Serotonin-immunoreactive neurons in the ventral nerve cord of Remipedia (Crustacea): support for a sister group relationship of Remipedia and Hexapoda?

摘要: Remipedia were initially seen as a primitive taxon within Pancrustacea based on characters considered ancestral, such the homonomously segmented trunk. Meanwhile, several morphological and molecular studies proposed more derived position of Pancrustacea, including sister group relationship to Hexapoda. Because these conflicting hypotheses, fresh data are crucial contribute new insights into euarthropod phylogeny. The architecture individually identifiable serotonin-immunoreactive neurons has successfully been used for phylogenetic considerations in Euarthropoda. Here, we identified three species with an antiserum against serotonin compared our findings reconstructed ground patterns other taxa. Additionally, traced neurite connectivity neuropil outlines using antisera acetylated α-tubulin synapsin. ventral nerve cord displays typical rope-ladder-like arrangement separate metameric ganglia linked by paired longitudinally projecting connectives. peripheral projections comprise intersegmental nerve, consisting two branches that fuse shortly after exiting connectives, segmental anterior posterior nerve. distribution morphology interneurons trunk segments is highly conserved remipede analyzed, which allows reconstruction pattern: one pair possess single contralateral projection. pairs immunoreactive found medial part each hemiganglion. In (Cryptocorynetes haptodiscus), missing. anatomy its mirrors external animal’s structure principal corresponds closely A comparison cell major taxa supports homology Pancrustacea. These unbranched across midline, pointing towards similarities hexapod pattern. Our line growing number investigations proposing be rather crustacean lineage perhaps close affinities