Scanning electron microscopy study
The eyelids of two specimens were cut into small pieces and directly fixed in 5% glutaraldehyde in a cacodylate buffer for 48 h at 4°C and washed in three changes of 0.1% cacodylate buffer, and then, the specimens were post-fixed in a cacodylate-buffered solution of 1% osmium tetroxide for 2 h at 37°C. The specimens were washed in the same buffer three times, dehydrated through an ascending series of ethyl alcohol, and then infiltrated with amyl acetate for 3 two days. The drying of the specimens was accomplished by the critical point drying using liquid carbon dioxide, mounted and sputter-coated with gold. The specimens were examined on a Jeol scanning electron microscope (JS M-5400IV) at 15 kv.