| 1. |
- Beal, Jacob, et al.
(författare)
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Robust estimation of bacterial cell count from optical density
- 2020
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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| 2. |
- Coates, Melissa M., et al.
(författare)
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The spectral sensitivity of the lens eyes of a box jellyfish, Tripedalia cystophora (Conant)
- 2006
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Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 1477-9145 .- 0022-0949. ; 209:19, s. 3758-3765
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Tidskriftsartikel (refereegranskat)abstract
- Box jellyfish, or cubomedusae (class Cubozoa), are unique among the Cnidaria in possessing lens eyes similar in morphology to those of vertebrates and cephalopods. Although these eyes were described over 100 years ago, there has been no work done on their electrophysiological responses to light. We used an electroretinogram ( ERG) technique to measure spectral sensitivity of the lens eyes of the Caribbean species Tripedalia cystophora. The cubomedusae have two kinds of lens eyes, the lower and upper lens eyes. We found that both lens eye types have similar spectral sensitivities, which likely result from the presence of a single receptor type containing a single opsin. The peak sensitivity is to blue-green light. Visual pigment template fits indicate a vitamin A-1 based opsin with peak sensitivity near 500 nm for both eye types.
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| 3. |
- Coates, Melissa
(författare)
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Visual ecology and functional morphology of Cubozoa (Cnidaria)
- 2003
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Ingår i: Integrative and Comparative Biology. - : Oxford University Press (OUP). - 1557-7023 .- 1540-7063. ; 43:4, s. 542-548
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Tidskriftsartikel (refereegranskat)abstract
- Jellyfish belong to one of the oldest extant animal phyla, the Cnidaria. The first Cnidaria appear in the fossil record 600 million years ago, preceeding the Cambrian explosion. They are an extremely successful group present in all marine environments and some freshwater environments. In contrast to many animal phyla in which vision is a primary sense Cnidarians do not, generally, employ image forming eyes. One small class stands alone: the Cubozoa. Cubomedusae are commonly known as box jellyfish. They possess image forming eyes (Coates et al., 2001) which certainly evolved independently from other metazoans. Cubomedusae therefore offer a unique perspective on the evolution of image forming eyes. This literature review collects, into one place, what is known about: the multiple eye types of box jellyfish, cubomedusan life history and ecology, and the sensory and neural systems of box jellyfish. Here I discuss how these features set cubomedusae apart from scyphomedusae and hydromedusae. Knowledge in these areas is sparse; the work done to date inspires increased efforts.
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| 4. |
- Garm, Anders, et al.
(författare)
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The lens eyes of the box jellyfish Tripedalia cystophora and Chiropsalmus sp. are slow and color-blind
- 2007
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Ingår i: Journal of Comparative Physiology A. - : Springer Science and Business Media LLC. - 1432-1351 .- 0340-7594. ; 193:5, s. 547-557
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Tidskriftsartikel (refereegranskat)abstract
- Box jellyfish, or cubomedusae, possess an impressive total of 24 eyes of four morphologically different types. Compared to other cnidarians they also have an elaborate behavioral repertoire, which for a large part seems to be visually guided. Two of the four types of cubomedusean eyes, called the upper and the lower lens eye, are camera type eyes with spherical fish-like lenses. Here we explore the electroretinograms of the lens eyes of the Caribbean species, Tripedalia cystophora, and the Australian species, Chiropsalmus sp. using suction electrodes. We show that the photoreceptors of the lens eyes of both species have dynamic ranges of about 3 log units and slow responses. The spectral sensitivity curves for all eyes peak in the blue-green region, but the lower lens eye of T. cystophora has a small additional peak in the near UV range. All spectral sensitivity curves agree well with the theoretical absorbance curve of a single opsin, strongly suggesting color-blind vision in box jellyfish with a single receptor type. A single opsin is supported by selective adaptation experiments.
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| 5. |
- Nilsson, Dan-E, et al.
(författare)
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Advanced optics in a jellyfish eye
- 2005
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 435:7039, s. 201-205
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Tidskriftsartikel (refereegranskat)abstract
- Cubozoans, or box jellyfish, differ from all other cnidarians by an active fish-like behaviour and an elaborate sensory apparatus(1,2). Each of the four sides of the animal carries a conspicuous sensory club ( the rhopalium), which has evolved into a bizarre cluster of different eyes(3). Two of the eyes on each rhopalium have long been known to resemble eyes of higher animals, but the function and performance of these eyes have remained unknown(4). Here we show that box-jellyfish lenses contain a finely tuned refractive index gradient producing nearly aberration-free imaging. This demonstrates that even simple animals have been able to evolve the sophisticated visual optics previously known only from a few advanced bilaterian phyla. However, the position of the retina does not coincide with the sharp image, leading to very wide and complex receptive fields in individual photoreceptors. We argue that this may be useful in eyes serving a single visual task. The findings indicate that tailoring of complex receptive fields might have been one of the original driving forces in the evolution of animal lenses.
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| 6. |
- Theobald, Jamie, et al.
(författare)
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Flight performance in night-flying sweat bees suffers at low light levels.
- 2007
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Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 1477-9145 .- 0022-0949. ; 210:22, s. 4034-4042
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Tidskriftsartikel (refereegranskat)abstract
- 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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