas and the moment you switch off the lights, you will see them get frightened and terrified. Moreover, you must know when they fall asleep and when they are awake so that you consider their sleeping as failure to see in the dark.
As mentioned previously, Bettas remain active in the presence of light during the day. When the lights are off, they need rest for which they will look for a comfortable spot in the aquarium to sleep. During this period, they might appear so inactive such that you would think they do not see at all. Nevertheless, that is not the case. Consequently, Betta fish can see in the dark. In addition, they mostly use their sensory organs that are connected to the nervous system to activate the vision even when there is no light. Even if they are many Bettas in the aquarium and there is darkness, they will still be able to detect others so that they avoid bumping on one another. Furthermore, Bettas have the ability to locate the edges of the tank.
(Source: bettabuzz.com)