Bal Harit K, Taylor Robin A J, Grewal Parwinder S
Department of Entomology, The Ohio State University, OARDC, Wooster, Ohio 44691.
J Parasitol. 2014 Aug;100(4):422-32. doi: 10.1645/12-165.1. Epub 2014 Mar 20.
Ambush foragers must employ a long-distance dispersal strategy to maximize reproductive success in the absence of hosts. This hypothesis was tested by comparing lateral dispersal of the ambusher, Steinernema carpocapsae , and the cruiser, Heterorhabditis bacteriophora , nematodes from infected host cadavers in autoclaved, silt-loam soil in large microcosms (0.05-1.5 m(2)) with or without vegetation in the absence of hosts. Dispersal was estimated by taking soil cores (5 × 2 cm in diameter) from the microcosms at different intervals (6-240 hr) and distances (3.8-61 cm) from the infected host cadavers and baiting with Galleria mellonella larvae. The numbers of baited larvae killed and the numbers of infective juveniles (IJs) penetrated in dead baits were counted to compute the percentage of IJs dispersed from the source cadavers, based on the emergence potential and penetration efficiency of the 2 species, and analyzed. Vegetation enhanced dispersal of both species but more so for H. bacteriophora . Although the pattern of dispersal differed spatio-temporally for the 2 species, average population displacement was similar (∼6 cm/day). A majority of the S. carpocapsae population ambushed close to the source cadaver (<3.8 cm), whereas a majority of H. bacteriophora population dispersed between 7-12 cm away from the source cadaver. About 4% of the S. carpocapsae population dispersed faster than the fastest H. bacteriophora , reaching 30-61 cm, compared to only 2% of the H. bacteriophora population dispersing this far. This use of 'sprinters' for long-distance dispersal may represent an adaptive dispersal strategy by the otherwise ambush forager S. carpocapsae in the absence of hosts.
伏击性觅食者必须采用远距离扩散策略，以便在没有宿主的情况下最大化繁殖成功率。通过比较伏击性线虫小卷蛾斯氏线虫（Steinernema carpocapsae）和巡游性线虫嗜菌异小杆线虫（Heterorhabditis bacteriophora）在大型微观环境（0.05 - 1.5平方米）中经高压灭菌的粉质壤土中、有无植被且无宿主的情况下，从受感染宿主尸体扩散的横向情况，对这一假设进行了检验。通过在不同时间间隔（6 - 240小时）和距离（3.8 - 61厘米）从微观环境中采集土壤芯（直径5×2厘米），并以大蜡螟幼虫作为诱饵，来估计扩散情况。计算被诱饵幼虫杀死的数量以及在死亡诱饵中穿透的感染性幼虫（IJ）数量，根据这两个物种的羽化潜力和穿透效率，计算从源尸体扩散出的IJ百分比，并进行分析。植被促进了两个物种的扩散，但对嗜菌异小杆线虫的促进作用更大。尽管这两个物种的扩散模式在时空上有所不同，但平均种群位移相似（约6厘米/天）。大多数小卷蛾斯氏线虫种群在靠近源尸体处（<3.8厘米）伏击，而大多数嗜菌异小杆线虫种群在距离源尸体7 - 12厘米处扩散。约4%的小卷蛾斯氏线虫种群扩散速度比最快的嗜菌异小杆线虫还快，可达30 - 61厘米，相比之下，只有2%的嗜菌异小杆线虫种群能扩散到这么远。这种利用“短跑者”进行远距离扩散可能代表了原本的伏击性觅食者小卷蛾斯氏线虫在没有宿主时的一种适应性扩散策略。
