Question

The nematocysts of cnidarians are used primarily for: a. capturing prey. b. detecting light and dark. c. courtship. d. sensing chemicals. e. gas exchange.

Short answer

The primary use of the nematocysts of cnidarians is for capturing prey.

Step-by-step solution

Understand the Function of Nematocysts

Nematocysts are specialized cells found in cnidarians, such as jellyfish, sea anemones, and corals. They contain a stinging structure used for both defense and capturing prey.

Eliminate Irrelevant Options

Options b, c, d, and e are not related to the primary function of nematocysts. Detecting light and dark, courtship, sensing chemicals, and gas exchange are functions served by other structures or processes in cnidarians.

Identify the Correct Answer

Since nematocysts are known for their role in capturing prey through their stinging mechanism, option a is the correct answer.

Key concepts

Capturing Prey

Nematocysts are one of the most fascinating adaptations in the animal kingdom, with a primary role in capturing prey. Found in cnidarians such as jellyfish, sea anemones, and corals, these microscopic stinging cells are a defining feature of the group. Each nematocyst comprises a small capsule that contains a coiled, thread-like tube that can deliver toxins to subdue prey.

When the cnidarian encounters a potential meal, the nematocyst fires the thread into the target organism, injecting it with a paralyzing toxin. This rapid-fire mechanism enables cnidarians to catch prey much faster than they can escape. Thus, ensuring their survival in various marine environments. This highly effective mechanism not only captures food but also serves as a deterrent against predators.

Cnidarian Defense Mechanisms

For cnidarians, defense is as crucial as capturing prey, and they employ their nematocysts for this purpose as well. When threatened, these organisms deploy their nematocysts as a rapid response defense system. The toxic sting serves as an effective deterrent, often causing potential predators to think twice before attacking.

The toxins found in nematocysts can cause varying effects upon contact - from mild irritation to severe pain and paralysis. In some cases, the sting can even be lethal. Interestingly, the sheer presence of nematocysts can even prevent some attacks, as predators may recognize and avoid well-known stinging species altogether. This mechanism is an essential aspect of the survival strategies of cnidarians, allowing them to persist in competitive and often aggressive marine ecosystems.

Biology of Jellyfish

Jellyfish are one of the most well-known members of the cnidarian family, characterized notably by their gelatinous bodies and their usage of nematocysts. Their biology is specialized for life in the water. Jellyfish lack complex organs such as a brain or heart; instead, they have a simple nerve net to help them navigate and respond to their environment.

Their body is mostly made up of water and is structured with an umbrella-shaped bell and trailing tentacles. These tentacles are loaded with nematocysts, which provide jellyfish with their remarkable ability to capture prey and defend against threats. Because of this simple yet effective biological design, jellyfish have thrived in marine ecosystems for millions of years.