Poison frogs in the anuran family Dendrobatidae use bright colors on their bodies to advertise toxicity. The species Dendrobates pumilio Schmidt 1858, the strawberry poison frog, shows extreme polymorphism in color and pattern in Panama. It is known that females of D. pumilio preferentially choose mates of their own color morph. Nevertheless, potential predators must clearly see and recognize all color morphs if the aposematic signaling system is to function effectively. We examined the ability of conspecifics and a model predator to discriminate a diverse selection of D. pumilio colors from each other and from background colors. Microspectrophotometry of isolated rod and cone photoreceptors of D. pumilio revealed the presence of a trichromatic photopic visual system. A typical tetrachromatic bird system was used for the model predator. Reflectance spectra of frog and background colors were obtained, and discrimination among spectra in natural illuminants was mathematically modeled. The results revealed that both D. pumilio and the model predator discriminate most colors quite well, both from each other and from typical backgrounds, with the predator generally performing somewhat better than the conspecifics. Each color morph displayed at least one color signal that is highly visible against backgrounds to both visual systems. Our results indicate that the colors displayed by the various color morphs of D. pumilio are effective signals both to conspecifics and to a model predator.

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Differential gene expression and coding sequence evolution play complementary roles in the adaptive diversification of cichlid sensory systems.

We investigated female mate choice on the basis of visual cues in two populations of Dendrobates pumilio, the strawberry poison frog, from the Bocas del Toro Archipelago in Panama, Central America. Mate choice experiments were carried out by presenting subject females of each of two morphs of this species (orange and green) from two di¡erent island populations (Nancy Key and Pope Island) with object frogs (one of each morph) under glass at one end of a terrarium. Recorded calls were played simultaneously from behind both object frogs. The experiments were carried out under two light regimes: (i) white light, and (ii) relatively monochromatic ¢ltered blue light. Subject females from each population displayed a signi¢cant preference for their own morph under white light, but not under blue light. These results indicate that female D. pumilio use visual cues in mate choice, and suggest that colour may be the visual cue they use.

Opsin proteins are essential molecules in mediating the ability of animals to detect and use light for diverse biological functions. Therefore, understanding the evolutionary history of opsins is key to understanding the evolution of light detection and photoreception in animals. As genomic data have appeared and rapidly expanded in quantity, it has become possible to analyse opsins that functionally and histologically are less well characterized, and thus to examine opsin evolution strictly from a genetic perspective. We have incorporated these new data into a large-scale, genome-based analysis of opsin evolution. We use an extensive phylogeny of currently known opsin sequence diversity as a foundation for examining the evolutionary distributions of key functional features within the opsin clade. This new analysis illustrates the lability of opsin protein-expression patterns, site-specific functionality (i.e. counterion position) and G-protein binding interactions. Further, it demonstrates the limitations of current model organisms, and highlights the need for further characterization of many of the opsin sequence groups with unknown function.

Visual ecology is the study of how animals use visual systems to meet their ecological needs, how these systems have evolved, and how they are specialized for particular visual tasks. This book provides the first up-to-date synthesis of the field to appear in more than three decades. Featuring some 225 illustrations, including more than 140 in color, spread throughout the text, the book begins by discussing the basic properties of light and the optical environment. It then looks at how photoreceptors intercept light and convert it to usable biological signals, how the pigments and cells of vision vary among animals, and how the properties of these components affect a given receptor's sensitivity to light. The book goes on to examine how eyes and photoreceptors become specialized for an array of visual tasks, such as navigation, evading prey, mate choice, and communication. A timely and much-needed resource for students and researchers alike, the book also includes a glossary and a wealth of examples drawn from the full diversity of visual systems.

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The violet- and ultraviolet-sensitive visual pigments of birds belong to the same class of pigments as the violet-sensitive (so-called blue) pigments of mammals. However, unlike the pigments from mammals and other vertebrate taxa which, depending on species, have lambda(max) values of either around 430 nm or around 370 nm, avian pigments are found with lambda(max) values spread across this range. In this paper, we present the sequences of two pigments isolated from Humbolt penguin and pigeon with intermediate lambda(max) values of 403 and 409 nm, respectively. By comparing the amino acid sequences of these pigments with the true UV pigments of budgerigar and canary and with chicken violet with a lambda(max) value of 420 nm, we have been able to identify five amino acid sites that show a pattern of substitution between species that is consistent with differences in lambda(max). Each of these substitutions has been introduced into budgerigar cDNA and expressed in vitro in COS-7 cells. Only three resulted in spectral shifts in the regenerated pigment; two had relatively small effects and may account for the spectral shifts between penguin, pigeon, and chicken whereas one, the replacement of Ser by Cys at site 90 in the UV pigments, produced a 35 nm shortwave shift that could account for the spectral shift from 403 nm in penguin to around 370 nm in budgerigar and canary.