Goose barnacles attached to Loggerhead Turtles found in Plettenberg Bay
With a few days of rough seas and strong easterly winds there have been quite a few loggerhead turtles that have washed up, and attached to the turtles have been an incredible number of goose barnacles. This sparked my interest and I started doing some research into goose barnacles. Barnacles are highly modified crustaceans, and two forms exist: the stalked barnacle, and the sessile acorn barnacle. Goose barnacles are stalked barnacles, and the goose barnacles attached to the turtles were yellow-rimmed goose barnacles. The stalk of the yellow-rimmed goose barnacles can grow to 10 cm. The stalk is fleshy and dark purplish-brown in colour. The body at the end of the stalk is enclosed by 5 white shell plates edged with a yellow-orange border. Yellow-rimmed barnacles are a pelagic, cosmopolitan species found in dense aggregations on ships, driftwood, or other floating objects which, in this case, was loggerhead turtles.
Goose barnacles have a most fascinating history! At the time of their discovery and description, it was believed that the yellow-rimmed goose barnacle Lepas anatifera was the parent species of the barnacle goose Branta leucopsis. This knowledge dates back to the 1600’s when bird migration was not a known phenomenon. Barnacle geese do not breed in temperate Europe and so neither nests nor eggs of this species were ever seen there, and so it was believed they were the “preternatural production of a species of shell-fish called a barnacle.” The goose barnacles have feeding tentacles that protrude from the shell and look like the down of a gosling, which together with no sightings of nests, eggs, or young, founded the idea that goose barnacles birthed barnacle geese. This also explains their linked common names. This was eventually shown to be false, but how interesting!
Written by: Minke Witteveen
For further reading:
- Barreiros, J.P. and Teves, M. 2005. The sunfish Mola mola as an attachment surface for the Lepadid Cirriped Lepas anatifera – a previously unreported association. Journal of Ichthyology and Aquatic Biology 10: 1-4.
- Branch, G.M., Griffiths, C.L., Branch, M.L. and Beckley, L.E. 2010. Two Oceans: A guide to the marine life of southern Africa. Pp. 80. Random House Struik Publishers, Cape Town.
- Loudon, J.C. 1832. The Magazine of Natural History and Journal of Zoology, Botany, Mineralogy, Geology, and Meteorology Vol V: 339-344.