In the field of animal vision, there is an incredible amount of diversity. While nearly every animal species possesses its own unique set of vision-related characteristics, there are certain commonalities found among them. This article will explore the fascinating diversity of animal vision from the perspective of insects and mammals. We will look at the different types of vision, the physical structures of the eye and how animals utilize vision to interpret their environment. Ultimately, the article will demonstrate how even though the two animal classes may have different visual abilities, they are, in fact, very much alike.
Types of Animal Vision
Animals perceive the world around them differently based on the types of vision they possess. The three major types of animal vision are rod-, cone-, and ultraviolet vision.
Rod Vision
Rod vision is the most common form of animal vision. Rods are light-sensitive cells found in the retina of the eye and they are highly sensitive, but do not hold much colour detail. Rods are used to detect movement and detail in low light conditions. Rods are predominant among nocturnal and crepuscular animals, such as cats, mice and owls.
Cone Vision
Cone vision is the opposite of rod vision; cones are also light-sensitive cells found in the retina, but they are not as sensitive to light as rods. Cone vision allows animals to accurately discern colour and detail in bright light, so it is the preferred vision of most diurnal animals, such as birds and primates.
Ultraviolet Vision
Another crucial form of vision is ultraviolet vision, which is seen in some types of insects and mammals, including the honey bee and ferret. Ultraviolet vision allows animals to detect patterns in ultraviolet light and use this information to identify food sources, mates, and predators.
The Physical Structure of Animal Eyes
The physical structure of animal eyes is essential to understanding the diversity of animal vision, as each eye is perfectly tailored to match the vision they possess. All animal eyes are made up of three primary components; the cornea, lens and retina.
Cornea
The cornea is the outermost covering of the eye and it acts as a shield to keep out harmful environments and debris. The corneal shape and size of an animal’s eye will determine the amount of light let into the eye, thus influencing the overall vision capacity of the animal.
Lens
The lens is located behind the cornea and it is responsible for focusing light onto the retina. The lens can also adjust its shape to help an animal focus on objects at different distances, which can be extremely useful for predatory or foraging behaviours.
Retina
The retina is the innermost layer of the eye, and it is composed of photoreceptive cells which turn light into image signals that can be interpreted by the brain. Different photoreceptive cells enable certain types of vision; rods detect movement and are used in low-light conditions, while cones are sensitive to colour and detail in brighter light conditions. The retina also contains ganglion cells which send signals to the brain.
Insect Vision
The majority of insects have compound eyes made up of dozens, if not hundreds, of individual lenses. Insects generally have rod vision, meaning they can detect motion but not detail or colour. Insects use their vision to detect prey, find mates, and evade predators, relying heavily on the movement or slow speed to help them see their surroundings.
Mammal Vision
Mammals, on the other hand, typically have ‘camera-type’ eyes, composed of a single lens which focuses light onto the retina, allowing for higher resolution and colour vision. Mammals generally rely more heavily on their vision than insects, as most have stereoscopic vision, meaning they can focus on two points in space at once. This helps them find food, navigate their environment, and prepare for potential dangers.
It is clear that animal vision is incredibly diverse, with a wide variety of unique visual abilities. Insects and mammals, while vastly different in many ways, both use their vision to effectively navigate their environment and make sense of the world around them. In this article, we have explored the different types of vision, the physical structures of the eye and how animals use them. Lastly, it is important to note that although their vision may differ greatly, both insects and mammals share a fundamental need to see the world.
