Arrow tail cancers
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the arrow tail cancers or mol gap cancers (Limulidae) educate the only rezente family within the order of the sword tails (Xiphosura). The sword tails are added to the class of the Merostomata, which are opposite placed to the Arachnids within the Kieferklauenträger as group of sisters.
Since that Kambrium admitted arrow tail cancers are after a bloom time of the Silur to in law today only in four kinds well-known, which are arranged at the American Atlantic coast and in Southeast Asia to occur and all in the Limulidae. Those accordingly gladly as living fossils marked animals become long up to 60 centimeters. Beside the arrow tail cancers also the become extinct sea-scorpios are placed frequently to the Merostomaten.
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Way of life of the arrow tail cancers
of arrow tail cancers live at the flat sand coasts of tropical seas in depths between 10 and 40 meters. In addition, normally arrow tail cancers on the soil live, can swim (with the ventral side upward). They nourish themselves of shells and other soft animals, which find it in the soil and with the Chelicere or the run legs into the mouth area lead. All well-known kinds can roll themselves up and protect in such a way against enemies. By repeated Zusammenrollen and Auseinanderklappen the animals can itselfentrench in the soft sand.
building of the arrow tail cancers
of the bodies of the arrow tail cancers is roughly hufeisenförmig, why the kinds in the English-language area are called “Horseshoe crab”. The abdomen ends in a pointed, rigid Schwanzstachel, like an arrowto the rear rises up. The body becomes into a front body (Prosoma) and a Hinterkörper (Opisthosoma) with the Schwanzstachel divided, these are connected by a flexible joint. However the body arrangement does not correspond to that of the Arachnids, on the contrary are with the arrow tail cancers the first two abdomen segments part of the front body become.
The front body provided with a powerful tank possesses on both sides a collection, on which two complex compound eyes sit, in addition possesses the animals two point eyes at the front edge of the tank. On thatLower surface is in the comparison relative to the tank small bodies with five simply built pairs of legs, with which the first 4 legs in shears end. The last run leg ends in long bristles and possesses at the basic member (Coxa)a short second branch, the Flabellum. This seals the Kiemenraum forward.
Before the run legs is the claw-like Chelicere, which serves as mouth tool. The mouth area lies between the Hüftgliedern of the Laufbeinpaarse and forms a gutter-like structure.The Hinterkörper possesses six pair of plattenförmiger extremities, which kiemen the Kiemenraum with book lying on top of each other up to 150 take off.
reproduction and development
sex-mature animals collect themselves in the early summer within the tidal rangeat the flat coasts of their homeland seas, where the males festkrallen themselves with the help of their according to arranged Vorderbeine at the females. These put their eggs (200 to 1000) into a flat sand hollow, where they are then inseminated and covered.
Firstfully floating larva of the arrow tail cancers is called due to their form Trilobitenlarve. It possesses already all segments, however only 9 pair extremities. The remaining pairs of legs as well as the Schwanzstachel receive them after the first Larvenhäutung, sex-ripely become the animals after 9 to12 years.
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