Mushroom bodies

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Drosophila melanogaster brain expression patterns.jpg

The mushroom body ( Corpora pedunculata , English Mushroom body ) is a conspicuous, paired anatomical structure that occurs in the central brain ( upper pharyngeal ganglion: Protocerebrum ) of the arthropods and some annelids .

It serves as an olfactory center (2nd order olfactory center ), but also plays an important role in higher integrative services such as learning and memory and is one of the interconnection centers (glomeruli) of the protocerebrum.

construction

The mushroom body is divided into a calyx (cup), a pedunculus (stem) and several lobes. The calyx is innervated by the dendrites of numerous intrinsic neurons , traditionally known as Kenyon or globuli cells (50,000 in the migratory locust , 2,000 in the Drosophila fruit fly ). Their comparatively tiny cell bodies are always in the periphery of the brain. The axons of the Kenyon cells, which are initially arranged in parallel, pull bundled as a pedunculus into the interior of the brain, where they branch out terminally and thus form the individual praises. The number of lobes differs depending on the species - for example, the mushroom bodies of Drosophila have three pairs of lobes (alpha-, beta, gamma lobus) and those of the horseshoe shrimp Hutchinsoniella have a total of 19 lobes (eight pairs and three unpaired). While the two mushroom bodies of most insects are separated in pairs, the mushroom bodies of horseshoe shrimp, double- tailed prawns , millipedes , jaw-claw-bearers, and penny-pods, as well as many annelids, are connected in the middle.

development

In Drosophila , the fungal body on each side of the body has been shown to develop from four neuroblasts , each producing an identical set of Kenyon cells. The complex mushroom bodies of Hutchinsoniella develop - like the rest of the olfactory system - extremely early and are already fully functional by the time they hatch.

evolution

Due to the detailed structural homology of the individual components of the mushroom body and its matching olfactory function within the arthropods, it is now assumed that the marine ancestor of all Arthropoda in the Cambrian already had a pair of centrally connected mushroom bodies, i.e. H. had a well-equipped olfactory system. Although most crustaceans lack mushroom bodies, the more simply built olfactory centers of the higher crustaceans and Remipedia can be derived from the mushroom bodies of this original arthropod. The close relationship of the Arthropoda and Annelida ( Articulata hypothesis ) was previously supported by, among other things, the similarities of the fungal body of the two groups, but is now considered unlikely in view of the wealth of molecular data.

literature

  1. a b c Oberschlundganglion , on: Spektrum.de, Lexikon der Biologie
  2. ^ Text on the mushroom body from the University of Freiburg ( Memento from October 15, 2004 in the Internet Archive )
  3. Strausfeld, NJ; Sinakevitch, I .; Brown, SM; Farris, SM (2009): Ground plan of the insect mushroom body: Functional and evolutionary implications. Journal of Comparative Neurology 513: 265-291.
  4. a b Stegner, MEJ; Richter, S. (2011): Morphology of the brain in Hutchinsoniella macracantha (Cephalocarida, Crustacea). Arthropod Structure and Development 40: 221-243.
  5. Böhm, A .; Szucsich, NU; Pass, G. (2012): Brain anatomy in Diplura (Hexapoda). Frontiers in Zoology 9:26.
  6. Holmgren, N. (1916): On the comparative anatomy of the brain of polychætes, onychophores, xiphosures, arachnids, crustaceans, myriapods and insects. Kungliga Svenska Vetenskapsakademiens Handlingar 56.
  7. Strausfeld, NJ; Strausfeld, CM; Loesel, R .; Rowell, D .; Stowe, S. (2006): Arthropod phylogeny: Onychophoran brain organization suggests an archaic relationship with a chelicerate stem lineage. Proceedings of the Royal Society B-Biological Sciences 273: 1857-1866.
  8. Heuer, CM; Loesel, R. (2009): Three-dimensional reconstruction of mushroom body neuropils in the polychaete species Nereis diversicolor and Harmothoe areolata (Phyllodocida, Annelida). Zoomorphology 128: 219-226.
  9. ^ Text on the development of the mushroom bodies on Flybrain.org .
  10. Stegner, MEJ; Richter, S. (2015): Development of the nervous system in Cephalocarida (Crustacea): early neuronal differentiation and successive patterning. Zoomorphology.
  11. Wolff, G .; Harzsch, S .; Hansson, BS; Brown, S .; Strausfeld, N. (2012): Neuronal organization of the hemiellipsoid body of the land hermit crab, Coenobita clypeatus : Correspondence with the mushroom body ground pattern. Journal of Comparative Neurology 520: 2824-2846.
  12. Stemme, T .; Iliffe, TM; Bicker, G .; Harzsch, S .; Koenemann, S. (2012): Serotonin immunoreactive interneurons in the brain of the Remipedia: New insights into the phylogenetic affinities of an enigmatic crustacean taxon. BMC Evolutionary Biology 12.