title: Neuroanatomy of the optic ganglia and central brain of the water flea Daphnia magna (Crustacea, Cladocera).
abstract: We reveal the neuroanatomy of the optic ganglia and central brain in the water flea Daphnia magna by use of classical neuroanatomical techniques such as semi-thin sectioning and neuronal backfilling, as well as immunohistochemical markers for synapsins, various neuropeptides and the neurotransmitter histamine. We provide structural details of distinct neuropiles, tracts and commissures, many of which were previously undescribed. We analyse morphological details of most neuron types, which allow for unravelling the connectivities between various substructural parts of the optic ganglia and the central brain and of ascending and descending connections with the ventral nerve cord. We identify 5 allatostatin-A-like, 13 FMRFamide-like and 5 tachykinin-like neuropeptidergic neuron types and 6 histamine-immunoreactive neuron types. In addition, novel aspects of several known pigment-dispersing hormone-immunoreactive neurons are re-examined. We analyse primary and putative secondary olfactory pathways and neuronal elements of the water flea central complex, which displays both insect- and decapod crustacean-like features, such as the protocerebral bridge, central body and lateral accessory lobes. Phylogenetic aspects based upon structural comparisons are discussed as well as functional implications envisaging more specific future analyses of ecotoxicological and endocrine disrupting environmental chemicals.
authors.affiliation: Department of Zoology, Stockholm University, Svante Arrhenius väg 18A, SE-106 91, Stockholm, Sweden.
authors.forename: Timm
authors.initials: T
authors.lastname: Kress
authors.affiliation: Department of Cell and Evolutionary Biology, Zoological Institute and Museum, University of Greifswald, Soldmannstrasse 23, D - 17487, Greifswald, Germany.
authors.forename: Steffen
authors.initials: S
authors.lastname: Harzsch
authors.affiliation: Department of Zoology, Stockholm University, Svante Arrhenius väg 18A, SE-106 91, Stockholm, Sweden. dircksen@zoologi.su.se.
authors.forename: Heinrich
authors.initials: H
authors.lastname: Dircksen
mesh_terms: D000818:Animals; D001921:Brain / Q000033:anatomy & histology* / Q000166:cytology; D002449:Cell Aggregation; D003621:Daphnia / Q000033:anatomy & histology* / Q000166:cytology; D019835:FMRFamide / Q000378:metabolism; D017952:Ganglia, Invertebrate / Q000033:anatomy & histology* / Q000166:cytology; D006632:Histamine / Q000378:metabolism; D021621:Imaging, Three-Dimensional; D008954:Models, Biological; D009474:Neurons / Q000378:metabolism; D009479:Neuropeptides / Q000378:metabolism; D019581:Neuropil / Q000378:metabolism; D066194:Olfactory Cortex / Q000033:anatomy & histology; D010455:Peptides / Q000378:metabolism; D015320:Tachykinins / Q000378:metabolism; D014795:Visual Pathways / Q000033:anatomy & histology
chemical_list: D009479:Neuropeptides; D010455:Peptides; D015320:Tachykinins; D019835:FMRFamide; D006632:Histamine; C027714:melanophore-dispersing hormone
keywords: Central complex; Daphnia magna; Neuroanatomy; Neuropeptidergic neurons; Olfactory pathways