SEM method – for unarmoured or lightly armoured cells

1. Take round 1 cm diameter coverslips, and rinse in distilled water. Leave to dry.

2. Under the fume hood, place a drop of polylysine on the coverslip, leave 2 minutes. Pipette off the excess, and leave to dry. With a diamond pencil, write a letter or number (4 is good) on to the side of the coverslip with the polylysine.

3. Pipette cells of interest individually from samples into a small glass multiwell plate, with wells containing filtered seawater. Pipette cells from one well to the next to clean them. Repeat 5 times.

4. Place the final small drop on the coverslip.

5. Put under the fume hood. Put on gloves. Remove 2% osmium tetroxide in seawater from the fridge, open under the fume hood. Put one drop of this onto the coverslip with the cells. Leave for 20 minutes.

6. Pick up coverslip keeping the right way up. Place in small petri dish of distilled water. Leave 10 minutes.

7. Place in 10 % ethanol. Leave 10 minutes.

8. Repeat for 30, 50, 70, 90, 100 %. Leave in 90% only if you cannot CPD straight away.

9. Critical point dry – leave the coverslips in 100 % ethanol, fill up a small container with 100 % ethanol, put coverslips sideways in the small holder, place in 100 % ethanol in CPD machine.

10. Affix dried coverslip to stub (make sure its the right way up). Leave to be coated.

Alternatively, for species with thick thecal plates, after Step 8, place the coverslips in small petri dish containing a mixture of 30 % hexamethyldisilazane (HMDS) , 70 % ethanol, followed by 50 % HMDS, then 70 %, 90 %, 100%, and leave in this dish to dry overnight, until all of the HMDS is evaporated.