動物界不爲人知的10對"親戚"

Every living organism on Earth is in some way related to something else. This genetic web gets larger and weirder the more scientists look at it. Finding new relations is a fascinating genetic puzzle where the most unexpected creatures can turn out to be cousins. It is also the ultimate tool for learning about evolution. The more creatures are linked to each other, the more they reveal about the history of themselves as individual species, their family group, and the progression of life on Earth.

地球上的一切生命體在某種程度上都和其他某種事物有聯繫。基因網越大越不可思議，就有越多的科學家前去研究。探索物種間的新關係是一項令人着迷的基因謎題，可能會發現最意想不到的幾種生物居然是親戚。這也是研究進化論的最根本途徑。越多的生物之間存在相互聯繫，就越能夠暴露它們的個體、族羣和在地球上進化的歷史。

pions And Ticks

10.蠍子和蜱

Many people believe that ticks are insects, but they are not. They are true arachnids, closely related to scorpions and spiders. It’s an ancient lineage; one gene study tentatively suggested that these creatures were here before the dinosaurs, already crawling around the surface of the Earth 400–450 million years ago. For both ticks and scorpions, the next meal is primarily found by their excellent sense of smell, and they can only survive on liquid food. Ticks live on a diet of blood, while scorpions have a multipurpose venom that both paralyzes and liquifies their prey’s insides, which they then proceed to drink. Of the two, the scorpion is better adapted to survive the lack of nutrition and can go without eating for up to a year by adjusting its oxygen use and lowering its metabolism. Due to a lack of useful fossil evidence about the history of these arachnids, the same genetic study that placed them in primeval times also used their test results to support a theory that they hark back to a common, ocean-dwelling ancestor.

很多人認爲蜱是一種昆蟲，實則不然。他們是真正的蛛形綱動物，跟蠍子和蜘蛛有密切關係。它是一種古老物種的世系，一項基因研究初步表明這些生物存在於地球上的時間比恐龍還要早4-4.5億年。蠍子和蜱主要是用敏銳的嗅覺來尋覓食物，而且它們只能依靠流質食物生存。蜱要生存下去必須保證每餐有血可飲，而蠍子有多種用途的毒液，可以麻痹溶解被捕者的內臟，然後它們就可以開始飲食。它們兩個當中，蠍子更能夠在食物匱乏的環境下生存，即使一年不進食也能存活，因爲它們可以通過調節用氧量，降低新陳代謝的速度。由於缺少能證明其歷史的化石，一個對原始時代的基因研究測試結果同樣認爲它們的祖先曾居住在海洋裏。

yfish And Coral

9.水母和珊瑚蟲

One swims like a fish, and the other grows like a plant, but in truth, both are actually animals. Jellyfish and coral belong to the family group called cnidarians: bell- or tube-shaped animals that can deliver a burning sting with their tentacles. Despite this, they certainly don’t appear to be related. Jellyfish sting swimmers and pulse themselves through the water, while corals appear to be twig-like bonsais that do nothing. It comes down to body build, however. Cnidarians are sac-like creatures with a central opening around which the tentacles grow. This is more obvious with jellyfish. The coral frames often found in novelty stores are not the animal itself but a limestone coating built by them for protection and anchoring to a reef. The tiny individual corals are simplistic in design. They are cup-shaped sacs and have one opening that doubles as a means of both eating and excretion. They suck calcium carbonate from the ocean to build the branches that most people mistakenly see as coral. Thousands of minute coral animals stay around their limestone tree, using their tentacles to search for food.

一個可以像魚一樣的遊動，另一個像植物一樣的生長，但是事實上，他們都是動物。水母和珊瑚蟲都是刺細胞動物家族裏的一員，刺細胞動物就是鐘形或管型動物，它們可以通過觸鬚給你一種強烈的刺痛感。儘管這樣，你仍然會覺得它們之間看起來沒什麼聯繫。水母會刺痛游泳的人並且能夠在水裏自由跳動，而珊瑚蟲像是一盆滿是樹枝的盆栽，靜止不動。然而實質上是主體結構讓它們之間存在相互聯繫。刺細胞生物都是囊狀生物，它們中心張開，周圍生長着觸鬚。水母在這方面的特徵更加明顯。常現身於新奇小店裏的珊瑚蟲框架並不是它本身的樣子，事實上，那是由石灰岩塗層製作出來保護身體和定礁。那些小的個體珊瑚蟲外形簡單。它們杯狀的囊只有一個開口，用來吸食和排泄。它們從海洋裏吸收碳酸鈣來築建分枝，這也讓大部分人看到珊瑚蟲後會產生誤解。其實，成千的珊瑚蟲待在石灰岩“樹”周圍用它們的觸角尋找食物。

eshoe Crabs And Spiders

8.馬蹄蟹和蜘蛛

Horseshoe crabs were misidentified as crabs hundreds of years ago. Granted, they spend most of their time crawling over the sea floor and have a crab-like shell roughly resembling a horseshoe. However, they are grouped with arachnids. Horseshoe crabs date back 500 million years as a species. These prehistoric survivors, who perhaps never evolved to flourish on land like the rest of their cousins, can grow up to 0.6 meters (2 ft) wide and use their long tails as a tool to dig for food or to right themselves when upside down. Even more remarkably, the horseshoe crab has 10 eyes on its back and sides, can replace lost body parts, and has blue blood. The blood is medically valuable and is used to detect bacteria, for cancer research, and diagnosing leukemia as well as vitamin B12 deficiency. Sadly, a great number of horseshoe crabs are caught for their blood and also by the bait industry.

馬蹄蟹在幾百年前被錯認爲是蟹。大部分時間，它們都揹着馬蹄形的蟹殼在海底四處爬行。然而，它們卻被歸類爲蛛形綱動物。馬蹄蟹的起源可以追溯到五億年前。這些史前倖存者可能不能像它們的近親一樣在陸地上蓬勃繁衍。馬蹄蟹可以長到60釐米寬（2英尺），尾巴較長，用作挖掘食物的工具，還可以在它們翻倒的時候扶正身體。更引人注目的是，馬蹄蟹的背部和身側長有10對眼睛，身體的大部分器官都可以重生，並且血是藍色的。馬蹄蟹的血有極高的醫學價值，可用於觀察細菌、癌症研究和診斷白血病與維生素B12缺乏症。令人難過的是，人們爲了馬蹄蟹的血捕殺了大量馬蹄蟹，此外馬蹄蟹還被用於餌料工業。

審校：哎呀 校對：落花生 編輯：Freya然