棘冠海星可以在攻擊珊瑚礁前數(shù)年繁殖

棘冠海星可以在攻擊珊瑚礁前數(shù)年繁殖

Vast outbreaks of crown-of-thorns seastars can consume and devastate corals on tropical reefs, as if corals didn't already have enough problems. Prior to their coral-eating adulthood, however, the seastars (sometimes known as starfish) go through an algae-eating juvenile phase. New research reveals the starfish can wait in this phase, building their numbers, until the time is right to transform and descend on a reef like locusts.

大量的棘冠海星會吞噬和毀滅熱帶珊瑚礁上的珊瑚，好像珊瑚還沒有遇到足夠多的問題。然而，在它們吃珊瑚的成年期之前，海星(有時被稱為海星)經(jīng)歷了一個吃海藻的幼年期。新的研究表明，海星可以在這一階段等待，增加它們的數(shù)量，直到時機(jī)成熟，它們可以像蝗蟲一樣蛻變并降落在礁石上。

Stephen Luntz

Unlike most of the threats coral faces, crown-of-thorns attacks are not human-induced. Nevertheless, their rampages appear to be becoming more frequent, which is probably a consequence of our actions. One popular theory blames extra nutrients from fertilizer runoff increasing the phytoplankton starfish feed upon during their larval stage. However, Professor Maria Byrne of the University of Sydney is skeptical.

與珊瑚面臨的大多數(shù)威脅不同，棘冠類的攻擊不是人為造成的。然而，它們的暴行似乎越來越頻繁，這可能是我們行動的后果。一種流行的理論認(rèn)為是化肥徑流增加了浮游植物海星在幼蟲期的營養(yǎng)。然而，悉尼大學(xué)的瑪利亞·伯恩教授對此表示懷疑。

“The connection is tenuous,” she told IFLScience, pointing to coral untouched by runoff that have suffered major crown-of-thorns outbreaks. Instead, “there is this whole juvenile stage in between that has been ignored.”

她對IFLScience說:“這種聯(lián)系很薄弱。”她指的是那些沒有受到徑流影響的珊瑚，它們已經(jīng)遭受了棘冠類珊瑚的大規(guī)模爆發(fā)。相反，“在這兩者之間的整個青少年階段被忽視了。”

Juvenile crown-of-thorns seastars while still in their vegetarian phase. University of Sydney

It used to be thought that all it took for algae-eating juveniles to transition to adulthood was for the starfish to become large enough to wrap itself around some vulnerable coral. In Biology Letters, however, Byrne and PhD student Dione Deaker show transition timing depends not just on size but on the availability of coral, at least in the lab. One set of seastars fed on algae for 10 months, growing to 16-18 millimeters (1.6-1.8 centimeters) before making the transition. Others, raised without tempting corals to consume, went for 6.5 years without becoming adults, yet grew no larger in size. It seems they were just waiting for the right moment, and when this came, they proved just as voracious predators of corals as their younger counterparts. It helps explain how such enormous outbreaks can start so suddenly.

過去人們認(rèn)為，吃海藻的幼體到成年只需要海星長得足夠大，就可以把自己包裹在一些脆弱的珊瑚周圍。然而，在《生物學(xué)快報》上，拜恩和博士生迪昂·迪克(Dione Deaker)指出，轉(zhuǎn)變的時間不僅取決于珊瑚的大小，而且至少在實(shí)驗(yàn)室里，還取決于珊瑚的可獲得性。另一些則在沒有引誘珊瑚食用的情況下長大，在沒有成年的情況下生活了6.5年，但它們的體型并沒有變大。它們似乎只是在等待合適的時機(jī)，而當(dāng)時機(jī)到來時，它們證明了自己和年輕的同類一樣，都是貪婪的珊瑚捕食者。這有助于解釋為何如此大規(guī)模的疫情會如此突然地爆發(fā)。

Byrne told IFLScience no one knows how seastars move into predator mode, but she thinks it may involve the development of the capacity to consume the waxy esters that make corals inedible to many other animals.

Byrne告訴IFLScience，沒有人知道海星是如何進(jìn)入捕食模式的，但她認(rèn)為這可能涉及到消耗蠟質(zhì)酯的能力的發(fā)展，這種蠟質(zhì)酯使得許多其他動物無法食用珊瑚。

"Another important implication of our findings is the possibility that the current adult starfish killing programs used to manage crown-of-thorns starfish might, in fact, trigger a feedback mechanism in the starfishes' transition to coral predator as juveniles are released from adult competition," Byrne noted in a statement.

Byrne在一份聲明中指出:“我們的發(fā)現(xiàn)的另一個重要含義是，目前用于管理刺冠海星的成年海星捕殺程序，實(shí)際上可能會觸發(fā)一種反饋機(jī)制，使海星在從成年競爭中釋放出來后，過渡到珊瑚捕食者。”

Nevertheless, even if current reef protection methods are ineffective, it is not clear what should occur instead. Byrne sees little alternative to programs that remove all the adult crown-of-thorns from the reefs most frequented by tourism and she stresses that pollution and nutrients from the land damages coral in other ways.

然而，即使目前的珊瑚礁保護(hù)措施是無效的，也不清楚應(yīng)該采取什么措施。拜恩認(rèn)為，除了將所有成年棘冠魚從游客最常去的珊瑚礁上清除之外，幾乎沒有其他選擇。她強(qiáng)調(diào)，陸地上的污染和營養(yǎng)物質(zhì)會以其他方式損害珊瑚。

It's possible, Byrne noted, that animals that prey on juvenile crown-of-thorns have been depleted by human activity. If so, the best thing we can do is bring them back, but first they would need to be identified.

拜恩指出，有可能是人類活動耗盡了以幼冠棘為食的動物。如果是這樣，我們能做的最好的事情就是把他們帶回來，但首先他們需要被識別。

An adult crown of thorns. University of Sydney