Iwai Noriko, Kagaya Takashi
Graduate School of Agricultural and Life Sciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan.
Oecologia. 2007 Jul;152(4):685-94. doi: 10.1007/s00442-007-0682-6. Epub 2007 Mar 10.
In aquatic food webs consumers can affect other members of the web by releasing nutrients as a result of their feeding activity. There is increasing evidence of these positive effects on primary producers, but such nutrient regeneration can also affect detritivores, by favoring the activities of detritus-associated microbes. We examined the effects of nutrient regeneration by tadpoles on leaf-eating detritivores under laboratory conditions. We fed four species of tadpoles three different food items (leaf litter, algae, and sludgeworms). We then conditioned terrestrial dead leaves with water from reared tadpoles (treatments) or food items alone (controls), and compared the C:N ratios of the conditioned leaves and the growth of the isopod Asellus hilgendorfii fed on the conditioned leaves. Tadpole feeding activity reduced the C:N ratio of conditioned leaves, and the effect was greatest when tadpoles were fed algae. Isopod growth rates were often higher when they were fed the litter conditioned with water from reared tadpoles. Thus, nutrient regeneration by tadpoles had a positive indirect effect on detritivores by enhancing leaf quality. Tadpoles often occur in nutrient-limited habitats where leaf litter is the major energy source, and their facilitative effects on leaf-eating detritivores may be of great significance in food webs by enhancing litter decomposition.
在水生食物网中，消费者通过摄食活动释放营养物质，从而影响食物网中的其他成员。越来越多的证据表明这些对初级生产者有积极影响，但这种营养物质再生也可能通过促进与碎屑相关的微生物活动来影响碎屑食性动物。我们在实验室条件下研究了蝌蚪的营养物质再生对食叶碎屑食性动物的影响。我们给四种蝌蚪投喂三种不同的食物（落叶、藻类和颤蚓）。然后，我们用饲养蝌蚪的水（处理组）或仅用食物（对照组）处理陆生枯叶，并比较处理后叶子的碳氮比以及以处理后叶子为食的等足目动物希尔根多夫阿塞尔的生长情况。蝌蚪的摄食活动降低了处理后叶子的碳氮比，当给蝌蚪投喂藻类时，这种影响最大。当等足目动物食用用饲养蝌蚪的水处理过的落叶时，其生长速度往往更高。因此，蝌蚪的营养物质再生通过提高叶子质量对碎屑食性动物产生了积极的间接影响。蝌蚪经常出现在营养有限的栖息地，在那里落叶是主要的能量来源，它们对食叶碎屑食性动物的促进作用可能通过增强落叶分解在食物网中具有重要意义。
