Tag Archives: fluorescence

Chameleons display fluorescent bones on the skull, study shows

The lizard master of disguise is surely a very special creature, we can all agree. Researchers discovered a new outstanding feature of the chameleon: its bones shine with a blue hue in UV light.

Fluorescent tubercles showing sexual dimorphism under UV light at 365 nm (A–D) and fluorescence in further chameleon genera (E–G). (A) Male Calumma crypticum ZSM 32/2016. (B) Female C. crypticum ZSM 67/2005. (C) Male C. cucullatum ZSM 655/2014. (D) Female C. cucullatum ZSM 654/2014. (E) Brookesia superciliaris, male (only UV light at 365 nm). (F) Bradypodion transvaalense, male (dim light and additional UV light at 395 nm). (G) Furcifer pardalis, male (daylight and additional UV light at 365 nm).

Bioluminescence is not that uncommon among marine creatures and some insects (see fireflies), but most terrestrial animals don’t quite possess this eye-endearing feature. The fact that researchers found biogenic fluorescence in chameleons — an entirely earthbound animal — is surprising.

Male C. globifer (ZSM 141/2016) showing congruent tubercle/fluorescent patterns (from left to right); top row: alive in the field under sunlight, micro-CT scan of head surface (probable edge artefact in cheek region), micro-CT scan of the skull; bottom row: alive in the field under UV light, ethanol-preserved under UV light.

Male C. globifer (ZSM 141/2016) showing congruent tubercle/fluorescent patterns (from left to right); top row: alive in the field under sunlight, micro-CT scan of head surface (probable edge artefact in cheek region), micro-CT scan of the skull; bottom row: alive in the field under UV light, ethanol-preserved under UV light.

“We could hardly believe our eyes when we illuminated the chameleons in our collection with a UV lamp, and almost all species showed blue, previously invisible patterns on the head, some even over the whole body,” said David Prötzel, lead author of the new study and a Ph.D. student at the Bavarian State Collection of Zoology (ZSM).

German biologists found that the small bone bumps on chameleons’ heads fluoresce under UV light in a blueish shade. These tiny bone structures absorb UV radiation through small “windows” in the skin and then emit a soft blue light. Actually, the windows are just metaphorical, because the thin epidermis layer that covers the projections is transparent.

After seeing their shimmer under UV-lighting, scientists performed microCT scans and matched the small bone tuberosities to the blue colored pattern.

The fact that bones fluoresce under UV conditions was long-known. But using this phenomenon to intentionally fluoresce different body parts surprised the authors, as it was the first time scientists had encountered such a feature.

Okay, okay, but what’s the deal with all this effort to display such a multitude of colors, even fluorescence?

The myth that chameleons use color-change as camouflage has been debunked. A new theory states that these reptiles use skin color-shifting as a way to communicate with their kin. Taking into consideration that most males from the Calumna genus have significantly more fluorescent tubercles than the females, researchers suppose that their goal is to attract mates. Blue, being a rare color in the forest, should be quite eye-catching in this regard.

The well-known panther chameleon (Furcifer pardalis) which is also popular as a pet, shows fluorescent crests on the head. (David Prötzel; ZSM/LMU)

Another interesting observation is the distribution of fluorescence among different genera of chameleons. Researchers discovered that forest-living species are more prone to exhibit glowing tubercles than species which live in open environments.

“As shorter (UV, blue) wavelengths are scattered more strongly than longer wavelengths the UV component under the diffuse irradiation in the forest shade is relatively higher compared to the direct irradiation by the sunlight,” the authors write in the journal Nature.

“Consequently, using UV reflections for communication is apparently more common in closed habitats than in open habitats, as has been shown in chameleons of the genus Bradypodion.”

New camera for ultrafast photography shoots one hundred billion frames per second

High speed photography is no longer a new thing… but then again, it depends what you mean by high speed photography; you likely don’t mean one hundred billion frames per second (100,000,000,000 fps) – but that’s exactly what Liang Gao, Assistant Professor at Stony Brook University means. He and his team have developed the world’s  fastest receive-only 2-D camera.

Reflection of laser pulse. Credits: Liang et al, 2014. Note: ps stands for pico second, one trillionth of a second.

Using the Washington University technique, called compressed ultrafast photography (CUP), Wang and his colleagues have made movies of things we could have previously only imagined: laser pulse reflection, refraction, faster-than light propagation of what is called non-information, and photon racing in two media. You can see all these here.

As a matter of fact, the technology is too advanced – so there are quite some problems with it.

“For the first time, humans can see light pulses on the fly,” Wang says. “Because this technique advances the imaging frame rate by orders of magnitude, we now enter a new regime to open up new visions. Each new technique, especially one of a quantum leap forward, is always followed a number of new discoveries. It’s our hope that CUP will enable new discoveries in science — ones that we can’t even anticipate yet.”

Refraction of laser pulse. Credits: Liang et al., 2014

Of course the camera doesn’t look like your average Canon or Nikon – it’s actually a series of devices envisioned to work with high-powered microscopes and telescopes to capture dynamic natural and physical phenomena. The raw data is gathered, sent to a computer, and only there does the image form – this is called computational imaging.

 “These ultrafast cameras have the potential to greatly enhance our understanding of very fast biological interactions and chemical processes and allow us to build better models of complex, dynamical systems.” said Richard Conroy, PhD, program director of optical imaging at the National Institute of Biomedical Imaging and Bioengineering.

Indeed, aside for being incredibly cool, this camera also has many potential applications; the most obvious ones are in biomedicine, which is actually what the team had in mind. For example, scientists can detect extremely subtle changes in cellular environmental conditions like pH or oxygen pressure. The technique could also be applied to astronomy, where scientists could analyze the temporal activities of a supernova that occurred many light years away, and in forensics – for bullet trajectory analysis.

Speed of laser pulse in different mediums. Credits: Liang et al.

“Combine CUP imaging with the Hubble Telescope, and we will have both the sharpest spatial resolution of the Hubble and the highest temporal solution with CUP,” he says. “That combination is bound to discover new science.”

Another special area of application could be fluorescence – the emission of light by a substance that has previously absorbed light; one of the movies researchers published shows a green excitation light pulsing toward fluorescent molecules on the right where the green converts to red, which is the fluorescence. Wang explains why this is important:

Fluorescence excitation and emission. Credits: Liang et al, 2014.

“Fluorescence is an important aspect of biological technologies,” he says. “We can use CUP to image the lifetimes of various fluorophores, including fluorescent proteins, at light speed.”

Journal Reference:

  1. Liang Gao, Jinyang Liang, Chiye Li, Lihong V. Wang. Single-shot compressed ultrafast photography at one hundred billion frames per second. Nature, 2014; 516 (7529): 74 DOI: 10.1038/nature14005. *note: as we were telling you a few days ago, you can now freely access all the articles on Nature for free!