Sea anemones, or just anemones for short, are animals in the phylum Cnidaria. At the moment, more than 1000 different species of sea anemone exist in the ocean, in almost every ocean habitat imaginable. They derive their name from the anemone flower, due to the various bright colours that they exist in. Anemones are closely related to jellyfish, corals and hydroids. They vary in sizes as well – the smallest can be the size of a pinhead.
The largest sea anemone is called Mertens’ carpet sea anemone (Stichodactyla mertensii) and can grow to up to a metre in diameter. Sea anemones are, in general, sessile animals and do not move unless they really have to. Often movement is required to protect its territory from other anemones, however this movement is very slow and gradual. Some anemones do like living colonially with others, but most of them are solitary and prefer their own space.
At the Aquarium Foundation, we have the Sandy anemone. These animal ambassadors feature in our Discovery Centre lessons, and they travel all over Cape Town with our Oceans in Motion outreach van.
Species & IUCN status
The sandy anemone is a native species and currently not in danger due to population loss. There have been studies along the Cape Peninsula on the impact that plastic has on this species, as sandy anemones are known to ingest plastic pieces mistaking them for food.
This anemone can be found on the southern African coast, from Lüderitz, in Namibia, to Durban in South Africa. It is not an endemic species to this region, as you will also find it on the coast of Argentina, in South America.
The sandy anemone enjoys living in gullies and rocky shore environments with high wave actions. It has a very strong muscle that helps it attach to a surface, so that it does not get washed away by the waves. Living in such a turbulent environment assist the anemone with both constant oxygen supply, and the ability to find food.
All anemones are predators, even if they do not come across as the typical predator we are used to. Sea anemones have specialised stinging cells inside their tentacles, called nematocysts, which they use to stun prey. They feed on mussels, sea snails and small fish – whatever they can grab that floats past them. Once the anemone has taken hold of their prey, they move it towards their mouth, in the middle of their body and swallow it whole. The sandy anemone’s stinging cells are potent for the prey that they feed one, however humans are not affected by them, generally.
The sandy anemone’s body shape is that of a typical anemone – cylindrical, with a muscular ‘foot’ and a round oral disc on top, surrounded by up to 300 short tentacles. It is a medium-sized anemone, with a potential diameter of 10 cm. The reason it is called a sandy anemone is because its outer body is covered in sticky nodules, to which sand adheres to.
Often you will find these anemones in the rock pools, covered in sand. They come in a beautiful variety of colour, including pink, blue and green. Sea anemones only have one opening in their body, which is used for ingestion food and egestion of waste materials. They have a hydrostatic skeleton, which means that their body is filled with water, which keeps the animal upright and rigid.
Spotlight on educator
Chanelle Naidoo – Environmental
educator and marine sciences
Chanelle holds a bachelor’s degree in social sciences from the University of Cape Town, and an honours degree in geography, from UNISA. She has recently completed her postgraduate diploma in teaching. Chanelle teaches in our upper discovery centre and enjoys interacting with the younger grades. Her passion lies in making a difference in the lives of children, by teaching them about the ocean and the environment.
Spotlight on educator
Thabo Sabeko – Outreach teacher.
Thabo has been an outreach teacher for more than 10 years and takes live animals to schools all over Cape Town, and beyond. He is a bilingual, self-taught teacher who brings the ocean to children who do not have the resources to visit us. He strives to create change in his and other communities by teaching children about the importance of the environment and the animals that live in it.