desmin proten western blotting

[ecemku...@gmail.com]

I try the label desmin protein in western blot from zebrafish muscle tissue extract. But everytime I see 2 bands in membrane. I use SIGMA (D8281) rabbit polyclonal antibody to desmin. It’s known that desmin has 2 copies in zebrafish (desma and desmb). Their predicted molecular weights are very close to each other (desma: 55,7 kDa and desmb: 54,2 kD data from uniprot.org). The resolving gel concentration was %15 and I run the gel about 4 hours. There is about 0,5 cm between 2 bands ( I couldn't attach the images)
I did a little research and I saw western blot results (with different antibodies) that also has 2 bands. That’s why I do not think that it is a non-specific band. So , I don’t see a possibility but; could my bands be desma and desmb or maybe an isoform of desma or desmb?