Actinia equina

Actinia equina is a cnidarian belonging to the class Anthozoa, which is classified in the order Actinaria, family Actiniidae. It inhabits the bottoms of the Mediterranean Sea, the eastern Atlantic Ocean, from the coasts of western Europe and Great Britain to South Africa. Beadlet anemone are usually solitary species found on the rocky bottoms of coastal waters at depths of up to 20 meters. It is common to find specimens in the intertidal zone that are completely exposed to the air during low tides.

The body of Actinia equina consists of a wide base up to 5 cm in diameter, from which arises a smooth stem that at its end becomes a crown formed by up to 192 tentacles arranged in 6 concentric circles. The tentacles are of moderate length, and are covered with stinging cells called cnidocytes, which at the slightest contact will shoot injecting their prey with a paralyzing poison (echinatoxin). The tentacles and in general the entire crown of tentacles and part of the spine are retractile, so that sometimes we observe specimens as a hemispherical gelatinous mass clinging to the substrate. It is in this conformation that due to its intense red color it resembles a tomato. As for the coloration of Actinia equina, we not only find red specimens, but also green, brown or orange.

Despite being considered a static benthic species, specimens of Actinia equina have a certain capacity for movement, disengaging its flat basal disc from the bottom and being able to move short distances.

The diet of Actinia equina consists of small fish that it paralyzes and traps with its tentacles, as well as crustaceans and molluscs.

The reproduction of Actinia equina is viviparous, with up to 100 embryos developing inside each specimen before being released into the currents to be dispersed. Asexual reproduction by division of the originating specimen is also common, giving rise to two identical specimens.

It is possible that if we look closely at the specimens of Actinia equina, we can also observe the nudibranch Aeolidiella alderi. It feeds on the tissues not only of specimens of Actinia equina, but also of other cnidarians.