Morphometric Analysis and Sexual Dimorphism in the Golden Orb-Weavers (Family: Araneidae)

Abstract

In this study, body size, leg segment morphology, eye arrangement, genital structure, and web architecture were examined to provide an integrated description of functional adaptations in the golden orb-weaver Nephila pilipes. Females possess a large, elongated abdomen (30.14 ± 0.43 mm in length), while males have a very small abdomen (3.83 ± 0.11 mm). The extremely negative Sexual Dimorphism Index (SDI) values for abdominal length (−6.87) and width (−10.93) highlight the magnitude of this difference. Females possessed elongated first and fourth legs, particularly in the femur, tibia, and metatarsus, while the third leg was consistently shorter, reflecting functional specialization. One-way ANOVA showed significant differences among legs for most segments (P < 0.001), except claw length, which remained uniform. Males exhibited a similar leg-length pattern but at a much smaller scale. Female reproductive morphology was characterized by a strongly sclerotized, compact epigynum with large paired spermathecae, a short median septum, and closely positioned copulatory openings, features diagnostic of Nephila. The palp of male has a proximal femur. This femur is elongate, reddish-orange, and V-shaped at the distal end. A compact annular patella comes next. The tibia has a triangle shape. It has an apophysis that is retro-laterally undulating. The cymbium has a spoon-like form and is tawny. The dominant black palpal bulb is located there. This article has been registered in ZooBank under the Life Science Identifier (LSID): urn: lsid: zoobank.org: pub:6B0C37B8-9994-4A57-9F05-8F49E51D576D.