“…Numerous field guides and websites currently offer identifications of nudibranchs based on the external features visible in colour photographs, but due to supposed cryptic diversity, such identifications have become more and more problematic. Hidden genetic diversity has been reported for some nudibranchs at the very beginning of the molecular era (Morrow, Thorpe, & Picton, ) and recently several cryptic/“semi‐cryptic” species have been discovered (Carmona, Bhave, et al., ; Carmona, Lei, et al., ; Churchill, Alejandrino, Valdés, & Foighil, ; Jörger & Schrödl, ; Krug, Ellingson, Burton, & Valdés, ; Padula, Araújo, Matthews‐Cascon, & Schrödl, ; Padula et al., ; Wilson, Schrödl, & Halanych, ). However, taking into account that more than 6,000 opisthobranch species have already been described worldwide in premolecular times (Wägele et al., ), the few cryptic species cases so far reported are just the beginning of an expected explosive increase of the species number in the near future.…”