Eye design and color signaling in a stomatopod crustacean Gonodactylus smithii.

Many species of stomatopod crustaceans have multiple spectral classes of photoreceptors in their retinas. Behavioral evidence also indicates that stomatopods are capable of discriminating objects by their spectral differences alone. Most animals use only two to four different types of photoreceptors in their color vision systems, typically with broad sensitivity functions, but the stomatopods apparently include eight or more narrowband photoreceptor classes for color recognition. It is also known that stomatopods use several colored body regions in social interactions. To examine why stomatopods may be so 'concerned' with color, we measured the absorption spectra of visual pigments and intrarhabdomal filters, and the reflectance spectra from different parts of the bodies of several individuals of the gonodactyloid stomatopod species, Gonodactylus smithii. We then applied a model of multiple dichromatic channels for color encoding to examine whether the finely tuned color vision was specifically co-evolved with their complex color signals. Although the eye design of stomatopods seems suitable for detecting color signals of their own, the detection of color signals from other animals, such as reef fishes, can be enhanced as well. Color vision in G. smithii is therefore not exclusively adapted to detect its own color signals, but the spectral tuning of some photoreceptors (e.g. midband Rows 2 and 3) enhances the contrast of certain color signals to a large enough degree to make co-evolution between color vision and these rather specific color signals likely.

Chiao CC ，Cronin TW ，Marshall NJ 《BRAIN BEHAVIOR AND EVOLUTION》

Variation in stomatopod (Gonodactylus smithii) color signal design associated with organismal condition and depth.

In interactions, many tropical stomatopod species display conspicuous colored body spots that can communicate information about the sender's state (e.g., sex, aggressiveness, etc.). Species inhabiting a variety of depths experience large differences in illumination spectrum and intensity due to filtering of light by water and its constituents. Stomatopod spectral sensitivity is known to vary phenotypically with changes in light environment (associated with depth) that potentially affects the detection of color signals. Animals collected at different depths also have different body coloration. This study examines how spectral differences in colored body spots vary with organismal condition and models the effects of changing body coloration, light environment, and spectral sensitivity on the detection of color signals in a gonodactyloid species, Gonodactylus smithii. Of the seven conspicuous color spots that were measured in G. smithii, three had spectral differences that correlated with sex, aggression, and female reproductive state. A model of color detection in G. smithii indicates that longer-wavelength spectral content was affected most by varying body coloration and light conditions. Most color signals were perceived similarly both by shallow- and by deep-adapted photoreceptor sets over a range of depths (1-13 m). Eye spot ('meral spot') color detection also was invariant over the same depth range in shallow- and deep-adapted, long-wavelength receptors, but deep-adapted receptors continued to maintain a consistent detection of these spots down to 18 meters. These results suggest that meral spot coloration may have evolved as a constant signal when viewed by conspecifics from various depths.

Cheroske AG ，Cronin TW 《-》

Spectral tuning and the visual ecology of mantis shrimps.

Cronin TW ，Marshall NJ ，Caldwell RL 《-》

Evolution of anatomical and physiological specialization in the compound eyes of stomatopod crustaceans.

Porter ML ，Zhang Y ，Desai S ，Caldwell RL ，Cronin TW ... -  《-》

Ultraviolet filters in stomatopod crustaceans: diversity, ecology and evolution.

Stomatopod crustaceans employ unique ultraviolet (UV) optical filters in order to tune the spectral sensitivities of their UV-sensitive photoreceptors. In the stomatopod species Neogonodactylus oerstedii, we previously found four filter types, produced by five distinct mycosporine-like amino acid pigments in the crystalline cones of their specialized midband ommatidial facets. This UV-spectral tuning array produces receptors with at least six distinct spectral sensitivities, despite expressing only two visual pigments. Here, we present a broad survey of these UV filters across the stomatopod order, examining their spectral absorption properties in 21 species from seven families in four superfamilies. We found that UV filters are present in three of the four superfamilies, and evolutionary character reconstruction implies that at least one class of UV filter was present in the ancestor of all modern stomatopods. Additionally, postlarval stomatopods were observed to produce the UV filters simultaneously alongside development of the adult eye. The absorbance properties of the filters are consistent within a species; however, between species we found a great deal of diversity, both in the number of filters and in their spectral absorbance characteristics. This diversity correlates with the habitat depth ranges of these species, suggesting that species living in shallow, UV-rich environments may tune their UV spectral sensitivities more aggressively. We also found additional, previously unrecognized UV filter types in the crystalline cones of the peripheral eye regions of some species, indicating the possibility for even greater stomatopod visual complexity than previously thought.

Bok MJ ，Porter ML ，Cronin TW 《-》