Acontia (anatomy)
Thread-like defensive structures in sea anemones
Acontia are specialized thread-like structures found in certain species of sea anemones. These structures play a crucial role in the defense mechanism of these marine organisms. Acontia are equipped with cnidocytes, which are specialized cells that contain nematocysts, capable of delivering a sting to potential predators or prey.
Structure[edit | edit source]
Acontia are typically located within the gastrovascular cavity of the sea anemone. They are long, thin filaments that can be extended through the mouth or specialized pores in the body wall known as cinclides. The presence of cnidocytes along the length of the acontia allows them to effectively deter predators and capture prey.
Function[edit | edit source]
The primary function of acontia is defense. When a sea anemone is threatened, it can eject acontia through its mouth or cinclides to ward off predators. The nematocysts within the cnidocytes discharge toxins that can immobilize or deter potential threats. Additionally, acontia may assist in the digestion of prey by delivering nematocysts directly to the prey within the gastrovascular cavity.
Mechanism of Ejection[edit | edit source]
The ejection of acontia is a rapid process that involves the contraction of the mesenteries, which are internal structures that support the acontia. This contraction forces the acontia out of the body, allowing them to extend and make contact with the external environment. The retraction of acontia is similarly controlled by muscular action, allowing the sea anemone to retract the filaments back into the gastrovascular cavity when the threat has passed.
Species with Acontia[edit | edit source]
Not all sea anemones possess acontia. They are primarily found in members of the order Actiniaria, particularly within the families Actiniidae and Aiptasiidae. The presence and development of acontia can vary significantly between species.
Related pages[edit | edit source]
Acontia (anatomy)[edit | edit source]
Ejection and retraction of defense apparatus acontia in sea anemone Exaiptasia pallida
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