title: Olfactory pathway in Xibalbanus tulumensis: remipedian hemiellipsoid body as homologue of hexapod mushroom body.
abstract: The Remipedia have been proposed to be the crustacean sister group of the Hexapoda. These blind cave animals heavily rely on their chemical sense and are thus rewarding subjects for the analysis of olfactory pathways. The evolution of these pathways as a character for arthropod phylogeny has recently received increasing attention. Here, we investigate the situation in Xibalbanus tulumensis by focal dye injections and immunolabelling of the catalytic subunit of the cAMP-dependent protein kinase (DC0), an enzyme particularly enriched in insect mushroom bodies. DC0 labelling of the hemiellipsoid body suggests its subdivision into a cap-like and a core neuropil. Immunofluorescence of the enzyme glutamic acid decarboxylase (GAD), which synthesizes γ-aminobutyric acid (GABA), has revealed a cluster of GABAergic interneurons in the hemiellipsoid body, reminiscent of the characteristic feedback neurons of the mushroom body. Thus, the hemiellipsoid body of Xibalbanus shares many of the characteristics of insect mushroom bodies. Nevertheless, the general neuroanatomy of the olfactory pathway in the Remipedia strongly corresponds to the malacostracan ground pattern. Given that the Remipedia are probably the sister group of the Hexapoda, the phylogenetic appearance of the typical neuropilar compartments in the insect mushroom body has to be assigned to the origins of the Hexapoda.
authors.affiliation: Division of Cell Biology, University of Veterinary Medicine Hannover, Bischhofsholer Damm 15, 30173, Hannover, Germany.
authors.forename: Torben
authors.initials: T
authors.lastname: Stemme
authors.affiliation: Department of Marine Biology, Texas A&M University at Galveston, 200 Seawolf Parkway, Galveston, TX, 77553, USA.
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Iliffe
authors.affiliation: Division of Cell Biology, University of Veterinary Medicine Hannover, Bischhofsholer Damm 15, 30173, Hannover, Germany. gerd.bicker@tiho-hannover.de.
authors.forename: Gerd
authors.initials: G
authors.lastname: Bicker
mesh_terms: D000818:Animals; D004396:Coloring Agents / Q000378:metabolism; D003445:Crustacea / Q000166:cytology / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D005968:Glutamate Decarboxylase / Q000378:metabolism; D008954:Models, Biological; D024521:Mushroom Bodies / Q000166:cytology / Q000378:metabolism*; D009833:Olfactory Pathways / Q000378:metabolism*
chemical_list: D004396:Coloring Agents; D017868:Cyclic AMP-Dependent Protein Kinases; D005968:Glutamate Decarboxylase
keywords: Brain; Comparative neuroanatomy; Lateral protocerebrum; Morphology; Tetraconata; Xibalbanus tulumensis