Although most of us have never seen a real whale, this does not hinder our familiarity with whales. After all, pictures or videos about whales can be seen everywhere. Those who have observed carefully may have already discovered that there are usually some "pimples" on the body surface of whales, which look very unnatural.
Actually, most of those pimple-looking things on whales are an animal called " barnacles ", which are widespread in the ocean and will be on whales when they get a chance "Settled", after which the whales are basically unable to get rid of it, because of this, many whales are parasitic with a large number of barnacles, we can feel the feelings of the whales just by looking at the pictures.
However, barnacles are not a problem for another large marine animal, sharks, because barnacles are not found in sharks at all. So the question is, why do whales usually have a lot of barnacles on them, but sharks are clean?
The life of barnacles
Barnacles in taxonomy belong to arthropods phylum, crustaceans, cirripoda, sessile, barnacles , their whole life can be divided into no segments The three stages of larvae, glandular larvae and adults. The size of the newly hatched barnacle larvae is usually about 1 mm. Under normal circumstances, they will "float with the current" in seawater and feed on the small organic matter in the ocean.
If all goes well, the barnacle larvae will grow rapidly in seawater, and after 2-3 weeks they will enter the glandular larval stage, at which the barnacles hardly eat any more food, they can use their tentacles to swim in the seawater, their The main goal is to find a suitable place to "settle".
The adults of barnacles fix their calcareous shells on a harder substrate, and then prey on plankton in the water through their own vines, which is a passive way of survival as a whole, so barnacles are choosing When "settlement", the most important condition is the need for stable and sufficient water flow.
So those reefs and shells , marine life body surfaces in those shallow waters, and even the bottoms of human ships would be considered ideal "settlements" by barnacles.
After finding a suitable place, barnacles in the larval stage are usually very cautious and will use their tentacles to temporarily attach to the contact surface for "trial settlement", and may also move around the contact surface in order to detect the substrate. Physical and chemical properties, until they are satisfied with their current position, they will secrete barnacle glue to fix themselves, and once they are not satisfied, they will look elsewhere.
Since the skins of marine creatures like whales are constantly updated and iterative, those barnacles that can attach to marine life have evolved the ability to "nail" themselves on the surface of marine life.
For example, the "barnacle-crowned whale barnacle" commonly found on whales has evolved a mechanism of "folding the shell inwards and growing downwards at the same time", so that its shell is firmly "nailed" to the whale's skin among.
After " settles " the barnacles will start to thrive, in warm oceans, barnacles can breed all year round, they will spread a large number of eggs in the sea water, and these eggs hatch into larvae After that, the above process is repeated again.
Why can't barnacles be found on sharks?
The surface of the shark's body is covered with a large number of scales, which are called "shield scales". These tiny scales are spike-like and germinate from the bone substrate inside the shark's skin. The outer layer is enamel and the inner layer is enamel. As dentine, the texture is also much harder than whale skin.
Through the above introduction, we can know that in the life of a barnacle, the glandular larvae stage is a key stage for the barnacles to choose a "settlement", and the barnacles at this stage will be very important in determining the future "settlement". cautious.
It can be imagined that it is difficult for barnacles to be satisfied with the spiky "shield scales" that cover the whole body of sharks. It is also impossible to "nail" yourself firmly on the hard "shield scale".
More importantly, during the growth process of sharks, their "shield scales" will continue to increase, and they will continue to fall off and update, which undoubtedly further increases the difficulty of barnacle parasitism.
In addition, sharks are very fast, and when they move, the water currents on their body surface can be very strong, which also makes it difficult for the barnacle larvae to attach to the shark's body.
All in all, since barnacles are neither capable nor willing to "settle" on the surface of a shark, of course the shark is clean.
It is worth noting that not all whales have a large number of barnacles parasites. Generally speaking, only slower whales such as humpback whale , right whale , gray whale will be caught by barnacles Plenty of parasites.
And for faster whales like killer whale , blue whale, although they may also have a small amount of barnacles on them, it is relatively much less (although blue whales are large, but They are not slow to swim).
Okay, today we will talk about it here first, welcome everyone to pay attention to us, see you next time.
(Part of the pictures in this article are from the Internet, if there is any infringement, please contact the author to delete)
