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The Sea Ninjas - Sea Anemones
Sea anemones are like the middle children of marine life. They don’t get as much attention as their more popular siblings i.e. your corals and jellyfish. Like corals and jellyfish, sea anemones fall in the phylum known as Cnidaria. Cnidaria is an ancient venomous phylum, which is distinguished by a unique feature known as cnidae. Cnidae play a variety of role in predation, adhesion and defence. Cnidarians are incredibly diverse in terms of diet, behaviour and habitat.
The anemones of Singapore were neglected for a while. It’s only the last decade or so, that we started documenting and classifying the anemones of Singapore. The shores of Singapore are populated with mysterious and marvellous species of anemones.
|Haeckel's anemone (Actinostephanus haeckeli): This bizarre and scary-looking anemone is sometimes seen on our shores. Like all anemones, their tentacles can sting you real bad!|
|Bubble-tip sea anemone (Entacmaea quadricolor): This anemone with bulbous tips is sometimes seen on our seashores. The Tomato clownfish is one of several animals that lives happily among and unharmed by the tentacles of bubble tip anemones.|
Bubble-tip sea anemone (Entacmaea quadricolor) can form friendly relationships the anemone fish of Singapore. We have miniscule invaders in the form of Lined bead anemone (Diadumene lineata); an invasive orange stripped species of anemones who thrive in tropic to temperate terrains. We even have an anemone that can swim! The Swimming anemones (Boloceroides mcmurrichi), swims in a very endearing way by beating its tentacles in a coordinated way. When they swim, it looks like flower which blossoms and closes it petals repeatedly as it drifts through the sea.
|Lined bead anemone (Diadumene lineata): This tiny anemone is often seen on our Northern shores, on hard surfaces near the high water mark.|
|Lined bead anemone (Diadumene lineata) : Often found in clusters of numerous individuals, on hard surfaces such as jetty legs.|
Let’s not forget the handful of enigmatic anemones which haven't been classified yet.
Unlike jellyfish, most sea anemones are sessile. This sessile nature of sea anemones don't appear to slow them down as they stick to rocks like passive blobs and wait for a chance to capture their passing prey. The reality is that sea anemones are like sea ninjas. They have cunning and creative ways of capturing prey and fending off predators. They can disappear into the sand within seconds…never to be seen again. They have microscopic weapons in the form of cnidae. They have a treasure trove of potent and diverse toxins. Compared to other Cnidarians such as corals and jellyfish, the sea anemones have a wider variety of toxins in their venom.
|The different types of cnidae found in the Frilly Anemones (Phymanthus pinnulatus). Image taken from Yap et al. (2019).|
Let us dive into the saga of these merciless marine mercenaries!
About the writer:
Shabdita Vatsa recently graduated from the National University of Singapore with a Bachelors in Life Sciences (Molecular and Cell Biology). She spent most of her undergraduate days obsessing over sea anemones and their toxins. Her fascination became research projects, working with scientists from the Reef Ecology Lab and Protein Chemistry Lab to study anemone toxins.
A passionate writer, Shabdita loves creative writing, popular science writing, and scientific writing. You can find more of her writings on her personal page: https://lifesciencepotluck.tumblr.com/
- Shick (1991) Functional biology of sea anemones. Springer.
- Fautin et al. (1995) Costs and benefits of the symbiosis between the anemoneshrimp Periclimenes brevicarpalis and its host Entacmaea quadricolor. Marine Ecology Progress Series 129: 77-84.
- Fautin et al. (2009) Sea anemones (Cnidaria: Actiniaria) of Singapore: Abundant and well-known shallow-water species. Raffles Bulletin of Zoology Supplement No. 22: 121-143.
- Fautin et al. (2015) Sea anemones (Cnidaria: Actiniaria) of Singapore: Shallow-water species known also from the Indian subcontinent. Raffles Bulletin of Zoology Supplement No. 31: 44-59.