El preformismo concibe el desarrollo del embrión a partir de la existencia de un embrión preformado contenido en el espermatozoide o en el huevo; mientras que la epigénesis considera que este se origina a partir del desarrollo de un principio amorfo, como consecuencia de los cambios que se producen con la fecundación.

Boris Schwanwitsch

The information is sent to the visual cortex via the lateral geniculate nucleus (LGN) in three separate color-opponent channels that have been characterized psychophysically, physiologically, and computationally.

Comenzando al menos con Aristóteles, los científicos han tratado de ordenar los diferentes tipos de animales y plantas a lo largo de una escala lineal, llamada scala naturae (en latín, “escala de la naturaleza”; Lovejoy, 1936 ). La métrica de esta escala suele ser la similitud entre una especie determinada y el Homo sapiens, de modo que los animales más similares a nosotros se colocan en los peldaños más altos, mientras que las especies progresivamente más diferentes de nosotros se asignan a posiciones sucesivamente más bajas a lo largo de la escala. Un gran problema con esto (p. 11) es que la "similitud con los humanos" es una medida altamente multidimensional, y diferentes dimensiones producen diferentes clasificaciones de especies. Por ejemplo, las clasificaciones basadas en presunta inteligencia podrían colocar a los delfines en lo alto de la escala, mientras que las clasificaciones basadas en el modo de locomoción elevan a las aves no voladoras (por ejemplo, kiwis y avestruces) muy por encima de los delfines y otros mamíferos acuáticos. Independientemente de la medida utilizada, los partidarios del punto de vista de scala naturae tienden a equiparar los aumentos en la similitud con los humanos con el "progreso" evolutivo.

Estamos tan acostumbrados a ver el mundo a través de nuestros magníficos ojos humanos que es difícil imaginar cómo sería el mundo a través de los ojos de cualquier otra especie.

Cada aspecto de la visión, desde las proteínas de opsina hasta los ojos y las formas en que sirven al comportamiento animal, es increíblemente diverso. Solo con una perspectiva evolutiva se puede comprender y apreciar plenamente esta diversidad. En esta revisión, describo y explico la diversidad en cada nivel y trato de transmitir una comprensión de cómo el origen de la primera ops en hace unos 800 millones de años pudo iniciar la avalancha que produjo la asombrosa diversidad de ojos y visiones que vemos hoy. A pesar de la diversidad, muchos tipos de fotorreceptores, ojos y roles visuales han evolucionado varias veces de forma independiente en diferentes animales, revelando un patrón de evolución ocular estrictamente guiado por limitaciones funcionales e impulsado por la evolución de comportamientos gradualmente más exigentes.

En este tema se tratan las propiedades de la percepción del color del sistema visual humano, la tricomacia, las mezclas o igualación de colores, el sistema CIE de especificación del color y diagrama cromático, las discriminaciones cromáticas, los efectos cromáticos, la adaptación cromática y constancia del color, el contraste de color y las bases fisiológicas de la visión del color basadas en las señales tricromáticas y el procesamiento del color oponente.

mechanics

Birds and mammals have only one pigment cell type, the melanocyte, producing the pigment melanin (although in different shades) that is secreted into the skin or feathers and hairs.

In contrast, basal vertebrates such as fish, amphibia and reptiles develop several chromatophore types producing different colours. In these animals, colour patterns arise as mosaics of chromatophores distributed in the hypodermis of the body, and the epidermis of scales and fins (Box 1).

Although colour pattern formation has fascinated scientists since the beginning of modern biology [3], the field is still dominated by theories rather than detailed knowledge of the underlying molecular, cellular and developmental events.

Vertebrate colour patterns are composed of specialised pigment-producing cells, the chromatophores. These originate from the neural crest, a transient primordium of multipotent cells located at the dorsal neuroectodermal ridge from which progenitor cells emigrate to develop a variety of structures and tissues [2]. Neural crest is a developmental innovation that allowed vertebrates to get both large and colourful. Other neural crest-derived structures include elements of the skull and jaw, the neurons of the peripheral nervous system and glia.

In short, colour patterns are of high evolutionary relevance as targets of natural as well as sexual selection.

For example, many animals have dorsal coloration that reduces predation through crypsis or aposematism but ventral coloration that is used for short-range intraspecific signaling [e.g., (80)].

Lastly, mammals, such as deer, are born with striped coats but take on uniform pelage as adults (71).

The dyeing dart frog (Dendrobates tinctorius) is highly poisonous and conspicuous but also sexually dichromatic, indicating sexually selected coloration for mate choice.

For example, great reed warblers (Acrocephalus arundinaceus), frequent hosts of the common cuckoo (Cuculus canorus), show context-dependent rejection of foreign eggs (47) (Fig. 3). Mimetic eggs are typically accepted by these hosts, but in the presence of a cuckoo near the nest, or after exposure to a nonmimetic cuckoo egg, these same eggs are often rejected. Understanding how the host cognitive system adjusts its recognition thresholds to accommodate increased risks of cuckoo parasitism needs attention (48, 49).

In humans, percepts of color are also influenced by perceived surface texture, local configuration, context, and prior associations (38)

vertebrates have different vision subsystems, each tuned to one specific task.

birds see UV, and birds have more than three retinal cones types; some fish even change their color vision with diet (31) and use chlorophyll in far-red sensing (32).

Genes underlying color variation offer insight into the predictability of evolution. Convergent phenotypes commonly arise in parallel; the accurate characterization of color phenotypes has revealed independent changes in similar genetic mechanisms, leading to phenotypic similarity between species (19). For example, changes in pigmentation from weakly to deeply melanic can be controlled by parallel genetic changes in highly divergent lineages, such as in the case of the Kit ligand in pigmentation of sticklebacks and human skin; Oca2 in pigmentation of snakes, cavefish, and humans; and MC1R in numerous birds and mammals (19)

This will be a critical foundation for future understanding of ordered self-assembly in colored biological materials, from β-keratin in birds’ feathers (5)

BACKGROUNDThe interdisciplinary field of animal coloration is growing rapidly, spanning questions about the diverse ways that animals use pigments and structures to generate color, the underlying genetics and epigenetics, the perception of color, how color information is integrated with information from other senses, and general principles underlying color’s evolution and function. People working in the field appreciate linkages between these parallel lines of enquiry, but outsiders need the easily navigable roadmap that we provide here. ADVANCESIn the past 20 years, the field of animal coloration research has been propelled forward by technological advances that include spectrophotometry, digital imaging, computational neuroscience, innovative laboratory and field studies, and large-scale comparative analyses, which are allowing new questions to be asked. For example, we can now pose questions about the evolution of camouflage based on what a prey’s main predator can see, and we can start to appreciate that gene changes underlying color production have occurred in parallel in unrelated species. Knowledge of the production, perception, and evolutionary function of coloration is poised to make contributions to areas as diverse as medicine, security, clothing, and the military, but we need to take stock before moving forward. OUTLOOKHere, a group of evolutionary biologists, behavioral ecologists, psychologists, optical physicists, visual physiologists, geneticists, and anthropologists review this diverse area of science, daunting to the outsider, and set out what we believe are the key questions for the future. These are how nanoscale structures are used to manipulate light; how dynamic changes in coloration occur on different time scales; the genetics of coloration (including key innovations and the extent of parallel changes in different lineages); alternative perceptions of color by different species (including wavelengths that we cannot see, such as ultraviolet); how color, pattern, and motion interact; and how color works together with other modalities, especially odor. From an adaptive standpoint, color can serve several functions, and the resulting patterns frequently represent a trade-off among different evolutionary drivers, some of which are nonvisual (e.g., photoprotection). These trade-offs can vary between individuals within the same population, and color can be altered strategically on different time scales to serve different purposes. Lastly, interspecific differences in coloration, sometimes even observable in the fossil record, give insights into trait evolution. The biology of color is a field that typifies modern research: curiosity-led, technology-driven, multilevel, interdisciplinary, and integrative.

review how color is used for social signals between individual animals and how it affects interactions with parasites, predators, and the physical environment

Animals live in a colorful world, but we rarely stop to think about how this color is produced and perceived, or how it evolved.

extramission

extramission

extramission

extramission

extramission

extramission

extramission

extramission

extramission

extramission

extramission

extramission

extramission

extramission

extramission

(extramission

Aposematic signals are often characterized by high conspicuousness. Larger and brighter signals reinforce avoidance learning, distinguish defended from palatable prey and are more easily memorized by predators. Conspicuous signalling, however, has costs: encounter rates with naive, specialized or nutritionally stressed predators are likely to increase. It has been suggested that intermediate levels of aposematic conspicuousness can evolve to balance deterrence and detectability, especially for moderately defended species. The effectiveness of such signals, however, has not yet been experimentally tested under field conditions. We used dough caterpillar-like baits to test whether reduced levels of aposematic conspicuousness can have survival benefits when predated by wild birds in natural conditions. Our results suggest that, when controlling for the number and intensity of internal contrast boundaries (stripes), a reduced-conspicuousness aposematic pattern can have a survival advantage over more conspicuous signals, as well as cryptic colours. Furthermore, we find a survival benefit from the addition of internal contrast for both high and low levels of conspicuousness. This adds ecological validity to evolutionary models of aposematic saliency and the evolution of honest signalling.

Wallace

aposematism

The question, “Why should prey advertise their presence to predators using warning coloration?” has been asked for over 150 years. It is now widely acknowledged that defended prey use conspicuous or distinctive colors to advertise their toxicity to would-be predators: a defensive strategy known as aposematism. One of the main approaches to understanding the ecology and evolution of aposematism and mimicry (where species share the same color pattern) has been to study how naive predators learn to associate prey’s visual signals with the noxious effects of their toxins. However, learning to associate a warning signal with a defense is only one aspect of what predators need to do to enable them to make adaptive foraging decisions when faced with aposematic prey and their mimics. The aim of our review is to promote the view that predators do not simply learn to avoid aposematic prey, but rather make adaptive decisions about both when to gather information about defended prey and when to include them in their diets. In doing so, we reveal what surprisingly little we know about what predators learn about aposematic prey and how they use that information when foraging. We highlight how a better understanding of predator cognition could advance theoretical and empirical work in the field.

Bengal tiger

male

hummingbird

UV light

Bees

Vicia villosa

malvidin

delphinidin

petunidin

phenotypic plasticity

fluorescent components of the scorpions Centuroides vittatus and Pandinus imperator as beta-carboline

β-carboline

Crustacyanin

Several context-dependent behavioral and physiological roles have been attributed to fluorescent proteins, ranging from communication and predation to UV protection

bioluminescence

optical phenomena

luminescence

Fluorescence

biliverdin

This article has been corrected.

Junonia

Evolution via natural selection has continually shaped the coloration of numerous organisms. One coloration of particular importance is the eyespot: a phylogenetically widespread, conspicuous marking that has been shown to effectively reduce predation, often through its resemblance to the eye. Although widely studied, most research has been experimental in nature. We approach eyespots using a comparative phylogenetic framework that is global in scope. Herein, we identify the potential drivers of eyespot evolution in coral reef fishes; essentially the rules that govern their appearance in this group of organisms. We surveyed 2664 reef fish species (42% of all described reef fish species) and found that eyespots are present in approximately one in every 10 species. Most eyespots occur in closely related species and have been present in some families for over 50 million years. Focusing on damselfishes (family: Pomacentridae) as a study group, we reveal that eyespots are rare in planktivorous species, which is likely driven by the predation risk associated with their feeding location. Using a heatmapping technique, we also show that the location of eyespots is fundamentally different in active fishes that swim above the benthos vs. cryptobenthic fishes that rest on the benthos. These location differences may reflect different functions of eyespots among reef fish species.

Pomacentridae

coral reef fishes

natural selection

eyespot

Alfred Russel Wallace

photonic nanostructures

structural coloration

feathers

skin

dichromatism

urtication

stridulation

sexual dimorphism

Lasiurus borealis

pelage

We examined museum specimens

interference

helicoidal

cellulose

iridescence

tannin

cuticle

specimen

cyanosomes

Karl von Frisch

tissues

fruits

thin-film

purine

integumental

iridophores

Melanophores

Synchiropus splendidus

metabolic

anthocyanins

biosynthesis

flavonoid

co-pigmentation

tepals

transcriptomic

purple

Michelia crassipes

delphinidin

cyanidin

flowers

Consolida armeniaca

delphinidin

L.C. Marquart

Richard Willstatter

delphinidin

cyanidin

pelargonidin

Anthocyanins

bi-colored

polymorphic

pigment

carotenoids

anthocyanins

genus Iris

carotenoid

thermoregulation

biology of color

nanostructures

pigments

colorful

color

color

color

Gloss

tongue

photonic crystal

structural colors

integument

iris

pigments

chromatophores

photoreceptor

opsin

eye

vision

coevolution

Color

colours

retinae

cones