Research study 8
There are many types of barnacles that are parasitic on other animals, such as molluscs, crustaceans, sea turtles, and whales, to name a few. Larvae of species that inhabit benthic invertebrates should have no special challenges in finding their hosts, other than following chemical gradients to them, but what of a larva of a whale barnacle Coronula diadema that requires to seek out a humpback whale Megaptera novaeangliae? It is only from recent research that we learn that the larval development of C. diadema is similar to that of other barnacles, with 6 naupliar stages leading to a settling cypris stage (see photo series). Scientists from the Environmental Research Laboratory at Chiba, Japan are able to settle and metamorphose the larvae successfully, but only in the presence of a piece of skin from the original host whale. The only unusual feature of the post-metamorphic barnacle is apparently the presence of a ring-shaped structure with spines that may function in holding the juvenile to the whale. The authors do not comment on how the cyprid finds its host or climbs aboard, other than it presumably is done in response to a chemical cue from the whale’s skin. However, consider this: a cyprid attempting to intercept a swimming whale is not photograph of whale barnacle Coronula diadema in the skin of a humpback whalelike a person trying to jump on a speeding train. As it swimsor brushes close to the whale's surface, the larva will enter a velocity gradient that drops to zero at the boundary layer just at the skin surface. Thus, settlement could theoretically be done with the host in motion. Nogata & Matsumura 2006 Mar Biol Lett 2 (1): 92.