Autumn is coming, the crab season is here, and foodies can't hold back, eager to taste crab food.
When a small partner buys crabs, they will always find some crabs with strange appearances.
At first glance, the crab belly is bulging, the crab yellow is very full, it should be a relatively fat female crab, but careful observation, you will find that the crab is not large, the hand is relatively light, and the flesh in the body is almost empty.
Generally speaking, the abdomen is fuller, and the crab with more crab yellow is a good crab, why is this crab so "dry and thin"?
The belly bulge is not necessarily crab yellow, it may also be a parasite
It turned out that the yellow bulging part of the crab's abdomen that we saw was not crab yellow, but a part of a parasite called a crab slave.
The crab slave is a creature that parasitizes crabs and is a type of barnacles.
Barnacles are a kind of creature living in the ocean, the more common barnacles, wrapped in a calcareous shell of the shell, the shape is very similar to the shell of the snail, but the barnacles are an arthropod, and the relationship with shrimp and crabs is closer.
Some barnacles are edible and delicious, and the bergamot snail is called "food from hell".
Barnacles are also a kind of creature that clings to life, generally attaching to rocks, cliffs and the surface of boat bottoms to catch plankton life, and some types of barnacles will attach to creatures such as whales and turtles to parasitize life.
In general, the parasitism of barnacles does not have much impact on the host, the two are symbiotic relationships, that is, barnacles obtain nutrients from the host, but its existence, the host is not affected.
However, the crab slave is completely different, it is a complete predator.
Possess the crab's body and manipulate the crab's behavior
The main target of crab slaves is the green crab in the ocean, and other species also have parasitism and a wide range of distribution.
Its life history can be divided into three stages:
1. Infection stage: look for the best host
Young crab slaves drift freely, feeding on plankton in the ocean.
At a certain time, the female crab slave larvae will choose a suitable crab host, attach to its surface, and find a suitable position on its body.
In general, the root of the bristles on the crab's abdomen is the most commonly chosen part.
The female crab slave larvae then shed the hard shell, grow a probe-like structure, insert it into the crab, and inject the body into the crab.
2. Internal parasitic stage: dominate and manipulate the entire body
The parasites injected into the body begin to grow freely, growing a root-like structure, like a huge spider web, all over the crab's body, used to absorb nutrients from various parts of the stomach, intestines and nervous system, and control the behavior of the host, so that the crab becomes a real "crab slave".
The presence of parasites can inhibit the development of the crab's reproductive glands, resulting in the atrophy of the reproductive glands, and the crabs cannot molt normally, so that they are very small.
3, reproductive stage: the parasite as their own child to raise
At this stage, the crab slave allows its eggs to pass through the skin and stratum corneum of the host and develop outside the body.
The egg is like a small water bag, hanging on the belly of the crab, and at first glance, it looks like the crab yellow of a crab.
The host of the crab slave is gender-neutral, and both male and female crabs carry these eggs outside the body. The mother crab has its own maternal brilliance and will take great initiative to take care of and protect the eggs of the crab slave, just like her own children.
And male crabs, born with insufficient "motherhood", crab slaves will find ways to change the appearance and gender of male crabs.
It manipulates the body of the male crab, affects the hormone secretion of the male crab, makes the male crab transgender, and grows the same abdominal characteristics as the female crab, and even behaves similarly to the female crab.
Crucially, this transgender effect is almost irreversible.
If the parasites in the host are removed experimentally, the ovaries of the female crab usually regenerate, but the male crab undergoes a complete sex change and develops ovarian tissue.
When the eggs mature, the eggs hanging outside the body attract free-swimming male crab slave larvae and enter the body through small holes to fertilize.
The male individuals of crab slaves are small, do not grow up, and die soon after completing the task, while female individuals can survive in crabs for 1-2 years.
When the fertilized egg matures, the crab slave will manipulate the crab to climb onto a rock, shake the body to release the larvae, and a new parasite is about to begin.
In the end, the genitals of the crab slave will age and fall off, and if you are lucky, it will leave a "parasitic scar" for the crab, and the host will continue to live with the scar, and if you are unlucky, the crab will die due to nutrient depletion.
At last
Crab slave parasitism looks terrible, but in general, it will not cause large-scale death of crabs, but the economic value of crabs will be greatly reduced.
Its biggest impact on humans is that the quality of crabs has declined.
Crab slaves generally live in the sea, but they also occur in freshwater crabs, especially in coastal brackish water junction areas.
Crabs parasitic by crab slaves, if they are accidentally eaten, do not need to worry too much, after high temperature cooking, will not have a bad impact on the body.
The only regret is that the crab you eat, after being destroyed by the crab slave, there must be no meat.