The fiddler crab (蟹) is a living clock. It indicates(=shows) the time of day by the color of its skin, which is dark by day and pale by night. The crab’s changing color follows a regular twenty—four hour plan that exactly matches the daily rhythm (节奏) of the sun.

Does the crab actually keep time, or does its skin simply answer to the sun’s rays, changing color according to the amount of light strikes it? To find out, biologists kept crabs in a dark room for two months. Even without daylight, the crab’s skin color continued to change exactly on time.

This characteristic (特性) probably developed gradually in answer to the daily rising and setting of the sun, to help protect the crab from sunlight and enemies. After millions of years it has become completely regulated (受控制) inside the living body of the crab.

The biologists noticed that once each day the color of the fiddler crab is especially dark, and that each day this happens fifty minutes later than on the day before. From this they discovered that each crab follows not only the rhythm of the sun but also that of the tides (潮水). The crab’s period of greatest darkening is exactly the time of low tide on the beach where it was caught!

Winter begins in the north on December 22nd. People and animals have been doing what they always do to prepare for the colder months, Sqzeirrels, for example, have been busy gathering nuts from trees. 【小题1】They examined differences between red squirrels and gray squirrels in the American state of Indiana. The scientists wanted to know how these differences could affect the growth of black walnut trees.【小题2】The black walnut tree is also a central part of some hardwood forests.

Rob Swihart of Purdue University did the study with Jake Goheen, a former Purdue student now at the University of New Mexico. The two researchers estimate that several times as many walnuts grow when gathered by gray squirrels as compared to red squirrels. Gray squirrels and red squirrels do not store nuts and seeds in the same way. Gray squirrels bury nuts one at a time in a number of places.【小题3】So some nuts remain in the ground. Conditions are right for them to develop and grow the following spring. Red squirrels, however, store large groups of nuts above ground.

【小题4】But Professor Swihart says their numbers began to decrease as more forests were cut for agriculture. Red squirrels began to spread through the state during the past century. The researchers say red squirrels are native to forests that stay green all year, unlike walnut trees. They say the cleaning of forest land for agriculture has helped red squirrels invade Indiana.【小题5】

An interesting study of different languages identified Spanish as the happiest language of all because of its large number of happy, positive words.

Researchers worked together on a 2015 study, finding human language shows a common positive meaning. Their aim was to explore the positivity of human language. To do this, the teams examined 100,000 words in ten different languages: English, Spanish, French, German, Brazilian Portuguese, Korean, Chinese, Russian, Indonesian, and Arabic.

Their next step was to create a database of 10,000 common words in each language, later marking each word as positive or negative (消极的) in meanings. The researchers depended on teams of 50 different native speakers in each language to score these common words based on emotions. These participants (参与者) scored each word on a happiness scale of 1—9 based on the level of confidence it passed.

Until recently, strictly testing this positivity in languages has been difficult due to a lack (缺乏) of data across various languages, but the Internet has made it much easier. The researchers were able to depend on a wide range of online text sources for their study, including social media posts, news media, song lyrics, book and movie descriptions.

“Overall, our major scientific finding is that words, which are the most important in human language, show positive emotions,” the researchers say in the study. But Spanish is the happiest language of all!

While language positivity is the general rule, the researchers observed differences in the happiness between languages, with Spanish coming out on top in terms of joyful words. The results showed that Spanish-language web pages had the highest rates of positive words. The Romance language of Portuguese came in second, followed by English, Indonesian and French.

The study is part of a larger project to build a “hedonometer”, a happiness meter tool that tracks the “happiness signs” in social media posts almost in real time.