The narwhal, a medium-sized whale with a long tooth that looks like a unicorn's horn, feeds on fish that swim in Arctic seas such as Greenland halibut, arctic cod, polar cod, squid, shrimp and cuttlefish. Because narwhals do not have well-developed teeth, they swim close to their prey and suck it into their mouths.Know More
Narwhals feed in deep Arctic waters often covered in sea ice, and for this reason it has been difficult to observe them feeding. Information on narwhal feeding habits has been obtained from examining their stomach contents. From these, it has been determined that they follow a very restricted and specific diet of only a few species of fish. Unlike most sub-arctic whales, narwhals feed mostly in winter. During the ice-free months of summer their stomachs are nearly empty. To feed, they make long, deep dives of up to 25 minutes into the total darkness at depths up to 4,500 feet. Physiological adaptations such as a compressible rib cage and the ability to carry a large amount of oxygen in their lungs, muscles and blood enable them to make the dives.
In medieval times, narwhal tusks were more valuable than gold, as they were believed to be unicorn horns. People attributed magical powers to them. In fact, the narwhal tusk is a front tooth that grows right through the narwhal's lip up to about 9 feet in length. Usually only males have tusks, and if females grow them, they are not as long as those of the males. Scientists have speculated about the purpose of the tusks, but the most prominent belief is that they have something to do with narwhal mating rituals.Learn more about Marine Life
The operculum is a bony flap that protects the gills of bony fish. It also keeps water flowing in the right direction over the gills. In some fish it is essential for respiration, as these fish use it to help move water past their gills by changing their internal pressure.Full Answer >
An eel is considered to be a fish. They use gills to breathe and spend most of their lives under water. A true eel is a member of the fish order Anguilliformes.Full Answer >
Seahorses occupy a middle position in their food chain. They are carnivores that feed on tiny crustaceans, such as shrimp. The shrimp feed on algae, which are near the base of the food chain. Seahorses are preyed upon by crabs and fish, which are eaten by larger fish. These large fish are hunted by apex predators, including sharks that are at the top of the food chain.Full Answer >
Crayfish have a two-part stomach, with each stomach breaking apart food in a different manner. They also possess a digestive gland, sometimes called a liver, and an intestine that finishes the digestive process and excretes waste as the organ travels from the second stomach to the anus.Full Answer >