Those look like sea-lice that have been in a cooler for a while (perhaps while still fishing, then driving home?) and half of the original is missing, the abdominal section (Might be the thorax- it's been a long time since entymology/biology class) . That looks like just the head section.

Perhaps they are a different strain or at a different stage of life.
I'm betting on the cooler/storage theory.
Any parisitologists or entymologists out there?