Sexual dimorphism in shell coloration of Plectostoma (Caenogastropoda: Diplommatinidae) is caused by polyenes

Using resonance Raman microspectrometry (RRMS) to assess the chemical background for the red shell coloration in male P. concinnum from Gomantong Hill, Sabah, shows a clear colour difference: the first three to four whorls of the shell are bright red in adult males, but white to pale yellow in adult females.