User:MeatTaco/sandbox: Difference between revisions
No edit summary |
No edit summary |
||
| Line 4: | Line 4: | ||
==Ultraviolet Light Reflection and Absorption in Butterflies== |
==Ultraviolet Light Reflection and Absorption in Butterflies== |
||
One half of the private butterfly communication channel is the ability to send a signal either through UV reflectance or absorption via two separate means. The former is accomplished via structures on the wings’ scales and their systematic organization while the latter is achieved using pigments. The [[structural color]]’s mechanism has been elucidated through the study of the butterfly, ''[[Eurema lisa]]''. In this particular insect, a small yellow portion of the dorsal surface of the wings is directionally UV reflectant. In other words, the image from the UV reflection can only be seen at a distinct range of angles from the point of origin. Through electron micrographs of these UV reflecting scales, it was determined that thin layer interference resulting from parallel ridges with six to seven flanges arranged systematically along the length of the scales caused UV reflection. In other words, the arrangement of the scales and ridges resulted in a maximal constructive interference with a wavelength in the ultraviolet region of the electromagnetic spectrum. This constructive interference is the UV reflectance seen by other butterflies.<ref> Ghiradella, H et al. (1972): “Ultraviolet Reflection of a Male Butterfly: Interference Color caused by Thin-Layer Elaboration of Wing Scales.” Science: 178, 4066,Ppg. 1214-1217.</ref> The other ultraviolet signal in butterflies, absorbance, was determined to be governed by pigments called pterins. In wings containing this pigment, the wings are unable to reflect ultraviolet light as well as without the pigment because the pterins absorb the ultraviolet light.<ref>Obara Y. et al. (2008): "Mate Preference in Males of the Cabbage Butterfly, ''Pieris rapae crucivora'', Changes Seasonally with the Change in Female UV Color." Zoological Science 25, ppg 1-5.</ref> Thus, butterflies are able to reflect ultraviolet light as a result of the organization and composition of their wing scales resulting in thin layer constructive interference and can absorb ultraviolet through the action of pterin pigments. |
|||
==Basis for Ultraviolet Reception in Butterflies== |
==Basis for Ultraviolet Reception in Butterflies== |
||
The butterfly eye is |
The second half of the private butterfly communication channel is the ability to see an ultraviolet signal. The mechanism in perceiving ultraviolet light lies in the butterfly eye. The butterfly eye is similar to the average insect eye in that it is composed of numerous [[ommatidium]]. Each butterfly ommatidium contains nine photoreceptors with generally each photoreceptor utilizing a single visual pigment. A specific visual pigment is responsible for a butterfly’s ability to perceive UV light. The pigment responds maximally to ultraviolet light at approximately 350 nm and allows for the perception of ultraviolet light by butterflies.<ref>Stavenga, Doekele G. and Arikawa, Kentaro. (2006): "Evolution of color and vision of butterflies." Arthropod Structure & Development 35, ppg 307-318.</ref> Therefore, a visual pigment that responds to ultraviolet light is the mechanism behind ultraviolet light perception. |
||
==Sexual Behavior Initiated by UV light in Pieris rapae== |
==Sexual Behavior Initiated by UV light in Pieris rapae== |
||
Revision as of 19:26, 6 December 2009
Ultraviolet Light and Butterfly Communication
Butterflies, or members of the Papilionoidea superfamily, are known for their beautiful displays on their wings. In the visible region of the electromagnetic spectrum, the only region available to most vertebrates for vision, two different species of butterflies can look remarkably similar or even identical. If used in mimicry, this attribute could afford a butterfly an advantage in evading predators, but it could also hinder their ability to visually find a conspecific mate. However, butterflies are able to access a part of the electromagnetic region for vision that most vertebrates and their predators cannot, the ultraviolet region that allows them to recognize conspecifics. The ultraviolet region is the part of the electromagnetic spectrum between 10 nm and 400 nm. Sensitivity to this region provides butterflies several benefits such as nectar guides for nectar, but it also affords them a private communication channel unavailable to predators. With this closed line transmitted by UV reflectance or absorbance and received by a unique photoreceptor, butterflies are able to facilitate mating behavior and sex recognition.
Ultraviolet Light Reflection and Absorption in Butterflies
One half of the private butterfly communication channel is the ability to send a signal either through UV reflectance or absorption via two separate means. The former is accomplished via structures on the wings’ scales and their systematic organization while the latter is achieved using pigments. The structural color’s mechanism has been elucidated through the study of the butterfly, Eurema lisa. In this particular insect, a small yellow portion of the dorsal surface of the wings is directionally UV reflectant. In other words, the image from the UV reflection can only be seen at a distinct range of angles from the point of origin. Through electron micrographs of these UV reflecting scales, it was determined that thin layer interference resulting from parallel ridges with six to seven flanges arranged systematically along the length of the scales caused UV reflection. In other words, the arrangement of the scales and ridges resulted in a maximal constructive interference with a wavelength in the ultraviolet region of the electromagnetic spectrum. This constructive interference is the UV reflectance seen by other butterflies.[1] The other ultraviolet signal in butterflies, absorbance, was determined to be governed by pigments called pterins. In wings containing this pigment, the wings are unable to reflect ultraviolet light as well as without the pigment because the pterins absorb the ultraviolet light.[2] Thus, butterflies are able to reflect ultraviolet light as a result of the organization and composition of their wing scales resulting in thin layer constructive interference and can absorb ultraviolet through the action of pterin pigments.
Basis for Ultraviolet Reception in Butterflies
The second half of the private butterfly communication channel is the ability to see an ultraviolet signal. The mechanism in perceiving ultraviolet light lies in the butterfly eye. The butterfly eye is similar to the average insect eye in that it is composed of numerous ommatidium. Each butterfly ommatidium contains nine photoreceptors with generally each photoreceptor utilizing a single visual pigment. A specific visual pigment is responsible for a butterfly’s ability to perceive UV light. The pigment responds maximally to ultraviolet light at approximately 350 nm and allows for the perception of ultraviolet light by butterflies.[3] Therefore, a visual pigment that responds to ultraviolet light is the mechanism behind ultraviolet light perception.
Sexual Behavior Initiated by UV light in Pieris rapae
White Cabbage Butterflies, pieris rapae crucivora, is a prime example of how insects use ultraviolet patterns as a method of communication. In this species, ultraviolet reflection is sexually dimorphic with females exhibiting the ability to reflect ultraviolet light of 380 nm to 400 nm and males being less able to do so. Males who perceive an ultraviolet reflection from a female initiate a courtship behavior that involves approaching the female and attempting to copulate. It was shown that males visually discriminate by Yoshiaka Obara. Obara placed two pressed to death females and two like males on a piece of cardboard covered and counted the number of approaches by males to each female and male. All males approached only females with one exception out of a hundred and six.[4] Obara also eliminated olfaction as a cue by covering the female and male butterflies with petri dishes. Furthermore, olfaction was further excluded using evidence that male white cabbage butterflies deprived of their antennae, structures necessary for olfaction, were still able to copulate successfully. The female's ventral side of the hind wing was determined to be the greatest releaser of male sexual behavior by comparing the number of approaches towards female upper ventral wings and hind ventral wings. Although ultraviolet reflectance releases the sexual behavior, the strongest reflection of UV light is not the strongest releaser for the behavior. An optimal level of UV reflectance exists.[5]
Ultraviolet light is not only an activator of male sexual behavior. Its absence may also stop an approaching male and his attempt to copulate. Female White Cabbage Butterflies are not always receptive to male White Cabbage Butterflies and to communicate this message, they take upon the mate refusal posture. This behavior consists of opening the wings and straightening of the abdomen.[6] Opening of the wings in this manner exposes the dorsal side of the female wings which are known to be unable to reflect ultraviolet light, suggesting the absence of ultraviolet light is a signal that a female is unreceptive, resulting in the abrupt halt of male sexual behavior.
Ultraviolet Light as an Indicator of the Same Sex
In the butterfly species Eurema lisa, males possess the structural requirements necessary to reflect ultraviolet light discussed previously, but females lack the ultraviolet light reflecting ridges. In both sexes of this species, a flutter response, or the rapid opening and closing of the wings, is performed when a male approaches another butterfly; yet, males continue to copulate with females who perform this behavior while, retreating from males who perform the flutter response. It was shown by Ronald Rutowski that the wings are similar in appearance except for UV reflectance, the temporal qualities of the flutter response were not significantly different between sexes, and an approaching male is exposed to the ultraviolet reflection of a male's wings during a flutter response. As a result, it was concluded that ultraviolet light was being used as an indicator of the male sex, and as an inhibitor of the male sexual behavior.[7]
Ultraviolet light as an indicator of male sex to other rival males was also detailed in the butterfly species Colias eurytheme. In this species, only males are able to reflect ultraviolet light off the dorsal side of their wings, while females cannot. The male sexual behavior is similar to most butterflies. The male hovers over a sitting female and dips to one of the female's sides and flutters. Then, if the female remains still, the male will land on her, her wings, or on the vegetation and attempt copulation. Copulation tends to last for an hour and often other males attempt to approach the mating pair. However, the male in midst of mating flashes his UV reflecting hind wings and approaching males are deterred. It was concluded that male Colias eurytheme uses ultraviolet light as a signal to repel other males.[8]
References
- ^ Ghiradella, H et al. (1972): “Ultraviolet Reflection of a Male Butterfly: Interference Color caused by Thin-Layer Elaboration of Wing Scales.” Science: 178, 4066,Ppg. 1214-1217.
- ^ Obara Y. et al. (2008): "Mate Preference in Males of the Cabbage Butterfly, Pieris rapae crucivora, Changes Seasonally with the Change in Female UV Color." Zoological Science 25, ppg 1-5.
- ^ Stavenga, Doekele G. and Arikawa, Kentaro. (2006): "Evolution of color and vision of butterflies." Arthropod Structure & Development 35, ppg 307-318.
- ^ Obara Y. and Hidaka, T. (1968): “Recognition of the Female by the Male, on the basis of Ultra-Violet reflection, in the White Cabbage Butterfly, Pieris rapae crucivora Boisduval.” Proc. Japan Acad. Vol. 44 No. 8 ppg 828-832.
- ^ Obara Y. (1970): “Studies on the Mating Behavior of the White Cabbage Butterfly, Pieris rapae crucivora Boisduval.” Z. vergl. Physiologie: 60, ppg 99-116.
- ^ Obara Y. (1970): “Studies on the Mating Behavior of the White Cabbage Butterfly, Pieris rapae crucivora Boisduval.” Z. vergl. Physiologie: 60, ppg 99-116.
- ^ Rutowski, Ronald L. (1977): "The Use of Visual Cues in Sexual and Species Discrimination by Males of the Small Sulphur Butterfly Eurema Lisa (Lepidoptera, Pieridae). J. comp. Physiol. 115, ppg 61-74.
- ^ Silberglied, Robert E. and Taylor, Orley R. (1978): "Ultraviolet Reflection and Its Behavioral Role in the Courtship of the Sulfur Butterflies Colias eurytheme and C. philodice (Lepidoptera, Pieridae). Behav, Ecol. Sociobiol. 3, ppg. 203-243.