Arugula is very salty, and doesn’t look like arugula

I recently bought some arugula, partially to make salads with. I tasted some leaves though, and it's incredibly salty. It also doesn't look like any arugula I've ever had before:

I'm used to more "serrated spear"-shaped leaves. This looks more like spinach than anything. If I tear it up though, it releases the distinct, sharply-bitter smell that I associate with arugula.

I thought that the salt may be a result of a pesticide or something that was added to the leaves, but the packaging claims it's pesticide free, and also that it was grown via aquaponics. The salt taste also survives several rounds of washing.

Is there something wrong with the arugula, or is this a particular variety? If I search for "salty arugula", the results are almost exclusively recipes that involve adding salt, which isn't very helpful.