January 29, 2003
Turtle Barnacles from a Turtler's Perspective
These Chelonibia 'testudinaria' type species are from Baja and they are different from elsewhere.
For the past few years, I have grown increasingly more interested in turtle barnacles. There is very little information available on their natural history and no one has scrutinized the morphology of many species. In the world of barnacle research, taxonomists like to recoginize species by differences in shell morphology. This is done so that extant species can be compare to fossilized specimens; because the soft parts inside of the shell do not fossilize well. As a result, more contemporary analyses of the soft parts of barnacles (i.e. the cirri and muscle attachment to the shell) are revealing subtle differences between distinct regional populations.
Even genetic data agree with the analysis of soft part morphology in some cases. However, some intertidal species have shown drastic differences in regional population genetics, yet there has been no discernable changes in morphology. In other words, they all look the same but are vastly different on a genetic level when compared between ocean basins. Some herpetologists have experienced a similar trend in salamander analyses. There are several species of slimy salamanders (Plethodon glutinosis sp.) in the eastern US but they are very difficult, if not impossible, to tell the difference between species externally.
We are seeing interesting things with the barnacle Chelonibia testudinaria thanks to the many friends that have participated in a phylogeographic analysis of this turtle barnacle species. Recently, barnacle taxonomists, turtlers, and geneticists have aligned to start from scratch.
I say start from scratch because that is what one has to do when straightening out the taxonomy of turtle barnacles (genus Chelonibia). The authenticity of Linneaus' specimens are questionable and it is difficult to 'borrow' anything from the Darwin collections nowadays. Besides the specimens that were assigned to the Genus Chelonibia, the type specimens, have no data as to locality or host. That is, Ch. testudinaria according to Linne. could be what we call a Ch. patula from a horseshoe crab. We just don't know.
Paul Rawson at the University of Maine in Orono and a student of his, Rachel Macnamee, decided to take on a project I suggested examining te phylogeography of turtle barnacles. Knowing I could count on my friends abroad: Dimitris Margaritoulis, ALan Rees and the rest of the gang from Archelon in Greece, Yoshimasa Matsuzawa and Umigame in Japan, Dave Addison and the gang from the Conservancy of Southwest Florida and J. Nichols and his gang in Baja California Sur, Mexico; The Caretta Research Project dragged these poor souls into the sordid world of barnacle genetics.
The cool thing was that there were already tagging studies and genetic studies on loggerheads from these region to compare our data to - we did get all of our samples from nesting loggerheads, except for J's turtles which are immature individiuals from the Japanese nesting population.
The mtDNA analyses indicate that the barnacles currently recognized as Ch. testudinaria are actually at least three different species despite similar shell morphology (see picture above). The turtle barnacles from Florida, Georgia and Greece represent a single species, whereas the Baja barnacles and the Japanese barnacles were totally different on the species level. My friend and mentor, Arnold Ross agrees that the shell morphology (subtle differences) and perhaps soft part morphology jive with our results. Apparently, the life span of the testudinaria in the Pacific is not long enough for young turtles in Baja to transport the barnacles to Japanese host turtles. Ed Standora is doing some stats work on the shell morphometrics to help with this project as well.
We have more studies and their results are in prep right now. The aforementioned testudinaria data is under review right now. Within the next couple of years the information available on the natural history of turtle barnacles is sure to double.Posted by Michael Frick at January 29, 2003 09:58 PM | TrackBack