But none of that really had much bearing on the question I was trying to answer, which was whether sudden changes in ambient light could impact the overall well-being of fish. To get at that, I thought, it might help to understand how a fish’s eye reacts to light. Consulting an ichthyology textbook, I discovered that the eyes of most fish are not all that differently structured than our own. Like us, fish have a cornea, a lens, and a retina. And their retina, like ours, is packed with specialized cells called rods and cones that enable them to see in low light (rods) and perceive color (cones). These cells are quite delicate, so in humans, the amount of light reaching them is controlled by the pupil, which expands and contracts like the aperture of a camera as the light brightens or dims. We humans also have the ability to protect our eyes by squinting or blinking if the light becomes too intense.
Two New Deep Sea Fish Produce Light in Their Belly - Newsweek
Mesopelagic fish usually lack defensive spines, and use colour to themselves from other fish. are dark, black or red. Since the longer, red, wavelengths of light do not reach the deep sea, red effectively functions the same as black. Migratory forms use silvery colours. On their bellies, they often display producing low grade light. For a predator from below, looking upwards, this camouflages the silhouette of the fish. However, some of these predators have yellow lenses that filter the (red deficient) ambient light, leaving the bioluminescence visible.
These fish can produce red light and can see it when others cannot
Mesopelagic fish are adapted for an active life under low light conditions. Most of them are visual predators with large eyes. Some of the deeper water fish have tubular eyes with big lenses and only that look upwards. These give binocular vision and great sensitivity to small light signals. This adaptation gives improved terminal vision at the expense of lateral vision, and allows the predator to pick out , , and smaller fish that are silhouetted against the gloom above them.
Nearly all daylight fish have color vision that ..
The fangtooth, also known as Anoplogaster cornuta, is another menacing looking creature that inhabits the deep waters of the ocean. Although it may look like a monster, it only grows to a size of about six inches in length. It has a short body and a large head. The fangtooth gets its name from the long, sharp, fang-like teeth that line its enormous, over-sized mouth. Its gruesome appearance has earned it the name, "ogrefish". The color of the adults ranges from dark brown to black. Juveniles look completely different. They are light gray in color with long spines on their heads. The fangtooth is an extreme deep-water species that lives at depths of about 16,000 feet. The pressure at these depths is intense and the water temperature is near freezing. Food here is scarce, so the fangtooth will eat just about anything it can find. Most of its meals probably fall from the upper depths of the ocean. The fangtooth is found throughout the world in temperate and tropical ocean regions including the waters off the coast of Australia.The deep sea angler, known also as Melanocetus johnsoni, is a grotesque-looking fish that lives in the extreme depths of the ocean. Its round body resembles a basketball, and indeed, it looks like it could easily swallow one. It has a large mouth likes with sharp, fang-like teeth. Its appearance has earned it a second name of "common black devil". Despite its ferocious appearance, the angler only reaches a maximum length of about five inches. The angler gets its name from the long, modified dorsal spine which is tipped with a light producing organ known as a photophore. Like many other deep-water fish, the angler uses this organ like a lure to attract its prey. It will flash its light on and off while waving it back and forth like a fishing pole. When the prey fish gets close enough, the angler snaps it up with its powerful jaws. A strange fact about the deep sea angler is the fact that the male is smaller and different in appearance from the female, which is pictures above. The male of the species is about the size of a finger and has small hook teeth, which it uses to attach itself to the female. Once attached, its blood vessels join with that of the female and it will spend the rest of its life joined to her like a parasite, getting all of its nourishment from her body. If the male is unable to attach to a female, it will eventually dies of starvation. The deep sea angler is found throughout the world at depths of over 3000 feet.