Tso I-Min, Wu Hsuan-Chen, Hwang In-Ru
Department of Life Sciences, Tunghai University, Taichung 407, Taiwan.
J Exp Biol. 2005 Mar;208(Pt 6):1053-61. doi: 10.1242/jeb.01437.
Recent studies have demonstrated that orb-weaving spiders may alter web structures, foraging localities or silk output in response to prey variations. In this study we conducted field surveys and food manipulations to examine whether orb-weaving spiders may also adjust the protein of silk to prey variations. A comparison of dragline silks collected from nine giant wood spider Nephila pilipes populations in Taiwan showed a spatial variation. The percentage of all amino acids (except alanine and glycine) exhibited significant differences among populations. A survey of prey composition also revealed a significant spatial variation among N. pilipes populations. To determine whether prey variation was responsible for silk protein variation, we fed N. pilipes with different types of prey (dipteran vs orthopteran) then compared the percentage of five major dragline amino acids and secondary structures. The results showed that dragline of N. pilipes fed with orthopteran prey contained significantly higher proline and glutamine but lower alanine. Congruent with this result were those from FTIR spectroscopy, which showed that dragline of N. pilipes fed with crickets exhibited significantly higher percentage of proline- and glutamine-containing beta turns, and lower percentage of alanine-containing beta sheet structures. Since the results of feeding manipulations showed that diet significantly affected the compositions of dragline silks, the observed spatial variation seemed to reflect the different types of prey these spiders had consumed. Results of this study thus indicated that orb-weaving spiders can alter dragline protein in response to prey variations.
最近的研究表明，结网蜘蛛可能会根据猎物的变化改变蛛网结构、觅食地点或吐丝量。在本研究中，我们进行了实地调查和食物操控实验，以检验结网蜘蛛是否也会根据猎物的变化调整蛛丝蛋白。对从台湾9个大木林蛛种群采集的拖牵丝进行比较，发现存在空间差异。所有氨基酸（除丙氨酸和甘氨酸外）的百分比在不同种群间存在显著差异。对猎物组成的调查还显示，大木林蛛种群间存在显著的空间差异。为了确定猎物差异是否导致蛛丝蛋白的差异，我们用不同类型的猎物（双翅目昆虫与直翅目昆虫）喂养大木林蛛，然后比较5种主要拖牵丝氨基酸的百分比和二级结构。结果显示，以直翅目昆虫为猎物喂养的大木林蛛的拖牵丝中脯氨酸和谷氨酰胺含量显著更高，但丙氨酸含量更低。傅里叶变换红外光谱的结果与这一结果一致，该结果显示，以蟋蟀为食的大木林蛛的拖牵丝中含脯氨酸和谷氨酰胺的β转角百分比显著更高，而含丙氨酸的β折叠结构百分比更低。由于喂食操控实验的结果表明饮食显著影响拖牵丝的组成，观察到的空间差异似乎反映了这些蜘蛛所捕食的不同类型的猎物。因此，本研究结果表明，结网蜘蛛可以根据猎物的变化改变拖牵丝蛋白。
