Symbiosis between hermit crab and anemone
Symbiosis is quite frequent in the underwater world and in recent days we have witnessed one of the most classic forms of symbiosis in our Mediterranean Sea, that between the Hermit Crab (Pagurus bernhardus) and the Hermit Crab Anemone or Actinia (Calliactis parasitica). We are exploring a seabed composed of a coral wall that varies from 46 to 49-50 meters deep, which we often visit due to the exceptional presence of very tall and prosperous red Gorgonians of the Paramuricea clavata species. This type of seabed presents a certain biodiversity which almost always makes the dives unique, luck also favored us because the visibility on the seabed was unusually discreet, around ten metres, a rather exceptional case given the characteristics of the muddy seabed outside the cliff. Symbiosis between hermit crab and anemone Simbiosi tra paguro e anemone intotheblue.it
Precisely thanks to the more unique than rare visibility, we managed to see the Hermit Crab in movement with all its “baggage” of shell and two anemones”. The rest can be seen clearly from the video, perhaps excluding the dimensions of the entire “package ” about 25-30 cm. We have often encountered the Hermit Crab, but never in the most classic of configurations, i.e. with the two sea anemones for protection placed on the shell.
The temperature on the seabed is around 17°C, and is constant practically all year round, this note must make us reflect on the delicate balance of this ecosystem, already threatened by human factors such as rising sea temperatures and overfishing which is practiced on these reefs, both with gill nets and trawl nets. One of the first things we noticed when we arrived on the seabed was an entire gorgonian about 2 meters high completely torn from the cliff and lying dead on the seabed not far from the others.
We are almost certain that the cause of all this is precisely the grabbing of a net, in fact one rarely anchors in depths of around 50 metres, while the fishermen are more willing to approach these reefs with their nets trying to catch lobsters and fish such as the red scorpion fish and the very frequent Sparids on this type of seabed. That gorgonian torn from the cliff was probably hundreds of years old, which is why, we will never tire of repeating it, the only way to preserve these habitats are parks and marine protected areas.
Symbiosis (from Greek συμβίωσις “living together“, from σύν “together” and βίωσις “living”) is any type of close and long-term biological interaction between two different biological organisms, whether mutualistic, commensalistic or parasitic.
The organisms, each called a symbiont, can be of the same species or different species. In 1879, Heinrich Anton de Bary defined it as “the coexistence of different organisms”. The term has been the subject of centuries-old debate over whether it should specifically denote mutualism, as in the case of lichens; biologists have now abandoned this restriction. Symbiosis can be obligatory, meaning one or both symbiotics are entirely dependent on each other for survival, or facultative (optional) when they can generally live independently.
Symbiosis is also classified by physical attachment; the symbiosis in which the organisms have bodily union is called conjunctive symbiosis, and the symbiosis in which they are not in union is called disjunctive symbiosis. When an organism lives on the surface of another organism, like lice on human subjects, it is called ectosymbiosis; when one partner lives in the tissues of another, such as Symbiodinium in coral, it is called endosymbiosis.
https://it.wikipedia.org/wiki/Simbiosi
The Hermit crab (Pagurus bernhardus Linnaeus, 1758) is a decapod crustacean belonging to the Paguridae family. He is more commonly called the hermit.
Distribution
It is widespread along the European coasts. More precisely, it is widespread in the Mediterranean Sea and the Atlantic Ocean. It lives on rocky or sandy bottoms from 2 to 80 meters deep.
Description
It can reach up to 40 mm in length. It has a soft body and without a protective carapace; uses new abandoned shells every time the body grows. It is one of the largest hermit crabs in the Mediterranean. It is covered in white-yellow hairs with two hairless streaked claws. It has large eye stalks with red streaks. The color of the peduncles can vary from orange to not very bright red. The shell may show the anemone Calliactis parasitica and the sponge Suberites domuncula.
Ethology
It moves on stones and seabeds, dragging the shell with it. When the hermit crab feels in danger it goes back into its shell and comes out again when the situation has calmed down. It lives in environments with temperatures of around 18°-22°, but can reach high temperatures.
It is carnivorous. Eat everything of animal origin: waste from fish, shellfish, shrimp, etc.
https://it.wikipedia.org/wiki/Pagurus_bernhardus
Calliactis parasitica is a species of sea anemone associated with hermit crabs. It lives in the eastern Atlantic Ocean and the Mediterranean Sea at depths between the intertidal zone and 60 m (200 ft). It is up to 10 cm × 8 cm (3.9 in × 3.1 in) large, with up to 700 tentacles, and is highly variable in color. The relationship between C. parasitica and the hermit crab is mutualistic: the sea anemone protects the hermit crab with its stings and benefits from the food thrown into the water by the hermit crab’s movements.
Description
Calliactis parasitica is up to 100 millimeters (3.9 in) tall and 80 mm (3.1 in) wide, with the base of the column slightly wider. The surface of the column is rough and leathery with a grainy appearance, but it has no tubercles and is not divided into sections. It has a variable color, but is usually cream or buff in color, with spots and streaks of reddish or greyish brown, which tend to form vertical stripes.
Distribution
Calliactis parasitica is found in the northeast Atlantic Ocean and the Mediterranean Sea. Its Atlantic range extends from south-western Europe as far north as the western coasts of Wales and Ireland, and the English Channel. Although this species has been recorded in the southern North Sea, such records are considered doubtful. The depth distribution of C. parasitica varies from a depth of 60 meters (200 ft) to the sublittoral zone; it is rarely found in the coastal area.
https://en.wikipedia.org/wiki/Calliactis_parasitica
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