Evolution of Trichromatic Vision in Primates

Trichromatic Vision

Trichromatic vision has evolved over time in mammals. Primates are the only mammals to evolve to have trichromatic vision! This vision evolution has allowed for mammals to see multi colored, and in turn has helped in areas like hunting by giving these primates visual aid. In the article, Surridge A, K., et al, discuss the evolution of the trichromatic vision from the dichromatic vision as adaption to aid in finding food in the forest, fitness. Further, we are able to conceptualize how natural selection plays a role in this evolutionary trait across primates. Trichromatic vision requires three spectral receptor types and appropriate neural mechanisms ( Surridge A, K., et al 2003).

Cone Photoreceptors

Photo of a Cone Photorecptor

Cone cells is one of the two main classes of photoreceptor found in the vertebrate eye (rods are the other class). The cone cell is found in the retina of the eye, responsible for color vision, (day time) a wide variety of vibrant colors.

Spectral Sensitivity

Photograph of Spectral Sensitivity Technology

Spectral sensitivity is the relative effeciency if detetcing light. In primates, a given photoreceptor expresses one type of photopigment molecule ( Surridge A, K., et al 2003). The retinal and opsins protein work together to make this photopigment. Spectral sensitivity helps to understand color vision and irregular vision.

Understanding Nomenclature

In dichromatic eyes, there are 2 cone receptors. Called Long- wavelength (L) and Short- wavelength (S). Similarly, in Trichromatic vision there are Long-wavelength (L), short-wavelength (S) and middle-wavelength (M). The L,S,M wavelengths can commonly be associates with the colors blue=short, green=middle, long-red.

Fig.1

The figure is showing the relative sensitivity , spectral sensitivity of the following photorecptor types and the chromatic traits in a trichromatic primate. The photoreceptor types are shown in (a) as S,M,L (short, middle and long wavelenght). The pigments can be defined as y max in the figure. the red-green mechanism common of the primate is found in (b) denoted with the black line.

Figure 1. ( Surridge A, K., et al 2003)

The hylogenic tree is showing evolutinary relationships among primates and diversification among the primates vision types.

GUIDE:

------- Dichromatic Lineage

_______ Polymorphic Lineages, Allelic Trichromacy

________ Trichromatic Lineages

When Did Trichromatc Vision Evolve? A Timeline:

The figure shown to the lift, interprets and put together a phylogenic tree showing relationships among primates vision types across centuries and various species. It is seen across the Prosimians, early group of primates are seen to all descend from dichromatic lineages (600 Million years ago). The turning point is 40 million years ago, dichromatic lineages of prosimians crossed with platyrrhines, primate group pf monkeys, creating a group of polymorphic lineages (more than one type). Then the Catarrhines group, humans, monkeys an apes have evolved from ancestral roots to have adapted Trichromatic lineages close to 40 million years ago.

Whats a Phylogenic Tree?

Phylogenies illustrate evolutionary relationships! All phylogenies are based on common descent. A phylogeny is a hypothesis about evolutionary relationships inferred from a particular dataset by a particular technique! All the species on the phylogentic tree , increase the possibility of more hypothesis.

Visual: Prosimians>Platyrrhines>Catarrhines

This image by CK12-Foundation, helps to visualize and conceptualize what the differnt primates species look like in relation to understanding their ancestral relationships. the earliest primate ancestors, prosimians, the platyrrhines new world monkeys, and the catarrhines old world monkeys, apes and humans.

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