There are ~80 Palaearctic species in the Melitaea genus (family Nymphalidae, tr. Melitaeini). We investigated the mechanisms of color vision in six species using ophthalmoscopy, histology, visual pigment spectroscopy, and pupillary reflex measurement. Eye regionalization was documented with an ophthalmoscope. In the species M. athalia, M. trivia, M. diamina and M. cinxia, the eye shine differs between the sexes. The colors of the reflection of the eyes follow from dorsal to ventral from blue through green to yellow, and only in males of these species the ventral eye glow is red. The eyeshine of M. phoebe is not dimorphic, both sexes have a ventrally red eyeshine, in M. didyma the red region is smaller in the female than in the male. On non-contrasted histological sections, red filter pigment was present in the R5-8 diagonal photoreceptors in regions with a red eye glow. In male M. athalia, red filter pigment is dispersed distally in granules throughout the cross-section of the diagonal cells, and proximally in four condensed areas closely surrounding the rhabdom. The main visual pigment was measured spectroscopically and evaluated by analyzing the change in the spectrum of the eye glow at the start of illumination. In males of the species M. didyma, M. athalia and M. trivia, we estimated that the maximum absorption of rhodopsin is at a wavelength of ~560 nm. In female species M. phoebe and M. athalia, the estimated wavelengths of the rhodopsin absorption peak differed between the ventral and dorsal regions of the eye (M. athalia: ~560 nm dorsal, ~530 nm ventral; M. phoebe; ~530 nm dorsal, ~ 560 nm ventral). The speed of the pupillary reflex was measured as the time during which the brightness of the eye drops to half. In dark-adapted eyes, this time is 10~12 s, in light-adapted eyes the pupil is twice as fast. Pupil speed does not depend on the presence of red pigment.
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