what is concentric?
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guys,i got a question. which subspecies do someone refer to when he talk about “Concentric”? thanks a lot.
“Concentric” is a light phased Centrata. Not all Centratas have white skin with large black spots. Jonathan http://www.diamondbackterrapin.com_Ǖ__Q_Ǖ___Ǖ__
Jonathan has noted that concentric amongst this group refers to a phase of the centrata subspecies. I hope I don’t add to any confusion, but this seems like a good time to review some of the history of terrapin subspecies naming, as it is one factor in the confusion over the term concentric. The first scientific publication going into detail regarding the subspecies was William Perry Hay’s 1904 Bureau of Fisheries “A Revision of Malaclemmys, A Genus of Turtles:” Hay was already concerned about terrapin conservation in 1904 due to the booming food trade, so he studied all of the then recognized subspecies by observing specimens brought into the commerical “pounds” in Maryland. This publication includes some illustrations and fairly extensive narrative descriptions, based on what Hay saw brought into that one location. As of 1904, Hay noted the following 5 subspecies: Malaclemmys centrata concentrica. The Chesapeake Terrapin. Malaclemmys centrata. The Carolina Terrapin. Malaclemmys littoralis. Malaclemmys macrospilota. The Florida Terrapin. Malaclemmys pileata. The Louisiana Terrapin Hay’s descriptions for the 5 above subspecies have been copied into a folder in this group’s Files section. As per the above subspecies groupings,northern terrapins in 1904 were known scientifically as centrata concentricas. Hay’s observations led him to believe that virtually all terrapins from the Chesapeake Bay north had concentric lines visible on the carapace. Although he noted great color variability in the Carolina subspecies, he believed that few true Carolina had concentric lines on their shells. Those that did were thought to be intergrading with northerns around the Virginia area up into the Chesapeake. Here are Hay’s comments on the two subspecies circa 1904: Malaclemmys centrata concentrica. The Chesapeake Terrapin. Distribution. The littoral region of the eastern United States from Buzzards Bay, Massachusetts, to Virginia or North Carolina; Long Island Sound, Delaware and Chesapeake bays, &c. Characters. The carapace has in general the form of that of M. centrata, but is broader posteriorly and the marginal plates behind the bridge are seldom revolute; the plastron, also, is less convergent posteriorly; the plates of the carapace bear conspicuous concentric ridges, but those of the plastron are smoother, nearly always, however, except in some old individuals, showing at least traces of the lines of growth; the head is small, narrow, and neatly formed, the top of it flat, giving the nose a sharper appearance than is to be seen in the other form of this species. The color varies from uniform black to light brown, the latter always marked with darker concentric lines on each plate of the carapace and more or less blotched with darker on the plastron; the skin of the head, legs, and tail varies from nearly pure black to a very light green-gray, the latter more or less marked with specks and short crooked lines of black; the lips and top of the head are usually dusky, but individuals may be found with either or both white. The males resemble the females in the shape of the carapace, except that they are a little sharper posteriorly and the marginal plates are frequently a little revolute; the nose is much sharper than in the females. It seems very probable that some of the types of coloration indicate local variation, but the species has been so thoroughly mixed by the shipping of large consignments from one place to another that it is doubtful whether anything of this kind could be proved. All the specimens from Connecticut and northern localities, so far as I have seen, are very light in color, with conspicuous concentric markings, but very smooth shells; the Potomac River specimens are similar, but have rougher plates; those from the ocean and inclosed bays of the Atlantic coast of the Maryland-Virginia peninsula are, in more than 75 percent of the specimens, very dark and without markings of any kind. The terrapin from Delaware Bay are more like those of more northern localities, but usually present very little contrast in the color markings on the plates of the carapace. Many varieties are recognized by the dealers in terrapin – “Chesapeakes,” “Delaware Bays,” “Long Island terrapin,” “Connecticuts,” &c. – but in most cases the determinations are nothing more than guesswork. Malaclemmys centrata. The Carolina Terrapin. Distribution from Cape Hatteras to the coast of Florida The coloration is extremely variable and offers no diagnostic characters of value. A series of 85 terrapin from Enterprise, North Carolina, showed the following variation: 13 females. 5 inches long and under (measured on the middle line of the plastron), ranged from rather light slate-green individuals, very slightly marbled with darker, to some in which the scales of the carapace were black with more or less wide slate-green margins; the plastrons ranged from a rather pronounced orange yellow, through honey yellow, to greenish gray; in some cases the plastrons were uniformly colored, in others they were more or less blotched or clouded with dusky; the lips were white and the top of the head was white or light greenish. Eight females, 5 inches long and under, had the carapace entirely black and the plastron yellow organge much blotched and clouded with black; the upper lip and the top of the head were black, and the skin of the neck, legs, and tail was gray- green with many short crooked black lines and small specks. Five females, of about the same size as those just mentioned were almost perfectly intermediate in coloration, having brownish carapaces with more or less strong traces of green marbling, and plastrons varying from green-gray to orange yellow, some plain and others clouded. Of 8 females about 6 inches long, 2 were very light colored, the scales being marked with concentric lines of greenish gray or brown on a darker background; 2 were very dark brown, the others were intermediate; the plastron was yellowish gray-green, alomost uniform in the light colored individuals, but clouded with black in the darker colored specimens. Of the males 20 had the scales of the carapace broadly margined with greenish gray, around a center of black or light brown; the lips and top of the head were white or whitish; the plastrons were as variable as in the females described above, but the dusky markings had the form of small specks rather than indefinite cloudings. Eighteen males varied from uniform black to specimens in which the scales had a large black center and a margin of dark greenish-gray; the top of the head was black and in all but one case the lips were black; in 11 males the color was like those just described, except that the upper lip was white; in 2 males the color was dark, like those just described, but both the top of the head and the upper lip were white. This form, although variable, can readily be recognized by its large head, smooth carapace, and low dorsal ridge. From North Carolina northward, it begins to intergrade with the northern form, M. centrata concentrica, and is displaced altogether before the mouth of Chesapeake Bay is reached. The absence of concentric markings, usually mentioned as characteristic of the species, is apparently the common condition in typical M. centrata, although now and then an individual is found which shows them quite as plainly as the northern form. The usual coloration seems to be dark brownish or greenish black with a border of lighter green gray around each scale of the carapace. It is not exceptional to find individuals of this species with the transverse diameters of the shell before and behind the bridge nearly equal and the sides straight, the outline of the carapace thus a long oval. Dealers in terrapin regard Malaclemmys centrata with little favor, and it commands a much lower price in the markets than does the northern form. The reasons for this unpopularity are variously stated to be toughness and coarseness of flesh, large size of the bones, lack of flavor, uninviting appearance, and it would seem that all the disagreeable qualities are found combined in the terrapin from South Carolina and Georgia; those from North Carolina are more esteemed, probably owing to the fact that among them are to be found numerous individuals which can be made to pass muster as genuine “Chesapeakes.” Todd_Ǖ__Q_Ǖ___Ǖ__
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