揽瓜阁俱乐部第二期 Day6 2020.06.20
【自然科学-生物】 The Sea's Weirdest Creatures, Now in 'Staggering' Detail （709字 精读 必做篇）
The bizarre life of the sea’s middle depths has long been a challenge to see, study and fathom. The creatures of that realm live under crushing pressures at icy temperatures in pitch darkness. The fluid environment is unbound by gravity and hard surfaces, so natural selection allows for a riotous array of unfamiliar body parts and architectures. By human standards, these organisms are aliens.
Now, a new kind of laser is illuminating some of the most otherworldly life-forms. The soft bodies of the abyssal class are made of mucoid and gelatinous materials — somewhat like jellyfish, only stranger. They feature mazes of translucent parts and gooey structures, including long filaments, mucus housings and fine-mesh filters for gathering food. Recently, in the depths off Western Australia, scientists filmed a gelatinous type known as a siphonophore whose length was estimated at 150 feet — potentially the world’s longest example of oceanic life.
On June 3 in Nature magazine, a team of seven scientists from the Monterey Bay Aquarium Research Institute in California and the Pontifical Catholic University of Chile in Santiago described an imaging device for studying these translucent creatures. It emits a thin fan of laser light that scans through the animals, gathers backscattered rays from the inner flows and tissues, and feeds those gleanings into a computer that visually reconstructs the living organisms in subtle detail. The device, called the DeepPIV imaging system, reveals the insides much as CT scans do for human bodies.
“It’s staggering,” Bruce H. Robison, a marine biologist at MBARI who participated in the research, said of the new technique in an interview. “It’s going to open things up in a really good way.”
The team conducted its explorations off the California coast in Monterey Bay, which features a deep canyon. A robot holding the imager was lowered on a long tether, resulting in the scrutiny of scores of creatures at depths of up to a quarter mile.
Kakani Katija, an engineer at the marine institute and the paper’s lead author, said the new technique would help unveil how the gooey animals do such things as move, feed, procreate and protect themselves. “Now that we have a way to visualize these structures, we can finally understand how they function,” she said.
In the Nature article, the team told of directing the novel device at an abyssal creature known as a giant larvacean, a marvel of nature that can secrete balloon-like mucus feeding structures as wide as three feet. Within a large structure are smaller, fist-size filters that the animals use to gather prey and tiny particles.
Using the new technique, Dr. Katija and her collaborators were able, for the first time, to map the structure of the larvacean’s inner filter, identifying its precise shape and the exact function of its parts. Added computer power let team members turn the visualization into a movie that enabled them to effectively fly through the filter and scrutinize its flows.
Until now, no scientist has had the chance to examine such complicated structures in the deep creatures, Dr. Katija said. Such visualizations, she and her team wrote in their paper, “can shed light on some of nature’s most complex forms.”
The paper’s other authors are Giancarlo Troni, Joost Daniels, Kelly Lance, Rob E. Sherlock, Alana D. Sherman and Dr. Robison. Except for Dr. Troni, an engineer at the Catholic university in Santiago, the researchers work at the California marine institute.
The new technique could — at least potentially — have an enormous impact on marine science, because the world’s oceans are so vast and the denizens of their inky depths so mysterious. Scientists estimate that more than 99 percent of the planet’s biosphere resides in the oceans. Fishermen know its surface waters, but in general, compared to land, the global ocean is unknown.
Dr. Robison has estimated that up to half the creatures of the sea remain undiscovered — mainly the otherworldly ones of the middle depths.
“If an alien civilization came to look at the dominant life form on the planet, they’d be out looking at midwater creatures,” he said in 1994. “In terms of biomass, numbers of individuals, geographical extent — any way you want to slice it — these are the biggest ecological entities on earth. But we know virtually nothing about them.”
Source: The New York Times
【自然科学-生物】 Bioluminescence Helps Prey Avoid Hungry Seals （452字 2分38秒 精听 必做篇）
先做精听再核对原文哦~
Deep in the inky depths of what’s called the ocean’s mesopelagic zone, more than five hundred meters below the surface, the main source of light is not the sun. Even during the day. Most of the light comes instead from bioluminescent organisms, creatures that produce their own light. It's in these dark depths that southern elephant seals love to feast on squids and fish.
"Initially we wanted to know how elephant seals find their prey in the dark."
Pauline Goulet from the University of St. Andrews Sea Mammal Research Unit.
Thanks to data logging technology, researchers have a fairly good handle on how far elephant seals travel to feed, and how long and how deep they dive. But nobody really knew how they find their prey in the darkness. Do they track the lights, or is something else going on?
"So we built a sensor that could pick up flashes produced by animals that were being hunted by the elephant seal…because we thought that elephant seals might be looking for that light to catch a snack."
But it turned out that the fish actually used their bioluminescence to disorient seals after the seals began their attack.
"The thing is it seemed that the flashing prey were harder to catch than the non-flashing prey. Which we found out by looking at the duration of the chase, which was longer for flashing prey."
The fish flash was always emitted just after the seal launched an attack, making it a defensive, reactive maneuver to distract the seals. But at least one seal learned to turn that liability into a hunting strategy.
"This seal appeared to be a master in catching the flashing prey, because each time it tried to catch a prey, first it would do this little head movement that was probably mechanically sensed by the prey. Then it would induce the prey to flash because the prey reacts to this approaching predator."
This seal would twitch her head, see where the light came from, and only then start the chase.
So even if some seals can use bioluminescence as a way to find food, for most the light is a distraction. Goulet thinks that seals probably rely more on their whiskers to sense the movements their prey make in the water.
"It's just a step forward into understanding what's happening in these depths, in this ecosystem that we don’t really know much about, especially in the Southern Ocean."
Source: Scientific American
【笔记格式要求】
精读笔记格式要求： 1.总结文章中心大意 2.总结分论点或每段段落大意 3.摘抄印象深刻或者觉得优美的句子 4.总结文章中的生词 5.记录阅读时间、总结时间、总时间
精听笔记格式要求： 1.逐句听写整篇文章 2.对照原文修改听写稿，标记出错原因 3.总结文章中心大意 4.总结精听过程中的生词 5.记录听写时间、总结时间、总时间
这里也给大家两点学习小建议哦~ 精读：如遇到读不懂的复杂句，建议找出句子主干，分析句子成分，也可以尝试翻译句子来帮助理解~ 精听：建议每句不要反复纠结听，如果听 5 遍都没听出来，那就跳过，等完成后再回听总结原因，时间宝贵，不要过于执着哦~
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发表于 2020-6-19 20:30:44
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