The secret behind the eerie glow of two shark species has been revealed in a study that sheds light on the origin and possible advantages of their fluorescent green bodies.
Chain catsharks and swell sharks are deep-dwelling and live in the western Atlantic and eastern Pacific respectively, where they hide among rocks and rubble. While at first glance they appear to be in various shades of brown, recent studies have shown that under blue light they glow green. Crucially, only blue light penetrates the depths of the ocean.
Now scientists have pinpointed the chemicals behind the phenomenon, which not only cause the green glow, but possibly help defend the sharks against harmful microbes. “We have so much more to learn about life in the ocean and sharks,” said professor David Gruber, of City University of New York, a co-author of the study.
The green glow emitted by the sharks is a type of biofluorescence, which arises when blue light in the oceans is absorbed and then re-emitted, in this case as green light. Writing in the journal iScience, the team said the green glow of the sharks was limited to certain parts of their bodies — typically where the skin was paler or where there were white spots.
The team took skin tissue samples and analyzed them, finding between the two species a range of eight fluorescent molecules that glowed when blue light was shone on them. Among those predominantly found in the paler areas of the skin was one in particular, present in both species, that gave off a bright green glow.
The team’s previous research has suggested that the visual system of these sharks seems tuned in to such hues. “They just have one visual pigment in their eye,” said Gruber. “It sees right at the blue-green interface.”
Gruber said the research suggested the glow might aid communication between the sharks, noting that males and females showed different light patterns. “If these sharks are absorbing blue and then creating green [light], they are creating contrasts for each other, because there is no green [light] down there except the green that they are producing on their skin,” he added.
The study suggests that there might be additional benefits. The team tested the fluorescent substances for their action against certain bacteria: one found in marine environments and the other MRSA — the hospital superbug. Growth of both bacteria were found to be hampered by some of the substances within the sharks’ skin — a finding the team says might indicate that molecules involved in biofluorescence could also be part of microbial defense.
“These sharks lay on the bottom and the bottom has a high density of bacteria,” said Gruber, adding that substances in the skin might protect the animals. “We are just hypothesizing it could be a way to stop things from growing on the shark.”
1. fluorescent adj.
(ying2 guang1 de5)
2. microbe n.
(wei2 sheng1 wu4, xi4 jun4)
3. emit v.
(fa1 san4, pai2 fang4)
4. absorb v.
5. tune in phr.
(tiao2 zheng3 wei2)
6. hypothesize v.
The Western Section of the Taipei Metro’s Circular Line (the Yellow Line) in New Taipei City has been in operation since Jan. 31. On Sept. 6, someone riding in a Metro train car saw the quite moving scene of an elderly workman sitting on a paint pail that he had with him because he was afraid of dirtying the seats. Some netizens were moved to tears by the story. The person posted a photo on the “Baofei Commune” Facebook group. He said that when he was on the Circular Line in New Taipei City, he had come across an elderly workman
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Let’s go for a spin in my new set of wheels (2/5) 坐我的新車去兜風吧（二） A: How about we organize a road trip to test out my new set of wheels? B: Alright. Any thoughts on where to go? A: I’m thinking of driving along the east coast and staying in Taitung for a long weekend. What do you think? B: That’s a great idea — but does your vintage car have air conditioning? A: I’m afraid not, but at least the weather is starting to cool down now. How about this Saturday? B: Sure. Let’s do it! A: 我們來規劃一趟公路旅行，試試我的新車，你覺得如何？ B: 好啊。你有想到去哪裡嗎？ A: 我打算沿著東海岸開，然後週末連假待在台東。你覺得呢？ B: 那真是太棒了──不過，你的經典車有空調嗎？ A: 恐怕沒有哦，反正天氣開始變涼了。星期六出發怎麼樣？ B: 當然。就這麼做吧！ （Edward Jones, Taipei Times／台北時報章厚明譯） English 英文: Chinese 中文:
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