Study On The Structure And Color - Distinguishing Ability Of Niviventer Confucianus

Niviventer confucianus,as a species of rodents widely distributed in our country, mainly habitat in the mountains, shrubs and bushes of hills and rock crevices. They mainly feed on the seeds, fruits and young leaves of woody plants, as well as some starch crops. They always are active at night. Their feeding habits are wide, so they are harmful agroforestry rodents. Meanwhile N. confucianus itself contain a variety of pathogens, threaten the life safety of people and beasts in epidemic source area. So N. confucianus also occupy an important position in epidemiology study. Now the study of N. confucianus mainly focus on its physiology, behavior, prevention, and so on. Researches on the vision system characteristics of N. confucianus and the correlation between their visual system and living habits are less and unclear. Currently, rodents visual research mostly focuses on the visual organ structure, type and distribution of photoreceptor cells, opsins, visual pigments and color vision systems and other aspects.Vision is an important way for animals to obtain outside information. It plays important role in feeding, mate selection and message passing. It also has profound and extensive influence on animal evolution. So visual organ is the main object in most animal behavior and evolution study. Vision is composed of light sense, color sense and form sense, and the light sense is the basis of other two sense. Photoreceptor cells, as the only part of visual organ who can accept light, are sensitive to light. Generally, photoreceptor cells have two types of cells, rods and cones. Rod cells mediate scotopic vision, have no color vision function. While cone cells mediate photopic vision, have color vision function. In the process of evolution, organisms exhibit of adaptive features on the environment, and visual adaptation is the visual physiological adaptability performance of sense organs, which has vital significance to animal’s survival.With the methods of histology, immunofluorescence and ethology, this research studied the retinal structure, the type and distribution of photoreceptor cells and the ability of color discrimination of the visual system of N. confucianus in order to learn the characteristics of the N. confucianus visual system, make out whether this specie have color discrimination ability and discuss the relationship between the visual system and habit. The results were as bellow:1. The vision organ of N.confucianus is larger with the structure of eyelid, cornea, sclera, iris, lens, choroid and retinal. The ocular growth is normal and the retinal layers are obvious, which is similar to the structure of retina of the typical mammalian.2. We found obvious difference of the cell number between the outer nuclear layer and the ganglion cell layer in N. confucianus, with a proportion of 105:1. This ratio is similar to nocturnal rats’, that is to say, the visual system of N. confucianus is similar to the nocturnal rats.3. The structure of photoreceptor cells of N. confucianus is integral. The photoreceptor cells are composed of rod cells in majority and few cones. The rod cells mediate dark vision while the cone cells mediate photopic vision, which are adapt to the fact that N. confucianus are mainly active at night.4. S-cones (short wavelength-sensitive) and L-cones (long wavelength-sensitive) are included in N. confucianus retina, so N. confucianus is a typical dichromatic color vision rat. The number of S-cone cells is much larger than L-cone cells. The distribution of both cone cells in the retina is uneven as the central area is dense distribution area. There is a trend of decline of cone cells number from the central to the fringe area. The distribution of cones is generally similar to nocturnal mouse.5. Under different wavelengths of light irradiation, N. confucianus act differently. N. confucianus exercise less time and rest more under the blue light, on the contrary, while under the red light irradiation, it rest less and exercise more. This phenomenon state that N. confucianus can distinguish different wavelengths of light with the ability of color discrimination.In summary, the visual organ of N. confucianus is normal, with photosensitive ability, and the visual system adapts to short term ground activity. N. confucianus can distinguish the different spectrum and have the ability of color discrimination. The visual system of N. confucianus get used to its living habits.