The Spectral Transmission Of Corneal Lens In Spiders

Vision,especially ultraviolet(UV:<400 nm wavelength)vision,plays a dominant role in animal survival.Recently,many studies have shown that many vertebrates use UV vision for foraging,sexual selection and navigation.However,UV vision is poorly explored in invertebrates.A few studies have demonstrated that a few species of jumping spiders(Araneae:Salticidae)have UV vision and they use UV for foraging and sexual selection.How widespread UV vision in salticids and other non-salticid spiders is unclear.Since corneas can act as a filter in regulating the wavelengths reaching the retina of eyes,it is impossible for a spider with a UV-blocking cornea to perceive UV.However,having a UV-transmitting cornea a spider is most likely able to see UV although UV vision depends on both UV photoreceptors and UV transparent lens.In this study,using spectrometry I determined how widespread UV vision in spiders through measuring the spectral transmission properties of corneal lenses of spiders from different families.In chapter two,I described and assessed spectrometry in measuring the spectral transmission of spider corneas.In Chapter 3,I measured the spectral transmission of corneas of 128 salticid species which belong to 13 subfamilies,and found that all the salticid species examined have UV transmitted corneas in their eyes though there were differences in the spectral transmission properties of corneas.A majority of salticid species(85%)have corneas that can transmit both UV-A(220-400 nm)and UV-B(280-320 nm)while about 14%salticid species with corneas which transmitted only UV-A.I also examined the factors influencing the transmission characteristics of corneas,and found that light environments dominated animal UV-visual ability as well as the transmission characteristics of the corneal lens.In Chapter four,I measured the spectral transmission of corneas of 13 spider families which differ with phylogeny,vision,circadian rhythms and light habitats.The majority of spider species have UV-A transmitting corneas,while spiders that live in burrows tended to block UV wavelengths.This is the first study in which spectrometry was used in assessing the UV vision of spider order in arthropod,also attempted to answer the cloudy of the relationship between ecological factors and cornea transmission characteristics.