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Spectral sensitivity of the compound eyes of Anomala corpulenta motschulsky (Coleoptera: Scarabaeoidea)
Journal of Integrative Agriculture 2015, 14(4): 706–713 Available online at www.sciencedirect.com
ScienceDirect
RESEARCH ARTICLE
Spectral sensitivity of the compound eyes of Anomala corpulenta motschulsky (Coleoptera: Scarabaeoidea) Jiang Yue-li1, 2, Guo Yu-yuan1, 3, Wu Yu-qing2, Li Tong2, Duan Yun2, Miao Jin2, Gong Zhong-jun2, Huang Zhi-juan2 1
College of Plant Protection, Northwest A&F University, Yangling 712100, P.R.China Key Laboratory of Crop Pest Control of Henan Province/Institute of Plant Protection, Henan Academy of Agricultural Sciences, Zhengzhou 450002, P.R.China 3 State Key Laboratory for the Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, P.R.China 2
Abstract The scarab beetle, Anomala corpulenta Motschulsky (Coleoptera: Scarabaeoidea), is a widespread and destructive pest in China. Vision is one of the most important means of acquiring information about the external environment. In order to contribute to the understanding of the perception of visual stimuli in this species, the light sensitivity and spectral responses of the scarab beetle, A. corpulenta, were measured by using an electroretinogram (ERG) technique. In total, 14 monochromatic light intensities, between 340 and 605 nm, were applied to the compound eyes of A. corpulenta under varying levels of adaptation to dark and light conditions. The results showed that all light stimuli induced an ERG response, with varied amplitudes. The spectral sensitivity curve of dark-adapted eyes showed one major peak (~400 nm; near-ultraviolet), a secondary peak (from 498 to 562 nm; yellow-green) and the third peakat 460 nm. By contrast, in light-adapted eyes, only a near-UV peak was observed. From these results, we conclude that the compound eye of A. corpulenta is likely to have at least three spectral types of photoreceptor. Significance of differences were also recorded in the responses of male and female compound eyes, as well as diurnally and nocturnally. The amplitude of ERG in response to white-light stimuli varied with the light intensity: The stronger the luminance, the higher the ERG value. This suggests that the compound eye of A. corpulenta adapts quickly to changing light conditions, enabling A. corpulenta to maintain nocturnal activities. Keywords: Anomala corpulenta, electroretinogram, insect vision, spectral sensitivity, light intensity
1. Introduction Received 24 March, 2014 Accepted 23 July, 2014 JIANG Yue-li, Tel: +86-371-65738134, Mobile: 13838230695, E-mail: [email protected]; Correspondence GUO Yu-yuan, Tel: +86-10-62894786, E-mail: [email protected]; Correspondence WU Yu-qing, Tel: +86-371-65738134, E-mail: [email protected] © 2015, CAAS. All rights reserved. Published by Elsevier Ltd. doi: 10.1016/S2095-3119(14)60863-7
For insects, vision is one of the most important means of acquiring information about the external environment. It plays a significant role in finding hosts, intraspecific communication, foraging, escaping from predators and in flight (Moericke 1955; Chapman et al. 1981; Dixon 1985; Klingauf 1987; Powell et al. 1995; Egelhaaf and Kern 2002). Finch and Collier (2000) showed that visual cues were central
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link of host location phytophagous insects, for example, the butterfly Pieris rapae was found to respond strongly to blue and blue-green light over long distances to locate a suitable spawning host (Qin 1987), female fruit females tend to move to traps with red spheres attached to the center of yellow panels (Cornelius et al. 1999). In addition, many phytophagous insects prefer yellow as a cue to host location (Bernays and Chapman 1994). However, Frisch (1949) showed that the honeybee Apis mellifera detects polarized natural light and uses it for spatial navigation. Therefore, it is important to get a more comprehensive and clear understanding of the insect color vision. The scarab beetle, Anomala corpulenta Motschulsky (Coleoptera: Scarabaeoidea), is a widespread and destructive pest in China (Wu 2001). The larvae feed on the underground portion of crops, with a preference for peanuts and soybeans, whereas the adults feed on the leaves of various species of fruit and forest trees. The exocuticle of this beetle has a brilliant metallic appearance, and selectively reflects left circularly polarized light, as recorded for other jewel beetles (Sharma et al. 2009). Insects are sensitive to various characteristics of light, such as its intensity, color and polarization (Wernet et al. 2003; Horváth and Varjú 2004). In addition, visual cues are important in intraspecific communication and host location by beetles. Many studies on vision in the jewel beetles have focused on polarization (Horváth and Varjú 2004; Brady and Cummings 2010; Blahó et al. 2012). However, few have studied the presence of color vision in, and impact of light intensity on, such beetles. Therefore, there is a need to further understand the physiological basis of the color vision of jewel beetles, particularly the spectral sensitivity, and effects of light intensity. Electrophysiological spectral sensitivity has been examined for many insect species, including the cabbage root fly, Delia radicum (L.) (Brown and Anderson 1996), the cotton bollworm, Helicoverpa armigera (Hübner) (Wei et al. 2002), the western flower thrip, Frankliniella occidentalis (Pergande) (Matteson et al. 1992), Homopteran species-the glasshouse whitefly, Trialeurodes vaporariorum (Westwood) (Mellor et al. 1997), and the green peach aphid, Myzus persicae (Sulz.) (Kirchner et al. 2005), the click beetles, Pyrophorus punctatissimus in Coleoptera (Lall et al. 2000), etc. Most insects have two kinds of visual pigment, one detects light at approximately 550 nm (yellow-green) and the other detects blue-violet UV light, at less than 480 nm. However, there are no data available regarding the electrophysiological spectral sensitivity of the jewel beetles. In addition, mechanisms of adaptation to light intensity in A. corpulenta are unclear. Therefore, to investigate the spectral sensitivities and mechanisms of adaptation to light intensity of A. corpulenta, the response of A. corpulenta to different light wavelengths
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and intensities, and the effects of gender and circadian rhythm on them, were measured by means of electroretinogram (ERG) technique.
2. Results 2.1. Form of the ERG The ERG waveform of A. corpulenta elicited by a white light stimulus is a monophasic negative change in potential (Fig. 1). As can be seen from the waveform, the lower interference signals existed during stimulation. The ERG value was recorded as the negative ERG component. The greatest ERG amplitude was 35 mV.
A
18 mV B
0.2 s
Fig. 1 A typical electroretinogram recording from Anomala corpulenta under white-light stimulus. A, negative sustained potential. B, off-response.
2.2. Spectral sensitivity The spectra of ERG changes by the eyes of male and female A. corpulenta in response to light stimuli within the monochromatic 340–605 nm wavelength were recorded under certain dark and light adaptation times. The results showed that UV and most of the visible regions of the monochromatic light stimulus triggered an ERG response of A. corpulenta compound eyes with light and dark conditions adaptation. The spectral sensitivity response curves (Figs. 2–4) were obtained according to the size of the ERG amplitude. The spectral sensitivity of the dark-adapted compound eye of both male and female A. corpulenta showed one major distinct peak of sensitivity at 400 nm diurnally. The second distinct peak appeared at 524 nm (yellow-green). No clear peak was found at other wavelengths (Fig. 2). When the eyes were tested nocturnally, the spectral sensitivity curve showed three further peaks (Fig. 3). The main peak position was unchanged, whereas the secondary peak position moved from 524 to 498 nm (yellow-green). The third peak occurred at 460 nm. When the compound eyes were tested in the presence of adaptation to light, the spectral sensitivity curve of the female eyes showed only one peak, at 400 nm (Fig. 4), whereas those of the males showed three peaks: a major distinct peak at 400 nm, a second distinct peak at 498 nm (yellow-green) and the third peak at 460 nm. These peaks
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1.0
Female Male
0.9
Relative sensitivity
0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 320 340 360 380 400 420 440 460 480 500 520 540 560 580 600 620 Wavelength (nm)
Fig. 2 Spectral sensitivity curves of the compound eye of male and female A. corpulenta after dark adaptation of 60 min during the day. Data are means±SE of six individuals. The same as below. Male Female
1.0 0.9
Relative sensitivity
0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 320 340 360 380 400 420 440 460 480 500 520 540 560 580 600 620 Wavelength (nm)
Fig. 3 Spectral sensitivity curves of the compound eye of male and female A. corpulenta after dark adaptation of 60 min during the night.
were the same as, if smaller than, those recorded for the dark-adapted compound eye nocturnally. By using Mann-Whitney U test, a comparison of mean spectral efficiency between the sexes failed to show any significant differences on either day and night at corresponding wavelengths under light and dark adaptation (P>0.05). Circadian rhythm can also affect the spectral sensitivity of the compound eyes of A. corpulenta. As shown in Figs. 2 and 3, The peak was more distinct at night under dark-adaptation conditions than it was diurnally. There were no
significant differences in spectral efficiency between sexes (P>0.05), and therefore the data from males and females were combined. The Mann-Whitney U test revealed that the compound eye of A. corpulenta was significantly more efficient in the peak of 400 nm (P<0.05), 460 nm (P<0.05), 498 nm (P<0.05), 538–582 nm (P<0.05) region at night under dark-adaptation conditions than it was diurnally. There were no significant differences in 340–380 nm (P>0.05), 420–440 nm (P>0.05), 483 nm (P>0.05), 524 nm (P=0.05) and 605 nm (P>0.05) region between the day and night.
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1.0
Male Female
0.9
Relative sensitivity
0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1
320 340 360 380 400 420 440 460 480 500 520 540 560 580 600 620 Wavelength (nm)
Fig. 4 Spectral sensitivity curves of compound eye of A. corpulenta after light adaptation of 60 min.
2.3. Changes in the light intensity response of the compound eye
3. Discussion According to the ERG, we found that the ERGs recorded from the compound eyes of A. corpulenta were similar to that described in other insects, such as Curausius morosus (Kugel 1977), Periplaneta americana (L.) (Walther 1958) and many species of Lepidoptera (Eguchi et al. 1982). The results of this study show that UV and most visible monochromatic stimuli can trigger an ERG response of A. corpulenta compound eyes with light and dark conditions adaptation. Specially, we found spectral sensitivity of A. corpulenta. The curves in Figs. 2–4 suggest there are three peak regions of the spectral sensitivity system in A. corpulenta: One is in the near UV (400 nm), the second
Male Female
25 ERG response (mV)
By adjusting the neutral density filter, it was possible to stimulate the compound eyes with different intensities of white light both diurnally and nocturnally. The light intensity response of compound eyes of male and female A. corpulenta were recorded under dark-adaptation conditions (Figs. 5 and 6): The ERG value gradually increased with increases in light intensity across a range of intensity (log I=4.5–0). The increase was slow during initial light-intensity levels, but increased more quickly once the light intensity reached a certain level. The increase was not affected by gender or circadian rhythm, and the high-end platform of V-log I response was not found yet because of the limit of the light source.
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20 15 10 5 0
4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 −0.5 Relative intensity (log I)
Fig. 5 Response-intensity curves of the compound eye of male and female A. corpulenta to white light after dark adaptation of 60 min during the night.
is a broader green peak (498–562 nm) and the third peak is at 460 nm. With white adapting light, which reduces the sensitivity of any receptors in the visible range, the sensitivity curve peaks at 400 nm. From these results, one can conclude that A. corpulenta has at least three types of photoreceptor. Thus, this species is obviously similar in its visual system to other Coleoptera, such as North American fireflies (Lall et al. 1980b; Lall 1981) and Lepidoptera, such as Papilio protenor, Celastrina argiolus, Minois dryas, Neope goschkevitschii, Celastrina argiolus, Ochlodes venata and Parnara guttata (Eguchi et al. 1982) and Aglais urticae (Steiner et al. 1987).
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30
ERG response (mV)
25
Male Female
20 15 10 5 0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 −0.5 Relative intensity (log I)
Fig. 6 Response-intensity curves of the compound eye of male and female A. corpulenta to white light after dark adaptation of 60 min during the day.
Evidence of the near UV receptor (400 nm) of A. corpulenta comes from the results of both the dark adaptation (both nocturnally and diurnally) and the light adaptation tests, because the peak at 400 nm was unchanged. During the diurnal dark-adaptation test, the blue peak (at 460 nm) disappeared, but reappeared during the nocturnal dark-adaptation test. This discrepancy in results might be because A. corpulenta is nocturnal insect and, therefore, is most active during night and so has evolved a suitable dark-adapted visual system. With adaptation to white light, which reduces the sensitivity of any receptors in the visible range, the clear sensitivity curve peaked only at 400 nm, indicating the existence of a UV receptor. The near-UV spectral sensitivity recorded in A. corpulenta is a common feature of the compound eye of many insects (Briscoe and Chittka 2001). It has been demonstrated that many insects use near-UV wavelengths in navigation (Wehner 1976), and eliciting phototaxis of many insects mainly rely on the spectrum region, because it is the most effective (Helen and Moray 1996). Some researchers suggested that the UV receptor might be optimally suited to detect the open sky or to detect small objects (such as flying mates) against the bright sky (Menzel 1979). It has been hypothesised that near-ultraviolet light serves to elicit escape responses in the butterfly, Pieris (Scherer and Kolb 1987). For the green-sensitive visual pigment, a broader secondary peak in the spectral sensitivity curve, between 498 and 562 nm, was recorded from compound eyes of A. corpulenta under dark-adapted conditions. These results are similar to those from other species of Coleoptera (Hasselmann 1962; Lall et al. 1982; Lin and Wu 1992). Briscoe and Chittka (2001) reported that green-sensitive photoreceptors are also a common feature of the compound eyes
of a variety of insects. Green-sensitive photoreceptors are quite effective region of inducing some insects to greenyellow colors (Harris and Miller 1983; Prokopy et al. 1983; Bernays and Chapman 1994). Phytophagous insects may use green-sensitive photoreceptors for host location (Bernays and Chapman 1994), and wide-field motion detection (Wehner 1981). Vision is the main sense used for acquiring information from the external environment, enabling many species of insect to find mates, obtain food, escape from predators and fly (Egelhaaf and Kern 2002). In the current study, we compared the visual spectral sensitivity and the color on the exoskeletal surface in both male and female A. corpulenta. There was an approximate correlation between green color on the exoskeletal surface and the broad green visual spectral sensitivity of this insect. However, the biological meaning of the phenomenon is hard to explain. A similar phenomenon was reported in lycaenid butterflies (Michio and Kaoru 2008). The color vision of A. corpulenta beetles might be more sensitive in discriminating conspecific signals from background light (contrast enhancement) because this remarkable ability is known to mediate sexual signaling and mate choice in the scarab beetle Chrysina gloriosa (Brady and Cummings 2010). However, additional work is required to investigate this hypothesis further. The trichromatic theory of insect colour vision suggests that insects see three primary colours, green, blue and UV (Briscoe and Chittka 2001). In the current study, A. corpulenta possesses 3 types of photoreceptors, it was remarkable that the ERG of the click beetles (Coleoptera: Elateridae) was found to have just 2 spectral peaks in the ERG (Lall et al. 2000), studies showed that some members of Coleoptera lost blue opsin (Jackowska 2007; Oba 2009). Blue photoreceptors are mainly reponseable for eliciting phototaxis of many insects, such as blue sticky traps for monitoring Frankliniella bispinosa (Morgan) (Thysanoptera: Thripidae) (Childers and Brecht 1996). Further studies are required to examine molecular evidence on 3 types of photosensitive receptors and its function in A. corpulenta. A small sexe difference in spectral sensitivity curves was found in A. corpulenta beetles (Figs. 2 and 3), but there were no statistical differences between the sexes. A similar result was reported in Ephestia cautella (Helen and Moray 1996), Trialeurodes vaporariorum and Encarsia formosa (Mellor et al. 1997). It showed that the sex differentiation was not obvious. As other studies have shown, circadian rhythm can affect the spectral sensitivity of insects (Kral and Stelzl 1998; Wei et al. 2002). In the current study, we found that circadian rhythm can affect the peak position of ERG. The second distinct peak appeared from 524 nm during daylight hours to 498 nm during the night as a result of the compound eyes
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becoming dark adapted. The peak at 460 nm appeared under dark-adapted conditions nocturnally but not during daylight hours or under conditions of nocturnal light adaptation. The peaks of spectral sensitivity curves in male and female A. corpulenta were more distinct at night than it was at day, showing that the compound eyes of this species are more sensitive during the night. Such a result supports the fact that these beetles are more active during the night. In addition, intensity response of A. corpulenta is also a significant founding. In certain intensity range of the whitelight, the stronger the luminance, the higher the ERG value of eyes from A. corpulenta. This suggests that the compound eye of A. corpulenta has a strong ability to adapt to light, as also reported by Wei et al. (2002) and Yan et al. (2007). In the current study, the ERG technique was used to examine adaptive aspects of color vision in insects. This technique is not capable of exploring the characteristics of receptors or pigments which play a role in color perception and consequently it can not be used to investigate evolutionary aspects of the visual system. In order to improve our understanding of the visual physiology and photosensitive mechanisms of A. corpulenta, further study on the intracellular potential is necessary. Therefore, a combination of research at the molecular-, cellular- and whole-eye-level approach, is required to further our understanding of the physiological mechanism of A. corpulenta color vision.
4. Conclusion The compound eye of A. corpulenta is sensitive to nearUV, green-yellow and blue light, circadian rhythm can also affect the light sensitivity and spectral responses of the beetles. A. corpulenta is likely to have at least three spectral types of photoreceptor. Its compound eyes have a strong ability to adapt to light. Specifically, in part of the tested white-light intensity range, the stronger the luminance, the higher the ERG values recorded from the compound eyes of this beetle.
5. Materials and methods 5.1. Insects A. corpulenta used in the study were taken from a natural population that had been collected during the summer of 2012 in the Yuanyang Experimental Station (113.46°E, 35.08°N), Henan Academy of Agricultural Sciences, Henan Province, China. The beetles were reared on tomato plants after collecting under the following environmental conditions: 25°C 70% relative humidity (RH) and a 16 h L:8 h D photoperiod. The insects used in the experiment were l–2-wk-old adults.
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5.2. Optical system A 150-W high-pressure xenon lamp was used as a light source. The wavelength of stimulated light was obtained by using an interference filter. The light passed first through a quartz heat-protecting glass, which absorbed the infrared light, and then through a set of interference filters and neutral filters, which produced monochromatic light with different intensities. The wavelengths of monochromatic light were 340, 360, 380, 400, 420, 440, 460, 483, 498, 524, 538, 562, 582 and 605 nm. The optical path system comprised a quartz thermal-isolating glass, an interference filter, a neutral filter and neutral wedge filter, which was used to adjust the light intensity. In addition, there was a quartz condenser lens, which made parallel light sources converge on the focal plane of the light guide (inner diameter of 3 mm). The shutter drive was controlled by a computer, which was used to trigger the shutter in real-time, to regulate the time interval of light stimulating, and to enable the light beam to reach the compound eye through the light guide.
5.3. Intensity calibration The neutral filter and neutral wedge filter were used to keep the light intensity of different monochromatic lights the same; this was monitored using a thermal photoelectric-coupled illuminance meter and a galvanometer (street lighting photometer, EVANS Electroselenium Ltd., England). Each duration of light stimuli was set for 20 ms and the interval between stimuli was 40 s. In the light-intensity experiment, the light intensity of white light was increased gradually logarithmically, with a grade of 4.5, 4, 3.5, 3, 2.5, 2, 1.5, 1, 0.5 and 0 (log I), by means of a number of neutral filters. The maximum intensity was at the log 0. Each duration of light stimuli was set for 20 ms and the interval between stimuli was 10 s.
5.4. Experimental procedures Each insect was then mounted on a multidimensional adjustable ball-joint sample stage using low-melting-point wax melted onto the abdomen-thorax. The head of the insect was carefully immobilized using melted wax. Under an anatomical lens, a triangular microhole in the cornea of the left compound eye was made using microscissors. Vaseline was used to seal the hole to prevent water loss before a recording electrode was inserted into the left eye through the hole in the cornea. Try to keep a consistent depth when recording electrodes were inserted into the eye every test, the reference electrode was placed in the thorax. Each glass microelectrode was filled with 3 mol L–1 potassium acetate.
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The resistance of the said microelectrode was approximately 60 megohm. The sample stage with the mounted insect was placed on the holder of the micro-electrode propeller. The signal, which was amplified using a preamplifier (electrode amplifier L/M-1, UST-Medical-Electronic, Germany) was monitored using an oscilloscope (PM3234 0–10, Philips) and the data saved to a computer. After insertion of the electrode into the eye, the position in which the light elicited the maximum response of the eye was chosen for stimuli application. The amplitude and duration of potential was used as a proxy for the size of the retinal cell potential. The spectral sensitivity was investigated under two different conditions: (i) dark adaptation, with an adaptation time of 60 min; and (ii) light adaptation using white light, where the light intensity was approximately 100 lx and the adaptation time was also 60 min. The effects of light intensity were investigated using dark-adapted conditions, with an adaptation time of 60 min. Adaptation time refer to reported similar insect (Lall et al. 2000).
5.5. Data analysis Each ERG value from experimental recording in A. corpulenta was converted to a sensitivity value (Sn) using the following equation: Sn=100×10–(log Imax–log In)% Where, log Imax is the equivalent strength of the maximum voltage response, log In is the equivalent strength of every voltage response (Defrize et al. 2011). Graphs were produced using the software origin 8.0. Mann-Whitney U tests (Grimm 1993) were applied to determine differences in efficiency at corresponding wavelengths between sexes and between circadian rhythm of A. corpulenta.
Acknowledgements We especially thank Prof. Wei Guoshu, Hebei Agricultural University, Baoding, China, for kindly providing the equipment. We are also grateful to Dr. Zhao Xincheng, Henan Agricultural University, Zhengzhou, China, for assistance in modifying the article. This work was supported by the China Agricultural Research Stem (CARS-03) and the Special Fund for Agro-Scientific Research in Public Interest, China (201003025).
References Bernays E A, Chapman R F. 1994. Host-Plant Selection by Phytophagous Insects. Chapman & Hall, London, New York. Blahó M, Egria A, Hegedüs R, Jósvai J, Tóth M, Kertész K, Biró LP, Kriska G, Horváth G. 2012. No evidence for behavioral
responses to circularly polarized light in four scarab beetle species with circularly polarizing exocuticle. Physiology & Behavior, 105, 1067–1075. Brady P, Cummings M. 2010. Differential response to circularly polarized light by the jewel scarab beetle Chrysina gloriosa. The American Naturalist, 175, 614–620. Briscoe A D, Chittka L. 2001. The evolution of color vision in insects. Annual Review of Entomology, 46, 471–510. Brown P E, Anderson M. 1996. Spectral sensitivity of the compound eye of the cabbage root fly, Delia radicum (Diptera: Anthomyiidae). Bulletin of Entomological Research, 86, 337–342. Chapman R F, Bernays E A, Simpson S J. 1981. Attraction and repulsion of the aphid, Cavariella aegopodii by plant odours. Journal of Chemical Ecology, 7, 881–888. Childers C C, Brecht J K. 1996. Colored sticky traps for monitoring Frankliniella bispinosa (Morgan) (Thysanoptera: Thripidae) during flowering cycles in citrus. Journal of Economic Entomology, 89, 1240–1249. Cornelius M L, Duan J J, Messing R H. 1999. Visual stimuli and the response of female oriental fruit flies (Diptera: Tephritidae) to fruit mimicking traps. Journal of Economic Entomology, 92, 121–129. Defrize J, Lazzari C R, Warrant E J, Casas J. 2011. Spectral sensitivity of a colour changing spider. Journal of Insect Physiology, 57, 508–513. Dixon A F G. 1985. Aphid Ecology. Blackie, Glasgow, London. Egelhaaf M, Kern R. 2002. Vision in flying insect. Current Opinion in Neurobiology, 12, 699–706. Eguchi E, Watanabe K, Hariyama T, Yamamoto K. 1982. A comparison of electrophysiologically determined spectral responses in 35 species of Lepidoptera. Journal of Insect Physiology, 28, 675–682. Finch S, Collier R H. 2000. Host plant selection by in sects a theory based on appropriate/inappropriate landings by pest insects of cruciferous plants. Entomologia Experimentalis et Applicata, 96, 91–102. Frisch K. 1949. Die Polarisation des Himmelslichtes als orientierender Faktor bei denTänzen der Bienen. Experientia, 5, 142–148. (in German) Grimm L G. 1993. Statistical Applications for the Behavioural Sciences. John Wiley and Sons, Chichester. Harris M O, Miller J R. 1983. Color stimuli and oviposition behaviour of the onion fly Delia antiqua (Meigen) (Diptera: Anthomyiidae). Annals of the Entomological Society of America, 76, 766–771. Hasselmann E M. 1962. Über die relative spektrale Empfindlichkeit von Käfer- und Schmetterlingsaugen bei verschiedenen Helligkeiten. Physiological and Biochemical Zoology, 69, 537–576. (in German) Helen L G, Moray A. 1996. The spectral efficiency of the eye of Ephestia cautella (Walker) (Lepidoptera: Pyralidae). Journal of Stored Products Research, 32, 285–291. Horváth G, Varjú D. 2004. Polarized Light in Animal Vision. Springer-Verlag, Berlin Heidelberg, New York. Jackowska M, Bao R, Liu Z, McDonald E C, Cook T A. 2007.
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Genomic and gene regulatory signatures of cryptozoic adaptation: Loss of blue sensitive photoreceptors through expansion of long wavelength-opsin expression in the red flour beetle Tribolium castaneum. Frontiers in Zoology, 4, 24. Kirchner S M, Doring T F, Saucke H. 2005. Evidence for trichromacy in the green peach aphid, Myzus persicae (Sulz.) (Hemiptera: Aphididae). Journal of Insect Physiology, 51, 1255–1260. Klingauf F A. 1987. Host plant finding and acceptance. In: Minks A K, Harrewijn P, eds., Aphids—Their Biology, Natural Enemies and Control. Elsevier, Amsterdam. pp. 209–224. Kral K, Stelzl M. 1998. Daily visual sensitivity pattern in the green lacewing Chrysoperla carnea (Neuroptera: Chrysopidae). European Journal of Entomology, 95, 327–333. Kugel M. 1977. The time course of the electroretinogram of compound eyes in insects and its dependence on special recording conditions. Journal of Experimental Biology, 71, 1–6. Lall A B. 1981. Electroretinogram and the spectral sensitivity of the compound eyes in the firefly Photuris vermicular (Coleoptera: Lampyridae): A correspondence between green sensitivity and species bioluminescence emission. Journal of Insect Physiology, 27, 461–468. Lall A B, Chapman R M, Trouth C O, Holloway J A. 1980a. Spectral mechanisms of the compound eye in the firefly Photinus pyralis (Coleoptera: Lampyridae). Journal of Comparative Physiology, 135, 21–27. Lall A B, Lord E T, Trouth C O. 1982. Vision in the firefly Photuris Lucicrescens (Coleoptera: Lampyridae): spectral sensitivity and selective adaptation in the compound eye. Journal of Comparative Physiology, 147, 195–200. Lall A B, Seliger H H, Biggley W H, Lloyd A E.1980b. Ecology of colors of firefly bioluminescence. Science, 210, 560–562. Lall A B, Ventura D S F, Etelvino J H B, Souza J M, ColepicoloNeto P, Viviani V R. 2000. Spectral correspondence between visual spectral sensitivity and bioluminescence emission spectra in the click beetle Pyrophorus punctatissimus (Coleoptera: Elateridae). Journal of Insect Physiology, 46, 1137–114. Lin J T, Wu C Y. 1992. A comparative study on the color vision of four coleopteran insects. Bulletin of the Institute of Zoology Academia Sinica, 31, 81–88. (in Chinese) Matteson N, Terry I, Ascoli-Christensen A, Gilbert C. 1992. Spectral efficiency of the western flower thrips, Frankliniella occidentalis. Journal of Insect Physiology, 38, 453–459. Mellor H E, Bellingham J, Anderson M. 1997. Spectral efficiency of the glasshouse whitefly Trialeurodes vaporariorum and Encarsia formosa, its hymenopteran parasitoid. Entomologia Experimentalis et Applicata, 83, 11–20. Menzel R. 1979. Spectral sensitivity and colour vision in invertebrates. In: Autrum H, ed., Invertebrate Photoreceptors Handbook of Sensory Physiology. Springer-Verlagk, Berlin. pp. 503–580.
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Michio I, Kaoru T. 2008. Spectral sensitivity and wing colors of Narathura and Panchala species. Journal of Insect Physiology, 54, 1511–1515. Moericke V. 1955. Über die Lebensgewohnheiten der geflügelten Blattläuse (Aphidina) unter besonderer Berücksichtigung des Verhaltens beim Landen. Zeitschrift für Angewandte Entomologie, 37, 29–91. (in German) Oba Y, Kainuma T. 2009. Diel changes in the expression of long wavelength-sensitive and ultraviolet-sensitive opsin genes in the Japanese firefly, Luciola cruciata. Gene, 436, 66–70. Powell G, Hardie J, Pickett J A. 1995. Responses of Myzus persicae to the repellent polygodial in choice and nochoice video assays with young and mature leaf tissue. Entomologia Experimentalis et Applicata, 74, 91–94. Prokopy R J, Collier R H, Finch S.1983. Visual detection of host plants by cabbage root flies. Annual Review of Entomology, 28, 337–364. Qin J D. 1987. The evolution and reciprocity of insect and plant. In: Qin J D, eds., The Relation of Insect and Plant. Science Press, Beijing. pp. 58–136. (in Chinese) Scherer C, Kolb G. 1987. Behavioural experiments on the visual processing of colour stimuli in Pieris brassicae L. (Lepidoptera). Journal of Comparative Physiology, 160, 647–656. Sharma V, Crne M, Park J O, Srinivasarao M. 2009. Structural origin of circularly polarized iridescence in Jeweled beetles. Science, 325, 449–451. Steiner A, Rudiger P, Gemperlein R. 1987. Retinal receptor types in Aglais urticae and Pieris brassicae (Lepidoptera), revealed by analysis of the electroretinogram obtained with fourier interferometric stimulation (FIS). Journal of Comparative Physiology (A), 160, 247–258. Walther J B. 1958. Changes induced in spectral sensitivity and form of retinal action potential of the cockroach eye by selective adaptation. Journal of Insect Physiology, 2, 142–151. Wehner R. 1976. Polarised-light navigation by insects. Scientific American, 235, 106–115. Wehner R. 1981. Spatial vision in arthropods. In: Handbook of Sensory Physiology. vol. 7. Springer-Verlag, Berlin. pp. 287–616. Wei G S, Zhang Q W, Zhou M Z. 2002. Characteristic response of the compound eyes of Helicoverpa armigera to light. Acta Entomologica Sinica, 45, 323–328. (in Chinese) Wernet M F, Labhart T, Baumann F, Mazzoni E O, Pichaud F, Desplan C. 2003. Homothorax switches function of Drosophila photoreceptors from color to polarized light sensors. Cell, 115, 267–279. Wu J X. 2001. Agricultural Entomology (The North Version). China Agriculture Press, Beijing. pp. 49–50. (in Chinese) Yan H X, Wei G S, Wu W G, Yan H Y, Zhang H Q, Li Z B. 2007. Spectral sensitivity of the compound eye in the lacewing Chrysopa sinica Tejedar. Acta Entomologica Sinica, 50, 1099–1104. (in Chinese) (Managing editor SUN Lu-juan)
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RESEARCH ARTICLE
Spectral sensitivity of the compound eyes of Anomala corpulenta motschulsky (Coleoptera: Scarabaeoidea) Jiang Yue-li1, 2, Guo Yu-yuan1, 3, Wu Yu-qing2, Li Tong2, Duan Yun2, Miao Jin2, Gong Zhong-jun2, Huang Zhi-juan2 1
College of Plant Protection, Northwest A&F University, Yangling 712100, P.R.China Key Laboratory of Crop Pest Control of Henan Province/Institute of Plant Protection, Henan Academy of Agricultural Sciences, Zhengzhou 450002, P.R.China 3 State Key Laboratory for the Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, P.R.China 2
Abstract The scarab beetle, Anomala corpulenta Motschulsky (Coleoptera: Scarabaeoidea), is a widespread and destructive pest in China. Vision is one of the most important means of acquiring information about the external environment. In order to contribute to the understanding of the perception of visual stimuli in this species, the light sensitivity and spectral responses of the scarab beetle, A. corpulenta, were measured by using an electroretinogram (ERG) technique. In total, 14 monochromatic light intensities, between 340 and 605 nm, were applied to the compound eyes of A. corpulenta under varying levels of adaptation to dark and light conditions. The results showed that all light stimuli induced an ERG response, with varied amplitudes. The spectral sensitivity curve of dark-adapted eyes showed one major peak (~400 nm; near-ultraviolet), a secondary peak (from 498 to 562 nm; yellow-green) and the third peakat 460 nm. By contrast, in light-adapted eyes, only a near-UV peak was observed. From these results, we conclude that the compound eye of A. corpulenta is likely to have at least three spectral types of photoreceptor. Significance of differences were also recorded in the responses of male and female compound eyes, as well as diurnally and nocturnally. The amplitude of ERG in response to white-light stimuli varied with the light intensity: The stronger the luminance, the higher the ERG value. This suggests that the compound eye of A. corpulenta adapts quickly to changing light conditions, enabling A. corpulenta to maintain nocturnal activities. Keywords: Anomala corpulenta, electroretinogram, insect vision, spectral sensitivity, light intensity
1. Introduction Received 24 March, 2014 Accepted 23 July, 2014 JIANG Yue-li, Tel: +86-371-65738134, Mobile: 13838230695, E-mail: [email protected]; Correspondence GUO Yu-yuan, Tel: +86-10-62894786, E-mail: [email protected]; Correspondence WU Yu-qing, Tel: +86-371-65738134, E-mail: [email protected] © 2015, CAAS. All rights reserved. Published by Elsevier Ltd. doi: 10.1016/S2095-3119(14)60863-7
For insects, vision is one of the most important means of acquiring information about the external environment. It plays a significant role in finding hosts, intraspecific communication, foraging, escaping from predators and in flight (Moericke 1955; Chapman et al. 1981; Dixon 1985; Klingauf 1987; Powell et al. 1995; Egelhaaf and Kern 2002). Finch and Collier (2000) showed that visual cues were central
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link of host location phytophagous insects, for example, the butterfly Pieris rapae was found to respond strongly to blue and blue-green light over long distances to locate a suitable spawning host (Qin 1987), female fruit females tend to move to traps with red spheres attached to the center of yellow panels (Cornelius et al. 1999). In addition, many phytophagous insects prefer yellow as a cue to host location (Bernays and Chapman 1994). However, Frisch (1949) showed that the honeybee Apis mellifera detects polarized natural light and uses it for spatial navigation. Therefore, it is important to get a more comprehensive and clear understanding of the insect color vision. The scarab beetle, Anomala corpulenta Motschulsky (Coleoptera: Scarabaeoidea), is a widespread and destructive pest in China (Wu 2001). The larvae feed on the underground portion of crops, with a preference for peanuts and soybeans, whereas the adults feed on the leaves of various species of fruit and forest trees. The exocuticle of this beetle has a brilliant metallic appearance, and selectively reflects left circularly polarized light, as recorded for other jewel beetles (Sharma et al. 2009). Insects are sensitive to various characteristics of light, such as its intensity, color and polarization (Wernet et al. 2003; Horváth and Varjú 2004). In addition, visual cues are important in intraspecific communication and host location by beetles. Many studies on vision in the jewel beetles have focused on polarization (Horváth and Varjú 2004; Brady and Cummings 2010; Blahó et al. 2012). However, few have studied the presence of color vision in, and impact of light intensity on, such beetles. Therefore, there is a need to further understand the physiological basis of the color vision of jewel beetles, particularly the spectral sensitivity, and effects of light intensity. Electrophysiological spectral sensitivity has been examined for many insect species, including the cabbage root fly, Delia radicum (L.) (Brown and Anderson 1996), the cotton bollworm, Helicoverpa armigera (Hübner) (Wei et al. 2002), the western flower thrip, Frankliniella occidentalis (Pergande) (Matteson et al. 1992), Homopteran species-the glasshouse whitefly, Trialeurodes vaporariorum (Westwood) (Mellor et al. 1997), and the green peach aphid, Myzus persicae (Sulz.) (Kirchner et al. 2005), the click beetles, Pyrophorus punctatissimus in Coleoptera (Lall et al. 2000), etc. Most insects have two kinds of visual pigment, one detects light at approximately 550 nm (yellow-green) and the other detects blue-violet UV light, at less than 480 nm. However, there are no data available regarding the electrophysiological spectral sensitivity of the jewel beetles. In addition, mechanisms of adaptation to light intensity in A. corpulenta are unclear. Therefore, to investigate the spectral sensitivities and mechanisms of adaptation to light intensity of A. corpulenta, the response of A. corpulenta to different light wavelengths
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and intensities, and the effects of gender and circadian rhythm on them, were measured by means of electroretinogram (ERG) technique.
2. Results 2.1. Form of the ERG The ERG waveform of A. corpulenta elicited by a white light stimulus is a monophasic negative change in potential (Fig. 1). As can be seen from the waveform, the lower interference signals existed during stimulation. The ERG value was recorded as the negative ERG component. The greatest ERG amplitude was 35 mV.
A
18 mV B
0.2 s
Fig. 1 A typical electroretinogram recording from Anomala corpulenta under white-light stimulus. A, negative sustained potential. B, off-response.
2.2. Spectral sensitivity The spectra of ERG changes by the eyes of male and female A. corpulenta in response to light stimuli within the monochromatic 340–605 nm wavelength were recorded under certain dark and light adaptation times. The results showed that UV and most of the visible regions of the monochromatic light stimulus triggered an ERG response of A. corpulenta compound eyes with light and dark conditions adaptation. The spectral sensitivity response curves (Figs. 2–4) were obtained according to the size of the ERG amplitude. The spectral sensitivity of the dark-adapted compound eye of both male and female A. corpulenta showed one major distinct peak of sensitivity at 400 nm diurnally. The second distinct peak appeared at 524 nm (yellow-green). No clear peak was found at other wavelengths (Fig. 2). When the eyes were tested nocturnally, the spectral sensitivity curve showed three further peaks (Fig. 3). The main peak position was unchanged, whereas the secondary peak position moved from 524 to 498 nm (yellow-green). The third peak occurred at 460 nm. When the compound eyes were tested in the presence of adaptation to light, the spectral sensitivity curve of the female eyes showed only one peak, at 400 nm (Fig. 4), whereas those of the males showed three peaks: a major distinct peak at 400 nm, a second distinct peak at 498 nm (yellow-green) and the third peak at 460 nm. These peaks
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1.0
Female Male
0.9
Relative sensitivity
0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 320 340 360 380 400 420 440 460 480 500 520 540 560 580 600 620 Wavelength (nm)
Fig. 2 Spectral sensitivity curves of the compound eye of male and female A. corpulenta after dark adaptation of 60 min during the day. Data are means±SE of six individuals. The same as below. Male Female
1.0 0.9
Relative sensitivity
0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 320 340 360 380 400 420 440 460 480 500 520 540 560 580 600 620 Wavelength (nm)
Fig. 3 Spectral sensitivity curves of the compound eye of male and female A. corpulenta after dark adaptation of 60 min during the night.
were the same as, if smaller than, those recorded for the dark-adapted compound eye nocturnally. By using Mann-Whitney U test, a comparison of mean spectral efficiency between the sexes failed to show any significant differences on either day and night at corresponding wavelengths under light and dark adaptation (P>0.05). Circadian rhythm can also affect the spectral sensitivity of the compound eyes of A. corpulenta. As shown in Figs. 2 and 3, The peak was more distinct at night under dark-adaptation conditions than it was diurnally. There were no
significant differences in spectral efficiency between sexes (P>0.05), and therefore the data from males and females were combined. The Mann-Whitney U test revealed that the compound eye of A. corpulenta was significantly more efficient in the peak of 400 nm (P<0.05), 460 nm (P<0.05), 498 nm (P<0.05), 538–582 nm (P<0.05) region at night under dark-adaptation conditions than it was diurnally. There were no significant differences in 340–380 nm (P>0.05), 420–440 nm (P>0.05), 483 nm (P>0.05), 524 nm (P=0.05) and 605 nm (P>0.05) region between the day and night.
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1.0
Male Female
0.9
Relative sensitivity
0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1
320 340 360 380 400 420 440 460 480 500 520 540 560 580 600 620 Wavelength (nm)
Fig. 4 Spectral sensitivity curves of compound eye of A. corpulenta after light adaptation of 60 min.
2.3. Changes in the light intensity response of the compound eye
3. Discussion According to the ERG, we found that the ERGs recorded from the compound eyes of A. corpulenta were similar to that described in other insects, such as Curausius morosus (Kugel 1977), Periplaneta americana (L.) (Walther 1958) and many species of Lepidoptera (Eguchi et al. 1982). The results of this study show that UV and most visible monochromatic stimuli can trigger an ERG response of A. corpulenta compound eyes with light and dark conditions adaptation. Specially, we found spectral sensitivity of A. corpulenta. The curves in Figs. 2–4 suggest there are three peak regions of the spectral sensitivity system in A. corpulenta: One is in the near UV (400 nm), the second
Male Female
25 ERG response (mV)
By adjusting the neutral density filter, it was possible to stimulate the compound eyes with different intensities of white light both diurnally and nocturnally. The light intensity response of compound eyes of male and female A. corpulenta were recorded under dark-adaptation conditions (Figs. 5 and 6): The ERG value gradually increased with increases in light intensity across a range of intensity (log I=4.5–0). The increase was slow during initial light-intensity levels, but increased more quickly once the light intensity reached a certain level. The increase was not affected by gender or circadian rhythm, and the high-end platform of V-log I response was not found yet because of the limit of the light source.
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20 15 10 5 0
4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 −0.5 Relative intensity (log I)
Fig. 5 Response-intensity curves of the compound eye of male and female A. corpulenta to white light after dark adaptation of 60 min during the night.
is a broader green peak (498–562 nm) and the third peak is at 460 nm. With white adapting light, which reduces the sensitivity of any receptors in the visible range, the sensitivity curve peaks at 400 nm. From these results, one can conclude that A. corpulenta has at least three types of photoreceptor. Thus, this species is obviously similar in its visual system to other Coleoptera, such as North American fireflies (Lall et al. 1980b; Lall 1981) and Lepidoptera, such as Papilio protenor, Celastrina argiolus, Minois dryas, Neope goschkevitschii, Celastrina argiolus, Ochlodes venata and Parnara guttata (Eguchi et al. 1982) and Aglais urticae (Steiner et al. 1987).
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30
ERG response (mV)
25
Male Female
20 15 10 5 0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 −0.5 Relative intensity (log I)
Fig. 6 Response-intensity curves of the compound eye of male and female A. corpulenta to white light after dark adaptation of 60 min during the day.
Evidence of the near UV receptor (400 nm) of A. corpulenta comes from the results of both the dark adaptation (both nocturnally and diurnally) and the light adaptation tests, because the peak at 400 nm was unchanged. During the diurnal dark-adaptation test, the blue peak (at 460 nm) disappeared, but reappeared during the nocturnal dark-adaptation test. This discrepancy in results might be because A. corpulenta is nocturnal insect and, therefore, is most active during night and so has evolved a suitable dark-adapted visual system. With adaptation to white light, which reduces the sensitivity of any receptors in the visible range, the clear sensitivity curve peaked only at 400 nm, indicating the existence of a UV receptor. The near-UV spectral sensitivity recorded in A. corpulenta is a common feature of the compound eye of many insects (Briscoe and Chittka 2001). It has been demonstrated that many insects use near-UV wavelengths in navigation (Wehner 1976), and eliciting phototaxis of many insects mainly rely on the spectrum region, because it is the most effective (Helen and Moray 1996). Some researchers suggested that the UV receptor might be optimally suited to detect the open sky or to detect small objects (such as flying mates) against the bright sky (Menzel 1979). It has been hypothesised that near-ultraviolet light serves to elicit escape responses in the butterfly, Pieris (Scherer and Kolb 1987). For the green-sensitive visual pigment, a broader secondary peak in the spectral sensitivity curve, between 498 and 562 nm, was recorded from compound eyes of A. corpulenta under dark-adapted conditions. These results are similar to those from other species of Coleoptera (Hasselmann 1962; Lall et al. 1982; Lin and Wu 1992). Briscoe and Chittka (2001) reported that green-sensitive photoreceptors are also a common feature of the compound eyes
of a variety of insects. Green-sensitive photoreceptors are quite effective region of inducing some insects to greenyellow colors (Harris and Miller 1983; Prokopy et al. 1983; Bernays and Chapman 1994). Phytophagous insects may use green-sensitive photoreceptors for host location (Bernays and Chapman 1994), and wide-field motion detection (Wehner 1981). Vision is the main sense used for acquiring information from the external environment, enabling many species of insect to find mates, obtain food, escape from predators and fly (Egelhaaf and Kern 2002). In the current study, we compared the visual spectral sensitivity and the color on the exoskeletal surface in both male and female A. corpulenta. There was an approximate correlation between green color on the exoskeletal surface and the broad green visual spectral sensitivity of this insect. However, the biological meaning of the phenomenon is hard to explain. A similar phenomenon was reported in lycaenid butterflies (Michio and Kaoru 2008). The color vision of A. corpulenta beetles might be more sensitive in discriminating conspecific signals from background light (contrast enhancement) because this remarkable ability is known to mediate sexual signaling and mate choice in the scarab beetle Chrysina gloriosa (Brady and Cummings 2010). However, additional work is required to investigate this hypothesis further. The trichromatic theory of insect colour vision suggests that insects see three primary colours, green, blue and UV (Briscoe and Chittka 2001). In the current study, A. corpulenta possesses 3 types of photoreceptors, it was remarkable that the ERG of the click beetles (Coleoptera: Elateridae) was found to have just 2 spectral peaks in the ERG (Lall et al. 2000), studies showed that some members of Coleoptera lost blue opsin (Jackowska 2007; Oba 2009). Blue photoreceptors are mainly reponseable for eliciting phototaxis of many insects, such as blue sticky traps for monitoring Frankliniella bispinosa (Morgan) (Thysanoptera: Thripidae) (Childers and Brecht 1996). Further studies are required to examine molecular evidence on 3 types of photosensitive receptors and its function in A. corpulenta. A small sexe difference in spectral sensitivity curves was found in A. corpulenta beetles (Figs. 2 and 3), but there were no statistical differences between the sexes. A similar result was reported in Ephestia cautella (Helen and Moray 1996), Trialeurodes vaporariorum and Encarsia formosa (Mellor et al. 1997). It showed that the sex differentiation was not obvious. As other studies have shown, circadian rhythm can affect the spectral sensitivity of insects (Kral and Stelzl 1998; Wei et al. 2002). In the current study, we found that circadian rhythm can affect the peak position of ERG. The second distinct peak appeared from 524 nm during daylight hours to 498 nm during the night as a result of the compound eyes
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becoming dark adapted. The peak at 460 nm appeared under dark-adapted conditions nocturnally but not during daylight hours or under conditions of nocturnal light adaptation. The peaks of spectral sensitivity curves in male and female A. corpulenta were more distinct at night than it was at day, showing that the compound eyes of this species are more sensitive during the night. Such a result supports the fact that these beetles are more active during the night. In addition, intensity response of A. corpulenta is also a significant founding. In certain intensity range of the whitelight, the stronger the luminance, the higher the ERG value of eyes from A. corpulenta. This suggests that the compound eye of A. corpulenta has a strong ability to adapt to light, as also reported by Wei et al. (2002) and Yan et al. (2007). In the current study, the ERG technique was used to examine adaptive aspects of color vision in insects. This technique is not capable of exploring the characteristics of receptors or pigments which play a role in color perception and consequently it can not be used to investigate evolutionary aspects of the visual system. In order to improve our understanding of the visual physiology and photosensitive mechanisms of A. corpulenta, further study on the intracellular potential is necessary. Therefore, a combination of research at the molecular-, cellular- and whole-eye-level approach, is required to further our understanding of the physiological mechanism of A. corpulenta color vision.
4. Conclusion The compound eye of A. corpulenta is sensitive to nearUV, green-yellow and blue light, circadian rhythm can also affect the light sensitivity and spectral responses of the beetles. A. corpulenta is likely to have at least three spectral types of photoreceptor. Its compound eyes have a strong ability to adapt to light. Specifically, in part of the tested white-light intensity range, the stronger the luminance, the higher the ERG values recorded from the compound eyes of this beetle.
5. Materials and methods 5.1. Insects A. corpulenta used in the study were taken from a natural population that had been collected during the summer of 2012 in the Yuanyang Experimental Station (113.46°E, 35.08°N), Henan Academy of Agricultural Sciences, Henan Province, China. The beetles were reared on tomato plants after collecting under the following environmental conditions: 25°C 70% relative humidity (RH) and a 16 h L:8 h D photoperiod. The insects used in the experiment were l–2-wk-old adults.
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5.2. Optical system A 150-W high-pressure xenon lamp was used as a light source. The wavelength of stimulated light was obtained by using an interference filter. The light passed first through a quartz heat-protecting glass, which absorbed the infrared light, and then through a set of interference filters and neutral filters, which produced monochromatic light with different intensities. The wavelengths of monochromatic light were 340, 360, 380, 400, 420, 440, 460, 483, 498, 524, 538, 562, 582 and 605 nm. The optical path system comprised a quartz thermal-isolating glass, an interference filter, a neutral filter and neutral wedge filter, which was used to adjust the light intensity. In addition, there was a quartz condenser lens, which made parallel light sources converge on the focal plane of the light guide (inner diameter of 3 mm). The shutter drive was controlled by a computer, which was used to trigger the shutter in real-time, to regulate the time interval of light stimulating, and to enable the light beam to reach the compound eye through the light guide.
5.3. Intensity calibration The neutral filter and neutral wedge filter were used to keep the light intensity of different monochromatic lights the same; this was monitored using a thermal photoelectric-coupled illuminance meter and a galvanometer (street lighting photometer, EVANS Electroselenium Ltd., England). Each duration of light stimuli was set for 20 ms and the interval between stimuli was 40 s. In the light-intensity experiment, the light intensity of white light was increased gradually logarithmically, with a grade of 4.5, 4, 3.5, 3, 2.5, 2, 1.5, 1, 0.5 and 0 (log I), by means of a number of neutral filters. The maximum intensity was at the log 0. Each duration of light stimuli was set for 20 ms and the interval between stimuli was 10 s.
5.4. Experimental procedures Each insect was then mounted on a multidimensional adjustable ball-joint sample stage using low-melting-point wax melted onto the abdomen-thorax. The head of the insect was carefully immobilized using melted wax. Under an anatomical lens, a triangular microhole in the cornea of the left compound eye was made using microscissors. Vaseline was used to seal the hole to prevent water loss before a recording electrode was inserted into the left eye through the hole in the cornea. Try to keep a consistent depth when recording electrodes were inserted into the eye every test, the reference electrode was placed in the thorax. Each glass microelectrode was filled with 3 mol L–1 potassium acetate.
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The resistance of the said microelectrode was approximately 60 megohm. The sample stage with the mounted insect was placed on the holder of the micro-electrode propeller. The signal, which was amplified using a preamplifier (electrode amplifier L/M-1, UST-Medical-Electronic, Germany) was monitored using an oscilloscope (PM3234 0–10, Philips) and the data saved to a computer. After insertion of the electrode into the eye, the position in which the light elicited the maximum response of the eye was chosen for stimuli application. The amplitude and duration of potential was used as a proxy for the size of the retinal cell potential. The spectral sensitivity was investigated under two different conditions: (i) dark adaptation, with an adaptation time of 60 min; and (ii) light adaptation using white light, where the light intensity was approximately 100 lx and the adaptation time was also 60 min. The effects of light intensity were investigated using dark-adapted conditions, with an adaptation time of 60 min. Adaptation time refer to reported similar insect (Lall et al. 2000).
5.5. Data analysis Each ERG value from experimental recording in A. corpulenta was converted to a sensitivity value (Sn) using the following equation: Sn=100×10–(log Imax–log In)% Where, log Imax is the equivalent strength of the maximum voltage response, log In is the equivalent strength of every voltage response (Defrize et al. 2011). Graphs were produced using the software origin 8.0. Mann-Whitney U tests (Grimm 1993) were applied to determine differences in efficiency at corresponding wavelengths between sexes and between circadian rhythm of A. corpulenta.
Acknowledgements We especially thank Prof. Wei Guoshu, Hebei Agricultural University, Baoding, China, for kindly providing the equipment. We are also grateful to Dr. Zhao Xincheng, Henan Agricultural University, Zhengzhou, China, for assistance in modifying the article. This work was supported by the China Agricultural Research Stem (CARS-03) and the Special Fund for Agro-Scientific Research in Public Interest, China (201003025).
References Bernays E A, Chapman R F. 1994. Host-Plant Selection by Phytophagous Insects. Chapman & Hall, London, New York. Blahó M, Egria A, Hegedüs R, Jósvai J, Tóth M, Kertész K, Biró LP, Kriska G, Horváth G. 2012. No evidence for behavioral
responses to circularly polarized light in four scarab beetle species with circularly polarizing exocuticle. Physiology & Behavior, 105, 1067–1075. Brady P, Cummings M. 2010. Differential response to circularly polarized light by the jewel scarab beetle Chrysina gloriosa. The American Naturalist, 175, 614–620. Briscoe A D, Chittka L. 2001. The evolution of color vision in insects. Annual Review of Entomology, 46, 471–510. Brown P E, Anderson M. 1996. Spectral sensitivity of the compound eye of the cabbage root fly, Delia radicum (Diptera: Anthomyiidae). Bulletin of Entomological Research, 86, 337–342. Chapman R F, Bernays E A, Simpson S J. 1981. Attraction and repulsion of the aphid, Cavariella aegopodii by plant odours. Journal of Chemical Ecology, 7, 881–888. Childers C C, Brecht J K. 1996. Colored sticky traps for monitoring Frankliniella bispinosa (Morgan) (Thysanoptera: Thripidae) during flowering cycles in citrus. Journal of Economic Entomology, 89, 1240–1249. Cornelius M L, Duan J J, Messing R H. 1999. Visual stimuli and the response of female oriental fruit flies (Diptera: Tephritidae) to fruit mimicking traps. Journal of Economic Entomology, 92, 121–129. Defrize J, Lazzari C R, Warrant E J, Casas J. 2011. Spectral sensitivity of a colour changing spider. Journal of Insect Physiology, 57, 508–513. Dixon A F G. 1985. Aphid Ecology. Blackie, Glasgow, London. Egelhaaf M, Kern R. 2002. Vision in flying insect. Current Opinion in Neurobiology, 12, 699–706. Eguchi E, Watanabe K, Hariyama T, Yamamoto K. 1982. A comparison of electrophysiologically determined spectral responses in 35 species of Lepidoptera. Journal of Insect Physiology, 28, 675–682. Finch S, Collier R H. 2000. Host plant selection by in sects a theory based on appropriate/inappropriate landings by pest insects of cruciferous plants. Entomologia Experimentalis et Applicata, 96, 91–102. Frisch K. 1949. Die Polarisation des Himmelslichtes als orientierender Faktor bei denTänzen der Bienen. Experientia, 5, 142–148. (in German) Grimm L G. 1993. Statistical Applications for the Behavioural Sciences. John Wiley and Sons, Chichester. Harris M O, Miller J R. 1983. Color stimuli and oviposition behaviour of the onion fly Delia antiqua (Meigen) (Diptera: Anthomyiidae). Annals of the Entomological Society of America, 76, 766–771. Hasselmann E M. 1962. Über die relative spektrale Empfindlichkeit von Käfer- und Schmetterlingsaugen bei verschiedenen Helligkeiten. Physiological and Biochemical Zoology, 69, 537–576. (in German) Helen L G, Moray A. 1996. The spectral efficiency of the eye of Ephestia cautella (Walker) (Lepidoptera: Pyralidae). Journal of Stored Products Research, 32, 285–291. Horváth G, Varjú D. 2004. Polarized Light in Animal Vision. Springer-Verlag, Berlin Heidelberg, New York. Jackowska M, Bao R, Liu Z, McDonald E C, Cook T A. 2007.
JIANG Yue-li et al. Journal of Integrative Agriculture 2015, 14(4): 706–713
Genomic and gene regulatory signatures of cryptozoic adaptation: Loss of blue sensitive photoreceptors through expansion of long wavelength-opsin expression in the red flour beetle Tribolium castaneum. Frontiers in Zoology, 4, 24. Kirchner S M, Doring T F, Saucke H. 2005. Evidence for trichromacy in the green peach aphid, Myzus persicae (Sulz.) (Hemiptera: Aphididae). Journal of Insect Physiology, 51, 1255–1260. Klingauf F A. 1987. Host plant finding and acceptance. In: Minks A K, Harrewijn P, eds., Aphids—Their Biology, Natural Enemies and Control. Elsevier, Amsterdam. pp. 209–224. Kral K, Stelzl M. 1998. Daily visual sensitivity pattern in the green lacewing Chrysoperla carnea (Neuroptera: Chrysopidae). European Journal of Entomology, 95, 327–333. Kugel M. 1977. The time course of the electroretinogram of compound eyes in insects and its dependence on special recording conditions. Journal of Experimental Biology, 71, 1–6. Lall A B. 1981. Electroretinogram and the spectral sensitivity of the compound eyes in the firefly Photuris vermicular (Coleoptera: Lampyridae): A correspondence between green sensitivity and species bioluminescence emission. Journal of Insect Physiology, 27, 461–468. Lall A B, Chapman R M, Trouth C O, Holloway J A. 1980a. Spectral mechanisms of the compound eye in the firefly Photinus pyralis (Coleoptera: Lampyridae). Journal of Comparative Physiology, 135, 21–27. Lall A B, Lord E T, Trouth C O. 1982. Vision in the firefly Photuris Lucicrescens (Coleoptera: Lampyridae): spectral sensitivity and selective adaptation in the compound eye. Journal of Comparative Physiology, 147, 195–200. Lall A B, Seliger H H, Biggley W H, Lloyd A E.1980b. Ecology of colors of firefly bioluminescence. Science, 210, 560–562. Lall A B, Ventura D S F, Etelvino J H B, Souza J M, ColepicoloNeto P, Viviani V R. 2000. Spectral correspondence between visual spectral sensitivity and bioluminescence emission spectra in the click beetle Pyrophorus punctatissimus (Coleoptera: Elateridae). Journal of Insect Physiology, 46, 1137–114. Lin J T, Wu C Y. 1992. A comparative study on the color vision of four coleopteran insects. Bulletin of the Institute of Zoology Academia Sinica, 31, 81–88. (in Chinese) Matteson N, Terry I, Ascoli-Christensen A, Gilbert C. 1992. Spectral efficiency of the western flower thrips, Frankliniella occidentalis. Journal of Insect Physiology, 38, 453–459. Mellor H E, Bellingham J, Anderson M. 1997. Spectral efficiency of the glasshouse whitefly Trialeurodes vaporariorum and Encarsia formosa, its hymenopteran parasitoid. Entomologia Experimentalis et Applicata, 83, 11–20. Menzel R. 1979. Spectral sensitivity and colour vision in invertebrates. In: Autrum H, ed., Invertebrate Photoreceptors Handbook of Sensory Physiology. Springer-Verlagk, Berlin. pp. 503–580.
713
Michio I, Kaoru T. 2008. Spectral sensitivity and wing colors of Narathura and Panchala species. Journal of Insect Physiology, 54, 1511–1515. Moericke V. 1955. Über die Lebensgewohnheiten der geflügelten Blattläuse (Aphidina) unter besonderer Berücksichtigung des Verhaltens beim Landen. Zeitschrift für Angewandte Entomologie, 37, 29–91. (in German) Oba Y, Kainuma T. 2009. Diel changes in the expression of long wavelength-sensitive and ultraviolet-sensitive opsin genes in the Japanese firefly, Luciola cruciata. Gene, 436, 66–70. Powell G, Hardie J, Pickett J A. 1995. Responses of Myzus persicae to the repellent polygodial in choice and nochoice video assays with young and mature leaf tissue. Entomologia Experimentalis et Applicata, 74, 91–94. Prokopy R J, Collier R H, Finch S.1983. Visual detection of host plants by cabbage root flies. Annual Review of Entomology, 28, 337–364. Qin J D. 1987. The evolution and reciprocity of insect and plant. In: Qin J D, eds., The Relation of Insect and Plant. Science Press, Beijing. pp. 58–136. (in Chinese) Scherer C, Kolb G. 1987. Behavioural experiments on the visual processing of colour stimuli in Pieris brassicae L. (Lepidoptera). Journal of Comparative Physiology, 160, 647–656. Sharma V, Crne M, Park J O, Srinivasarao M. 2009. Structural origin of circularly polarized iridescence in Jeweled beetles. Science, 325, 449–451. Steiner A, Rudiger P, Gemperlein R. 1987. Retinal receptor types in Aglais urticae and Pieris brassicae (Lepidoptera), revealed by analysis of the electroretinogram obtained with fourier interferometric stimulation (FIS). Journal of Comparative Physiology (A), 160, 247–258. Walther J B. 1958. Changes induced in spectral sensitivity and form of retinal action potential of the cockroach eye by selective adaptation. Journal of Insect Physiology, 2, 142–151. Wehner R. 1976. Polarised-light navigation by insects. Scientific American, 235, 106–115. Wehner R. 1981. Spatial vision in arthropods. In: Handbook of Sensory Physiology. vol. 7. Springer-Verlag, Berlin. pp. 287–616. Wei G S, Zhang Q W, Zhou M Z. 2002. Characteristic response of the compound eyes of Helicoverpa armigera to light. Acta Entomologica Sinica, 45, 323–328. (in Chinese) Wernet M F, Labhart T, Baumann F, Mazzoni E O, Pichaud F, Desplan C. 2003. Homothorax switches function of Drosophila photoreceptors from color to polarized light sensors. Cell, 115, 267–279. Wu J X. 2001. Agricultural Entomology (The North Version). China Agriculture Press, Beijing. pp. 49–50. (in Chinese) Yan H X, Wei G S, Wu W G, Yan H Y, Zhang H Q, Li Z B. 2007. Spectral sensitivity of the compound eye in the lacewing Chrysopa sinica Tejedar. Acta Entomologica Sinica, 50, 1099–1104. (in Chinese) (Managing editor SUN Lu-juan)