sentences:  Females may also have smaller and rounder heads.When spawning, the colours of the males become deeper, the orange bands becoming red in the case of "Brachygobius doriae".This genus is informally divided by taxonomists into the dwarf Brachygobius nunus"-species group (e.g., "B. nunus", "B. aggregatus", and "B. mekongensis") and the bigger Brachygobius doriae"-species group (e.g., "B. doriae", "B. sabanus", and "B. xanthomelas").