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Conservation

Underwater Ambassadors

Stars of the Sea

 

Turtles

Stars of the Sea

Anemones

Shysharks

Seals

Stars of the Sea

The echinoderms are truly one of the most fascinating groups of animals in the ocean. Especially since they are the only major phyla in the animal kingdom that is exclusively marine. The echinoderms include sea stars, sea urchins, feather stars, sea cucumbers and brittle stars. They have no hearts, eyes or brain. And all of them have a pentaradial body structure, even if it does not seem so at first glance. Echinoderms are found in all corners of the ocean, from the deep sea to the shallow shorelines of continents.

The smallest echinoderm that has been found is a sea cucumber (Psammothuria ganapati), that lives in the sandy shores of India. It only grows to a maximum length of 4 mm. On the other end of the size spectrum lies a sea star. There are two different species vying for first place, one due to its weight and the other due to its arm length. Catala’s sea star (Thromidia catalai) is the heaviest echinoderm, weighing in at around 6 kg. The sea star with the longest arms is scientifically called Midgardia xandaros. It currently does not have a common name, mainly because it has not been studied all that much because it lives in depths of 100 m in the Gulf of Mexico. Its arms are up to 67 cm long, with a tiny body that only measures 2.6 cm across.

At the Aquarium Foundation, we usually have examples of all five classes of echinoderms during our Marine Sciences Academy courses, however in our Discovery Centres, we have sea stars and sea urchins that act as ambassadors in our daily lessons. The red sea star and the cape sea urchin also travel with Thabo to schools, in our specially designed Oceans in Motion outreach van.

Spotlight on educator

Bianca Engel – Deputy head of education and environmental educator.

Bianca completed her undergraduate degree in zoology at the University of Cape Town. She also completed a postgraduate diploma in teaching and has taught ever since. Adult education is something that Bianca specialises in, having trained countless volunteers for the Aquarium and collaborating with WWF to educate restaurant and retail staff on sustainable fishing. She has immense knowledge about environmental ocean education and acts as a mentor to the other teachers.

Red sea star

(Callopatiria granifera)

Species & IUCN status

The red sea star has not been assessed as a species and can be found quite commonly along the shores of southern Africa.

Range

This sea star can be found in the sub-tidal zone, from as far north as Angola, to the shores of Durban.

Habitat

The red sea star lives in the subtidal zones along the shore, away from wave action and where it can be permanently submerged. It does not do well when exposed to the sun and wind.

Diet

These sea stars are detritivores – animals that feed on decomposing animals and sea plants. This is true for most sea star species. Like all sea stars, the red sea star eats its food by expelling its stomach outside of its body and wrapping it around its food. Digestion takes place externally, after which the stomach will be pulled back into the body cavity.

Physical Characteristics

The red sea star is an average-sized star that can grow up to 15 cm from arm to arm. It has a deep orange to red colour which covers its body. When looking at the body closely, its skin looks like it is covered in tiny platelets. It has the typical pentaradial body structure of an echinoderm, with five short arms that grow from the central disk. We have, however, had red sea stars with more than five arms.

This sometimes happens when a sea star loses an arm and regrows two instead. Sea stars are very good at re-growing lost limbs; however, it does take them quite long to do so. The red sea star has rows of tube feet along its five arms, a common characteristic amongst most echinoderms. These operate The mouth of the sea star can be found at the bottom of its body and the anus on the top. This animal has no eyes, however it has small sensory organs at the tip of each of its arms, to sense danger or to seek out food.

Scientific name

Callopatiria granifera

 

Conservation status

Not assessed

Spotlight on educator

Anzio Abels – Outreach teacher
and tech guru

Anzio has been part of our team for more than 5 years and runs the Smart Living outreach programme. He holds a bachelor’s degree in biodiversity and conservation biology from the University of the Western Cape. He has many years of experience working with birds of prey and was one of the first to complete our Young Biologist course. He enjoys the variety that outreach teaching brings and is great at teaching children about marine sciences and environmental concepts.

Cape sea urchin

(Parechinus angulosus)

Species & IUCN status

The Cape sea urchin is an endemic species to the coastline of southern Africa. Their population is in good health, however in 1994 a local population in the southwest Cape was almost wiped out by west coast rock lobsters. 

Range

This sea urchin can be found from Lüderitz, Namibia, to Durban South Africa. 

Habitat

This animal is commonly found in the lower zones of the rocky shores, all the way as deep as 100 m.

Diet

The Cape sea urchin is a grazer, with a particular appetite for kelp. It can regulate the growth of kelp forests, to a point of eradication. When there is a large group of cape sea urchins in an area, they can create urchin barrens since they can devour all of the sea plants. The urchins have a natural predator in the West coast rock lobster.

Kelp forests are a finely balanced ecosystem, with cape sea urchins and west coast rock lobsters playing an important role in upholding that balance. Cape sea urchins also provide shelter to juvenile abalone.

Physical Characteristics

The cape sea urchin is a small, round sea urchin with a diameter of around 60 mm. The spines are sharp and short, and densely packed along its body. The cape sea urchin external skeleton, also called a test, is a light green in colour. The spines, however, come in a variety of colours, ranging from red to purple to white.

Due to the grazing behaviour of cape sea urchins, they need strong teeth to be able eat tough sea plants like kelp. The mouth of a sea urchin is at the bottom of its body and reveals a set of five teeth. Even though sea urchins do not exhibit the obvious pentaradial symmetry that sea stars do, there are certain characteristics, such as five teeth, that reveal the family connection.

Scientific name

Parechinus angulosus

 

Conservation status

Not assessed

Spotlight on educator

Wandiswa Jonga – School group
coordinator and environmental
educator.

Wandiswa is passionate about making a difference within her communities and improving the lives of children and adults through social activism. She has been an important advocate of including indigenous knowledge in some of our courses and enjoys interacting with the children that visit our facilities each day.