Substrates of Life
It was a sunny afternoon and my chickens were busy bathing. To my wife’s annoyance, they had dug up the soft soil near a veggie patch. They were constantly throwing dust up their feathers and shaking their bodies to get rinsed with the dust. The child in me was astonished. We claim to have shower or bath to get rid of dirt and here they were bathing in the dirt!
Not just chickens, many other birds do this too. They apparently do this to keep their feathers in a healthy condition. It is also said to cleanse their feathers and bodies of some parasites. So the purpose is more or less the same as ours when we take a shower.
I wasn’t content with this macro-level scientific explanation though. This incident took me deeper. The living world appears to have various levels of substrates that organisms occasionally love to immerse themselves completely just as a child feels secure in his/her mother’s embrace when desperate. Water is the most obvious such substrate and the most used one too. There are many life forms that spend most of their lives constantly in touch with natural water. Those who don’t, such as we humans, frequently soak themselves in water in various ways. While plants and other land animals depend on rain water, we humans take shower to saturate our exterior fully with water.
Soil is the next best option where access to water is limited. Soil indeed is the substrate of life on land. Plants grow on it, animals roam around and return to it. We all contribute to the organic content of the soil — in life and after death. Is that why chickens feel so satisfied rinsing their bodies with soil?
What could be the next level substrate after water and soil? Plant leaf surface? Animal skin?
Flies love animal skin. Last night while watching a David Attenborough narrated story on lions of Africa, I could not take my eyes off the flies on the faces of lions. Insects riding on animal skin is a common sight. Some, such as mosquitoes, could be deadly but most are harmless. It is not odd then to think of animal skin as a massive substrate of life if we combine the skin surface areas of all animals.
There are numerous tiny animals, and I am leaving aside the microbes, that complete their life cycles on or inside the skin. One such interesting creature is Demodex mite which lives on human skin. Demodex mites have been living in hair follicles and sebaceous glands of all humans for tens of thousands of years now. Even people who have migrated across continents are found to have maintained specific mite lineage associations. Such is the mites’ association with humans that evolution of one mite species D. folliculorum has been studied to verify out-of-Africa human migration hypothesis.
Demodex mites prefer to live on human faces perhaps because the facial skin has larger pores. One of the curious facts about these mites is that they lack anus. They accumulate their waste inside their body throughout their lifetimes and throw them out once they die. Right on your face. Disgusting, no? But they are deemed harmless. They just use your skin as a substrate. All their lives.