In particular, I'm thinking about a most unlikely "couple," sloths and blue-green algae. Their pairing has provided a home for the algae and a bit of camouflage - the slight greenish hue we see in the sloth's coat.
Location, location, location is the mantra for many of us in our macro world but it is also true for the world of the small and the domain of the wee blue-green algae.
Blue green algae is a term used to describe any of a large, heterogeneous group of prokaryotic, principally photosynthetic organisms. These little oxygenic (oxygen-producing) fellows appeared about 2,000,000,000 to 3,000,000,000 years ago and are given credit for greatly increasing the oxygen content of the atmosphere, making possible the development of aerobic (oxygen-using) organisms.
But all this heavy breathing aside, we go back to sloths... and the wonder of making do where you are. The sloth's body and shaggy coat, or pelage, provides a comfy habitat to two types of wee blue-green algae along with various other invertebrates. The hairs that make up the sloth's coat have grooves that help foster algal growth.
And, while Kermit the Frog says, "it's not easy being green," it couldn't be further from the truth for this slow-moving tree dweller. The blue-green algae gives the sloth a natural greenish protection against predators, an arrangement that is certainly win-win.