“TURTLE BARNACLES”

Most people think of barnacles as being attached to one another [in colonies] or attached to boat bottoms, submerged bottles, sea shells, rocks, or even shoreline plants [see my recent post, June 2, 2023, on "Barnacles Living in Salton Sea of Southern California]. There are, however, some species of specialized barnacles that can attach to the carapaces of sea turtles and crabs, as well as to the skin of dugongs, and whales, etc. The generalized name “turtle barnacles” is commonly given to all these various specialized barnacles. 

This present post concerns a species of turtle barnacle found associated with a washed-up, dead sea turtle on a beach in the warm waters of the Gulf of California in Baja California, Mexico. An anonymous collector had identified the material as the barnacle Coronula testudinaria Linnaeus, 1758. Based on the available literature, I provide the updated taxonomy of this barnacle, which is be more accurately identified as Cheloniba testudinaria (Linnaeus, 1758). 

 Three views (top, bottom, and side) (length 31 mm, width 27 mm, and height 6 mm, respectively) of the shell of a sea-turtle barnacle “Chelonia testudinaria” from the carcass of a sea turtle found in the Gulf of California, Baja California. The total length and total width of the opercular plates (those in the center of the shell) are 11 mm and 3 mm, respectively. 

The classification of turtle barnacles is the following:

Phylum Arthropoda/Class Crustacea/Subclass Cirripedia/Order Thoraeica/Suborder Ballanomorpha/Superfamily Coronuloidea/Family Coronulidae.

Chelonibia is the largest and least specialized genus of turtle barnacles, and C. testudinaria is common in all warm seas, including the eastern Pacific (Morris et al., 1980). According to Zardus and Hadfield (2004), this barnacle is perhaps the most cosmopolitan of turtle barnacles, and is the largest in size (diameter up to 120 mm). It is occasionally found on the scales of the head and flippers of sea turtles. In total, it is known to associate with seven species of marine turtles.

The shell of this species characterized by its low, dome-shaped shell, supported internally by numerous closely spaced, radiating septal buttresses (Morris et al., 1980). The shell is strong, oval shaped, smooth, and white in color, and grooved with six prominent radii that create a “star-like” appearance (Darwin, 1854). The widest part of the shell is on the posterior of the shell. The four opercular plates (those that close off the operculum) are long and narrow. 

Chelonibia is the least specialized genus of turtle barnacles. Superficially, its wall appears to be made up of six plates, but studies show that early in its development, there are actually eight plates. In the initial shell development (within only 24 hours) however, the rostro-lateral plates undergo coalescence (fusion), thereby producing seemingly only six plates (Zardus and Hadfield, 2004). This apparent “tripartite” rostrum of Chelonibia is a vestiage of the eight-plated ancestry of all balanomorphs (Morris et al., 1980).

Based on fossil occurrences in the Mint Springs and Byram formations of Mississippi, genus Chelonibia has a geologic range from the Oligocene to recent (Zullo, 1982).

References Used: 

Darwin, C. 1854. A monograph on the sub-class Cirripedia with figures of all the species. The Balanidae, the Verrucidae, etc. London: Ray Society, 684 pp. Available online (free) at: darwin-onliine.org.uk

Morris, R.H., D.P. Abbott, and E.C. Haderlie. 1980. Intertidal invertebrates of California. Stanford University Press, Stanford, California, 690 pp.

Zardus, J.D. and M.G. Hadfield. 2004. Larval development and complemental males in Cheloniba testudinaria, a barnacle commensal with sea turtles. Journal of Crustacean Biology 24, issue 3, pp. 409-421. Available online (free) at: https://doi.org/10.1651/C-2476

Zullo, V. A. 1982. A new species of the turtle barnacle Chelonbia Leach, 1817, (Cirripedia, Thoracica) from the Oligocene Mint Spring and Byram Formations of Mississippi. Mississippi Geology 2, no. 3:1-6. Available online (free).