Sunfish eat small fish, squid, jellyfish and crustaceans.
11 feet (3.3 m)
2,600 feet (800 m)
Temperate and tropical oceans, often basking near the surface.
Drifting slow through the open ocean, the Sunfish waves its large dorsal and anal fins to move itself. At almost 10 feet long and 14 feet tall, this is the largest bony fish on the planet, and yet it only appears like half a fish. Nicknamed ‘the swimming head’, their peculiar morphology of a curved, truncated shape forms as their back fin never grows; it folds within itself as the fish develops, creating a rounded rudder called a clavus, which the fish uses to steer through the water.
Its appearance is also the inspiration for its latin name, with mola meaning ‘millstone’, due to the sunfish’s circular shape and stone-like skin. Their rough texture is caused by the tendency of this species to become highly infested with skin parasites. This explains some of the peculiarities of its behaviour, as often they are seen breaching the surface up to 10 feet, and splashing back down to shake off the parasites. In a similar fashion to many sharks and turtles, the sunfish allows smaller fish to pick at the parasites on its skin; a symbiotic relationship, in which both organisms benefit. Being such slow-moving creatures, they feed on creatures that drift with the ocean currents. This includes jellyfish, plankton and algae, which they engulf in their small, beaked mouths that are unable to close completely.
The Mola mola truly are a beautiful species, and yet like all marine life they are threatened by human activity. With many suffocating on plastic which they mistake for jellyfish, or getting snagged in nets as they are clumsy swimmers, they are classified as vulnerable. This is evidence for the important role of marine conservation in preserving unique and threatened species like the sunfish.
With enlarged eyes, bioluminescent photophores, and often growing to enormous sizes, fish of the deep are oddly fascinating.
The deeper you dive beneath the waves, the larger the invertebrates become. This demonstrates the phenomenon of deep sea gigantism.
Many mammals, from seals to the mighty cetaceans of the open seas, frequent the depths of the ocean, diving down in search of prey.
Though they may not dominate the seas as they once did, reptiles still play a vital part in the marine ecosystem, from turtles to sea snakes.
Read our in-depth write-ups about the environment, ecosystems, adaptations, and discoveries related to the deep sea. Individual animal profiles can be found by clicking 'fact files' in the menu above.
Ah, the ocean. Rolling blue waves, picturesque seascapes, and a bottomless abyss of sheer darkness. With only 5% of the ocean having been discovered, there is much to explore.
Environmental degradation has reached even the isolated depths of the ocean, a realm we know little about, yet have caused much damage to with our destructive nature.
We are only now beginning to understand the importance of deep sea ecosystems, from hydrothermal vents that mitigate climate change, to whale-falls that provide a large carbon sink.