Barnacles are marine crustaceans often found attached to whales. This association raises curiosity about their interaction. Understanding why barnacles inhabit whales involves exploring the specialized types of barnacles and the unique benefits they gain.
The Species of Barnacles Found on Whales
The barnacles inhabiting whales are specialized species. One prominent group includes whale barnacles from the family Coronulidae, such as Coronula diadema and Cryptolepas rhachianecti. Coronula diadema is often found on humpback whales, presenting a barrel-shaped or crown-like appearance with six broad wall plates. These barnacles embed themselves into the whale’s skin, forming a tight grip.
Another type seen with whale barnacles is the stalked barnacle, such as Conchoderma auritum. These have a fleshy stalk that attaches them to a surface, often to Coronula diadema shells or other hard surfaces on the whale. Different whale species often host specific barnacle species; for example, Cryptolepas rhachianecti is found almost exclusively on gray whales.
The Commensal Nature of Their Relationship
The relationship between barnacles and whales is commensalism, where one organism benefits and the other is generally unaffected. Barnacles gain several advantages by living on whales, primarily a mobile platform that transports them to nutrient-rich feeding grounds. As filter feeders, barnacles use their feathery cirri to capture plankton and other food particles. The whale’s continuous movement ensures a constant food supply.
Whales also provide barnacles with protection from predators. Being affixed to a large, moving host helps barnacles avoid being dislodged by strong currents or wave action. Furthermore, the whale’s extensive migratory patterns aid in the dispersal of barnacle larvae, allowing them to colonize new habitats. While a large aggregation of barnacles can add some weight and minor drag, this impact is insignificant to the whale’s overall health or behavior.
How Barnacles Attach and Thrive on Whales
Barnacle attachment to a whale begins with microscopic larval stages: nauplius and cyprid larvae. The cyprid larva is the non-feeding stage responsible for finding a suitable surface for permanent settlement. These larvae explore potential hosts using specialized antennules, which possess adhesive discs.
Once a suitable spot on the whale’s skin is identified, the cyprid larva attaches head-first by secreting a strong, protein-based adhesive from specialized cement glands. This natural cement is powerful and can cure underwater, forming a durable bond. As the barnacle grows, it embeds itself into the whale’s skin, often causing a slight depression, and the whale’s skin can grow around the barnacle’s base, further strengthening the attachment without significant injury. Once attached, the barnacle develops its hard shell plates and extends its cirri to filter feed as the whale swims. Barnacles can remain attached for up to a year or more, and while whales naturally shed their skin, new barnacles frequently replace older ones that may be dislodged.