Configuration of nerve cord and characterization of brain neurosecretory cells in adult firefly, Luciola gorhami (Coleoptera: Lampyridae)

Abstract

Nerve cord configuration and brain neurosecretory cell (NSC) characteristics were studied in adult firefly, Luciola gorhami, applying two methods, in situ and section staining. Nerve cord was of primitive type and consisted of brain, subesophageal ganglion, three thoracic and seven abdominal ganglia which were connected to each other serially through a pair of longitudinal connectives. Thoracic ganglia were separated and had the same size. All abdominal ganglia had the same size except the last one which was twice larger than the others. Abdominal ganglia were not fused with thoracic ganglia. Using in situ staining, 26 neurosecretory cells (NSCs) stained as median neurosecretory cells (MNSCs) and lateral neurosecretory cells (LNSCs). MNSCs consisted of 20 cells in three groups in pars intercerebralis. MNSCs had a U shaped arrangement in such a way that 4 round and large cells were located in front and two parallel groups (8 pryiform to round cells in each group) located in back. LNSCs were comprised of 6 large cells in two groups (one group on each lateral lobe of protocerebrum). MNSCs pathways were not clear but LNSCs pathways were clear and ipsilateral. Using section staining, large number of NSCs in pars intercerebralis stained gray and purple in color. Gray cells were large, more in number and appeared in many sections. Purple cells were large and grouped in the middle of gray cells. Both types of cells were on the surface area of brain and had large nucleus. Their axons were bundled together and extended backwards to the rear of brain.