Hi Nehzat,

Have you run a DNA ladder along with your sponge DNA? Was the electrophoresis went alright?

Also, have you quantified the extracted DNA before loading onto the gel?

What were the conditions of the extraction? What was the kit you use? have you quantified your extracted DNA with a NanoDrop before running the gel?

Hi

I don't have any experience on extracting DNA but I attach a paper , maybe it be suitable for you.

God luck

Use CTAB protocol from Winnepenninckx, B., Backeljau, T. & De Wachter, R. 1993. Extraction of high molecular weight DNA from molluscs. Trends in Genetics, 9(12):407 or the kit: DNeasy Blood and tissue (QIAGEN)

DNeasy Blood and tissue kit would be good for you. Follow each step carefully and during agarose gel electrophoresis don't forget to use a ladder.