把一條魚(yú)放入一個(gè)有著吃不完的食物的魚(yú)缸，它會(huì)狼吞虎咽直至體形增大了數(shù)倍,。這或許是因?yàn)轸~(yú)有一個(gè)比實(shí)際需求大得多的消化系統(tǒng),。然而考慮到魚(yú)在野外不可能吃這么多，那么為什么還要花這么大的力氣來(lái)保持所有這些消化道呢,？
根據(jù)7月6日《自然》雜志網(wǎng)絡(luò)版報(bào)道,，對(duì)600種魚(yú)（包括圖中的太陽(yáng)魚(yú)）進(jìn)行的一項(xiàng)新的分析表明，大的消化道有助于魚(yú)類(lèi)應(yīng)對(duì)野外的盛宴或饑荒,。兩到三倍于所需的一個(gè)消化系統(tǒng)能夠幫助魚(yú)類(lèi)在發(fā)現(xiàn)食物的時(shí)候足吃足喝,，并儲(chǔ)備卡路里以備食物短缺時(shí)之需。并且,，從長(zhǎng)遠(yuǎn)來(lái)看,，這使得拖著一肚子內(nèi)臟變得有了價(jià)值。（生物谷Bioon.com）
生物谷推薦原文出處：
Nature doi:10.1038/nature10240
Excess digestive capacity in predators reflects a life of feast and famine
Jonathan B. Armstrong; Daniel E. Schindler
A central challenge for predators is achieving positive energy balance when prey are spatially and temporally heterogeneous. Ecological heterogeneity produces evolutionary trade-offs in the physiological design of predators; this is because the ability to capitalize on pulses of food abundance requires high capacity for food-processing, yet maintaining such capacity imposes energetic costs that are taxing during periods of food scarcity1, 2. Recent advances in physiology show that when variation in foraging opportunities is predictable, animals may adjust energetic trade-offs by rapidly modulating their digestive system to track variation in foraging opportunities1. However, it is increasingly recognized that foraging opportunities for animals are unpredictable3, which should favour animals that maintain a capacity for food-processing that exceeds average levels of consumption (loads)2, 4. Despite this basic principle of quantitative evolutionary design, estimates of digestive load:capacity ratios in wild animals are virtually non-existent1. Here we provide an extensive assessment of load:capacity ratios for the digestive systems of predators in the wild, compiling 639 estimates across 38 species of fish. We found that piscine predators typically maintain the physiological capacity to feed at daily rates 2–3 times higher than what they experience on average. A numerical simulation of the trade-off between food-processing capacity and metabolic cost suggests that the observed level of physiological opportunism is profitable only if predator–prey encounters, and thus predator energy budgets, are far more variable in nature than currently assumed.
