News Plus慢速英语:我国发现6亿年前原始海绵动物化石 海鱼变色伪装捕食幼鱼

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A new study has confirmed the theory that animals have been on Earth for at least 600 million years.
The study, by Chinese scientists, described a well-preserved, rice grain-sized primitive sponge fossil recovered from 600-million-year-old rocks in southwestern China.
The scientists say the fossil is the world's earliest and most credible record of primitive animal bodies. The discovery will help to remove doubts as towhether animals have emerged on Earth 600 million years ago.
The fossilized animal is 1.2 millimeter long and 1.1 millimeters wide. It displays multiple independent characters of modern adult sponges.
The specimen is composed of hundreds of thousands of cells. Flat tile-like features on the surface resemble modern sponges. It also has a simple canal system for water inflow and outflow.
The results show that this is a primitive animal very similar to modern sponges and have lived a filter-feeding life on the shallow sea floor.
Sponges are the most primitive living animals. They have differentiated cells only, without real organs or tissues. Previously, the oldest known primitive sponge fossil only dated back to 530 million years ago, in the early Cambrian period.

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A small fish that lives on Australia's Great Barrier Reef preys on smaller fish by changing color and pretending to be an adult of their own species.
The dusky dotty-back is a small predatory fish that is found throughout the Indo-Pacific and has the ability to change color.
Its ability to vary its coloration has baffled scientists until an international research team from the University of Basel has developed a theory.
The zoologists are now able to show that dotty-backs can quickly change their color in order to mimic other fish species and chase their prey. It also helps dusky dotty-back fish to protect itself from predators.
The team says this strategy is very similar to the classic example of the wolf in sheep's skin. However, while the wolf may be found out eventually, dotty-backs are able to change back again.