Isopods of the genus Saduria are common nearshore animals in Arctic shores of Alaska. Saduria entomon gets pretty big, this one is over 2 inches long. We have a couple of species in Alaska including S. entomon and S. sibirica. Sadurid isopopds are canivores and scavengers feeding opportunistically on anything they can find.
Here is a photo of the head. These are amazingly adaptive and resilient animals. They survive in freezing conditions, low oxygen, little food, and in a wide range of habitats from gravel to mud. Once, a student assistant was sorting a poorly preserved benthic sample and after ~6 months of preservation, he found a small Saduria swimming in the jar. No other organisms were present indicating it ate everything else in the sample! Talk about tough, it was surviving in a weak formalin solution, there would have been little oxygen, eventually, no food, and the animals it ate contained formalin as well. I vote for these as being the tough guys of the Arctic.