When you think of a marine creature, what kind of shape first comes to mind? Just like the many creatures living on land, these mammals, fish, and invertebrates take on a myriad of shapes; some are spiny, others are flat, and some look just like torpedoes, designed for speed. No matter what their shape, these animals are mostly capable of outmaneuvering even the most agile diver. They have been formed to evade predation of all types, and in many cases, even the chunkiest of fish can speed away from divers who get too close, all in the blink of an eye. Let’s take a quick look at how form and function affects which animals we might encounter while exploring the world beneath the waves.
Shape, Adaptation, and Movement for Speed
The fastest marine creatures are designed to prevent drag and pressure resistance from slowing them down; their bodies are shaped in such a way that water flows very easily over their surface, meaning that they tend to have long, sleek shapes. Think of some of the ocean’s fastest swimmers, including barracuda, tuna, sharks, and wahoo, and you’ll get the general idea. Dolphins take it a step further; their skin is capable of changing instantaneously at a microscopic level in order to allow the animals to optimize the way water flows across their bodies, enabling them to move even more efficiently.
Some very fast fish can only maintain their speed for short durations. Many sea bass and other predators fall into this category; they are capable of lightning-quick bursts of speed.
Commonly Encountered Shapes
There are a few common ways in which fish are shaped; so common are they, that scientists have categorized them into five groups. These groups are:
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Fusiform – With slightly rounded heads, tapering bodies, and a signature torpedo shape, these fish are usually the fastest swimmers in the sea.
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Dorsoventrally Compressed – Flattened from top to bottom, these fishes are often referred to as “Flatfish.” Think halibut and flounder, or picture a stingray or manta ray, and you’ll get the picture.
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Laterally Compressed – Think of tall and skinny fish, like angelfish, butterfly fish, file fish, sunfish, and others, and you’ll get the picture. These fish can fit in cracks and between rocks, enabling them to escape common reef predators with ease.
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Attenuated – Long and thin, fish such as eels are designed to hide in burrows and holes, where they lie in wait for prey.
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Unusual – Some fish defy categorization in other common groups. Some examples here are boxfish, porcupine fish, sea horses, and cowfish.
Other creatures, particularly crustaceans, have articulated legs, and are capable of moving very quickly. Most crabs and lobsters fall into this group. Sea stars, sea urchins, sea cucumbers, and some other species use water vascular systems to move from place to place, while squid and octopus have the ability to speed forcefully through the water via natural jet propulsion systems called siphons.
Strong flippers aid seals, sea lions, and sea turtles in maneuvering on land while enabling them to swim gracefully through the water; whales’ tails do the same thing. Try swimming like some of these creatures sometime, and watch each little animal you encounter carefully. You’ll find that even the simplest of them is astonishing in its own way.