Structure and properties of silk from the African wild silkmoth Gonometa postica reared indoors.

Addis Teshome,Fritz Vollrath,S K Raina,Henry Hagedorn

doi:10.1093/jis/14.1.36

Addis Teshome, Fritz Vollrath + Show 2 more

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https://doi.org/10.1093/jis/14.1.36

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Abstract

African wild silkmoth, Gonometa postica Walker (Lepidoptera: Lasiocampidae), were reared indoors in order to examine the influence of rearing conditions on the structure and properties of silk cocoon shells and degummed fibers by using a scanning electron microscope, an Instron tensile tester, and a thermogravimetric analyzer. The cocoons reared indoors showed inferior quality in weight, length, width, and cocoon shell ratio compared to cocoons reared outdoors. There were no differences in cocoon shell and fiber surfaces and cross sectional structures. Cocoon shells were covered with calcium oxalate crystals with few visible fibers on their surface. Degummed fibers were smooth with minimum unfractured surfaces and globular to triangular cross sections. Indoor-reared cocoon shells had a significantly higher breaking strain, while the breaking stress was higher for cocoons reared outdoors. Fibers from indoor cocoons had a significantly higher breaking stress while outdoor fibers had higher breaking strain. Thermogravimetric analysis curves showed two main thermal reactions revealing the dehydration of water molecules and ir-reversible decomposition of the crystallites in both cocoons and fibers reared indoors and outdoors. Cocoon shells underwent additional peaks of decomposition with increased temperature. The total weight loss was higher for cocoon shells and degummed fibers from indoors. Rearing conditions (temperature and relative humidity), feeding method used, changes in total life span, days to molting, and spinning might have influenced the variation in the properties observed.The ecological and commercial significances of indoor rearing of G. postica are discussed.

Highlights

Non-mulberry silk production is a unique eco-friendly agro practice for income generation and is compatible with conservation goals focusing on countering loss of forest biodiversity. Craig (2008) described “wild” silk as any type of silk other than that spun by the domesticated silkworm, Bombyx mori
In this paper, we report the influence of indoor rearing on quality, structure, and properties of the cocoon shell and degummed fibers of G. postica
There was a highly significant variation in cocoon shells for most of the parameters considered between males and females reared indoors

Summary

Introduction

Non-mulberry (wild) silk production is a unique eco-friendly agro practice for income generation and is compatible with conservation goals focusing on countering loss of forest biodiversity. Craig (2008) described “wild” silk as any type of silk other than that spun by the domesticated silkworm, Bombyx mori. Wild silk is produced all over the world by different species of silkmoths across a wide range of ecologies. About 80 silkmoth species in Asia and Africa are known to produce wild silk of economic value (Jolly et al 1975). More than 60 species of wild silk producing insect species have been identified in eastern Africa (Kioko 1998). Only four wild silkmoth species namely, Gonometa postica (Lepidoptera: Lasiocampidae), Anaphe panda, Argema mimosae, and Epiphora bauhiniae have been commercially exploited so far in different parts of Africa. Despite excellent properties and enormous economic potential, silk fibers from these silkmoths have largely escaped the notice of the modern commercial and scientific world until recently

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