The Structure Of Visual Organ In Myospalax Cansus And The Study Of Color Discrimination

Myospalax cansus is the rodent that lives underground. It lives in dark tunnel witha close end, and surface activity is rarely. As a result, the body structure,physiologicalfunction and the sense organ are affected deeply by the living conditions. The structureand function of the sense system changed enormously after long time adaptation.Among those changes, eyes degeneration is the most distinctive. The eyes are atrophicand much less than other rodents which moves above ground.In previous studies, most of the visual nucleus showed strong C-Fos expressionwhen Myospalax cansus was stimulated by light after fostering in darkness, indicatingthat in Myospalax cansus the brain is able to process light information. In attempt toclarify whether it is able to distinguish different spectrum, many biological technologyand methods, such as ethology, morphology, nervous anatomy, immunohistochemistryand immunoflurescence, will be applied in this project to study the visual system ofMyospalax cansus. It has been shown, however, that Myospalax cansus is subterraneanrodents that are rarely exposed to environmental light, the eyes are still existent, yetpossess the basic structures: eyelid,cornea,iris,lens,choroid layer and retina,suggesting that Myospalax cansus is adaptive to short-term surface-dwelling habitat.Ultra structure of the retina shows that photoreceptors in Myospalax cansus areintact. And there are lots of photoreceptor bodies in the outer nuclear layer (ONL).Large numbers of synaptic ribbons are located in the outer plexiform layer (OPL), whilethe ganglion cells which transfers light information to the brain are sparse, indicatingthat light information were disposed in the retina and few information can reach thebrain. The activities of pigment granule increased, indicating that it will protect theretina in Myospalax cansus, preventing the damage to the photoreceptors when exposedto strong light. Compared with other surface-dwelling rodents, the most distinct featureof the Myospalax cansus is that the ganglion cells are sparse, much less than otherrodents. At the electron microscope, apoptotic nuclei were detected in the ganglion celllayer, indicating that cell apoptotic is the reason that the ganglion cells are sparse.Using immunoflurescence technology, the short-wave-sensitive cones (S-cone)were labeled by Blue-sensitive Opsin sc-14363 and the long-wave-sensitive cones (L-cone) were labeled by Opsin Red/green AB-5405. Myospalax cansus has twokinds of cones, a majority of S-cones, and a minority of L-cones, suggesting that theMyospalax cansus was dichromatic color vision. And it can distinguish differentspectrum.The activity of Myospalax cansus is significantly different when stimulated by bluelight and red light. It also suggests that Myospalax cansus can distinguish differentspectrum.In both red-light-stimulated and blue-light-stimulated animals, the rudimentarysuperior colliculus exhibited slight immunoreactivity, indicating that in Myospalaxcansus the brain is able to process light. The C-Fos labeling has greatly significantdifference when simulated by red light and blue light, further elucidating thatMyospalax cansus can distinguish different spectrum.In conclusion, the visual organ in Myospalax cansus is adaptive to short termsurface dwelling habitat, receiving the light stimulation and distinguishing the differentspectrum. However, the imagine ability in Myospalax cansus needs to be furtherelucidated.