Structural origins of coloration in the spider Phoroncidia rubroargentea Berland, 1913 (Araneae: Theridiidae) from Madagascar

Sarah Kariko*, Jaakko V.I. Timonen, James C. Weaver, Dvir Gur, Carolyn Marks, Leslie Leiserowitz, Mathias Kolle, Ling Li

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

5 Citations (Scopus)


This study investigates the structural basis for the red, silver and black coloration of the theridiid spider, Phoroncidia rubroargentea (Berland, 1913) from Madagascar. Specimens of this species can retain their colour after storage in ethanol for decades, whereas most other brightly pigmented spider specimens fade under identical preservation conditions. Using correlative optical, structural and chemical analysis, we identify the colour-generating structural elements and characterize their optical properties. The prominent silvery appearance of the spider’s abdomen results from regularly arranged guanine microplatelets, similar to those found in other spiders and fish. The microplatelets are composed of a doublet structure twinned about the [021] axis, as suggested by electron diffraction. The red coloration originates from chambered microspheres (approx. 1 mm in diameter), which contain structured fluorescent material. Co-localization of the red microparticles on top of the reflective guanine microplatelets appears to enhance the red coloration. The spider’s thick cuticular layer, which encases its abdomen, varies in its optical properties, being transparent in regions where only guanine reflectors are present, and tanned, exhibiting light absorption where the red microspheres are found. Moreover, colour degradation in some preserved spider specimens that had suffered damage to the cuticular layer suggests that this region of the exoskeleton may play an important role in the stabilization of the red coloration.

Original languageEnglish
Article number20170930
JournalJournal of the Royal Society Interface
Issue number139
Publication statusPublished - 1 Jan 2018
MoE publication typeA1 Journal article-refereed


  • Guanine
  • Phoroncidia
  • Spider
  • Structural colour


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