Barnacles are never seen on killer whales. Do barnacles bully the weak and fear the strong?

Earlier, people were not particularly familiar with barnacles, a marine parasite, but as it entered the seafood market, it quickly became a household delicacy.

Judging from their appearance and taste, barnacles seem to belong to the same category as other shellfish in the seafood market, but in fact this is not the case, because barnacles are not shellfish at all, but arthropods. What are arthropods? The insects, spiders, shrimps and crabs we are familiar with are all arthropods. But unlike the above arthropods, barnacles are parasitic, and the places where they are most likely to attach are the bottom of ships, offshore oil platforms and submarine cables. In short, any object with a hard surface can become its attachment object. In addition to attaching to these places, barnacles also have a special liking for whales. For example, humpback whales, right whales and gray whales are their favorite hosts.

So how do barnacles, which appear to be motionless, attach themselves to these moving objects?

Barnacles are hermaphroditic arthropods. In theory, they can reproduce on their own, but in most cases, barnacles reproduce cross-species. One barnacle will insert a thin tube into another barnacle and transfer its sperm through this thin tube. When the barnacle egg is successfully fertilized, a new barnacle is born. However, the newborn barnacles are nothing like their parents. They need to undergo several metamorphosis to become like their parents. The initial barnacle larvae are a kind of plankton, after which they develop into nauplii and then into cyprids. Cyprids are a very special larval form of barnacles.

The reason why the glandular larvae are called a special form of larvae is that barnacles in this form do not need to eat. Their only task at this stage is to choose a suitable attachment.

The larvae of barnacles have a certain swimming ability, but their main way of moving is still passive traction by the water flow. When they are brought to an attachment by the water flow, they will not rush to bind to it. They will use their small tentacles to move slowly on it, the purpose is to examine whether the attachment meets their conditions. If they are sure that it is the "right person", they will use their tentacles to attach to the contact surface, but the attachment at this time is called "temporary attachment" because this attachment is easy to move. After that, the larvae will further confirm whether the contact surface is suitable for attachment. If it is confirmed, the temporary attachment will be converted into permanent attachment.

Once the barnacle has completed its permanent attachment, it will begin the final metamorphosis of its life, transforming from a cyprid into a true barnacle.

After completing the last metamorphosis, the barnacles will release a liquid substance, which will form a colloid through assembly and cross-linking, making the attachment more secure. This substance is called "barnacle glue". This hermaphroditic organism reproduces very quickly. Once a small number of barnacles are attached to a place, it will soon develop into a large area. The attachment of a large number of barnacles is not a good thing for all attachments. Barnacles on the bottom of the ship will slow down the speed of the ship, barnacles on the oil platform will increase the deadweight of the structure, and barnacles on the submarine optical cable will accelerate its corrosion rate.

Barnacles are even more annoying to living things. Whales that are heavily attached to them will suffer.

So, the question is, why are barnacles almost never seen on killer whales? Could it be that barnacles are also bullies, only daring to attack baleen whales and not daring to provoke fierce toothed whales? Of course not, because blue whales, which are also baleen whales, rarely have barnacles on their bodies. The main objects of barnacle attachment are humpback whales, right whales and gray whales. In fact, barnacles also have conditions for choosing hosts. This parasite has obvious "energy tropism", that is, the higher the surface energy of the attached object, the more barnacles like it. So what substances have higher surface energy? Roughly speaking, the rougher the surface and the darker the color of the object, the higher the surface energy, and the more barnacles like it.

Humpback whales and right whales are both dark black, and gray whales are also darker in color, so they are more favored by barnacles, while blue whales are blue in color, so they are not favored by barnacles.

Aren't killer whales also dark black? Yes, but color is not the only factor. Killer whales can swim at speeds of more than 50 kilometers per hour, far beyond the humpback whales, which can only swim at about 10 kilometers per hour. The swimming ability of barnacle larvae is limited, so it is difficult for them to attach to killer whales. Killer whales are also much smaller than those baleen whales, so it is even more difficult for barnacles to hit their targets. It can be seen that in order to become a host for barnacles, at least three conditions must be met. The first is that the body is large enough, the second is that the swimming speed is slow, and the third is that the body color must be dark. Among the three factors, the swimming speed is the most important. Of course, ships also sail very fast, but they always stop, so they fall into the trap of barnacles.

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