Studies On The Causation And Function Of The Variation Of Body Color In Octonoba Digitate(Araneae:Uloboridae)

There is an inextricable connection between biological evolution and environment,and organisms always evolve in the direction of adapting to the environment.When a certain environmental factor changes in the living environment,and this change exceeds the tolerance range of the organism to this factor,the organism will be affected by predation,courtship and other aspects of the influence and even the threat of survival.Changes in animal body color are a manifestation of adaptation to the environment during long-term natural selection.Many animals may change their body color because of the change of ecological environment in order to attract mates and catch prey.In addition,the change of body color can also confuse the visual of predators,therefore to protect themselves and avoid predators.Studying the diversity of animal body color is of great significance to the study of animal ecology.The change of body color is mostly due to the number of pigment cells and the content of tyrosinase in the body and parasites in vivo and in vitro.The main environmental factors causing the change of animal body color are temperature,humidity,light and so on.At present,there are many studies on the mechanism and function of animals' body coloration,but for spiders in arthropods,there are relatively few studies in this field.The study of the change of spider body coloration has an important role in the research of the development and evolution of the spider,and may also help to study the protection and utilization of the dominant spiders in the field.Octonoba digitata belongs to the genus Octonoba in family Uloboridae.In the field,the color of the back of the females in this species is varied,mainly in black and white.This experiment mainly studied the function and the mechanism of body color change of this spider.The main contents and results of this experiment are as follows:1.A preliminary study on the causation of color change of O.digitata.Field investigation found that there were differences in the body color of female spiders,and the color of spiders collected in different habitats was different.However,mating experiments in the laboratory showed that the spiders with different body color could successfully mate and lay eggs,and the egg sacs can hatch,proving that they are the same species(no hybridization has been found in spiders yet).In the experiment,the number of melanocytes in the epidermis and the content of tyrosinase,the key enzyme for melanin synthesis,were compared in different color of the spider epidermis.Firstly,the number of melanocytes in spider epidermis was observed by paraffin embedded slice method under microscope,and the difference of melanocytes in spider epidermis was also observed under microscope.The results showed that the number of melanocytes in the epidermis of dark spider was significantly more than that in bright spider,which proved that the two colours of spider epidermis were caused by the different number of melanocytes.Meanwhile,the content of tyrosinase in the epidermis of different body colors was determined by enzyme-linked immunosorbent assay(ELISA).The results showed that the tyrosinase content in the epidermis of bright-colored spiders was significantly less than that of dark-colored spiders(t=4.427,p=0.002).2.The influence of light on the color of epidermis.I observed that the color of the spider collected in the habitat with high light was lighter than that in the environment with weak light,so I assumed that the change of the color of the spider was mainly related to the light in its habitat.To test this hypothesis,I raised spider individually in reverse(dark spider in bright condition,bright spider in dark condition)for 90 days,measuring the white light reflectivity of the back color of the spider every 30 days.Finally,chose 300nm-700 nm wavelength range to draw the reflection spectrum to determine the trend of spider body color in three months.The result showed that light was the main environmental factor that change the body color of O.digitata.3.Function of the changes of spider body color.In this part,a predator-prey model was established.I used the chickens that were incubated for 3-4 days to simulate predators.They pecked spiders of two colors under the background of either black or white.The number of chickens pecking black spiders or white spiders under the twobackgrounds was compared.The results showed that among 73 chickens,60 of them pecked the light-colored spider,13 chickens pecked the dark-colored spider under the black background,while in the white background,19 chickens pecked the light-colored spider,and 54 chickens pecked the dark-colored spider.Chi-square test showed that there was a significant difference in the number of chickens pecking bright-colored spiders and dark-colored spiders in the black background(?2=46.368,df=1,p < 0.001).There was also a significant difference in the number of chickens pecking bright-colored spiders and dark-colored spiders in white background(?2=46.368,df=1,p < 0.001),which proved that the spider had the function of avoiding natural enemies by having different body colors in different environment.