How Freshwater Fish Eat: Usually in One Go
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The importance of our hands for feeding ourselves is huge. We use them to catch food, to process it, and to carry it to our mouths, where we can hold it in place while we bite it. It may be obvious to point out that fish lack arms, yet this does not inhibit them! Fish also differ from humans in that while we chew our food, eating it a bite at a time, fish usually eat their prey in one go, with very little chewing. To complicate matters further for fish, they often eat other live animals, which usually did not plan to feature on the menu, and that try to make things as difficult as possible for their predator.
How do fish overcome the problem of getting hold of their prey?
The solution for many fish is to vacuum up their food. By opening their mouths and expanding their buccal cavity, fish create an area of low pressure and water rushes in from outside to equalize this. If they manage to time it just right, their hapless prey is also impelled into their mouths. When the fish close their mouths, the food is trapped there when the excess water is pushed out of the gills. Fish, especially those that eat other fish, have extraordinarily large mouths, enabling them to produce a powerful suction current and to accommodate large prey items when they catch them.
Do fish have teeth?
Teeth are an essential part of a fish's foraging toolbox and an amazingly wide variety of types and shapes exist between species, each adapted to that specie's particular diet. Generalist fish, such as tiger barbs, often have simple peglike teeth that can grab and hold pretty much anything. Specialists, like Chinese algae-eaters, have flatter teeth for rasping at algae, whereas fish predators have wickedly sharp, backward-pointing teeth that efficiently trap struggling prey. Fish do not only have teeth in their jaws, like us.They very often also have pharyngeal teeth in the roof of the mouth, and specialized tongues, both of which provide extra grip.
How much food can fish eat?
In an unpredictable world, it can often pay fish to jam themselves with food whenever possible; who knows when the next meal might come along, especially if you are a predator. Consequently, fish can expand their stomachs far more than humans. Certain species can accommodate enormous meals -- out-and-out predators can often tackle prey that is half their own size - and their whole bodies become distended. However, as the food is broken down, the fish revert back to their typical shape. They store fat in a totally different way to humans and, as a result, do not usually look podgy.
The greatest problem with eating under water is getting hold of the food. As a simple test, try pushing your finger towards something small, such as a cichlid pellet All being well, you should make a good contact. In fact you should be able to push the pellet along quite easily for a distance. Now try the same, but with the pellet in a tub of water It is far more difficult because as your finger moves along, it pushes a wave of pressure along in front of it which knocks the pellet to one side. To counteract this, fish feed in an ingenious way.