Colour vision in stomatopod crustaceans

Abstract

The stomatopod crustaceans, or mantis shrimps, are colourful marine invertebrate predators. Their unusual compound eyes have dorsal and ventral regions resembling typical crustacean apposition designs separated by a unique region called the midband that consists of from two to six parallel rows of ommatidia. In species with six-row midbands, the dorsal four rows are themselves uniquely specialized for colour analysis. Rhabdoms of ommatidia in these rows are longitudinally divided into three distinct regions: an apical ultraviolet (UV) receptor, a shorter-wavelength middle tier receptor and a longer-wavelength proximal tier receptor. Each of the total of 12 photoreceptors has a different spectral sensitivity, potentially contributing to a colour-vision system with 12 channels. Mantis shrimps can discriminate both human-visible and UV colours, but with limited precision compared to other colour-vision systems. Here, we review the structure and function of stomatopod colour vision, examining the types of receptors present in a species, the spectral tuning of photoreceptors both within and across species, the neural analysis of colour and the genetics underlying the multiple visual pigments used for colour vision. Even today, after many decades of research into the colour vision of stomatopods, much of its operation and its use in nature remain a mystery. This article is part of the theme issue ‘Understanding colour vision: molecular, physiological, neuronal and behavioural studies in arthropods’.

High diversity of arthropod colour vision: from genes to ecology

“…On top of this, the compound eyes of many insects and crustaceans show some form of regionalization of opsin gene expression. Some stomatopod crustaceans, for instance, express two opsins in the ommatidia of the large ventral and dorsal hemispheres of their eyes, but a large number in photoreceptors of the midband ommatidial rows, and moreover, different subsets of opsins in each of the six midband rows (comprehensively reviewed by Cronin et al [20]). Dragonflies express different subsets of opsins not only between the larval and adult eyes, but also between the dorsal and ventral halves of their eyes [28].…”

“…As SWS-sensitive receptors commonly contribute their rhabdoms to the most distal layer, this structure often removes the UV-sensitivity of the opsin-based MWS and LWS pigments expressed in the more proximal retinal layers. Layered retinae have been described in many crustaceans [20] and diverse insects, including, among others, odonates (e.g. [57]), flies [15] and butterflies [43,44,48] and the principal eyes of jumping spiders [18,58].…”

“…How colour coding works in the retinae of stomatopod crustaceans with up to 12 different spectral sensitivities in photoreceptors in the midband rows of their eyes, remains an open question. The similarities in the structure of the neural substrate [20,73,74] and the presence of a high number of spectrally diverse photoreceptors in some butterfly species [44,48] indicate that colour coding in the arthropod subphylum of pancrustaceans may share the same basic mechanisms of neural colour coding.…”

“…[119]). Patterns of multiple colours are found in flowers with nectar guides [99] and the bodies and appendages of animals such as mantis shrimps [20], fiddler crabs [108], spiders [120] or butterflies (e.g. [111]).…”

“…[16][17][18]) and crustaceans (e.g. [19,20]). This special issue aims to present the current state of knowledge on arthropod colour vision by combining reviews, new research articles and a methods paper reporting a novel tool for generating colour stimuli.…”