Amphipoda

Amphipod from marine plankton

The amphipods ( Amphipoda ) are an order of crustaceans, which belongs to the class of higher crustaceans ( Malacostraca ). The order is divided into four sub-orders.

Physique

The body of the amphipods is in contrast to the closely related isopods ( Isopoda ) flattened on the side. It is available in three body sections, divided the tagmata. The first Tagma represents the cephalothorax, the head - chest - piece, which is a hybrid of the head (caput, Cephalon ) with the first Thorakalsegment ( 1 Torah Como ). The second is called Tagma Paereon or mesosoma and consists of seven other thoracomers, sit on them, the seven sternum Couples ( Thorakopoden, Peraeopoden ), of which the five posterior pairs are formed as walking legs. The two front Peraeopoden are designed as gripping tools ( Gnathopoden ). The last section is the body consisting of six segments Pleon; the person sitting at his legs serve as swimming legs ( pleopods ).

The name " Amphipoda " goes back to the opposite position of the sternum ( Peraepoden ), of which the anterior four pairs of forward and the rear three pairs are angled backwards.

The gills are in crustaceans parts of the extremities: cancers have so-called gap feet, of which (Simplified badly expressed ) of inner branch ( endopodite ) can function as a running leg, for example, parts of the outer ( exopodite ), for example, as a respiratory organ ( gill ) can be used. In amphipods the gills are shifted inwards and project into a "channel", which is formed by the running and swimming legs. Through their movement is a constant water flow from front to back along the inner side of the leg pairs instead and supplies the gills with fresh water.

Amphipods generally have body sizes of a few millimeters to a few ( usually less than two) centimeters. An exception are the two deep-sea species Alicella gigantea and Thaumatops loveni that can be up to 14 inches long. In the 10 km deep Kermadecgraben off the coast of New Zealand and up to 28 centimeters long were specimens found in a research expedition in 2012.

Number of species and their distribution

There are more than 9,500 described species, which represents only about a quarter of the world up to 40,000 suspected species. From modern research vessels and the marine base in Arctic and Antarctic waters and in the deep sea can now be investigated. It turned out that the amphipods are marked in all these habitats not only by a great variety of species, but usually also by a large number of individuals. They therefore constitute an important link in the food chain.

Most freshwater species belonging to the suborder Senticaudata, including indigenous to Germany freshwater shrimp ( Gammarus pulex ) or the recently immigrated from the Danube Delta Large Dikerogammarus ( Dikerogammarus villosus ). Is known of the species flock of Lake Baikal: about 300 closely related amphipods that colonize different habitats there.

Most amphipods live in the sea, such as Hyperia macrocephala ( from the subordination of Hyperiidea ) in the plankton or Jassa falcata ( from the partial order Corophiida the subordination Senticaudata ) on ship hulls. Their distribution is worldwide, they are also rich in species found in the Arctic and Antarctic waters, such as at the equator. Also from the deep sea discoveries of new species of amphipods are known over again. Some, especially tropical amphipods live in moist leaf litter. Terrestrial living amphipods are called " sand fleas " means. In Florida, the species Talitrus specificus and Talitroides allaudi occur. Also Talitrus sylvaticus ( it reaches a length of 8 mm) is in the U.S. widespread Art

Gammaracanthuskytodermogammarus loricatobaicalensis is the longest proposed name for a living thing. He was awarded in 1927 by B. Dybowski on a small freshwater shrimp from Lake Baikal, however, explained according to the International Code of Zoological Nomenclature invalid.

Amphipods are old fossil from 40 million years known Bernstein. The phylogenetically most primitive forms of life in the Pacific Ocean, the most derived in the Caribbean.

Submissions

• Gammaridea ( about 4000 species)
• Hyperiidea ( about 300 species)
• Ingolfiellidea ( about 40 species)
• Senticaudata (about 5000 species ) including the previous submissions Corophiidea and
• Caprellidea