Pleopeltis macrolepis has a moderately dense covering of tightly appressed scales that are silvery to amber in color and are fairly reflective. At the Cuericí Biological station it frequently grows alongside Elaphoglossum paleaceum. Watkins et al. demonstrated that the reflective scales on the leaves of E. paleaceum protect that species against photoinhibition. I suspect the same thing might be going on with Pleopeltis macrolepis.
Watkins Jr, J. E., Kawahara, A. Y., Leicht, S. A., Auld, J. R., Bicksler, A. J., & Kaiser, K. (2006). Fern laminar scales protect against photoinhibition from excess light. American Fern Journal, 96(3), 83-92.