Cell Type And Color Discrimination Ability Vole Brown Cones

Mammalian visual system is of great significance in all sensory systems,80%of outside information is received, processed and acknowledged by the visual system。 Living habits of animals, especially feeding behavior are closely related with visual system. Vision consists of three aspects:vision of lightness, vision of shape, and vision of color etc., one of these important functions is the vision of light perception. Opsin exists in the visual system in two ways, one is the opsin in the rod cells, the other is the opsin cone cells. The rod cell is sensitive to light in dark environment, able to sense weak light, but cannot distinguish colors. Cone cells show weak sensitivity to lightness but under strong light can be active and able to distinguish colors. For different cone cell opsin are different in terms of sensitivity to light of different wavelength, the eventual color animals see depends on the types of cone cell;As the eye and retina morphology and function of subterranean rodents are greatly degraded due to lack of light stimulation, their eyes were considered incapable of imaging and distinguishing colors. The sensory organs of animal evolves with their adaptions to the inhabiting environment, different living conditions dissimilate their biological structure and sensory organs. Subterranean rodents all live in dark burrows but their eyes, lens and retinas varies in detail structure due to their adaptive evolution process of different burrow structure and different level of dark environment. By immunohistochemical methods, after light stimulation, certain nuclei in Cryptomys pretoriae brain region has a strong c-fos protein expression, which demonstrates that Cryptomys pretoriae still have visual perception. For some Crypt mammals, study found that the types of cone cells in these species vary greatly. Cryptomys pretoriae are typical dichroic which have a large number of S-cones and a small amount of L-cone; moles are for monochrome as they only have L-cones and no S-cones. Some scholars believe that the color vision of primates, birds and insects are a result of adaptive evolution of feeding on colored food, but recent studies found that the evolution of plants and flowers are far behind the evolution of color vision. Some subterranean mammals have certain sensory features of terranean animals; the evolution of color vision is not dependent on the color of their food. so researches of whether Subterranean rodents still have color vision, not only supplement the study of their visual function, but can also provide theoretical basis of how visual system evolved, in the meantime, this can further illustrate how the dark environmental affects the organ evolution of subterranean rodent.Microtus mandarinus, also known as the North voles, mainly distributes in North China, East China and Henan etc. They are mainly nocturnal, leads a stringent underground burrow living habits, their visual organ, like many other subterranean rodents, have degraded correspondingly. The research of Microtus mandarinus focuses on the morphological characteristics, physiological characteristics, ecological habits and genetic characteristics, the research of their photoreceptor cells and color vision have not been reported. In this experiment, Microtus mandarinus, immunofluorescence and behavioral research methods are used to study the Microtus mandarinus cone cells color vision, and to discuss if Microtus mandarinus are capable of distinguish light of different wavelength, and final conclusions are as follow:The results show that there are two types of cone cells in Microtus mandarinus, more L-cone cells and less S-cone cells, the average density of the L-cone cells19682±1710/mm2, and S-Cones13869±3424/mm2, and a uniform distribution in different areas in the retina is observed as there is no obvious densely populated areas or dispersed areas. The Microtus mandarinus is a typical two-color animal, as the different types of cone cells in the retina make it possible for them to feel different colors of light, their color vision comply with their ecological habits.There are significant differences in their behavioral responses to red and blue light stimulation. Different wavelengths of light significantly affects the sniffing behavior, and have a great impact on the resting, moving, mining, looking around and smoothing behavior, but have no effect on their feeding behavior. Microtus mandarinus was relatively quiet in the blue, but restless in the red light, this is compliant with the ecological habits as the majority of their life is in the dark underground environment.All in all, above research shows that though the Microtus mandarinus lead a long term underground life, their visual organs haven’t degraded completely, there are still light sensitive cells in their eyes, and they still react to light stimulation so they are capable of short term ground activities. Their two types of cone cells make them possible for a two-color vision, and able to distinguish lights of different wavelength, researches are still needed to study if their eyes are capable of imaging.