Is inter-breeding between species common? For instance, is the dogfish and bull huss scenario a new development?

NEIL STEPHENSON, BY EMAIL

DL says: As far as I am aware, there is no evidence of lesser-spotted and greater-spotted dogfish (bull huss) having inter-bred.

Both species display massive variations in colour, and often it is this that causes confusion. In reality, both species are easy to distinguish because bull huss have distinct nasal flaps, whereas lesser-spotted dogfish do not.