Thank you sergtab. That is very helpful.
I'll change the sentence just a tiny bit and include commas.
Current knowledge of (the) nematode fauna of these countries, especially the Czech republic, is quite limited.
The comment about the Czech republic is not essential to the sentence so should be separated from it with commas. Have a look at THIS LINK
, which calls these "bracketing commas".
I suggest that you insert "the" because it is specific nematode fauna, the nematode fauna of these countries, that you are talking about, not nematode fauna in general.
I changed "and especially in the Czech republic", removing "and" and "in".
"and" is not necessary and "in" makes me think you mean to talk about "knowledge in the Czech republic".
I hope that's clear