Effect Of Light On Activity Patterns, Rhythm And Visual Organ Development Of Mandarin Voles

(Department of Bioengineering, Zhengzhou University, Zhengzhou,450001) (Institute of Biodiversity and Ecology, Zhengzhou University, Zhengzhou,450001)Mandarin vole(Lasiopodomys mandarinus) which is a great agricultural rodent pest in the northern of China, spends almost all its life span underground that would made the vision degenerated after the long term subterranean evolution to adept. Those researches on vision degeneration and its mechanism have always been attention. To understand the effection of light to the behavior rhythem and eyespot growth, to settle basic data for future studies on behavior ecology and physiology ecology, and to provide data for researching the mechanism of vision regulation and evolution of eyespot in rodents within dark condition, here we comparaed the activity rhythem at different light intensity and dark-light cycle in mandarin vole and Kunming mouse (Mus musculus) which we employed for control, and detested the retina growth at different dark cycle in two redents, as follows:1 Light intensity exert important role on activity patterns of nocturnal and diurnal mammals. Under laboratorial conditions and being given four levels of light intensity,<20,200,800, and 1600 Lux, variations in body mass and behavior of Mandarin vole and KM mouse (Mus musculus) were investigated via employing focal animal sampling auto-vedio system. The results showed that:1) the interaction between light intensity and species was remarkable, the static behavior was significantly and negatively related to light intensity in Mandarin voles, while this behavior was insignificantly affected by light intensity KM mice; 2) behavioral patterns of movement were in contrast to static behavior mentioned-above both in Mandarin voles and KM mice; 3) under light conditions, the relative activity in Mandarin voles was significantly stronger than that in KM mice; and 4) light intensity played different influences on body masses of two rodent species, and the body mass was positively related to light intensity in Mandarin voles, whereas body mass in KM mice appeared not to be remarkably affected by light intensity. The result from this research tested the different response to light adaptation between subterranean and ground inhibited rodent species. Light would enhance activities for subterranean rodents, and appeared to change activity pattern unobvious.2 We measured the effect of dark-light cycles on the activity rhythm in Mandarin vole and KM mice by using video. As results domenstrated, both rodents had significant differences in the daily activity rhythm between dark and dark/light=12h/12h in two rodents. There was no daily activity rhythm of Mandarin vole under dark/light=12h/12h, while the daily activity rhythm of Mandarin vole was not significant under dark condition. For KM mice, the activity rates in dark/light=12h/12h was higher than that in dark condition, while the resting rate was reversed. There was significant daily activity rhythm in KM mice under dark/light=12h/12h, and also in dark. The activity rates in dark/light=12h/12 was lesser than that under dark, and resting rates exhibited reversely.3 We measured the effect of dark-light cycles on the retina growth of 6 d,12 d,18 d,24 d and adult mice after birth in Mandarin vole and KM mouse using conventional paraffin-embedded and production slice method. The results showed that:Between Mandarin vole and KM mouse, there were remarkable significant differences on the growth of body mass, lens diameter, pigmented layer, nuclear layer and retina; the effect of photoperiods on cell density of the outer nuclear layer was remarkable; the interaction between photoperiods and species was remarkable on the growth of body mass and retina. The retina growth rate of KM mice in normal light conditions was faster than that in dark conditions. However the Mandarin vole showed the opposite trend. The results suggested that the effect of photoperiods on two rodents was opposited, and light could restrain growth of retina in Mandarin voles (subterranean rodent), whereas promote retina growth in KM mice which derived from ground-lived ancestor.