20.10.2025 – Doing their thing
October 26, 2025
21.10.2025 – Piloting the way
October 27, 2025
Source: https://www.inaturalist.org/photos/916904?size=large
Speaking about nature we often hear the words and phrases “Survival of the fittest”, “Competition” or “The larger eats the smaller”, but what if sometimes working together can be more beneficial. This concept is not as strange as you might think. In biology this is called mutualism, cooperation or symbiosis. One of my favourite examples is the interaction between some crab species with sponges and sea anemone.
The stars of this story are the Sponge crab (Dromia personata) and the Red hermit crab (Dardanus calidus) which interact with the Breadcrumb sponge (Halichondria panicea) and the Hermit-crab anemone (Calliactis parasitica). The sponge crab collects a sponge and adheres it to its carapace holding it there in place with its hind legs. It shapes the sponge so that it fits perfectly around the back. The crabs benefits from this as it gets a perfect camouflage to the surrounding area, while the sponge gets a guardian, as the crab will defend his sponge from any predator and even should he loose the sponge he has the ability to find it again to attach it back.
Hermit crabs and anemones have a similar relationship. In this case the hermit crab gets the protection from the stinging cells of the anemone while the anemone gets free transportation and free food delivered by the hermit crab. This works as the anemone is attached on the shell in which the hermit crab lives. Not like with the sponge where the crab initiates the relationship, here the relationship is instigated by the anemone. Later, should the hermit crab need to change the shell, the anemone is then also transferred to the new shell inhabited by the crab.
So you see that these small critters can have some really interesting life stiles and I hope that now you see the ocean a tiny bit in a different way.
By Horst Schulte
