When birds live on an island where there are no predators, their wings tend to shrink and they lose the ability to fly.
The reason for this is that flight consumes a lot of energy, causing the bird to eat more food.
At the same time, the hunt and search for food is almost constant and tiring. Every day is an exercise in precarious balance.
But everything changes on this peaceful island, where nothing tries to kill them: life is so comfortable and safe that the birds don’t need an escape plan. And so, in an evolutionary change, their wings shrink.
A similar thing happened with microscopic mites (Demodex folliculorum) that live in our pores and mate happily on our faces at night.
Where once mites were parasites, they have become much more simplified organisms – and have developed a more symbiotic relationship with humans.
A fascinating new study suggests that they “become one” with people.
Think of them as home help on a really good wicket.
Dust mites settle when we are born
Our first life in the womb is the only time in our life when we are free from mites.
We pick them up when we are born and carry them for the rest of our lives.
Each mite is about 0.3mm long. There are more than five residing on every square inch of your face and nipples, and they can be found in and around your eyelashes.
These mites favor the hair follicle where they feed on sebum – the oily, waxy substance produced by your body’s sebaceous glands.
Sebum mixes with fat molecules (lipids) and serves to protect the skin.
Excess oil leads to clogged pores and blackheads and subsequent irritation.
Dust mites are often blamed for irritating the skin, but an overabundance of oil suggests you may need more of it than less.
At night, in the dark, if you feel a tingling sensation on your face, it’s probably not mites moving between follicles to mate. In fact, they do, but you probably won’t feel them.
New study: more than you want to know
A research team led by the University of Bangor and the University of Reading, in collaboration with the University of Valencia, the University of Vienna and the National University of San Juan, has completed the first genome sequencing study from D.folliculorum moth.
The researchers found that “their isolated existence and resulting inbreeding causes them to shed unnecessary genes and cells and evolve into a transition from external parasites to internal symbionts.”
Dr Alejandra Perotti, associate professor of invertebrate biology at the University of Reading, who co-led the research, said: ‘We found that these mites had a different arrangement of body part genes compared to other similar species due to their adaptation to indoor sheltered living. pores. These changes to their TSWT resulted in unusual bodily characteristics and behaviors.
Tiny vampires confined to the night
The in-depth study of Demodex folliculorum TSWT has revealed that by living in isolation, mites are not exposed to outside threats.
They have no competition for food (all that delicious sebum) – and they don’t meet other mites with different genes to reproduce.
This means that their gene pool as a species has shrunk – but they have lost a host of genes that “caused them to become extremely simple organisms with tiny legs powered by just three single-celled muscles”.
It’s like those island birds losing their wings.
A consequence of their evolved simplicity is that these mites “survive with the minimum protein repertoire – the lowest number ever seen in this and related species”.
This left them with fewer tools to fight the outside world.
They are forced to be active at night, partly because their genetic reduction has removed their built-in UV protection, and also because they have also lost the gene “that causes animals to wake up by daylight.”
A strange example of humans helping
Humans produce melatonin, which produces sleep.
In small invertebrates, melatonin works to keep them active at night.
But face mites are no longer able to produce melatonin, which potentially prevents them from moving around day or night.
So how come they stay up all night making our pores burst? They access the melatonin that we secrete through our skin when the sun goes down.
Downstairs moved upstairs
Overall, their mating habits are a bit odd, as is their marriage material.
The mites’ reproductive organs have moved toward the head of their body, and the males “have a penis that protrudes upward from the front of their body.”
Scientists say this means they have to position themselves below the female when mating, “and copulate while they both cling to human hair”.
The mites have evolved extra mouth appendages to collect food, which makes it easier for them to survive at a young age.
Although there are a range of openings for food, some researchers had assumed that the mites had no anuses “and therefore must accumulate all their faeces throughout their lives before releasing them when they die, causing inflammation of the skin”.
This so-called trough is false. They have an anus that does what anuses do.
And they probably aren’t responsible for as many skin infections as once thought.
Dr. Henk Braig, co-lead author from Bangor University and San Juan National University, said: “Mites have been blamed for many things. The long association with humans might suggest that they might also have simple but important beneficial roles, for example, keeping our facial pores unplugged.
The end of days
The lack of exposure to partners outside the species means that the mite gene pool is dangerously lacking in diversity.
The researchers believe this may have put them on the path to “evolutionary dead end and potential extinction”.
In other words, they could become the Dodo of the dust mite world.