Behavioural evidence of spectral opponent processing in the visual system of stomatopod crustaceans.

Stomatopods, commonly known as mantis shrimps, possess an intricate colour vision with up to 12 photoreceptor classes arranged in four specialised ommatidia rows (rows 1-4 in the midband region of the eye) for colour perception. While 2-4 spectral sensitivities suffice for most visual systems, the function and mechanism behind stomatopods' 12-channel colour vision remains unclear. Previous anatomical and behavioural studies have suggested that binning and opponent processing mechanisms may coexist in stomatopods' colour vision.

Deep-sea fish reveal alternative pathway for vertebrate visual development.

Vertebrate vision is accomplished by two phenotypically distinct types of photoreceptors in the retina: the saturation-resistant cones for the detection of bright light and the highly sensitive rods for dim light conditions [1]. The current dogma is that, during development, all vertebrates initially feature a cone-dominated retina, and rods are added later [2, 3]. By studying the ontogeny of vision in three species of deep-sea fishes, we show that their larvae express cone-specific genes in photoreceptors with rod-like morphologies.

Short-wavelength-sensitive 1 () opsin gene duplications and parallel visual pigment tuning support ultraviolet communication in damselfishes (Pomacentridae).

Damselfishes (Pomacentridae) are one of the most behaviourally diverse, colourful and species-rich reef fish families. One remarkable characteristic of damselfishes is their communication in ultraviolet (UV) light. Not only are they sensitive to UV, they are also prone to have UV-reflective colours and patterns enabling social signalling.

Ultraviolet vision in anemonefish improves colour discrimination.

In many animals, ultraviolet (UV) vision guides navigation, foraging, and communication, but few studies have addressed the contribution of UV signals to colour vision, or measured UV discrimination thresholds using behavioural experiments. Here, we tested UV colour vision in an anemonefish (Amphiprion ocellaris) using a five-channel (RGB-V-UV) LED display. We first determined that the maximal sensitivity of the A.

Multiple rod layers increase the speed and sensitivity of vision in nocturnal reef fishes.

Most vertebrates have one layer of the dim-light active rod photoreceptors. However, multiple rod layers, known as a multibank retina, can be found in over 100 species of fish, including several deep-sea species and one family of nocturnally active reef fish, the Holocentridae. Although seemingly associated with increased photon catch, the function of multibank retinas remained unknown.

Higher ultraviolet skin reflectance signals submissiveness in the anemonefish, .

Ultraviolet (UV) vision is widespread among teleost fishes, of which many exhibit UV skin colors for communication. However, aside from its role in mate selection, few studies have examined the information UV signaling conveys in other socio-behavioral contexts. Anemonefishes (subfamily, Amphiprioninae) live in a fascinating dominance hierarchy, in which a large female and male dominate over non-breeding subordinates, and body size is the primary cue for dominance.

The brain structure and the neural network features of the diurnal cuttlefish .

Cuttlefish are known for their rapid changes of appearance enabling camouflage and con-specific communication for mating or agonistic display. However, interpretation of their sophisticated behaviors and responsible brain areas is based on the better-studied squid brain atlas. Here we present the first detailed description of the neuroanatomical features of a tropical and diurnal cuttlefish, , coupled with observations on ontogenetic changes in its visual and learning centers using a suite of MRI-based techniques and histology.

Long-wavelength-sensitive (lws) opsin gene expression, foraging and visual communication in coral reef fishes.

Coral reef fishes are diverse in ecology and behaviour and show remarkable colour variability. Investigating the visual pigment gene (opsin) expression in these fishes makes it possible to associate their visual genotype and phenotype (spectral sensitivities) to visual tasks, such as feeding strategy or conspecific detection. By studying all major damselfish clades (Pomacentridae) and representatives from five other coral reef fish families, we show that the long-wavelength-sensitive (lws) opsin is highly expressed in algivorous and less or not expressed in zooplanktivorous species.

Developing and adult reef fish show rapid light-induced plasticity in their visual system.

The visual capabilities of fish are optimized for their ecology and light environment over evolutionary time. Similarly, fish vision can adapt to regular changes in light conditions within their lifetime, e.g.

Polarization vision mitigates visual noise from flickering light underwater.

In shallow water, downwelling light is refracted from surface waves onto the substrate creating bands of light that fluctuate in both time and space, known as caustics. This dynamic illumination can be a visual hindrance for animals in shallow underwater environments. Animals in such habitats may have evolved to use polarization vision for discriminating objects while ignoring the variations in illumination caused by caustics.

Colour vision in stomatopod crustaceans.

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.

Development of dim-light vision in the nocturnal reef fish family Holocentridae. I: Retinal gene expression.

Developmental changes to the visual systems of animals are often associated with ecological shifts. Reef fishes experience a change in habitat between larval life in the shallow open ocean to juvenile and adult life on the reef. Some species also change their lifestyle over this period and become nocturnal.

Development of dim-light vision in the nocturnal reef fish family Holocentridae. II: Retinal morphology.

Ontogenetic changes in the habitats and lifestyles of animals are often reflected in their visual systems. Coral reef fishes start life in the shallow open ocean but inhabit the reef as juveniles and adults. Alongside this change in habitat, some species also change lifestyles and become nocturnal.

Differentiation in Posterior Tibial Slope by Sex, Age, and Race: A Cadaveric Study Utilizing 3-Dimensional Computerized Tomography.

Background: Posterior tibial slope (PTS) has recently gained increased attention for its possible role in anterior cruciate ligament and posterior cruciate ligament injury. The possible differences among age, sex, and ethnicity in PTS have not yet been reported.

Purpose: To describe demographic variances of proximal tibial anatomy and to detect differences in regard to ethnicity, sex, and age.

Colour discrimination thresholds vary throughout colour space in a reef fish (Rhinecanthus aculeatus).

Animals use colour vision in a range of behaviours. Visual performance is limited by thresholds, which are set by noise in photoreceptors and subsequent neural processing. The receptor noise limited (RNL) model of colour discrimination is widely used for modelling colour vision and accounts well for experimental data from many species.

Seeing Picasso: an investigation into the visual system of the triggerfish Rhinecanthus aculeatus.

Vision is used by animals to find food and mates, avoid predators, defend resources and navigate through complex habitats. Behavioural experiments are essential for understanding animals' perception but are often challenging and time-consuming; therefore, using species that can be trained easily for complex tasks is advantageous. Picasso triggerfish, Rhinecanthus aculeatus, have been used in many behavioural studies investigating vision and navigation.

Colour vision in stomatopod crustaceans: more questions than answers.

Stomatopod crustaceans, or mantis shrimps, are known for their extensive range of spectral sensitivity but relatively poor spectral discrimination. Instead of the colour-opponent mechanism of other colour vision systems, the 12 narrow-band colour channels they possess may underlie a different method of colour processing. We investigated one hypothesis in which the photoreceptors are proposed to act as individual wave-band detectors, interpreting colour as a parallel pattern of photoreceptor activation, rather than a ratiometric comparison of individual signals.

CRISPR/Cas9-mediated generation of biallelic F0 anemonefish (Amphiprion ocellaris) mutants.

Genomic manipulation is a useful approach for elucidating the molecular pathways underlying aspects of development, physiology, and behaviour. However, a lack of gene-editing tools appropriated for use in reef fishes has meant the genetic underpinnings for many of their unique traits remain to be investigated. One iconic group of reef fishes ideal for applying this technique are anemonefishes (Amphiprioninae) as they are widely studied for their symbiosis with anemones, sequential hermaphroditism, complex social hierarchies, skin pattern development, and vision, and are raised relatively easily in aquaria.

Comparative brain structure and visual processing in octopus from different habitats.

Octopods are masters of camouflage and solve complex tasks, and their cognitive ability is said to approach that of some small mammals. Despite intense interest and some research progress, much of our knowledge of octopus neuroanatomy and its links to behavior and ecology comes from one coastal species, the European common octopus, Octopus vulgaris. Octopod species are found in habitats including complex coral reefs and the relatively featureless mid-water.

Molecular Evolution of Ultraviolet Visual Opsins and Spectral Tuning of Photoreceptors in Anemonefishes (Amphiprioninae).

Many animals including birds, reptiles, insects, and teleost fishes can see ultraviolet (UV) light (shorter than 400 nm), which has functional importance for foraging and communication. For coral reef fishes, shallow reef environments transmit a broad spectrum of light, rich in UV, driving the evolution of diverse spectral sensitivities. However, the identities and sites of the specific visual genes that underly vision in reef fishes remain elusive and are useful in determining how evolution has tuned vision to suit life on the reef.

Thresholds of polarization vision in octopuses.

Polarization vision is widespread in nature, mainly among invertebrates, and is used for a range of tasks including navigation, habitat localization and communication. In marine environments, some species such as those from the Crustacea and Cephalopoda that are principally monochromatic, have evolved to use this adaptation to discriminate objects across the whole visual field, an ability similar to our own use of colour vision. The performance of these polarization vision systems varies, and the few cephalopod species tested so far have notably acute thresholds of discrimination.

The visual ecology of Holocentridae, a nocturnal coral reef fish family with a deep-sea-like multibank retina.

The visual systems of teleost fishes usually match their habitats and lifestyles. Since coral reefs are bright and colourful environments, the visual systems of their diurnal inhabitants have been more extensively studied than those of nocturnal species. In order to fill this knowledge gap, we conducted a detailed investigation of the visual system of the nocturnal reef fish family Holocentridae.

More than noise: context-dependent luminance contrast discrimination in a coral reef fish ().

Achromatic (luminance) vision is used by animals to perceive motion, pattern, space and texture. Luminance contrast sensitivity thresholds are often poorly characterised for individual species and are applied across a diverse range of perceptual contexts using over-simplified assumptions of an animal's visual system. Such thresholds are often estimated using the receptor noise limited model (RNL).

Does conspicuousness scale linearly with colour distance? A test using reef fish.

To be effective, animal colour signals must attract attention-and therefore need to be conspicuous. To understand the signal function, it is useful to evaluate their conspicuousness to relevant viewers under various environmental conditions, including when visual scenes are cluttered by objects of varying colour. A widely used metric of colour difference (Δ) is based on the receptor noise limited (RNL) model, which was originally proposed to determine when two similar colours appear different from one another, termed the discrimination threshold (or just noticeable difference).