This was followed by washing 3–4 times with phosphate buffer and dehydration in ethanol series (50, 70, 80, 90% (v/v) and in absolute ethanol, 10 min per dehydration). Specimens were then critical point dried, mounted on aluminum stubs, sputter coated with gold–palladium and viewed under the scanning electron microscope (Hitachi S-570, Tokyo, Japan) and photographed