Effects of juvenile host density and food availability on adult immune response, parasite resistance and virulence in a Daphnia-parasite system.
Effects of juvenile host density and food availability on adult immune response, parasite resistance and virulence in a Daphnia-parasite system.
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DOI：
10.1371/journal.pone.0094569
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发表时间：
2014
期刊：
影响因子：
3.7
通讯作者：
Little TJ
中科院分区：
文献类型：
--
作者：
Schoebel CN;Auld SK;Spaak P;Little TJ
宿主密度会增加感染率并降低宿主适应性，因为增加的人口密度会增加感染的风险，无论是通过增加接触率还是因为宿主状况可能下降。可以想象，潜在的宿主可以将高宿主密度作为上调其防御系统的提示。然而，由于寄主密度通常与食物供应量相关，因此很难单独检查寄主密度的重要性。因此，我们进行了两项全因子实验，独立地改变大型溞（一种淡水甲壳类动物）的幼体密度和食物供应量。我们还进行了模拟高密度处理，将幼年实验动物饲养在先前将水蚤保持在高密度的过滤介质中。成年后，我们将水蚤暴露于具有杀菌作用的细菌寄生虫巴斯德氏菌中，并研究了幼体处理如何影响感染的可能性和严重程度（实验一）和宿主免疫投资（实验二）。幼鱼密度和食物处理均不会影响感染的可能性；然而，幼体时期营养丰富的宿主在绝育前比营养不良的宿主产生更多的后代。相比之下，寄生虫的生长独立于寄主幼体资源或寄主密度。暴露于寄生虫的宿主比对照组具有更多数量的循环血细胞（即存在细胞免疫反应），但免疫反应的程度并非由食物供应或宿主密度介导。这些结果表明，密度对疾病的影响主要是通过食物供应的相关变化产生的：食物量低可以限制寄生，并可能通过减少宿主和寄生虫的繁殖来减少流行病，因为两者都依赖于相同的食物。
Host density can increase infection rates and reduce host fitness as increasing population density enhances the risk of becoming infected either through increased encounter rate or because host condition may decline. Conceivably, potential hosts could take high host density as a cue to up-regulate their defence systems. However, as host density usually covaries with food availability, it is difficult to examine the importance of host density in isolation. Thus, we performed two full-factorial experiments that varied juvenile densities of Daphnia magna (a freshwater crustacean) and food availability independently. We also included a simulated high-density treatment, where juvenile experimental animals were kept in filtered media that previously maintained Daphnia at high-density. Upon reaching adulthood, we exposed the Daphnia to their sterilizing bacterial parasite, Pasteuria ramosa, and examined how the juvenile treatments influenced the likelihood and severity of infection (Experiment I) and host immune investment (Experiment II). Neither juvenile density nor food treatments affected the likelihood of infection; however, well-fed hosts that were well-fed as juveniles produced more offspring prior to sterilization than their less well-fed counterparts. By contrast, parasite growth was independent of host juvenile resources or host density. Parasite-exposed hosts had a greater number of circulating haemocytes than controls (i.e., there was a cellular immune response), but the magnitude of immune response was not mediated by food availability or host density. These results suggest that density dependent effects on disease arise primarily through correlated changes in food availability: low food could limit parasitism and potentially curtail epidemics by reducing both the host’s and parasite’s reproduction as both depend on the same food.
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影响因子：
2.9
作者：
Guinnee, MA;West, SA;Little, TJ
通讯作者：
Little, TJ
影响因子：
2.9
作者：
Boersma, M;Spaak, P;De Meester, L
通讯作者：
De Meester, L
DOI：
10.1098/rspb.2000.1331
发表时间：
2001-01-07
影响因子：
4.7
作者：
Barber, I;Arnott, SA;Huntingford, FA
通讯作者：
Huntingford, FA
DOI：
10.1098/rstb.1996.0151
发表时间：
1996-12-29
期刊：
PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY OF LONDON SERIES B-BIOLOGICAL SCIENCES
影响因子：
--
作者：
Ebert, D;Rainey, P;Scholz, D
通讯作者：
Scholz, D
影响因子：
2.7
作者：
Ebert, D;Zschokke-Rohringer, CD;Carius, HJ
通讯作者：
Carius, HJ