#0048 Knobby argonaut – Argonauta nodosus

Beautiful and almost mythical, these pelagic octopus are structural engineers and reproductive marvels – with a bit of the bizarre thrown in.

Female Knobby argonauts are much larger than males – their total length is up to 50cm while the males are only about 2cm – and use webs on their first arm pair to secrete a thin calcium carbonate shell in which to brood their eggs (see slide 4 for an image of the eggs).

These delicate structures have fascinated biologists for centuries. In the 1800s, it was believed that the octopus inside the shells were parasites that had killed the rightful shell owners. This theory was strengthened when the shells were also found to contain multiple detached arms.

The debunking of this delivered a mind-blowing discovery about the argonaut’s reproductive process. The dwarf males, who live freely in the ocean without a shell, transfer spermatophores to a specialised arm, which then detaches from his body, crawls autonomously into the female’s mantle cavity and finds her reproductive tract, where it deposits a sperm packet. The detached arm might remain inside the female for weeks, with spermatophores stored until she is ready to spawn.

Some females can have multiple detached arms inside their shells! In this act of sacrifice, the tiny males give both life and limb – believed to die after delivering their genetic legacy.

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Here’s some feel-good news to start your weekend! 🐙

Images: @unsplash @the_rewilding

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Any idea how many species of kelp are in the Great African Seaforest? Know what a holdfast is? Our latest blog is a 101 on all things kelp (think of your next family Scrabble game…). Link in bio 🐙

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#0047 Sucker-foot sea hare – Aplysia juliana

A rabbit in the ocean that whips up clumps of spaghetti? Well, not really. These large sea hares – some as big as rugby balls – are a type of sea slug and are so named because their rhinophores resemble bunny ears. These sensory organs allow the sea hare to taste, smell and detect chemicals in the water to find food and locate mates. And the ‘spaghetti’? These are the animal’s eggs, which they lay in cream-coloured tangles on various seaweeds.

This particular species is variably coloured, its whitish, yellow or dark-brown body spotted or striped in brown or black. The yellow and brown ones are almost delicious looking, as though made from custard and chocolate.

However, predators of these algae-munching animals are in for a surprise: Sucker-foot sea hares secrete a purple dye when disturbed – a behaviour known as ‘phagomimicry’. The dye consists of a melange of chemicals that mimic the smell of food, which overwhelm the predatory senses and make the sea hare undetectable. A true case of pulling a rabbit out of a hat!

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#0046 Giant jelly – Rhizostoma luteum

What this large jelly lacks in tentacles, it more than compensates for with mouths. Giant jellies, which are often washed ashore, lack a central primary mouth; instead, their four pairs of thick oral-arms are lined with numerous small mouthlets. The bell, firm and scalloped at the edges, can span up to 60cm, while the oral-arms may trail club-shaped appendages that stretch to twice that length. Though they drift gracefully through the water feeding on zooplankton, they too become prey when stranded on beaches, where plough shells eagerly munch on them.

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In our hurtling human world, nature invites us to return to love. 💙

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Often out of sight, kelp forests are found across the world — each one unique ecosystems that not only support thousands of marine species but all life on Earth. 🌍

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Chacma baboon – Papio ursinus

A baboon in the ocean? Snacking on mussels and limpets? On the shores of the Great African Seaforest, this unlikely scene is real. While marine foods make up only 10% of their diet, some troops on the Cape Peninsula have acquired a taste for seafood, descending to the rocky shore at low tide to get their protein fix. They prise open mussels with their dexterous hands and, once their bellies are full, retreat to nearby cliffs to rest. Managing baboon and human interactions is an ongoing debate, as built-up areas offer quick, high-calorific food. However, the preferred diet of these omnivorous animals includes fruits, leaves and invertebrates, and they have been observed hunting reptiles, birds and small mammals.

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All kelp is seaweed, but not all seaweed is kelp …. explore why kelp forests deserve our attention in our latest blog. Click the link in our bio.

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#0044 Elegant feather star – Tropiometra carinata

As the name suggests, this striking species has 10 straight, upward directed arms that bear up to 100 evenly spaced lateral branches (pinnules) that resemble the flight-feather of a bird. And seeing these animals in ‘flight’ is truly special. While they are usually attached to shallow reefs, sometimes among other smaller feather stars, they are capable of swimming when disturbed, their arms moving up and down in a slow, graceful movement, almost puppet-like. Elegant feather stars also use these arms to snag floating plankton or other organic matter, feeding the food via tube feet that line the pinnules into a groove running along the length of the arm. There, cilia (tiny, hair-like structures) propel mucous and food particles to the mouth, situated on the upper surface of the central disc. The pinnules have another important function – reproduction. While we’re still researching the exact process of this species, male feather stars store gonads in these branches, which rupture when the gametes are mature, releasing sperm and eggs into the water column. Here, they develop as planktonic larvae that then settle on the reef … and so begins a new generation of these yellow-hued wonders.

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