I'm working on my reseach, the topics about gen barcoding of local sea cucumber in my city (i assumed that the sea cucumber is belong to Caudinidae).

But i have a problem. Whenever I do my PCR there is always no band, I've tried this more than 20 times. I've tried to change the temperature and the primer (to searh which one can be optimize my sample)

by the way, I'm using COICE and COIE as as primer.

I've read your paper about sea cucumber from antartic's sea. can anyone give me some suggestion for this troubleshooting?