acephalous

Acephalous is an adjective used in biology and zoology to describe organisms that lack a head. This term is often used to describe certain invertebrates, such as cnidarians (e.g., jellyfish, corals) and some flatworms (e.g., planarians). The absence of a head in these organisms is a result of their evolutionary history and adaptation to their specific environments.

The lack of a head in acephalous organisms does not imply a lack of sensory organs or nervous system complexity. Instead, these organisms have evolved unique ways to perceive their surroundings and respond to stimuli. For example, jellyfish use their tentacles to detect changes in their environment, while planarians have a simple nervous system that allows them to respond to touch and chemical signals.

Acephalous organisms are an important part of many ecosystems, serving as both predators and prey. Their unique biology and adaptations make them fascinating subjects of study for scientists and enthusiasts alike.