Depending on the animals in question, the amount of DNA per cell may be associated with body size, metabolic rate, developmental rate, or other traits. With an old fashioned cytogenetic staining method (the Feulgen reaction) and a new image analysis densitometry setup, we can estimate genome size for vertebrate species quite readily with only an air-dried sample of blood cells on a microscope slide. Getting the blood is the limiting step in many instances -- in particular from cool and recently discovered critters like these that are now officially on my blood smear wish list.

If you taxonomists out there wouldn't mind making smears for me when you find these kinds of beasts, that would be excellent.