As divers, many of us have gained interest in marine biology. We’re fascinated by the creatures we encounter underwater, and we want to learn as much about them as possible. One of the best ways to advance our learning is to observe the marine life we see, and to determine why certain aspects of their physiology are the way they are. Here, we look at fish from an interesting perspective in an effort to gain greater knowledge about how different types of fish use their mouths.
No Paws, Claws, or Opposable Thumbs: What’s a Fish to Do?
Unlike humans and other mammals equipped with paws, claws, and opposable thumbs used for important tasks such as gripping items, carrying things, and cracking hard shells, fish have just one tool at their disposal: Their mouths! Various fish species use their mouths for a variety of tasks, including:
- Grabbing things
- Carrying items
- Excavating burrows
- Maintaining living spaces
- Tending to nests
- Accommodating young fry
Depending on where and when you dive, you might get the opportunity to see many of these things in action.
Methods of Eating
Some fish are herbivores, some are carnivores, and still others are omnivorous or are opportunistic feeders. All these fish are equipped with mouths that are perfectly designed to accommodate their method of feeding, and to capture the prey they prefer. For example, parrotfish have a sturdy set of fused front teeth which enable them to effectively nibble at corals, while wolf eels have stout front teeth for grabbing the crustaceans they prefer, along with powerful crushing teeth at the back of their jaws.
Butterfly fish look elegant, with their long, pointed snouts; besides adding an aerodynamic edge to the fish’s body shape, this snout is useful for reaching into cracks and crevices where tiny prey animals are hiding.
These are just a few examples of methods fish use for capturing and eating their food – and though they’re all different, most fish mouths have something in common: their teeth are composed of dentin covered with enamel. If that sounds familiar, it’s because our own teeth are made of the same stuff! As fish use their teeth for so many important jobs however, nature has equipped many of them with the ability to regrow teeth on a constant basis. They don’t have permanent adult teeth like we do. Damaged teeth are simply shed, and new ones replace them so the fish never loses its ability to eat properly.
Some fish have no need for teeth, and others, such as barracuda, have extraordinarily sharp teeth which they use to tear their prey into manageable bite-sized chunks. Others, including groupers, have simple rasping teeth that hold their prey in place while they gulp it down.
Position and Orientation
If you want to learn more about a fish’s habits, take a look at the way the fish’s mouth is oriented on its face. The orientation and location of a fish’s mouth tell us a lot about its feeding habits. There are three main ways a fish’s mouth is oriented:
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Upturned mouth – fish with upturned mouths are generally surface feeders
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Front-facing mouth – fish that feed in mid-water usually have front-facing mouths
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Downturned mouth – bottom-feeding fish or fish that feed from surfaces and the sea floor tend to have downturned mouths.
Besides position, look for appendages catfish, goatfish, and some other species are equipped with barbels, which are whisker-like appendages that allow them to feel and taste their surroundings in order to find appropriate food items. Nurse sharks, wobbegong sharks, angel sharks, blind sharks, and toadfish are some other species equipped with these important sensory organs.
Size, Shape, and Design
The shape and size of a fish’s mouth is another good indicator of its lifestyle. If you look at predatory fish such as most sharks and groupers, you’ll notice that their mouths are very large, with wide openings that allow them to easily grab and consume prey.
In herbivorous fishes like surgeonfish and tangs, and in omnivorous species including anemonefish, you’ll notice that the mouth is quite small in relation to body size.
Some fish have mouths that are useful for a variety of things. The Moorish idol has a long, tube-shaped snout much like an angelfish’s; this appendage allows the fish to forage effectively. At the end of this snout, a small mouth equipped with long, bristly teeth allows for the easy capture of elusive prey. Sharks jaws have special hinges that make capturing prey easier, and their teeth allow them to easily disable and quickly kill the fish and animals they eat, while at the same time allowing them to defend themselves and their food from others.
Still other fish are filter feeders; the whale shark and the manta ray are two examples of fish that prey on plankton. Their mouths are very large, enabling them to take in copious amounts of water; as they suck the water into their mouths, plankton is captured by gill rakers while water is expelled. This explains how massive creatures are able to effectively and efficiently subsist on tiny, nearly microscopic animals.
Lures and Special Appendages
Some fish have the ability to hunt for prey without making much effort at all. One great example of a fish like this is the frogfish, which simply camouflages itself, then waves its osculum, which is a lure-like appendage located just above the mouth. When curious creatures come close, thinking the osculum is food, the frogfish quickly nabs them and gulps them down. These fish open their mouths faster than nearly any other animal on the planet; in addition, they are equipped with what some scientists refer to as a “killer vacuum” which creates a pressure differential that enables them to easily suck prey into their mouths while preventing the prey animals from putting up an effective struggle.
Besides these examples, you’ll find many other fish using their mouths in interesting ways. Some can be seen picking up bits of sand and larger pebbles, and still others can be seen holding eggs in their mouths or even allowing their young to hide inside for protection from prey. Next time you’re diving, pay close attention to fish’s mouths – you’ll be surprised at what they have to say to you!
Comments
Very interesting and informative