Using previously magnesium chloride could help you in relaxing body structures. I haven't an idea in ostracods but in tiny bivalves, hot water (~30°C) have a similar result.

Hi Miguel!

Perhaps this paper can help you in all the techniques:

Martens & Horne (2016). Collecting and processing living, non-marine ostracods. Journal of Crustacean Biology 36 (6): 849-854.

https://academic.oup.com/jcb/article/36/6/849/2735737

Cheers,

Jordi

Hi Miguel.

That is very difficult. Sometimes with very fine needles if you can find a small separation between the valves you can. But otherwise it is very easy to break one of the valves trying to open that. The best would be to have fixed the sample with low ethanol concentration initially (up to about 30%) and so the adductor muscle keeps relaxed and ostracods die with open valves. But otherwise you can try the methods suggested in this paper:

Article Two new methods for opening closed carapaces of preserved Os...

you have to put less alcohol at first as to let them relax and after a few hours you put as much alcohol as needed to be preseved.

I have recently started placing a small piece of synthetic sponge in the petri dish and then placing the ostracod ventral side up in one of the small cavities. It keeps them in place without crushing them while using two fine needles to open the shell. Its really helped when shells are tightly closed. The sponge I use is the sort that goes on the end of a mop.

Thank you all for the very helpful responses!!