My theory is that being so small makes them very vulnerable and susceptible to many things in the environment from climate, radiation, toxins and other factors. For example, a drop from boiling water won't kill you or I, but will kill an ant.
My simple 2 cents anyway.
And 30 years at - 20 Celsius ! And some of their species can survive 6x's the pressure found in the deepest ocean trenches @justtryme90 .
I wonder what the evolutionary stimulus was to develop these characteristics.
My theory is that being so small makes them very vulnerable and susceptible to many things in the environment from climate, radiation, toxins and other factors. For example, a drop from boiling water won't kill you or I, but will kill an ant.
My simple 2 cents anyway.