West Atlantic riding crab
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Western Atlantic rider crab ( Ocypode quadrata ) |
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| Fabricius , 1787 |
The West Atlantic Rider Crab ( Ocypode quadrata ), also known as the racing crab , is a species in the riding crab genus from the order of the decapod crabs .
features
The West Atlantic rider crab has a typical crab habit with a more or less square shell on the front body, which is called the carapace . This has a single spike each at the anterior-lateral corners. The abdomen is very much receded and is folded tightly under the front body. The animals reach a side length of about 30 mm. The stalk eyes and the fillets provided for them are unusually long. The scissors are short and designed differently in both sexes on the right and left. Whether the ratio of numbers is close to 50:50 ("racemic distribution mode"), as is the case with male fiddler crabs, or whether a scissor side is preferred, remains to be investigated. The color of the crabs varies from gray to pepper to pale yellow, depending on the color of the sand on which the individual lives.
distribution and habitat
The range of the West Atlantic Rider Crabs extends in the north to Rhode Island in the United States and in the south to Santa Catarina in Brazil . Main areas of distribution are in Florida and the Caribbean .
The species lives amphibiously on sandy beaches . In doing so, she digs underground “U” -shaped galleries, which, for ventilation, extend into the area of the beach that is higher than the tides.
nutrition
The West Atlantic Rider Crab is a carnivore; it feeds on washed up dead fish and on mussels , especially of the genus Donax ( triangular mussels ), but also on other shell molluscs . It also hunts crabs or insects (mainly flies ).
Way of life
The crabs are particularly active in the evening and start hunting at dusk. They move - sideways - very quickly over the beach: "In case of danger, they run to their cave with such great speed that a person can hardly follow". Hence their second German name Rennkrabben . If they feel threatened, they also flee into the water. The crabs spend the day in their underground galleries, where they then dig.
West Atlantic Rider Crabs essentially produce three different sounds. A tearing noise with scissors on the substrate, a rasping stridulation with the legs, and a bubbling noise made by the crabs in the gill cavity .
The fight among males is strongly ritualized and there is usually no contact. It usually begins with a simple threatening gesture in which the larger scissor bone is held in front of the body like a shield. An increase is the stretching of the body on the legs. An intimidated opponent sinks to the ground in a "gesture of humility" . The threatening position can also lead to a fight and mutual jumping.
Reproduction and development
The fertilized eggs are carried by the females on the bristles of the abdomen for a certain time. As soon as they are ready to hatch, they are shaken off in the sea water. After a planktonic stage, the development includes five larval stages before it leads to the first crab stage. The development of the young takes about two months.
Movies
- Hermann Schöne: Ocypode quadrata (Ocypodidae) - Threatening and fighting behavior. SW, 5 min; Published: IWF (Göttingen), 1965
literature
- Füller, H., Gruner, H.-E., Hartwich, G., Kilias, R., Moritz M .: Urania Tierreich, Invertebrates 2 (Annelida to Chaetognatha) . Urania-Verlag, Berlin 1994, ISBN 3-332-00502-2 , p. 529
- Debelius, H., Cancer Guide Worldwide: Shrimps, Crabs, Lobsters, Lobsters, Mantis Shrimp, Jahr-Verlag, Hamburg 2000, ISBN 3-86132-504-7 , p. 104
- MC de Vries, DL Wolkott, CW Holliday: High Amonia and Low pH in the Urine of the Ghost Crab Ocypode quadrata. Biol. Bull. 186, 342-348, June 1994. ( PDF )
