These predatory marine animals are named after flowers but hunt with harpoon-like venom cells.

Nature · Published 29 September 2026 Swipe more like this →

In short: Sea anemones are not plants, but complex predatory invertebrates related to jellyfish and corals. They anchor themselves to the seabed or drift, using tentacles armed with stinging cells to paralyze prey. Despite their simple appearance, they exhibit remarkable behaviors, including symbiotic partnerships, complex regeneration, and even the ability to swim.

Sea anemones belong to the order Actiniaria within the phylum Cnidaria. Unlike their jellyfish relatives, they lack a medusa stage, existing primarily as sessile polyps. A typical anemone features a columnar body topped by an oral disc and a ring of tentacles. These tentacles are equipped with cnidocytes, specialized cells containing venom-filled nematocysts. When triggered by touch, these organelles evert like a harpoon, injecting actinotoxins into prey, which are then moved to the central mouth for digestion within a gastrovascular cavity.

The survival strategies of these animals are diverse. Many species form mutualistic relationships with algae like zooxanthellae, gaining nutrients from photosynthesis, while others host clownfish or crabs for mutual protection. Some anemones, such as the brooding anemone Epiactis prolifera, exhibit complex reproductive behaviors, including parthenogenesis and self-fertilization. Their capacity for regeneration is equally impressive; they can reproduce asexually through fragmentation or binary fission, with some species capable of regrowing entire bodies from small pieces within weeks.

While most anemones are harmless to humans, a few species can cause severe injury. Their ecological importance is significant, though they face threats from habitat destruction, pollution, and the global trade in marine ornamentals. Recent fossil discoveries, such as the 2024 find of Silurian-era Arenactinia ipuensis in Brazil, provide rare three-dimensional insights into their ancient evolution. As deep-sea mining projects threaten to expand by 2024, the stability of these resilient but vulnerable organisms remains a concern for marine conservationists.

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