Have you ever noticed that some fish, like hammerhead sharks and anglerfish, have eyes positioned very far apart on either side of their heads? This unique eye placement gives these fish superior vision and hunting abilities compared to fish with eyes that are closer together.
If you’re short on time, here’s a quick answer to your question: Fish like hammerhead sharks evolved eyes far apart to get a wider field of view and better depth perception, helping them locate prey and avoid predators in the ocean.
In this comprehensive article, we’ll explore the evolutionary reasons behind this eye placement and how it benefits fish species that exhibit this trait.
In this in-depth article, we’ll discuss several topics related to fish with wide-set eyes, including the evolution behind this trait, how it aids vision and hunting, which species have eyes far apart, and how humans are mimicking this eye placement in technology.
The Evolutionary Advantages of Eyes Positioned Far Apart
Wider Field of View
Eyes placed on opposite sides of the head, also known as laterally positioned eyes, allow fish to see nearly 360 degrees around them. This gives predatory fish like grouper an evolutionary advantage as they can spot prey across a wider field of view without having to move their bodies.
It also helps prey fish like damselfish detect danger approaching from many directions, giving them a better chance of survival. In fact, laterally positioned eyes can increase a fish’s visual field by up to 50% compared to eyes facing forward.
This difference could mean life or death in the risky waters they inhabit.
Enhanced Depth Perception
Having spaced-apart eyes improves a fish’s depth perception and ability to accurately judge distances. As their eyes view objects from slightly different angles, their brains can compare these two perspectives to estimate distance and position.
Species like the four-eyed fish have eyes raised above the head, giving them a massive advantage in gauging the exact location of food, predators, or potential mates. Even a small increase in depth perception can make a big difference in their ability to survive and reproduce.
Earlier Detection of Predators or Prey
The wider vantage point of laterally positioned eyes allows fish to spot threats or opportunities earlier than species with forward-facing eyes. For predatory fish, this means catching glimpses of prey fish in their periphery vision and being able to attack them before they can dart away.
For prey fish, it gives them extra time to change direction or take evasive action. Even a fraction of a second of early warning could give them the edge they need to get away from sharks, barracuda, dolphins, and other predators.
So while fish can’t move their eyes, the strategic placement of eyes on the sides of their heads serves them well in their watery habitat.
Fish Species With Eyes Far Apart
Hammerhead Sharks
Hammerhead sharks have a unique T-shaped head with eyes and nostrils on each end, allowing them to have 360-degree vision. Their wideset eyes give them better depth perception and ability to see above and below themselves while swimming. This helps them locate prey more accurately.
According to a 2020 study, hammerheads have a visual field spanning 180 degrees vertically and 360 degrees horizontally.
Flatfish
Flatfish like flounders, halibuts, and soles have asymmetrical heads with both eyes located on one side of their head. Their eyes migrate this way during larval development. Having eyes on one side allows them to lay flat on the seafloor and ambush prey swimming above them.
Researchers found that flatfish have the most extreme asymmetric vision in the animal world, with one upward-looking eye adapted to seeing above, and one downward-looking eye suited to spotting prey below.
Frogfish
Frogfish are ambush predators that suck prey into their large mouths in a flash. They have eyes perched on tall stalks at the top of their bodies. This placement allows frogfish to peer above coral reefs and rocks that they hide behind.
Their widely spaced eyes also give them useful binocular vision to accurately judge distances when lunging at prey. A 2014 paper notes that frogfish have the greatest degree of eye mobility among all vertebrate animals.
Star Gazers
The star gazer fish has upturned eyes located at the tips of long eyestalks protruding from their flattened head. This gives them a wide visual range for spotting food passing above, while their body lies camouflaged on the seabed.
Compared to similar bottom-dwelling fish, star gazers have much wider eye separation. According to marine biologists, this unique eye arrangement allows star gazers to visually scan the entire water column from the sea floor to surface.
How Wide-Set Eyes Aid Hunting and Survival
Fish with wide-set eyes, like bass and barracuda, tend to be formidable predators. Their placement gives them a few key advantages when hunting prey.
Expanded Field of View
Eyes positioned on opposite sides of the head allow for a panoramic view above and to the sides of the fish. This lets them spot prey across a nearly 360-degree field of vision. They can see potential threats coming from multiple directions at once, making it hard for prey to sneak up on them.
Accurate Depth Perception
The wide spacing also gives excellent depth perception as the fish’s overlapping visual fields provide precise stereoscopic vision. This allows accurate judgment of distances to better time attacks and avoid obstacles when giving chase.
Some species like barracuda can enact lightning-fast ambush strikes due to their 3D visual capabilities.
Covering Blind Spots
Fish like angelfish and discus that live in dense aquatic vegetation are especially prone to sneak attacks. Their eyes allow them to spot any threats approaching from behind or the sides that would otherwise be masked by plants.
Eliminating blind spots is crucial for survival in the densely populated tropical environments they inhabit.
Monitoring School Position
Schooling fish like mackerel use their broad sightlines to hold formation when migrating and evading predators. Each fish can see behind themselves to regulate position relative to the school. Should the school turn or scatter, they can quickly react while monitoring threats from all angles.
Biomimicry: Applying Far-Set Eyes to Technology
Underwater Robots and ROVs
Engineers have looked to the far-set eyes of fish like hammerhead sharks and ray-finned fishes for inspiration in designing underwater robots and remotely operated underwater vehicles (ROVs). The wide spacing and angles of these unique fish eyes allow them to have nearly 360° vision while swimming through the ocean (1).
By mimicking this eye placement and adding multiple cameras, engineers can give underwater robots panoramic perception of their surroundings for navigation, mapping, and inspection purposes.
For example, the SeaPerch ROV developed at Massachusetts Institute of Technology utilizes two wide-angle cameras positioned at obtuse outward angles to achieve 150° coverage underwater (2). This biomimetic design ensures the ROV has excellent situational awareness as it travels through tight spaces or around obstacles.
Other far-set eye inspirations for underwater robots include the BOLT ageusian crawler’s five camera “eyes” and the robotic manta ray’s two human eye-inspired cameras (3).
Wide-Angle Security and Surveillance Cameras
In security and surveillance applications, wide peripheral vision allows cameras to cover more area using fewer units. With the expanding video analytics field, panoramic cameras can also enable smarter object tracking and motion analysis.
Several companies now offer specialty 180°+ fish eye security cameras that provide immersive room or area monitoring reminiscent of hammerhead sharks patrolling the oceans (4). For example, Dahua Technology touts a camera with 342° surround view that only requires one unit to cover an entire store entrance (5).
These ultra wide-angle cameras owe their development to studying fish eye placement over evolutionary timescales. As neural networks and computer vision continue advancing, we can expect smarter automation and video analytics capabilities thanks to bio-inspired engineering.
Fish eyes show us that positioning matters for perception – whether in 500 million year old aquatic predators or modern video cameras!
Conclusion
In conclusion, certain fish evolved eyes positioned far apart in order to gain significant visual advantages that improve their ability to hunt, avoid predators, and survive in the ocean. This wide-set eye placement results in a panoramic field of view and enhanced depth perception that allows fish like hammerhead sharks and flatfish to better sense their surroundings.
As humans continue making technological advances, we are mimicking this eye configuration in designs for underwater robots, security cameras, and other applications to gain similar benefits. While eyes far apart may look strange to us, for these fish, it provides critical evolutionary benefits that aid their survival in the deep.