Sun, Apr 15, 2018 - Page 9 News List

Fit for porpoise: Gene changes made ‘river pig’ unique
基因變異「豚」得其所 獨一無二的「江豚」

In this file picture taken on Nov. 9, 2006, a keeper plays with a finless porpoise in Wuhan Baji Aquarium.
在這張攝於二○○六年十一月九日的資料照中,一名武漢白鱀豚館的工作人員正在跟一隻江豚玩。

Photo: AFP
照片:法新社

China’s critically endangered Yangtze River porpoise is a distinct species, meaning it cannot interbreed with other porpoise types to pass on its DNA, a major analysis of the creature’s genome revealed on Tuesday.

The finless, dolphin-like creature, which sports a permanent, almost human grin on its snub-nosed face, is the world’s only freshwater porpoise.

However, there are only about 1,000 individuals left in the wild — a number shrinking by 14 percent per year — and conservationists warn the critter is poised to follow the long-snouted Yangtze River dolphin, or baiji, into extinction.

For the latest study, intended to spur conservation efforts, an international research team analyzed the genome of the Yangtze River porpoise and compared it to 48 other finless porpoises from different regions.

The exercise revealed that the animal known as “river pig” in China was a “distinct” species and “genetically isolated from other porpoise populations,” the experts wrote in the journal Nature Communications.

Previously, finless porpoises were classified as a single species with three sub-species, of which the freshwater Yantze River group was one. The new data showed the three main groups had, in fact, “not shared gene flow for thousands of years,” the study said. Also, each group shows “unique, individualized signatures of genetic adaptation to different environments.”

In nature, cross-species mating results in sterile offspring, if any at all. No such obstacles exist for mating between members of two different sub-species. Finless porpoise is one of the porpoise species, which form part of the marine mammal family known as cetaceans, which also includes whales and dolphins.

TODAY’S WORDS
今日單字

1. porpoise n. 鼠海豚 (shu2 hai3 tun2)

2. endangered adj. 瀕臨絕種的

(bin1 lin2 jue2 zhong3 de5)

3. interbreed v. 異種繁殖

(yi4 zhong3 fan2 zhi2)

4. adaptation n. 適應 (shi4 ying4)


Though they look somewhat alike, dolphins have longer noses, pointier teeth and longer, leaner bodies than porpoises, with a curvier, backward-pointing dorsal fin, according to America’s National Ocean Service.

All finless porpoises, said the researchers, originated from an ocean-dwelling ancestor. The Yangtze River group split from its seawater cousins some 5,000-40,000 years ago and “rapidly adapted to their new environment,” said Rasmus Nielson, one of the authors. Rasmus Nielsen is a professor of the Department of Integrative Biology at University of California, Berkeley.

The team found evidence for changes to genes regulating kidney function as well as the blood water-salt balance. The Yangtze River porpoise had a “unique, individualised” signature of genetic adaptation for living in freshwater, said the team.

“The authors hope that the genetic data, illustrating the distinctive genetic makeup of the Yangtze population, will spur ongoing efforts to prevent habitat destruction,” added the research press release on Nature Communications.

The Yangtze River porpoise is listed as endangered on the International Union for the Conservation of Nature (IUCN)’s “Red List.” The biggest threats are pollution from riverside industry, boat strikes, and getting caught in gillnets or other fishing gear. In 2015, China relocated a number of the creatures, which are rarer than pandas, to reserves in a species conservation bid.

(AFP)

中國極度瀕臨絕種的揚子江江豚是一個獨特的物種,也就是說,它們無法和其它種類的鼠海豚進行異種繁殖,將DNA傳遞給後代。這項該生物基因體的重大分析於週二被揭露。

這種長得像海豚,卻沒有鰭的生物,塌鼻子的臉上總掛著一抹幾乎像人類一般的露齒笑,是世界上唯一的淡水型鼠海豚。

只是,今日它們野生的個體僅存約一千隻──而這個數字正以每年百分之十四的速率逐步遞減──保育人士因此發出警示,指出這種動物很可能會追隨長吻揚子江豚(又稱白鱀)的命運步向絕種。

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