Barnacles are small, shell-covered creatures that live in the ocean and feed on filter food like plankton and other microorganisms.
They are found in marine environments, and can usually be seen hitching a ride on the body of a host animal, the most common being whales! Whales and plankton have a symbiotic relationship, however, only the barnacles seem to benefit in this case.
If whales do not benefit from this relationship, then why do they let barnacles grow on their heads and bodies? The most likely answer is that these hitchhikers make no difference to them. Being such large mammals, these cetacean species do not mind the large number of barnacles growing on their bodies. Barnacles are not parasites either, and the hard covering they form on whales actually can help offer them protection from other dangerous creatures in the sea!
What are barnacles?
Barnacles are small crustaceans that can be found in marine environments. These arthropods are thought to be one of the oldest species living on Earth, and there is no doubt about it, looking at their primitive structure and appearance.
They gain nourishment by suspension-feeding, feeding on small food particles which are suspended in the water which they consume as they pass through their systems, or by filter-feeding. These hitchhikers are considered to be erosive in nature, as they attach themselves to and gradually reproduce on the bottoms of ships, oil rigs, and other deep-sea manufacturing equipment and cause a lot of damage.
There are over 1,000 species of barnacles, and though some are considered parasites, the barnacles found attached to whales are usually in a symbiotic relationship with them. Fortunately, the type of symbiotic relationship between whales and barnacles is a commensalism one, in which only one species, the barnacles, actually benefit. They do not cause any significant harm to whales in the process. They are simply harmless hitchhikers, taking advantage of a whale's large body to escape predators and find lots of food to eat.
Barnacles are very easy to identify. Most barnacles are circular in shape and covered with six fused plates made of hardened cement. The soft body of a barnacle protrudes from the center of the scales. It has have more plates on top, which can open and close by will to protect the inner flesh of the organism. Barnacles can also be called shellfish, mollusks, or simply crustaceans. Though barnacles are not poisonous or toxic, it is recommended not to touch them as the sharp plates can cut through skin very easily, leading to painful wounds.
Why do barnacles sit on whales?
Barnacles find the bellies and backs of whales an ideal breeding ground. By hitching a free ride on whales, barnacles get a relatively safe place to live, enough water passing by them to engage in filter-feeding as a whale swims, and a proper ground to expand their colonies.
It is not very clear how and when barnacles actually attach themselves to whales, but they begin their life in the ocean as small, larvae-like creatures. They have evolved over the years to breed at the same time and place as whales, in warm, shallow waters. Once they get in close range of each other, barnacle larvae seem to embed into whale skin and stay there. As they grow, they build hard, pointy shells around themselves, which cover their soft insides as well as dig into the whale's skin further for good grip. They have tube-shaped cavities inside their shells, with which they can properly anchor themselves to a whale and not fall off. The upper layer of their skin sheds off.
The plates are formed by juvenile barnacles secreting a cement-like substance, which hardens around them to form plates. These plates mold together, pulling the upper layers of the whale's skin into the gaps between them, causing a permanent fusion of the barnacles to the skin. Barnacles can usually be found getting a free ride on the backs and stomachs of whales, however, it seems that they prefer to attach themselves to chins and heads. These are strategically good places for them to live, as when whales pass through plankton-rich waters they are able to indulge in filter-feeding and eat to their heart's content. Barnacles actually feed the same way that whales do. They filter tiny food items through their mouths as they travel through the ocean.
Though barnacle colonies can often grow very large, with their combined weight going up to 1,000 lb (453.5 kg), this seems to cause no harm to a whale. They cause no significant harm to whale skin either as they are not parasites, except in cases where too many barnacles are concentrated in a single place, which can scratch off the upper layers of skin and cause irritation. In this case, the whale will attempt to scrape the barnacle colony off on its own.
Should barnacles be removed from whales?
As barnacles do not seem to cause any lasting damage to whales, it is not necessary to remove them. The only situation in which they must be removed is if there are too many barnacles clinging to whales, which can cause skin irritation. As barnacles dig into a whale's skin, hosting too many of them may result in the top layer of whale skin being scraped off.
Barnacles themselves are not harmful at all. However, sometimes parasites attach themselves to the barnacles, like whale lice, and seek shelter in the hardshell covering, which can cause harm to the whale. In this situation, it is probably best to remove the barnacles from a whale. However, it is best to not interfere in this matter and let whales deal with the problem themselves, as improperly scraping off barnacles can do more harm than good. As the barnacles dig deep into a whale's skin and cling there, it would be quite difficult to remove them without damaging the upper surface of its skin.
Whales have been observed to scrape the affected area against rocks or the seafloor if it seems to become unbearable for them. This removes the barnacle species and whale lice naturally. However, for the most part, barnacles are completely harmless for whales. In fact, in some cases, they are even quite useful with thick layers of barnacles acting as a natural armor for whales!
Why do humpback whales have barnacles on them?
Barnacles seem to be partial to which species of whale they want to latch on to, with the largest percentage of barnacles being spotted on humpback whales and gray whales. This usually depends on the location and temperature of water that the barnacles and host whale are found in.
For example, humpback whales that are found in the Pacific Ocean are usually covered with the Coronula diaderma species, which are not found on any other whale species. On the other hand, the gray whale is only covered with the Cryptolepas rhachianecti barnacle species. Other species like Semibalanus balanoides (acorn barnacles) and Pollicipes pollicipes (goose barnacles) grow on humpback whales as well. In total, humpback whales grant shelter to three species of barnacles and one species of whale lice!
Whales like killer whales, blue whales, and orcas do get barnacles, however this is very rare and only in small amounts. Barnacles can be observed more on humpback whales because of the convenience of location. These whales travel to warmer waters during the mating season, where males usually compete to win the favor of females, usually perching on top of them. This is why male whales can be observed hosting more barnacles than females. They also may have a lot of scars from the sharp edges of the barnacles. If too many barnacles grow on a whale's body, the whale will scrape them off naturally.
In fact, humpback whale individuals have been observed to actually roll over when faced with predators. Also making sure the barnacle-covered surface of their bellies greets them. It seems that these hitchhikers are beneficial to a humpback whale after all!
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