Barnacles often adorn the massive bodies of whales in the ocean. These crustaceans, permanently affixed to their hosts, prompt curiosity about this unique biological relationship. Understanding why these marine organisms make whales their home reveals fascinating aspects of their life cycles and the marine environment.
The Nature of Whale Barnacles
Whale barnacles are a type of acorn barnacle. These barnacles specifically target cetaceans, primarily baleen whales, though some can be found on toothed whales. They begin their lives as microscopic, free-swimming larvae, before reaching a cyprid larval stage. Once a suitable host is encountered, the cyprid larvae settle and permanently attach themselves with a strong adhesive. They then develop a crown-shaped or cylindrical shell, composed of six calcium carbonate plates, which embeds into the whale’s skin for stability.
Why Whales Provide a Home
Whales offer a mobile habitat for barnacles. Their large size provides ample surface area for attachment, accommodating hundreds of pounds of barnacles on a single whale. The relatively slow swimming speeds of many baleen whales create a stable platform. This consistent movement through the water ensures a continuous flow of food particles, as barnacles are filter feeders.
Whales’ migratory patterns also benefit barnacles, transporting them to nutrient-rich waters. Once a larva finds a suitable spot, it secretes a strong cement to anchor itself to the whale’s skin. As the barnacle matures, its shell integrates with the whale’s growing skin, creating a secure attachment that lasts for the barnacle’s lifespan, often around a year.
The Whale-Barnacle Interaction
The relationship between whales and barnacles is considered commensalism, where the barnacle benefits while the whale is generally neither helped nor harmed. Barnacles gain a stable place to live, protection from many predators, and constant access to food as the whale moves through plankton-rich waters. They extend feathery appendages, called cirri, to filter feed on small organisms from the passing water.
While a heavy infestation can add weight and increase drag, potentially affecting swimming efficiency, this impact is minimal relative to the whale’s size. Some theories suggest that barnacles could offer protective armor against predators or add to a whale’s striking power during mating battles. However, these potential benefits to the whale are still debated, and the barnacle remains the primary beneficiary.
How Whales Manage Barnacles
Despite the benign nature of the relationship, whales employ various natural behaviors to manage barnacle accumulation. One strategy is breaching, where whales leap out of the water and crash back down, using the force of impact to dislodge barnacles and shed dead skin. Whales also rub themselves against hard surfaces, such as rocky seafloors or buoys, to scrape off attached barnacles. This “sandpapering” action exfoliates their skin.
Some whale species exhibit natural skin sloughing, a process similar to molting, which helps to shed barnacles along with old skin cells. While these methods can reduce the barnacle load, they may not remove all of them. The synchronization of barnacle reproduction with whale migration patterns also means that barnacles may naturally slough off in calving grounds or along migratory routes.