茶叶挥发物对鞍形花蟹蛛觅食行为的影响

为了探明茶叶挥发物在鞍形花蟹蛛(Xysticus ephippiatus Simon)搜寻猎物——茶尺蠖(Ectropis obliqua Prout)过程中的作用,采用固相微萃取气相色谱质谱联用技术研究了茶尺蠖取食对茶树叶片挥发物释放的影响,并通过蜘蛛行为观测平台研究了蟹蛛在不同味源侧(觅食斑块)的活动行为。结果表明:对照叶片没有释放出挥发物,经茶尺蠖幼虫取食后的叶片能释放31种挥发物,其中有12种绿叶挥发物、9种萜类及其衍生物、4种芳香族挥发物和6种未知化合物。行为观测表明,雌、雄蟹蛛进入处理味源侧(茶尺蠖取食后的茶树叶片)和对照味源侧(未损伤茶树叶片)的初次选择均不存在差别(P>0.05),雌蛛进入处理味源侧和对照味源侧的频次分别为3.37±0.18和3.43±0.15,二者无明显区别(P>0.05);雄蛛进入两侧的频次分别为3.86±0.21和3.66±0.20,也无明显区别(P>0.05);雌蛛在处理味源侧和对照味源侧的停留时间分别为(922.57±19.59)s和(818.89±29.63)s,有极显著差异(P<0.01),雄蛛在两侧的停留时间分别为(937.97±18.05)s和(814.83±18.97)s,也有极显著差异(P<0.01),表明雌蛛、雄蛛在处理侧的停留时间明显延长。这说明,猎物取食诱导改变了茶树叶片挥发物的释放,而鞍形花蟹蛛能感知挥发物的变化并由此调整在不同觅食斑块中的停留时间。另外,本文还讨论了挥发物在蟹蛛搜寻猎物过程中的生态学意义。

Effects of tea plant volatiles on foraging behavior of Xysticus ephippiatus Simon

Although the attractiveness of emitted plant volatiles under attack by herbivores has been demonstrated in tritrophic sys-tems,how these semi-chemicals affect foraging behaviors of crab spiders remains poorly understood.We therefore examined whether the saddle crab spider,Xysticus ephippiatus Simon,showed preferences to volatiles emitted from the most recent prey-consumed fields.Such fields consisted of two chambers or foraging patches-a control chamber of undamaged tea leaf and a stimulus chamber of Ectropis obliqua-damaged tea leaf.We collected and identified the volatiles emitted from different treated tea leaves by solid phase micro-extraction-GC-MS(SPME-GC-MS).The results showed that E.obliqua-damaged tea leaves released an average of about 31 volatiles.The main constituents of the volatiles were 12 green leaf volatiles (Z)-3-hexenal,(E)-2-hexenal,(Z)-3-hexen-1-ol,(Z)-3-hexenyl acetate,2-ethyl-1-hexenol,(Z)-3-hexenyl butyrate,(Z)-3-hexenyl iso-butyrate,(E)-2-hexenyl butyrate,(Z)-3-hexenyl 2-methyl butyrate,(Z)-3-hexenyl 3-methyl butyrate,(Z)-3-hexenyl hexanoate and(E)-2-hexenyl hexanoate],9 terpenoids (E)-β-ocimene,(Z)-linalool oxide,linalool,nonanal,decanal,DMNT,1-nitro-2-phenyl ethane,(E,E)-α-farnesene and(Z)-6,10-dimethyl-5,9-undecadien-2-one],4 aromatic compounds benzyl alcohol,phenylethyl alcohol,Indole and benzyl nitrile] and 6 unknown compounds.No volatiles were,however,detected from undamaged tea leaves.X.ephippiatus females and males were not preferential to undamaged leaves or E.obliqua-damaged leaves as first choice(χ2=0.26,P=0.612,n=35 for female;χ2=0.71,P=0.398,n=35 for male).The frequencies of the females moving into different odor sources were similar(mean=3.37±0.18 for E.obli-qua-damaged leaves and mean=3.43±0.15 for undamaged leaves).Also the frequencies of the males moving into different odor sources were similar(mean=3.86±0.21 for E.obliqua-damaged leaves and mean=3.66±0.20 for undamaged leaves).The residence time of females and males in foraging patches with E.obliqua-damaged leaves was significantly longer than that in foraging patches of undamaged leaves.The results suggested that tea leaves damaged by E.obliqua emitted more volatiles than undamaged leaves and X.ephippiatus exploited these indirect cues to make patch residence time decisions.The ecological importance of volatiles on forag-ing behaviors of crab spiders was discussed also in the paper.