Split leg

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Structure of a split leg: schematic basic plan

In crustaceans, split legs are specially formed pairs of legs, in which each leg ends in two branches. This is an early phylogenetic feature of the arthropods , which has already been proven in the fossil trilobites .


A protopodite , which is divided into coxopodit and basipodit , has two branches: the one pointing towards the body is called an endopodite (also telopodite or walking branch), the one pointing away from the body is called exopodit (also swimming branch). On the outside ( dorsal ) of the protopodite there can be an epipodite (also called exit ), on the inside (ventral) an endite .

Both endopodite and exopodite consist of several other members. The original endopodit is divided into from the base to the tip

  • Ischium,
  • Merus,
  • Carpus,
  • Propodus and
  • Dactylus.

The original tip can be transformed into a claw or scissors.


Various forms of the gap legs of crustaceans:
A Pleopod of a crayfish , B floating leg of a hopper compact ,
C antenna of the larva of a Kiemenfüßers ,
D and E : first and second Thorakalbein at Anaspides ( malacostraca )
ex exopodite, s endopodite, ep Epipodit, cx Coxopodit, bs Basipodit

The parts of the split bone can be functionally modified and specialized. The epipodite, for example, often has a gill function , the endopodite serves as a walking or swimming leg, and the exopodite is usually also used for swimming . In the head area, the split bones can be specialized for mouth parts or antennae. The endites often serve as chews on mouthparts. The transformations and specializations of the split legs can often be observed in the larval development of crustaceans.

In a leaf bone (phyllopodium), the proto-endo and exopodite are widened and surrounded by a thin cuticle . If the exopodite is missing or if it is greatly reduced, one speaks of a rod leg .


  • Rüdiger Wehner and Walter Gehring: Zoology. Chapter E (Arthropoda). 24th edition. Thieme, Stuttgart, June 2007 ISBN 3133674242
  • Volker Storch and Ulrich Welsch: Kükenthal zoological internship. 25th edition. Spectrum Academic Publishing House, December 2005 ISBN 3827416434
  • Edwin Ray Lankester (Editor): A Treatise on Zoology . Vol. 7. A. and C. Black, London, 1900-1909