Sea anemones are marine invertebrates, often appearing as colorful, stationary “flowers” anchored to the seafloor. Many people perceive them as immobile. However, these animals possess various methods for movement, challenging the common misconception of their static existence.
The Truth About Anemone Movement
Contrary to popular belief, sea anemones do move. While most species spend extended periods attached to a substrate, they are not permanently fixed. Their movements are typically slow and subtle, making them difficult to observe without time-lapse photography. This often imperceptible motion contributes to the belief that they are immobile.
Methods of Anemone Locomotion
Sea anemones employ several physical mechanisms to relocate.
Gliding and Crawling
One common method is gliding or crawling, where they slowly slide across surfaces using their pedal disc, an adhesive base. This process involves wave-like contractions across the pedal disc, resembling the movement of a snail.
Somersaulting and Drifting
Some anemone species can also perform a somersaulting or inchworming motion. This involves detaching their pedal disc from the substrate, extending their body, and reattaching the disc further along in a looping fashion. Anemones can detach completely from their substrate and allow ocean currents to carry them to a new location. Certain specialized species, like the floating anemone, possess a base with air bubbles, enabling them to remain buoyant and drift.
Limited Swimming
While less common, some species, such as Stomphia and Boloceroides mcmurrichi, exhibit limited swimming abilities. They achieve this by undulating their bodies or tentacles, propelling themselves through the water. This swimming behavior is a rapid response to immediate threats, allowing them to quickly vacate an unfavorable area.
Reasons for Anemone Relocation
Anemones relocate for various reasons.
Food and Safety
A primary reason is to find areas with better food availability. They also move to escape predators, relocating to safer zones.
Habitat and Resources
Finding a more suitable habitat is another frequent driver. This includes seeking optimal light conditions, especially for species that host symbiotic algae, and locating stable substrates for attachment. Anemones may also shift positions to avoid overcrowding and reduce competition for resources.
Reproduction
Some species even move as a form of asexual reproduction, splitting into new individuals by moving in opposing directions or leaving behind fragments of their pedal disc that regenerate.
Environmental Triggers for Movement
External stimuli and environmental factors often initiate an anemone’s movement.
Light and Temperature
Changes in light intensity can prompt relocation, as anemones seek optimal sunlight for their symbiotic algae. Fluctuations in water temperature can also trigger movement, as anemones attempt to find more comfortable thermal conditions.
Water Chemistry and Physical Disturbances
Unfavorable water chemistry, such as changes in salinity or pH, can stress anemones and cause them to seek a more hospitable environment. Physical disturbances, like being touched, bumped, or dislodged, often provoke a defensive move.
Chemical Cues and Water Flow
The presence of chemical cues in the water, indicating nearby predators or potential food sources, can also prompt movement. Proper water flow is a factor, as anemones may adjust their position to optimize nutrient intake and waste removal.