Aega antarctica fish. It has strong muscles in its oesophagus and large salivary glands and rapidly fills its dilatable hind gut with blood. It then drops off the fish and spends several months on the seabed digesting the blood. In a research study, specimens of "Aega antarctica" were kept in a marine aquarium at the University of Oldenburg, Germany, where they were maintained at a temperature of . It was found that they would feed on a number of species of fish native to the North Sea and in this research they were fed on live European plaice ("Pleuronectes platessa"). One fish
Flatfish around "ponds" of sulphur at hydrothermal vents on the seafloor. No other flatfish is known from hydrothermal vents. Many species will enter brackish or fresh water, and a smaller number of soles (families Achiridae and Soleidae) and tonguefish (Cynoglossidae) are entirely restricted to fresh water. The most obvious characteristic of the flatfish is its asymmetry, with both eyes lying on the same side of the head in the adult fish. In some families, the eyes are usually on the right side of the body (dextral or right-eyed flatfish), and in others, they are usually on the left (sinistral or left-eyed