Examples of Melanistic Pond Sliders That Look a *LOT* Like Western Pond Turtles

If you are struggling accepting that the speckled turtle you've seen is a pond slider rather than a western pond turtle, here are some examples of melanistic sliders:

https://www.inaturalist.org/observations/199303483
https://www.inaturalist.org/observations/197627830
https://www.inaturalist.org/observations/174342503
https://www.inaturalist.org/observations/26791671

I get it, these turtles have all the beautiful marbling and speckling that are the western pond turtle's trademark namesake (=marmorata). Don't be fooled; this is the melanism in action. It is bringing out secondary markings. These turtles are red-herrings without their namesake "red" ears and stripes.

You can learn more about what little is known about melanistic turtles in Jeff Lovich's 1990 conference paper on melanism in slider turtles, available at the link below; see page 238-239 (.pdf page 5 and 6) for images of shell and head markings, but before you click, be forewarned, page 6 is a little graphic for anyone squeamish: https://www.researchgate.net/publication/243655879_The_development_and_significance_of_melanism_in_the_slider_turtle [and select the blue (Download) option]

If I may summarize Lovich, ontogenetic melanization involves a "process of pattern reorganization" rather than any increase in pigmentation, and in Trachemys scripta first appears on plastral scutes, then the carapace, and lastly the skin of the legs, tail, head, and neck; in males in particular, this process proceeds as follows (see page 237; .pdf page 4):

1. Deposition of a smudgy black spot in the center of each plastral scute; these spots gradually enlarge to form a rough-to-complete ring of pigment surrounded by, and enclosing areas of yellow; these smudgy spots are also eventually redistributed to locations along the central shell suture/seam roughly approximate to the human "sternum" and "belly-button" until the pigment is concentrated along the sutures, leaving the center of each plastral scute yellow.
2. Along the carapace, the juvenile pattern becomes obscured by a deposition of melanin over the scutes, followed by a depigmentation of the same scutes as the melanin concentrates along the sutures until each scute is ringed in melanin with a greenish yellow center; in some individuals/populations this reorganization proceeds one step further until the achieve a uniformly black carapace.
3. A complete obliteration of any striped patterns along the head, neck, legs, and tail through a gradual darkening resulting in a "black-mottled melanic pattern on an olive ground color".
4. In some cases, this process proceeds one step further with reorganization of black pigment across the entire plastron, obliterating any pattern around the sutures (Lovich 1995).

SOURCE: Lovich, Jeff, William R. Garstka, and Clarence J. McCoy. 1990. The Development and Significance of Melanism in the Slider Turtle. Life History and Ecology of the Slider Turtle, pp. 233–254. In: J.W. Gibbons (ed.), Life History and Ecology of the Slider Turtle. Smithsonian Institution Press, Washington, DC, USA

Posted on 15 de março de 2024, 04:10 AM by matthew_bettelheim