Fig. 2: Larval development of the ensheathing glia.

a, b Schematic view on a first instar larval central nervous system. All neuropil-associated glial cells were annotated in a serial section TEM volume. Yellow dots indicate the position of the nuclei of astrocyte-like cells, magenta dots indicate the positions of the ensheathing glial cell nuclei, green dots indicate the positions of the ensheathing/wrapping glial nuclei. The arrow points to a segmental position where only one instead of two ensheathing/wrapping glial cell was identified. c Representative section through the fourth abdominal hemineuromer of a L1 larva showing the position of three different ensheathing glial cells around the neuropil. d Representative section through the fourth abdominal neuromere of a third instar larval ventral nerve cord. Note that ensheathing glia completely cover the neuropil. It was not determined whether the red marked glial processes belong to the blue or green ensheathing/wrapping glial cell. Scale bar (c, d): 10 µm, (e–h): 5 µm, (i, j): 0.2 µm. e Ensheathing glia in a first and (f) in a third instar larva. g Ensheathing/wrapping glial cells in a first and (h) in a third instar larva. Note the thin processes that engulf cell bodies of dorsally located neurons (asterisk). i On the ventral face of the neuropil an ensheathing glial cell and a cortex glial cell form a two-layered sheath between cortex and neuropil. j A highly multilayered glial cell layer is found at the dorsal face of the neuropil.