The Use of Ultraviolet Light as a Non-destructive Method for Revealing Fragments of Lost Pigmentation in Faded Alcohol-preserved Collection Specimens

ABSTRACT. A method for visualizing previously pigmented areas of the body with the employment of black-light spectrum bulbs is described. Under ultraviolet (UV) light, fish musculature fluoresces, whereas melanophores absorb incident light, revealing nearly lost contrast between once strongly and poorly pigmented areas of the body that has faded over time. Although a yet unknown extent of melanophore preservation is necessary to expose such contrast, the method was successful on a partially faded holotype of Characidium fasciadorsale Fowler, a nearly completely faded holotype of Characidium etheostoma Cope, and most remarkably for the blackened, previously mold-infested and nearly destroyed holotype of Holotaxis laetus Cope. In the latter case, the method also allowed better recognition of scale pockets on the skin.