ANOMURA - MITTELKREBSE - HERMITS & CO

Einsiedlerkrebs (Pagurus bernhardus) Einsiedlerkrebse leben in Schneckenhäusern, um ihren ungepanzerten weichen Hinterleib gegen Freßfeinde zu schützen. Dabei ist ihr Hinterleib rechts gedreht und paßt exakt in die Windungen des Schneckenhauses. Manchmal kann man große Mengen kleiner Einsiedlerkrebse finden, die nur etwa 1cm groß sind und in den Gehäusen der Strandschnecke(Littorina littorea) spazieren gehen. Sie lassen sich gut im Aquarium halten und benötigen bereits nach einem Jahr ein Wellhornschneckengehäuse. Wenn der Krebs wächst, sucht er sich natürlich ein neues Schneckenhaus, weil das alte nicht mitwächst. Manchmal leben Einsiedlerkrebse zusammen mit Aktinien, um sich durch deren Nesselgifte gegen Feinde zu schützen. Die Aktinien wiederum profitieren von den Futterresten des Krebses.

Einsiedlerkrebs mit Schneckenhaus, auf dem Hydractinia echinata wächst Hermit-crab with common-whelk, on which Hydractinia echinata settles

Hermit-crab (Pagurus bernhardus) The hermit-crab settles in empty houses of snails to protect his soft back against predators. His back-body is drawn right, so that it fits exactly into the snail-houses. Sometimes masses of 1cm hermit-crabs can be found in the houses of the shore-snail Littorina littorea. They can be kept in an aquarium very well and grow so quick, that they need the house of a common whelk after one year. When the hermit-crab grows, he needs of course a bigger snail-house, because his home doesn`t grow with him. Sometimes hermit-crabs live in symbiosis with anemones, which give them protection against predators by their poison. The anemone takes profit from the food, the hermit- crab makes prey of.

Königskrabbe(Lithodes maja) Die Stein- oder Königskrabbe der Nordsee, Lithodes maja, kommt in tiefen Regionen der Nordsee über Geröllböden vor und erreicht eine Beinspanne von etwa 30cm. Wie die Seespinne bewegt sie sich sehr langsam und löst ihren Körperumriss mit Hilfe von Algen auf, die sie auf ihrem dornigen Panzer befestigt. So ist sie für potentielle Feinde nur sehr schwer zu entdecken. Mitte der 90er Jahre des vorigen Jahrhunderts tauchte eine größere Verwandte der Steinkrabbe vor Norwegens Küsten in großen Mengen auf: Paralithodes camschatica, mit einer Beinspannweite bis zu etwa 2m, die von den Russen aus Kamschatka importiert und vor der Kola-Halbinsel ausgesetzt wurde. Die ökologische Dimension dieser Faunenverfälschung ist bisher nicht abzusehen; den Süden der Nordsee dürften diese Tiere jedoch nicht erreichen, da sie arktische Temperaturen benötigen.

Kings`Crab(Lithodes maja) The kings`crab Lithodes maja can be found in deep regions at stony ground. Its legs can be spread over a wideness of 30cm. Like the spider-crab she moves slowly and gives camouflage to her body with algae and other things, which she puts on her spiny body. So it is very difficult for her enemies to find her. During the midst of the 1990s a big relative of this crab appeared in crowds before the coast of Norway: Paralithodes camschatica, which can spread its legs about a wideness of 2m. The Russians had imported this crab from the pacific- coast of Kamschatka and had put them into the Barents-Sea. The meaning for the ecological dimension is not clear, but the animals won`t migrate to the southern parts of The North-Sea, because they need arctic temperatures.

Partnerships of hermit-crabs Of course hermit-crabs do always owe a snail-house, which gives them protection against a large variety of enemies, but against enemies like an octopus a snail- house doesn`t offer complete protection. If the octopus searches with his arms for a hermit-crab and touches the mantle-anemone, the octopus will be nettled by the anemone and will stop his attack aigainst the hermit. The mantle-anemone makes her profit by eating little particles of the hermits meals. Furthermore the hermit draws her tentacles over the ground like a dusting- brush, that she may catch everything what`s left. A sulfure sponge, which includes the hermits snail- house, offers two advantages to his host. The one is, that the hermits enemies recognize the sulfure-spongue as not eadible, the other one is, that the spongue liquidates the snail-house, so that the hermit gets a soft domicile and is not in danger, when he has to change the snail-house because of his own growth. The hermit transports his spongue to any place, so that the spongue may inhalate little and littlest particles from the hermits meals.

Mantelaktinie und Einsiedlerkrebs Mantle-anemone + Hermit crab Adamsia palliata + Pagurus prideaux

Squat lobster(Galathea squamosa) These curious crabs can be found in the Mediterranean-Sea, the Atlantic-Ocean and the North-Sea. They prefer a depth below 20 meters on rocky grounds between algae and stones. They can rarely be seen in public aquariums. Similar to the kings`crab their last pair of legs is smaller than the other and has a cleaning function. But in contradiction to the kings`crab they owe long feelers. A popular relative of this crab(Pleuroncodes planipes) can sometimes be found in crowds before the coast of California and thousands of specimen get drifted on the beaches. Such crowds of Galathea-species haven`t been watched in the North-Sea yet.

Porzellankrebs aus Borkum (Pisidia longicornis from Borkum)

Porcelain-crab(Pisidia longicornis) Porcelain-crabs are so little dwarfs, that it is extremly difficult to find them. The photo shows a female with eggs and its male partner. Their carapax- length is less than 1cm! I found both many years ago in a pound of dried eggs of a common whelk. Because of its hidden surviving- strategy and its smallness they can only be kept in a little Aquarium without possible predators.

Porzellankrebs + Nacktschnecke zwischen Röhrenpolypen Pisidia longicornis + Aeolidia papillosa between Tubularia larynx

Symbiotic partnerships of Pisidia longicornis During a holiday at the German island Baltrum and during an extreme low tide I found some colonies of the yellow flowerhead Tubularia larynx, which settled on stones at a wavebreakers`end. Parts of these colonies can be found after storms on the beaches regularly. During this low tide I found a little porcelain-crab(Pisidia longicornis) between the yellow flowerheads, and it was the first specimen of them, I found alive. The crab had a length of 0,5cm. Until this day I just knew, that porcelain-crabs could be found in colonies of bryzoeas or between the eggs of the common whelk, Buccinum undatum. I guess, that the porcelain-crabs are protected by their hosts, because the host aren`t eadible for most predators. Furthermore I believe, that the porcelain-crabs clean their host-colonies and resist parasites, which try to disturb the host-organisms. It seems, that these circumstances haven`t been descibed yet, so that it seems possible, that I may have discovered some new kinds of symbiosis.