Flea crabs

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Flea crabs
Flea shrimp from the marine plankton

Flea shrimp from the marine plankton

Trunk : Arthropod (arthropoda)
Sub-stem : Crustaceans (Crustacea)
Class : Higher crabs (Malacostraca)
Subclass : Eumalacostraca
Superordinate : Satchel Shrimp (Peracarida)
Order : Flea crabs
Scientific name
Latreille , 1816

The amphipods (amphipods) are an order of crustaceans that the class of the Higher crabs heard (Malacostraca). The order is divided into four sub-orders. The small crustaceans are native to all of the world's oceans.



Idealized plan of the amphipods

In contrast to the closely related woodlice (Isopoda), the body of the amphipods is laterally flattened. It is divided into three body sections, the Tagmata . The first Tagma represents the cephalothorax, the head and chest piece, which is a fusion of the head (caput, cephalon) with the first thoracic segment (1st thoracomer). The second tagma is called paereon or mesosoma and consists of another seven thoracomeres, on which sit the seven pairs of sternum bones (thoracopods, peraeopods), of which the five rear pairs are designed as running legs. The two front peraeopods are designed as gripping tools (gnathopods). The final section of the body is the six-segment pleon; the legs sitting on it serve as swimming legs (pleopods).

The name "Amphipoda" goes back to the opposing position of the sternum (peraepod), of which the front four pairs are angled forward and the rear three pairs are angled back.

In crustaceans, the gills are parts of the extremities: crustaceans have so-called split feet , of which the inner branch (endopodite) z. B. can act as a running leg, parts of the outer (exopodite) z. B. can serve as a respiratory organ (gill). In the case of amphipods, the gills are shifted inwards and protrude into a "channel" that is formed by the walking and swimming legs. Due to their movement, there is a constant flow of water from front to back along the inside of the pairs of legs and supplies the gills with fresh water.

The color of the amphipods is usually light and ranges from reddish pink to yellowish to green and blue.


Flea shrimp are usually from a few millimeters to a few (usually less than two) centimeters in size. The two deep-sea species Alicella gigantea and Thaumatops loveni , which can be up to 28 centimeters long, are an exception . Specimens were found in the Kermadec Trench , which is more than 10 kilometers deep off the coast of New Zealand, during a research expedition in 2012.


All amphipods are sexually separated . The males are equipped with enlarged gnathopods with which the smaller female is carried around for a few days during the praecopula . After the partial moult , the male turns the female upside down and uses his pleopods to guide sperm into its marsupium , where the eggs are fertilized.

The number of eggs in a clutch varies from 1 to 250. There is no manca stage , the finished small amphipods hatch directly from the hatched eggs after 2 to 59 days. Young animals can remain in the brood pouch for 2 to 35 days. They are sexually mature after six to nine moults in a period of one to four months .

Number of species and their distribution

Over 9500 species are currently described, which corresponds to only about a quarter of the up to 40,000 suspected species worldwide. Modern research vessels can now also investigate the seabed in Arctic and Antarctic waters and in the deep sea. It turned out that the amphipods in all these habitats are not only characterized by a great diversity of species, but mostly also by a large number of individuals and therefore form an important link in the food chain . On the one hand, they serve as a food source for many fish, invertebrates, penguins , shorebirds, small cetaceans and seals , on the other hand, flea crabs are also important scavengers.

Most freshwater species belong to the suborder Senticaudata , including the indigenous to Germany freshwater shrimp ( Gammarus fossarum ) or the recently immigrated from the Danube Delta Large killer shrimp ( Dikerogammarus villosus ). The shoal of species of Lake Baikal is well known : around 300 closely related amphipods that colonize different habitats there.

Most amphipods live in the sea, for example Hyperia macrocephala (from the suborder of Hyperiidea) in plankton or Jassa falcata (from the suborder Corophiida of the suborder Senticaudata) on ship hulls. Their distribution is worldwide, in the Arctic and Antarctic waters the biodiversity is generally greater than at the equator. New species of amphipods are also being discovered again and again from the deep sea. Some, especially tropical amphipods, live in damp fallen leaves. Flea shrimp living on sandy beaches are known as " sandhoppers " or "beach fleas". The species Talitrus specificus and Talitroides allaudi occur in Florida . Also Talitrus sylvaticus (it reaches a length of 8 mm) is a widely used in the US Art.

Flea shrimp from Lake Baikal

Gammaracanthuskytodermogammarus loricatobaicalensis is the longest proposed name for a living being to date. It was awarded in 1927 by B. Dybowski to a small flea shrimp from Lake Baikal, butdeclared invalidaccording to the International Code of Zoological Nomenclature .

Fossil only a few amphipods are known, the oldest genus Paleogammarus , which has strong similarities to Crangonyx , was discovered in Baltic amber from the early Eocene (55.8 to 48.6 million years old). The phylogenetically most primitive forms live in the Pacific Ocean , the most derived in the Caribbean .


Beach flea ( Talitrus saltator )

Types (selection)

Flea crabs and humans

In August 2017 , a youngster was attacked unnoticed by a large number of scavengers in the cold ocean water near Melbourne and suffered extensive bleeding on his legs and feet.

Web links

Commons : amphipods  - Collection of images, videos and audio files
  • WoRMS: Amphipoda . In: T. Horton, J. Lowry, C. De Broyer: World Amphipoda Database. Accessed through: World Register of Marine Species (WoRMS), 2013, accessed April 3, 2014.
  • The order of the amphipods. In: Fauna Europaea Database. European Commission under the Fifth Framework Program, accessed on February 27, 2010 .

Individual evidence

  1. ^ Spiegel Online: Biologists catch giant cancer off New Zealand . Retrieved February 4, 2012.
  2. a b amphipods . In: Lexicon of Biology .
  3. a b c d Amphipod . In: Encyclopædia Britannica .
  4. ^ A b T. Horton, J. Lowry, C. De Broyer (Eds.): Introduction. World Amphipoda Database, 2013, accessed April 2, 2014
  5. Mini crabs as turbo scavengers . In: scinexx . August 6, 2015.
  6. James K. Lowry, Alan A. Myers: A Phylogeny and Classification of the Senticaudata subord. nov. (Crustacea: Amphipoda). In: Zootaxa. 3610, 1, 2013, pp. 1-80.
  7. Barbara Barkhausen: I didn't think I was going to be eaten. In: welt.de . August 7, 2017. Retrieved August 7, 2017 .