The sight of barnacles adhering to the skin of whales is a common observation, sparking curiosity about these marine organisms and their unique association. This article clarifies their relationship and whether these attached organisms pose any threat to whales.
What are Barnacles?
Barnacles are marine crustaceans belonging to the subclass Cirripedia, making them relatives of crabs and lobsters. Over 1,000 species have been identified, inhabiting diverse marine environments. Most adult barnacles are sessile, or stationary, permanently attaching themselves to hard surfaces such as rocks, ship hulls, or other marine animals.
They are characterized by hard, calcareous shells, composed of calcium carbonate plates, which offer protection. Barnacles are filter feeders, extending feathery, tentacle-like appendages called cirri from an opening in their shell. These cirri sweep through the water to capture plankton and other microscopic food particles, which are then drawn into the barnacle’s mouth.
The Whale-Barnacle Relationship
The interaction between whales and barnacles is commensalism, a symbiotic relationship where one organism benefits without significantly affecting the other. Attaching to a whale provides several advantages for barnacles. Whales serve as mobile habitats, transporting barnacles through vast ocean expanses and exposing them to a constant flow of nutrient-rich waters. This continuous access to food, primarily plankton, is crucial for these filter feeders.
The whale’s movement also aids in barnacle dispersal, allowing them to colonize new areas and access diverse food sources. This “free ride” provides a stable place to live, protection from some predators, and a consistent food supply. Certain whale barnacle species are specialized, attaching exclusively to specific whale species, such as Coronula diadema on humpback whales or Cryptolepas rhachianecti on gray whales.
How Barnacles Attach to Whales
Attachment begins with the barnacle’s larval stages. After hatching, barnacles undergo two free-swimming larval phases: the nauplius and the cyprid. The cyprid larva’s primary role is to locate a suitable surface for permanent attachment.
Upon encountering a whale, the cyprid larva searches for an ideal spot, often using its specialized antennules to “walk” across the whale’s skin. Preferred areas include the head, flippers, and tail, where water flow is consistent. Once a suitable location is identified, the cyprid secretes a powerful, fast-curing protein-based cement from glands in its antennae, permanently adhering itself head-first to the whale’s skin. Some whale barnacle species, like those found on right whales, embed deeply into the whale’s skin for stability, forming a crown-shaped shell that integrates with the host’s tissue.
Do Barnacles Harm Whales?
The relationship between barnacles and whales is generally commensal, meaning barnacles do not cause significant harm to their hosts. Unlike parasites, barnacles do not feed on the whale’s tissues or blood; they simply use the whale as a mobile platform for filter-feeding. While a single humpback whale can carry up to 450 kilograms (990 pounds) of barnacles, this weight is minimal relative to the whale’s massive size.
However, a heavy load of barnacles can increase drag, slightly affecting the whale’s swimming efficiency and requiring more energy. Minor skin irritation can occur if barnacle clusters grow large or penetrate the skin deeply, though severe infections are uncommon. Whales have been observed rubbing against the seafloor or breaching, which may help dislodge barnacles. Despite these minor aspects, barnacles are not detrimental to a whale’s overall health or survival.