I googled “mitochondrial ribosomes electron microscopy” and expected the first citations up to be pretty recent…. nope, this one Kleinaw Neupert and Miller (not this miller) 1974 popped up. Stating the obvious, muscles in the migratory locust certainly displayed many structures which were purported to be mitochondrial ribosomes. Two particular images caught my attention: isolated cytoplasmic ribosomes and isolated mitochondrial ribosomes. In the “older” publications micron markers were required so this made it easy to determine the approximate insect cytoplasmic ribosome size vs that of the mitochondrial ribosomes (and at the same time look at the cristae for clues as to the ATP synthases-related bending and also to look at what might be something akin to mitochondrial pores at the base of cristae). Just as an aside here, the materials and methods sounded like a trip down memory lane for me, ha ha… though i used the Siemens Elmiskop model 1A introduced in about 1964, older than the 101. Anyway some interesting measurements from an image here presented below.
About X=16nm is the distance between periods in the rhythm I see along side the mitochondrial RER tether. This is based on the micron marker from the publication and also an estimate of ribosomal size from the micrograph itself shown on the image. Cytoplasmic ribosome about 21nm here, mitochondrial ribosome is about 15nm. Black bar micron markers 100nm and area enlarged is the box in the image at left. Left image has the mitochondrial portion outlined in red (as it is also in the insert with the cytoplasm there on the right side, mitochondrion on the left.