Dolphins: Barnacles Pick Strategic Fin Locations

If you're a barnacle and are going to spend your still, presumably silent life on the side of a marine creature, you'll choose that location carefully, right? Highly specialized barnacles in the Coronolidae family (often seen in close-up photos of whales) may be able to identify and attach to quick-swimming dolphins' fins, finding areas suited for finding food and developing larvae, says a recent study by the University of Valencia, Spain, and the University of Southern Mississippi.

In other words, these fairly inactive creatures may be choosing wisely when it comes to real estate.

The coronulid barnacle, Xenobalanus globicipitis, attaches only to cetaceans, particularly dolphins from temperate and tropical waters. Generally, little has been known about the factors that drive where they locate.

In this paper, the researchers investigate patterns of microhabitat selection of the coronulid barnacle on the striped dolphin, with data based on occurrence, abundance, distribution, orientation, and size of the barnacles from 242 striped dolphins stranded on the Mediterranean coast of Spain from 1979 to 2009.

Location-wise, barnacles exclusively attach to fins, choosing most often the trailing edge facing away from water flow. Barnacles were larger, and their occurrence, abundance and density were higher, on the tail (caudal) fin than on the flippers and dorsal fin. If barnacles were on the tail fin, they tended to select the dorsal side and central portion.

Barnacles, it turns out, might be chemically sophisticated: They may be able to chemically recognize the dolphin skin and find a location through the "vortex" created by water flowing over and around the dolphin on the fins. The locations they choose might benefit from a better environment for filtering nutrients for food and protecting developing larvae. Because the study's data used stranded, deceased dolphins, understanding how these results apply to the general, active dolphin population still needs further study.