Chemical Architecture of Arthropod Neuromuscular Junctions as Phylogenetic Characters

• Applicants: Professor Dr. Gerd Bicker; Privatdozent Dr. Michael Stern
• Subject Area: Systematics and Morphology (Zoology)
• Term: from 2014 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 249531961

Organisms today retain information about their past in terms of amino acid sequences of their proteins and in the composition of nucleic acids. Thus, modern systematics is now based largely on DNA sequence analysis and comparisons. There is however a severe shortage of other, non-molecular characters with phylogenetic significance that can be used to confirm or adjust molecular-based phylogenetics and help to clarify any inconsistencies. Since cellular communication is important to organismic functioning, a phylogenetic analysis of the distribution of informational molecules could provide such a set of independent characters that may be helpful to gain additional insights into the evolutionary history. Throughout the animal kingdom, many diverse species use acetylcholine as a neurotransmitter at the neuromuscular junction of skeletal muscles. In contrast, glutamate appears to be the excitatory transmitter at neuromuscular synapses in some arthropod species. The project will test the hypothesis that in the arthropod phylum excitatory motoneurons of skeletal muscles are exclusively glutamatergic. Using electrophysiology as well as cytochemical and immuostaining techniques, we will examine whether this feature is a synapomorphy of the Euarthropoda or potentially of the Panarthropoda (Euarthropoda, Onychophora, Tardigrada). Peripheral inhibition by GABAergic motoneurons is widely distributed within the invertebrates, but it appears to be missing in several groups. To examine whether cell-specific chemical markers can be used as features to characterize systematic groups, the project will combine labelling for cholinergic, GABAergic, and glutamatergic markers with electrophysiology of the neuromuscular junction in arthropods and selected outgroup species. As a result, the project aims at providing a set of neurotransmitters at the neuromuscular junction that can be used as distinct characters for phylogenetic analysis.

• DFG Programme: Research Grants