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Internal anatomy of an insect. The Mixocoel fills the entire body and surrounds the organs, the circulating hemolymph is pumped through the dorsal heart (7)

The Mixocoel or Haemocoel (from gr. Μικτός - mixed or αίμα - blood and κοιλία - abdominal cavity) is the body cavity of the arthropods . It is a union of the primary body cavity (Blastocoel) with the secondary body cavity (Coelom) and is therefore also referred to as the tertiary body cavity . The coelom is created during the embryonic development as mesoderm strips or coelom sacs, after the formation of the muscles , the blood vessels including the heart tube , the fat body and the pericardial septum, these original coelom structures dissolve down to the gonads and the sacculi of the nephridia or become, in some crustaceans , compressed to collapse. As a result, blood and coelomic fluid combine to form hemolymph , which then circulates in an open blood circuit and in lacunae in the body cavity and washes around the organs . The role of the coelom, which acts as a hydroskeleton in other invertebrates , could be related to the formation of the exoskeleton in the arthropods.

Histologically , a fully developed Mixocoel cannot be differentiated from a Pseudocoel , i.e. a Coelom without a membrane surrounding the intestine . However, it can be concluded that it is present if individual remains of the Coelom space remain.


  • Wilfried Westheide, Reinhard Rieger (Hrsg.): Special zoology. part 1: protozoa and invertebrates . 2nd Edition. Spektrum Akademischer Verlag, Munich 2007, ISBN 978-3-8274-1575-2 , pp. 191, 443 .