That is a very unusual pattern. Notice that the bulk of the streaks travel in one direction, from top to bottom, but they have small horizontal extensions. Also note that they are lighter (less development) than the background.
I have seen this when the film is not prewet, but is splashed with liquid which runs down the film and then the film is set on edge and some of the liquid runs perpendicular to the original track. The development is retarded wherever there are splashes. That would only be the case if something like fix or stop hit the film just before the prewet.
In summary, it is as if the film were splashed with something, as Ian says, fixer or stop before development began. I would have to say that this is only a very very rough guess though.
PE