A Case of Blue Coloration and Color Change in Pelophylax esculentus (Linnaeus, 1758) (Anura: Ranidae) in Denmark

Abstract

One blue female Pelophylax esculentus was recorded in the outskirts of Copenhagen, Denmark, in August 2017. Minor green areas persisted. After capture and subsequent handling its base coloration darkened from what was first observed. No other individuals with blue coloration were found. Blue coloration is an anomaly due to lack of or reduction of xanthophores. This is a first record of truly blue-colored P. esculentus in North Europe though two cases from Central Europe are known. Within the genus Pelophylax blue individuals have been reported in various species at irregular intervals. The darkening agent α-melanocyte stimulating hormone (α-MSH) may well have been the reason why this individual turned darker after handling.