mean 1.46±0.98: range 0.1-4.0 µm^2
||Turtle Trachemys scripta elegans
||Yeow MB, Peterson EH. Active zone organization and vesicle content scale with bouton size at a vertebrate central synapse. J Comp Neurol. 1991 May 15 307(3):475-86 DOI: 10.1002/cne.903070310 p.478 left column bottom paragraphPubMed ID1856332
||Abstract: "The present study has addressed this issue [that axons differ in the size of their synaptic boutons] by using three-dimensional reconstruction of serial thin sections to examine the ultrastructure of synaptic boutons that vary in size. [Investigators’] observations are based on complete or near-complete reconstructions of 53 synaptic boutons contacting large neurons in the ventromedial gray matter of the upper cervical spinal cord (probable neck motor neurons)."
||P.478 left column bottom paragraph: "[Investigators] characterized the size of reconstructed boutons in terms of their volume and total apposition area (cf. Materials and Methods). The distribution of both variables is shown in Figure 2 ... Total apposition area is somewhat less variable (Fig. 2B range: 0.1-4.0 µm^2 X = 1.46 ± 0.98 µm^2) and the distribution is not so skewed as that of bouton volume [BNID 115068]. Nevertheless, large apposition areas are rare (40% ≤ 1 µm^2, 75% ≤ 2 µm^2)."