棒络新妇卵袋结构与组成

The Structure and Composition of the Nephila clavata Egg Case

采用SEM和氨基酸自动分析仪对棒络新妇Nephitaclavata卵袋进行了结构观察和氨基酸组成分析。结果表明棒络新妇的卵袋呈开放的网筛椭球状，结构简单，分为框架（大壶状腺丝）、金黄色或白色外层（主要含大壶状腺丝）和白色内层（主要含柱状腺丝）三部分，内外层都是由大（approx．6～13μm）、中（1．25～3．0μm）、小（approx．0．7～0．8μm）直径的丝纤维构成。卵袋框丝和外层丝的氨基酸组成相似，甘氨酸（分别占22．9％和32．5％）和丙氨酸（占24％左右）的含量最丰富，其次是谷氨酸（占16．5％左右）和丝氨酸（分别占8．3％和3％），苏氨酸含量低（分别占2．12％和0．68％）。与外层丝相比，卵袋内层丝纤维丝氨酸和苏氨酸的含量显著增加，分别为19．1％和6．11％左右，同时甘氨酸的含量显著减少，为7．2％左右，谷氨酸和脯氨酸的含量较低。大小侧链氨基酸比值（LC：SC）分析表明卵袋内层丝（1．03）〉卵袋框丝（0．85）〉卵袋外层丝（0．66）≈拖牵丝（0．64）〉蚕丝（0．34），似乎表明卵袋框丝是不同于同纺自大壶状腺的典型蛛丝（拖牵丝）的新型蛛丝纤维。卵袋内层的主要构成成分是另一种具有截然不同氨基酸组成的柱状腺丝。棒络新妇能调节卵袋层丝的颜色、直径、丝纤维的组成及覆盖层的氨基酸组成，使卵袋获得各方面最优化的功能，为卵或若蛛提供支持和保护。

The egg case of Nephila clavata was composed of simple covers with different colored silk, which were yellow frame （major ampullate gland silk）, golden or white outer （ mostly containing major ampullate gland silk）, and white inner （mostly containing cylindrical gland silk）. Scanning electron micrographs （SEM） showed the outer and inner covers all consisted of large-diameter （ approx. 6 - 13 μm）, middle-diameter （ 1.25 - 3.0 μm） and small-diameter （approx. 0.7- 0.8μm） fibers. The amino acid composition was similar in the frame silk and outer cover silk, with glycine （22.9% and 32.5% respectively） and alanine （about 24% ） the most abundant amino acids, glutamic acid （ about 16.5% ） and serine （8.3% and 3% respectively） the next most abundant, and threonine （2.12% and 0.68% respectively） the least abun- dant. In contrast to the yellow frame silk and outer cover silk, the inner cover silk of the N. clavata egg case contained a significant increase in serine （about 19. 1% ） and threonine （about 6.11% ） levels with a concomitant loss of glycine （a- bout 7.2% ）. The value of long chain（LC） ： short chain（SC） show that inner silk （ 1.03 ） 〉 frame silk （0.85） 〉 outer silk （0.66） ~ dragline （0.64） 〉 silkworm silk （0.34）. This result indicates that the inner egg case cover was mostly composed of cylindrical gland silk appearing to be distinct fibers based on mole percent amino acid composition as compared with am- pullate gland silk. The scaffolding silk may represent a novel silk. Spiders appear to use relatively few gland silks in varying combinations to achieve different physical, chemical （ e. g. color, diameter, amino acid composition） and functional （ me- chanical properties, resistance, etc） characteristics in different layers of the egg case providing protection for the eggs or spiderlings.