Running to the shelters!

.........................The presence of Elina alerts the hermit crabs.

As the naturalist approaches the sponge,he can notice a lot of tiny shells loosing their balance and falling down. In previous posts we saw the symbiosis (or the vicinity) between the sponge, mollusks and polychaeta. The structure of the sponge Aplysina aerophoba provides shelter also to the third major group of benthic fauna, the crustaceans. The little shells (except some Bittium sp) are the houses of the small hermit crabs. In the macro photo I think that you can see a young Pagurus anachoretus but it is too small to recognize. I was very impressed by the fast and simultaneous reaction of the tiny hermit crabs. As I got close to the sponge, at once all of them left their shell to fall from the walls of the sponge to the lower darker parts of the sponge. I don’t know if there is a possibility of communication between the hermit crabs, but what about the sponge? Sponges don’t have nerves but as an animal they find other ways to inform the rest of the body for what is happening. Maybe there is a sign by the sponge that can be recognized by the crabs? It’s very difficult to know but it’s nice as a scenario. Who knows maybe we learn in the next posts of the blog.

.......................................finally a successfull pic of the tricky hermit crabs!

the hermitcloak or anemocrab?

In an older post we talked about the association of Dardanus sp. with the anemone C.parasitica. Now I will describe to you the most admirable symbiosis relationship of the Mediterranean, between crabs and anthozoa. Pagurus prideaux is a hermit crab that can grow up to 6cm and lives usually on the sandy parts of cave entrances. Unlike their great population in the Norwegian coast of the Mediterranean you cannot meet them too often here. When they are young they start to have a symbiotic relationship with the Adamsia carciniopados anemone. Because P.prideaux doesn’t feel very comfortable inside the gastropod shell, they prefer to live with “something like a shell” which the anemone helps to build. That way it doesn’t need to change its shell throughout his lifetime, as the shell grows bigger, along with the crab and the anemone. The anemone covers all the sensitive parts of the crab and the tiny shell like a cloak. The anemone is responsible for her buddies defence. For that purpose when they are in danger the anemone produces a lot of bright pink tentacles with stinging cells. These tentacles are called “acontia” (Second photo “where these animals are frightened the crab runs as the anemone spreads its stinking defence). The most noticeable thing in this relationship is the feeding behaviour. The crab feeds the anemone by putting pieces of food near the anemones mouth! It is possible, even after a few hours, the crab pulls the food out of the anemone’s stomach and eats it.

Intertidal hermit crab.

Clibanarius erythropus is famous for a variety of reasons such as his funny name, the big range of shells and his usage as a bait. The last reason happens because it is very easy to trap him in the rockpools where it uses to sit. It has a foraging behavior and it selects substrates where there are a lot of filamentous algae and corticated macrophytes to eat. It moves big distances per day and research showed that the type of shell that it uses influences the extent of movement. In the video you can watch a strange meeting of hundreds of hermit crabs under a rock. Probably this happens for the reproduction. I made it in very shallow water (o,5m).

Greater Mediterranean hermit crabs

As most species of crabs Greater Mediterranean hermit crabs are susceptible to fights. Here you can admire the impact of Mike Tyson to the animal kingdom. (Video by Kostas Milonakis, unidentified if they are D.arrosor or D.calidus)


Dardanus calidus with some Calliactis parasitica on his shell.

Dardanus calidus

When you diving at Mediterranean you can meet two species of Big Hermit crabs (Bernard-l'ermites). The species Dardanus arrosor and Dardanus calidus can grow more than 6cm and both can be symbiotic with the anemone Calliactis parasitica. Unlike with the parasitic symbiosis that this anemone has with the Atlantic Hermit crab Pagurus bernhardus it is confirmed that D.arrosor assists the trasfer of C.parasitica to its shell. Also the same experiments showed that most of the D.arrosor that had accepted C.parasitica to their shell were females and males prefer to be on their own.

The marble hermit crab.

Crabs like this can run with unexpectedly quickness for Hermit crab like the one above.

It seems that it tastes good.

Most crabs are very possessive about the area that they living. That crabs prefer live at high populations in small areas and fight each other all day. In the photo above the two big ones fight while the small watching.

They also burried under the sand for cover. They have different sized claws and the one seems to be very big for their body size. They seem to pull the big claw like a torture.

All photos taken at Kolimpithres Paros at May09

Καρτσινάκι ή Πάγουρος

-They are used as a bait.
-They are climbing at sea grass and other sea inhabitants.
-Pagurus anochoretus may be a group of species.