Skip to main content


One of the most striking features of fish is their colorization. Coloring and body marks on fish help them avoid predators by staying out of sight. Many prey species, such as gulf flounder, avoid being eaten by blending in with their surroundings, matching the subtle shades of their habitats. Spotted fish look like the seafloor, and striped fish blend in with grasses. Some reef fish display bright colors because they live among brightly colored sponges and corals.

Sand gulf flounder
Sand gulf flounder

Conversely, coloring that mimics fish’s habitats helps predators get close to their prey. The ability to avoid detection is a significant advantage for such hunters as scorpion fish that wait quietly until prey comes within striking distance. A hunter is able to conserve both time and energy if it does not have to pursue its food. Most fish, including sea trout and grouper, display some degree of countershading.

This form of coloring reduces the clarity of the fish’s body outline in water. The simplest, and most common, form of countershading is a dark dorsal side and a pale ventral side, with intermediate colors between the two. When sunlight filters down through the water, it lightens the fish’s back and throws shadows on its underside. The overall effect of countershading lessens the degree of contrast between the fish and the water.

A few species of fish, such as the spotfin butterfly fish and the high hat fish, show disruptive or deflective colorization that includes bands, stripes, or dots of contrasting colors. These colors and patterns confuse predators by distorting the true shape, size, and position of the fish. Bright patterns draw the predator’s eye, causing it to see the pattern rather than the fish itself. This type of coloring can deflect the predator’s attention away from a fish’s vulnerable areas, such as its head and eyes.

Colorization can also be used as an advertisement. There is no point in being poisonous and unpalatable if no one knows it. Instead of hiding, poisonous fish announce their dangerous status. Fish may also advertise their age or sex with coloring. Males are generally more colorful than females, whose duller shades help camouflage and protect them. Young fish may be transparent or pale, making it hard for predators to spot them, as well as letting the older fish of their own species know that they are not a threat.

Popular posts from this blog

Advantages and Disadvantages of an Exoskeleton

More than 80 percent of the animal species are equipped with a hard, outer covering called an exoskeleton. The functions of exoskeletons are similar to those of other types of skeletal systems. Like the internal skeletons (endoskeletons) of amphibians, reptiles, birds, and mammals, exoskeletons support the tissues and give shape to the bodies of invertebrates. Exoskeletons offer some other advantages. Serving as a suit of armor, they are excellent protection against predators. Also, because they completely cover an animal’s tissues, exoskeletons prevent them from drying out. In addition, exoskeletons serve as points of attachment for muscles, providing animals with more leverage and mechanical advantage than an endoskeleton can offer. That is why a tiny shrimp can cut a fish in half with its claw or lift an object 50 times heavier than its own body.
Despite all their good points, exoskeletons have some drawbacks. They are heavy, so the only animals that have been successful with them …

Differences in Terrestrial and Aquatic Plants

Even though plants that live in water look dramatically different from terrestrial plants, the two groups have a lot in common. Both types of plants capture the Sun’s energy and use it to make food from raw materials. In each case, the raw materials required include carbon dioxide, water, and minerals. The differences in these two types of plants are adaptations to their specific environments.
Land plants are highly specialized for their lifestyles. They get their nutrients from two sources: soil and air. It is the job of roots to absorb water and minerals from the soil, as well as hold the plant in place. Essential materials are transported to cells in leaves by a system of tubes called vascular tissue. Leaves are in charge of taking in carbon dioxide gas from the atmosphere for photosynthesis. Once photosynthesis is complete, a second set of vascular tissue carries the food made by the leaves to the rest of the plant. Land plants are also equipped with woody stems and branches that …

Prokaryotic Cell Structure

Prokaryotic cells are about 10 times smaller than eukaryotic cells. A typical E. coli cell is about 1 μm wide and 2 to 3μm long. Structurally, prokaryotes are very simple cells when compared with eukaryotic cells, and yet they are able to perform the necessary processes of life. Reproduction of prokaryotic cells is by binary fission—the simple division of one cell into two cells, after DNA replication and the formation of a separating membrane and cell wall. All bacteria are prokaryotes, as are the archaea.

Embedded within the cytoplasm of prokaryotic cells are a chromosome, ribosomes, and other cytoplasmic particles (Fig. 1). Unlike eukaryotic cells, the cytoplasm of prokaryotic cells is not filled with internal membranes. The cytoplasm is surrounded by a cell membrane, a cell wall (usually), and sometimes a capsule or slime layer. These latter three structures make up the bacterial cell envelope. Depending on the particular species of bacterium, flagella, pili (description follows)…