Barnacles clinging to whales are a common and intriguing sight. These crusty passengers prompt a question about their presence: are barnacles truly beneficial for whales?
Understanding the Whale-Barnacle Relationship
The interaction between barnacles and whales is largely considered a commensal relationship. In this type of biological association, one species benefits while the other is generally unaffected. Barnacles, crustaceans related to crabs and lobsters, gain significantly from attaching to whales.
Whale barnacles, such as Coronula diadema and Xenobalanus globicipitis, are specialized species that exclusively attach to cetacean hosts. These barnacles begin as microscopic larvae that eventually settle on a whale’s skin, particularly on areas like the head, flippers, and tail. They secrete a powerful, protein-based biological cement, allowing them to firmly anchor themselves for life. For species like Coronula diadema, this involves forming tube-shaped cavities that draw in and embed into the whale’s skin.
The barnacles benefit by gaining a stable, mobile platform, a constant supply of nutrient-rich water for filter feeding, and protection from predators. This also aids in the dispersal of barnacle larvae across vast oceanic distances.
How Barnacles Affect Whales
While barnacles benefit from their whale hosts, their impact on whales is typically minimal. The relationship is generally not parasitic, as barnacles do not feed on the whale’s tissues or blood.
However, a heavy accumulation of barnacles can increase hydrodynamic drag, potentially reducing the whale’s swimming efficiency and increasing its energy expenditure.
In some instances, the presence of barnacles may cause minor skin irritation or discomfort, especially if they attach to sensitive areas. If a barnacle is dislodged, it can leave an open wound, creating a potential entry point for bacteria and secondary infections, though this is not a common occurrence.
Despite these minor downsides, whales generally tolerate barnacles, and they are not considered life-threatening. Some theories even suggest that barnacles might offer a degree of protection, acting as a form of armor against predators or during battles between whales.
The Persistence of Barnacles on Whales
Whales continue to carry barnacles due to their strong attachment capabilities and the whales’ limited ability to remove them. The specialized cement produced by barnacles is exceptionally strong, capable of withstanding the immense forces of ocean currents and whale movements. Once attached, the barnacles become deeply embedded in the whale’s outer skin layers.
Whales do engage in behaviors that can help dislodge some barnacles and shed dead skin. These include breaching, where they leap out of the water and crash back down, or rubbing against the seafloor, rocks, or even other whales.
While these actions can remove some of the external growth, they are often insufficient to clear all barnacles, particularly those in hard-to-reach areas. Given their size and lack of dexterous limbs, whales cannot effectively scrape off all the attached organisms. This long-standing interaction coexists without significant detriment to whales.