Could I modify sprite in runtime?

Hi, everybody!

I'm new in unity. I used to work with flash. But, now I'm trying to port my topdown shooter on unity. And in this case I've notice some differents between this platforms.

And, the most sophisticated task for me is how to draw spilled blood on the floor texture without increasing drawcalls and triangles amount.

I mean, in flash I can modify texture on runtime and draw blood stains directly on texture to save the resources. This method is called DrawBitmap.

Does Unity has any analogs? Should I draw changes directly on texture, without instantiating new gameobject?