Photo by ANAND VARMA
People are disgusted when they hear the word "parasite", and the English word for parasite comes from the Greek "parasitos", which means "he who sits next to someone else and eats; he who eats leftovers". But American evolutionary biologist Jimmy Bernot says that as "a very successful life form," parasitic states should be more respected.
A piece of 99 million-year-old amber, a tick clutching dinosaur feathers that feeds on dinosaur blood
供图：E. PEÑALVER VIA NATURE COMMUNICATIONS
Parasites appeared 515 million years ago, and human ancestors could not catch up with even a fraction of them. Hundreds of millions of years of evolution have allowed them to master KitKat's rich survival strategies; and some "parasitism" is not disgusting, for example, the parasitism of the squid is a sad and deformed love story.
In the lower right corner of the picture, a male squid (also known as anglerfish) is attached to the side of the huge female body like a "small bird", and they will breed offspring by in vitro fertilization. The petite male dissolves the skin tissue in the female's abdomen and burrows into it; the skin and blood vessels of the two fish merge into one, and they are attached to each other for life until death. Eventually the male has nothing but a nest and is ready to fertilize her eggs when the female ovulates — "In order to love you, I completely turned myself into you." ”
摄影：DARLYNE A. MURAWSKI, NATIONAL GEOGRAPHIC CREATIVE
The sturgeon is called Haplophryne mollis, and as shown in the figure, more than one male parasitizes a female, with the highest known record being 8.
Photo by PETER DAVID, GETTY IMAGES
There are many ways in which parasites get nutrients from their hosts: some are in vivo parasites that make their home in the host, such as tapeworms and skin flies, while others are extracorporeal parasites that suck directly on blood or eat the host's skin, such as mosquitoes and vampire bats.
With sharp teeth, flexible tongues, and anticoagulants in saliva, vampire bats sometimes go undetected by their hosts
Parasitic flatworm in the tail of the Oriya tilapia
摄影：JOEL SARTORE, NATIONAL GEOGRAPHIC PHOTO ARK
Parasites have burrowed into every crevice of the "tree of life," says Mackenzie Kwak, a parasitologist at the National University of Singapore: "If there's anything that sticks a huge ecosystem together, it's parasites." In food webs or ecological webs, parasites maintain more than half of the links between species. But to this day, we are still unable to know for sure all the species and numbers of parasites. Chelsea Wood, a parasitic ecologist at the University of Washington, has come up with a rough data —
Nearly half of the known creatures on Earth —
It's all parasites.
The earliest parasite in the fossil record is a worm that stole food from clam-like brachiopods 515 million years ago; the leech of the modern world is also a worm and one of the most famous parasites. There are as many as 700 species of leeches worldwide, and only half of them are blood-sucking leeches.
In the Dannong Valley Conservation Area in Borneo, Malaysia, a man is clearing leeches
摄影：MATTIAS KLUM, NAT GEO IMAGE COLLECTION
A few parasites can also subtly replace certain organs of their hosts, such as the Cymothoa exigua. They enter the mouth of the fish when they are larvae, suck their blood through the fish's tongue, until the fish tongue shrinks, and then connect their tail to the already atrophied tongue to replace the fish tongue.
供图：UNIVERSITY OF SALFORD
Parasites can also make it possible to control host behavior. For example, some cordyceps fungi will turn insects such as ants into "zombies", forcing them to climb higher and kill them, because the high place is the perfect place to spread fungal spores; the spores spread well, infecting more ants...
The eccentric cordyceps fungus (Ophiocordyceps unilateralis) devoured the host ant and grew from the carcasses of the ants.
Courtesy photo: ALEX WILD
There are also parasites that indirectly steal resources. Cuckoos, for example, give birth to eggs in other nests to trick other birds into raising their offspring.
The great cuckoo (Cuculus canorus) lays its eggs in the nest of the red-tailed plover (Phoenicurus), and the parasitic eggs, except for being slightly larger, are very similar in color to the eggs of the red-tailed plover (qú); in contrast, in the lower left, the parasitic eggs of the brown-headed bullbird (Molothrus ater) are covered with spots, which are significantly different from the pure white eggs of the host.
图源：Nature Education Courtesy of T. Grim & M. Hauber.
The Eastern Reed Warbler (left) is feeding a cuckoo chick, the cuckoo is about 8 times the weight of the Eastern Reed Warbler, and the small warbler is working hard to raise a giant baby (warbler)
Photograph by FRANKA SLOTHOUBER
There is also the seemingly peculiar but common phenomenon of "reparsitism", in which one parasite is parasitized by other parasites. For example, the parasitic bee Hyposoter horticola will be met by another parasitic bee, Mesochorus cf. Stigmaticus parasitizes, the latter laying eggs in the larvae of the former.
A fossilized cocoon of a parasitic bee, about 35 million years ago, hundreds of parasitic bee larvae formed cocoons after feeding their hosts and preparing to become adults.
Photo by GEORG OLESCHINSKI
Generated: THOMAS VAN DE KAMP
To make matters worse, such as the fungus of the parasitic fungus – in New Zealand, the fungus Rhino richella globulifera feeds on the dead part of the fungus Hypomyces c.f. aurantius, which during her lifetime eats another fungus that lives on beech trees: Fomes hemitephrus. The scientific name is too long, the relationship is too winding, in a word: you eat others before you die, and I eat you after you die.
Fomes hemitephrus
Source: jjharrison.com.au
There are also parasites that, while inconspicuous, play a huge role in ecosystems. Rhinanthus minor, for example, a parasitic plant native to Europe, inserts roots into grass, sucks up their sap, and weakens the wild grass's crazy growth. For example, a field without small nose flowers will become a grassland engulfed in weeds; conversely, the growth of wild grasses is limited, and flowers can bloom all over the field to provide living space for pollinators; insects will attract birds and amphibians. So the small nose flower became the founder of a wildflower meadow.
Rhinanthus minor
Source: plantsoftheworldonline.org
Jessica Stephenson, an assistant professor at the University of Pittsburgh, argues: "Despite the importance of parasites, they are strangely overlooked. Parasites are inherently unpleasant and often "left out in the cold," led by Skylar Hopkins, an ecologist at North Carolina State University who published the first global plan to save parasites in a special issue of The Conservation Journal, and made a similar observation: "Millions of parasites are threatened, many may be extinct; but oddly enough, we have barely documented their extinction." ”
In addition, many parasites are already at risk because their hosts are critically endangered.
Critically endangered species, the Condor of California
Photograph by JOEL SARTORE
For example, the critically endangered Species of the Condor of California, in the 1970s, scientists desperately wanted to save them, so they began to keep this bird in captivity, but the lice endemic to the Condor bird in California were considered harmful to birds (unidentified), and in order to "protect" the birds, scientists used insecticides to eliminate them. Decades later, decades later, in 2015, the Condor was still "critically endangered," while the California Condor was never seen again.
On the cover of the November 2014 issue, Dinocampus coccinellae lays eggs in ladybirds, where ladybird cocoon bee larvae develop and, when mature, crawl out of the still-alive ladybirds and form cocoons around them.
It takes a lot of courage to protect parasites that look disgusting, and Chelsea Wood, a parasitic ecologist at the University of Washington, is one such courageous man who is also a leader in the New Conservation Movement, which aims to save small animals on The Planet that are "unattractive."
A female parasite of the order Kudoptera burrows into the crickets. It will mate, procreate and die here
Photo by JEYARANEY KATHIRITHAMBY
Under Wood's research, we learned all this: climate change, the disappearance of hosts, deliberate elimination, and the parasites are destined to become extinct in the next 50 years– 1/10 of their total. There are more than 37,000 critically endangered species on the IUCN Red List of Threatened Species, but there are almost no places for parasites, and of the tens of thousands of critically endangered species registered, only one lice and some freshwater mussels are parasites.
This is not an ordinary large oblique snout crab, but a zombie crustacean invaded by a parasitic barnaclette. Parasitic vines use their abilities to enlarge the crab's abdomen, making the "male become female" - creating a uterus in the male crab to fill its eggs.
Bobbi Pritt, medical director of the Human Parasitism Laboratory at the Mayo Clinic Medical Center, is dedicated to studying parasites and preventing all kinds of parasitic diseases; as a "master of insect resistance," she says it fairly: "As a doctor, I support the eradication of parasites where they cause disease and suffering!" But if as a biologist, I don't subscribe to the idea of consciously exterminating parasites. ”
As many as 31 of the 54 main branches of the "Tree of Life" known as the "gate" are mostly parasites; then when all the parasites are destroyed, it is equivalent to cutting off the giant tree.
A wasp lays its eggs in oak leaves and produces a chemical that induces plants to grow pink "galls", or parasitic houses.
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