Relating to or designating the oral surface or side of a radially symmetrical creature like a sea star or sea anemone, where the mouth is located.
From Greek aktis meaning 'ray' combined with the adjective suffix -al; the term describes the ray-like structures (arms) and their arrangement in radial animals.
Sea stars and anemones have an 'actinal' side (with the mouth) and an 'abactinal' side (the back), which means these creatures are perfectly designed to eat whatever drifts across their central mouth no matter which direction it comes from!
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