Crayfish Adaptations

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Crayfish, also called crawfish or crawdads, live in lakes, ponds, streams and rivers across the country. They look like miniature lobsters, but they've evolved to live in freshwater instead of the ocean. Several of their adaptations help them survive in spite of a variety of predators, including large fish, small mammals, birds and people.

Eyes

Shallow-water environments aren't always the easiest places to see. The silt on the bottom of the lake or stream is easily disturbed, creating a murky environment that hides both prey and predator. Crayfish adapted eyes on short stems that move around, allowing them to see in all directions just by turning the stems. They also have two pairs of sensitive antennae that help detect movement in the water as well as chemicals transmitted through the water, such as that of a dead fish or a nearby potential mate.

Reproduction

Instead of fertilizing eggs immediately, female crayfish have adapted a way of storing sperm until they're ready to lay eggs. Crayfish typically mate in the fall, but the females don't lay eggs until the spring, when the babies have a better chance of surviving in warmer weather. After mating, the females store the eggs and sperm separately, then release them both at the same time in the spring, at which time the sperm fertilizes the eggs. The females hold the eggs under their bodies with their swimmerets, or small, leg-like appendages that help them swim. The babies hatch in a few weeks, then they stay with their moms for most of the summer until they're big enough to survive on their own.

Color

Crayfish don't start out red; that's just the color you get when you cook them. Crawfish come in a variety of colors that tend to reflect their habitats. They might be dark brown to help hide under rocks, yellow to blend in with a sandy lake bottom or green to help camouflage them in underwater vegetation, for example. Their hard exoskeletons don't grow with them, so they molt several times a year as they're growing, then periodically as adults. Their new exoskeletons are typically identical to the original one, keeping the same color scheme.

Pincers

Best known for their large front pincers, crayfish have smaller ones on their front two sets of legs. These legs are used for walking, but the pincers help bring food to the crayfish's mouth and tear it into smaller pieces. The large pincers grab and hold prey, and they help ward off predators. When threatened, crayfish often raise their pincers high and wave them around. Some also use their front pincers to help dig burrows. If a crayfish loses a leg or pincer, it grows back, usually during the animal's next molting cycle.

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