Rheotaxis

Rheotaxis is a form of taxis, which is a directed movement of an organism in response to a stimulus. In the case of rheotaxis, the stimulus is the flow of a fluid, typically water. Rheotaxis is observed in various aquatic organisms, including fish, invertebrates, and some microorganisms.

Types of Rheotaxis

Rheotaxis can be classified into two main types:

• Positive Rheotaxis: Movement of an organism against the direction of the fluid flow. This behavior is commonly observed in fish and other aquatic animals that swim upstream to maintain their position in a current.
• Negative Rheotaxis: Movement of an organism in the direction of the fluid flow. This type of rheotaxis is less common but can be observed in certain plankton and other small organisms.

Mechanisms of Rheotaxis

The mechanisms underlying rheotaxis involve sensory inputs and motor responses. Key sensory systems involved in detecting fluid flow include:

• Lateral line system: Found in fish and some amphibians, this system detects water movements and pressure changes.
• Mechanoreceptors: Sensory receptors that respond to mechanical pressure or distortion, aiding in the detection of fluid flow.

Ecological Significance

Rheotaxis plays a crucial role in the survival and behavior of aquatic organisms. It helps in:

• Migration: Many fish species exhibit positive rheotaxis during their upstream migration for spawning.
• Foraging: Rheotaxis aids in locating food sources by moving against the current where food particles are more likely to be encountered.
• Habitat selection: Organisms use rheotaxis to find suitable habitats with optimal flow conditions.

Examples of Rheotaxis

• Salmon: Exhibit strong positive rheotaxis during their upstream migration to spawning grounds.
• Trout: Use positive rheotaxis to maintain their position in fast-flowing streams.
• Daphnia: Small planktonic crustaceans that may exhibit negative rheotaxis in certain conditions.

Related Pages

• Taxis
• Lateral line system
• Mechanoreceptor
• Fish migration
• Plankton

See Also

• Chemotaxis
• Phototaxis
• Geotaxis