Macropinna
Macropinna is a genus of ray-finned fish belonging to Opisthoproctidae, the barreleye family. It contains one species, M. microstoma. It is recognized for a highly unusual transparent, fluid-filled shield on its head, through which the lenses of its eyes can be seen. It was originally believed that the tubular eyes of this fish were fixed in place and, therefore, only provided a tunnel vision view of what was seen above its head. However, in 2008, scientists discovered that its eyes were able to rotate both up and forward in its transparent shield. "M. microstoma" has a tiny  mouth and most of its body is covered with large scales. The fish normally hangs nearly motionless in the water, at a depth of about to , using its large fins for stability and with its eyes directed upward. In the low light conditions it is assumed the fish detects prey by its silhouette. MBARI researchers Bruce Robison and Kim Reisenbichler observed that when prey such as small fish and jellyfish are spotted, the eyes rotate like binoculars, facing forward as it turns its body from a horizontal to a vertical position to feed. Robison speculates that "M. microstoma" steals food  from siphonophores. Introduction. It was discovered in 1939 by marine biologist W. M. Chapman, found in deep temperate waters off of the Pacific, Indian, and Atlantic oceans. "Macropinna microstoma" is located in deep oceanic water due to their light-sensitive tubular eyes. The eyes are capped with bright green lenses, and surrounded by a fluid-filled shield. Mostly unknown until 2004. Environment. "Macropinna microstoma" is a deep-sea fish, living around 1015 meters below the water surface. It is found mostly off of California's coast and the North Pacific ocean. Living in such deep, dark waters results in the  light sensitivity "Macropinna microstoma" experiences. Due to this the barreleye has upwards ocular viewing. To be able to see prey the barreleye looks upwards towards the surface light. "Macropinna microstoma" can get as long as . It has a large, dome-shaped, transparent head. This protects its sensitive eyes from the nematocysts (stinging cells) of the siphonophores, from which it is believed to steal food. Through the dome, the entire inner part of the head can be seen, that is, their eyes, brain and all the nerve endings that make up their head. At first glance it seems that its eyes  are at the front of their head in the form of two black holes; these are its olfactory organs. Marine biologists used to believe that the barreleye's eyes were fixed in its head, which would only allow it to look upward. Its large, flat fins allow it to remain nearly motionless in the water, and to maneuver very precisely. Most of the time, the fish hangs motionless in the water, with its body in a horizontal position and its eyes looking upward. The green pigments in its eyes may filter out sunlight coming directly from the sea surface, helping  the barreleye spot the bioluminescent glow of jellyfish or other animals directly overhead. Diet. "M. Microstoma" shares its deep-sea environment with many different types of jellyfish. Some of the most common are siphonophores (length of 30 feet). The barreleye has a strong digestive system and it usually feeds on jellies and small drifting animals. The small marine creatures trapped on the tentacles of the jellies are also targeted by the barreleye fish. Reproduction. "Macropinna microstoma" is thought to be a pelagic spawner (the eggs are coated with a layer of oil that allows them to float on the closest  surface of the sea until they hatch). The female lays eggs in water and male releases sperms in water. After hatching, the larvae begin to descend to the depths as they grow, until they are located in the ideal habitat to live. During this time they feed on zooplankton and small particles of organic material that floats in the water. It is believed that there is no sexual dimorphism between the male and the female and that they do not care for their young. "M. microstoma" has been known to science since 1939, but is not known to have been  photographed alive until 2004. Old drawings do not show the transparent dome, as it is usually destroyed when brought up from the depths. It is broadly distributed across the northern Pacific Ocean, from the Bering Sea to Japan and Baja California.