Cool paper from my field. In every plant species there's a hormone receptor sitting there but we don't know what the hormone is yet! Finding the ligand has become a bit of a holy grail for many researchers. This study finds an endogenous ligand for a divergent homologue of this receptor, not of much consequence to most plant species but still enough to have people turning heads.
Nobody is saying that fish are moral agents that can empathise with other beings. That doesn't man that they're not moral subjects; the ability to understand that one is causing harm is not a prerequisite for the ability to suffer oneself. I think everyone knows this intuitively, but it does feel good to have our less moral habits be justified by memes that we would otherwise find to be illogical.