Retinal and optical adaptations for nocturnal vision in the halictid bee Megalopta genalis

Greiner, Birgit; Ribi, Willi A.; Warrant, Eric J.

doi:10.1007/s00441-004-0883-9

Cited by 144 publications

(145 citation statements)

References 43 publications

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“…It may be too early yet to decide (Warrant et al 2003), but we note that recently studied nocturnal bees have not developed optical superposition eyes. The only major modification is a huge increase of the rhabdom diameter, whereas the apposition optics is essentially unchanged (Greiner et al 2004).…”

Section: Discussionmentioning

confidence: 99%

Light on the moth-eye corneal nipple array of butterflies

et al. 2005

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The outer surface of the facet lenses in the compound eyes of moths consists of an array of excessive cuticular protuberances, termed corneal nipples. We have investigated the moth-eye corneal nipple array of the facet lenses of 19 diurnal butterfly species by scanning electron microscopy, transmission electron microscopy and atomic force microscope, as well as by optical modelling. The nipples appeared to be arranged in domains with almost crystalline, hexagonal packing. The nipple distances were found to vary only slightly, ranging from about 180 to 240 nm, but the nipple heights varied between 0 (papilionids) and 230 nm (a nymphalid), in good agreement with previous work. The nipples create an interface with a gradient refractive index between that of air and the facet lens material, because their distance is distinctly smaller than the wavelength of light. The gradient in the refractive index was deduced from effective medium theory. By dividing the height of the nipple layer into 100 thin slices, an optical multilayer model could be applied to calculate the reflectance of the facet lenses as a function of height, polarization and angle of incidence. The reflectance progressively diminished with increased nipple height. Nipples with a paraboloid shape and height 250 nm, touching each other at the base, virtually completely reduced the reflectance for normally incident light. The calculated dependence of the reflectance on polarization and angle of incidence agreed well with experimental data, underscoring the validity of the modelling. The corneal nipples presumably mainly function to reduce the eye glare of moths that are inactive during the day, so to make them less visible for predators. Moths are probably ancestral to the diurnal butterflies, suggesting that the reduced size of the nipples of most butterfly species indicates a vanishing trait. This effect is extreme in papilionids, which have virtually absent nipples, in line with their highly developed status. A similar evolutionary development can be noticed for the tapetum of the ommatidia of lepidopteran eyes. It is most elaborate in moth-eyes, but strongly reduced in most diurnal butterflies and absent in papilionids.

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Section: Discussionmentioning

confidence: 99%

Light on the moth-eye corneal nipple array of butterflies

et al. 2005

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“…Also, corneal facet diameters are 1.8 times larger, and rhabdom diameters 4-5 times larger, than those of diurnal halictids (Greiner et al, 2004a). These optical adaptations together make the eyes of M. genalis 27 times more sensitive than those of their diurnal counterparts (Greiner et al, 2004a;Warrant et al, 2004); this is a worthwhile improvement, but not enough to explain their visual behaviors, such as landing at the nest entrance at night (Warrant et al, 2004). What Megalopta The sweat bee Megalopta (Hymenoptera: Halictidae), unlike most bees, flies in extremely dim light.…”

Section: Introductionmentioning

confidence: 84%

Flight performance in night-flying sweat bees suffers at low light levels

Theobald

Coates

Wcislo

et al. 2007

Journal of Experimental Biology

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SUMMARY The sweat bee Megalopta (Hymenoptera: Halictidae), unlike most bees, flies in extremely dim light. And although nocturnal insects are often equipped with superposition eyes, which greatly enhance light capture, Megalopta performs visually guided flight with apposition eyes. We examined how light limits Megalopta's flight behavior by measuring flight times and corresponding light levels and comparing them with flight trajectories upon return to the nest. We found the average time to land increased in dim light, an effect due not to slow approaches, but to circuitous approaches. Some landings, however, were quite fast even in the dark. To explain this, we examined the flight trajectories and found that in dim light, landings became increasingly error prone and erratic, consistent with repeated landing attempts. These data agree well with the premise that Megalopta uses visual summation, sacrificing acuity in order to see and fly at the very dimmest light intensities that its visual system allows.

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“…The nocturnal halictid bee Megalopta genalis, for instance, is an insect with apposition eyes that is active at intensities about ten times dimmer than starlight Kelber et al, 2006). In order to achieve this, M. genalis has enlarged facets and rhabdoms, as well as compromised spatial and temporal resolution, all of which favour increased sensitivity Greiner et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

Visual sensitivity in the crepuscular owl butterfly Caligo memnon and the diurnal blue morpho Morpho peleides: a clue to explain the evolution of nocturnal apposition eyes?

Frederiksen

Warrant

2008

Journal of Experimental Biology

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SUMMARYInsects active in dim light, such as moths and many beetles, normally have superposition compound eyes to increase photon capture. But there are nocturnal and crepuscular insects -such as some species of bees, wasps and butterflies -that have apposition compound eyes. These are likely to have adaptations -including large eye and facet size and coarsened spatial and temporal resolution -that improve their sensitivity and thus their visual reliability. Is this also true for crepuscular insects that are active at intermediate intensities? To test this hypothesis, the visual performance of two closely related butterflies, the diurnal blue morpho Morpho peleides and the crepuscular owl butterfly Caligo memnon, were compared. Compared to the diurnal M. peleides, the crepuscular C. memnon does not appear to be adapted to a nocturnal lifestyle in terms of spatial resolution: the interommatidial angle ⌬ is similar in both species, and acceptance angles, ⌬, are only marginally larger in C. memnon. Moreover, temporal resolution is only a little coarser in C. memnon compared to M. peleides. Using a model for sensitivity, we found that the eyes of C. memnon are about four times as light-sensitive as those of M. peleides in the frontal visual field, much of this difference being due to the larger facet diameters found in C. memnon. In summary, greater visual sensitivity has evolved in C. memnon than in M. peleides, showing that adaptations that improve sensitivity can be found not only in nocturnal apposition eyes, but also on a smaller scale in crepuscular apposition eyes.

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Retinal and optical adaptations for nocturnal vision in the halictid bee Megalopta genalis

Cited by 144 publications

References 43 publications

Light on the moth-eye corneal nipple array of butterflies

Light on the moth-eye corneal nipple array of butterflies

Flight performance in night-flying sweat bees suffers at low light levels

Visual sensitivity in the crepuscular owl butterfly Caligo memnon and the diurnal blue morpho Morpho peleides: a clue to explain the evolution of nocturnal apposition eyes?

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