Jaffee B A, Santos P F, Muldoon A E
Department of Nematology, University of California, Davis, CA 95616-8668, USA Fax: 916-752-5809; e-mail:
Oecologia. 1997 Oct;112(3):412-423. doi: 10.1007/s004420050327.
The feeding biology of Enchytraeus crypticus and other enchytraeids is poorly understood as is their effect on nematophagous fungi. Because enchytraeids had been associated with nematophagous fungi in the field and had suppressed these fungi in soil microcosms, we tested the hypothesis that exclusion of enchytraeids, largely E. crypticus, would improve establishment of certain nematophagous fungi in field plots. The fungi, Hirsutella rhossiliensis and Monacrosporium gephyropagum, are being studied as potential control agents of plant-parasitic nematodes and were formulated as hyphae in alginate pellets. The pellets were mixed into soil without enchytraeids and placed in cages (PVC pipe, 80 cm volume) with fine (20 μm) or coarse (480 μm) mesh; cages were buried 15 cm deep in field plots and then recovered after 6-52 days. When fine mesh was used, enchytraeids were excluded and the fungi increased to large numbers. When coarse mesh was used, enchytraeid numbers in cages increased rapidly and the fungi did poorly. Although mesh also affected other potential fungivores, including collembolans and large dorylaimid nematodes, we suspect that enchytraeids were more important because large numbers were consistently found in cages with coarse mesh soon after the cages were placed in soil. Organisms smaller than enchytraeids (bacteria, fungi, and protozoa) also appeared to be important because the fungi did better in heat-treated soil than in non-heat-treated soil, regardless of mesh size. The rapid increase in enchytraeid numbers in cages with hyphal pellets and coarse mesh was probably caused by movement of enchytraeids toward the pellets with hyphae: increase in enchytraeid numbers was minimal when movement into cages was blocked (or when cages contained pellets without hyphae). Overall, the data were consistent with the hypothesis that enchytraeids, or other meso- or macrofauna, contributed to suppression of nematophagous fungi in our field plots.
人们对隐秘线蚓及其他线蚓科动物的取食生物学了解甚少，对它们对线虫寄生真菌的影响也知之甚少。由于在野外，线蚓科动物与线虫寄生真菌有关联，并且在土壤微观环境中对线虫寄生真菌有抑制作用，因此我们检验了这样一个假设：排除线蚓科动物（主要是隐秘线蚓）会促进某些线虫寄生真菌在田间地块的定殖。玫瑰被毛孢和格氏单顶孢这两种真菌正在作为植物寄生线虫的潜在防治剂进行研究，并被制成藻酸盐颗粒中的菌丝体形式。将这些颗粒与不含线蚓科动物的土壤混合，放入带有细网（20微米）或粗网（480微米）的笼子（80立方厘米的PVC管）中；笼子埋在田间地块15厘米深处，6至52天后收回。使用细网时，线蚓科动物被排除在外，真菌数量大量增加。使用粗网时，笼子里的线蚓科动物数量迅速增加，而真菌生长不佳。尽管网眼大小也会影响其他潜在的真菌食性动物，包括弹尾虫和大型矛线目线虫，但我们怀疑线蚓科动物更为重要，因为在笼子放入土壤后不久，在粗网笼子中就一直能发现大量的线蚓科动物。比线蚓科动物小的生物（细菌、真菌和原生动物）似乎也很重要，因为无论网眼大小如何，真菌在经过热处理的土壤中比在未经热处理的土壤中生长得更好。笼子中带有菌丝颗粒和粗网时，线蚓科动物数量的迅速增加可能是由于线蚓科动物向带有菌丝的颗粒移动所致：当进入笼子的移动被阻断时（或者当笼子中装有不含菌丝的颗粒时），线蚓科动物数量的增加极少。总体而言，这些数据与以下假设一致，即线蚓科动物或其他中型或大型动物导致了我们田间地块中线虫寄生真菌受到抑制。
