Peracarida

Australian water isopod

Satchel crabs or Peracarida are a superorder of the Higher crabs ( Malacostraca ) and belong to the crustaceans (Crustacea ). These include isopods, amphipods and suspended shrimp.

Occurrence

Satchel cancers occur in all types of water and on land. They have a worldwide distribution and is often a large density of individuals. To their success in different habitats of the deep seas, the Arctic and the Antarctic and in special habitats such as caves, groundwater or in the interstitial system of their own mechanism of parental care contributes.

Reproduction

Parental care: In a ventral brood chamber, Pouch, called the thorax, the eggs are kept ( one exception is only the group of Thermosbaenacea ). This space is delimited by tab-like, adjoining annexes to the extremities ( Oostegite ) from the external medium.

Nervous system and sense organs

The eyes are set in most cases sessile in the headstock.

Morphology

Satchel crabs have a carapace with a maximum of four fused thoracic segments. The head is merged into one (or two ) segments of the thorax. The Carapaxfalte is usually regressed.

Phylogeny

Early fossils of the knapsack Cancer orders as Isopoda, Cumacea and Tanaidacea are already known from the Paleozoic Era over 300 million years ago. From this era comes the ancestors of the Amphipoda, although no fossils of this group of animals have survived from this period. The further spread of the knapsack crabs took place in the Mesozoic. The current distribution of Crangonyctidae, a very original group of amphipods in the northern hemisphere points to their origin in Laurasia before the law down.

System

The superiority of the knapsack crabs ( Peracarida ) comprises nine orders:

  • Phreatoicidea
  • Asellota
  • Terrestrial isopods ( Oniscidea )
  • Valvifera
  • Anthuridea
  • Sphaeromatidea
  • Cymothoidea

West Heath and Rieger differ in their particular zoology only seven orders. Make the satchel crabs ( Peracarida ) the Thermosbaenacea as Pancarida opposite, because these use in contrast to the rest of their Peracarida located on the back Carapaxhöhle as a brood chamber. The brood chamber of the remaining Peracarida is located on the ventral side. Furthermore, the Mysida and Lophogastrida be summarized to the order Mysidacea.

Pouch (marsupial) Porcellio scaber Woodlouse
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