Cocoons

C,2H220ii,2H20. M.p. 9TC. A non-reducing disaccharide, which forms the principal carbohydrate of insect haemolymph. It comprises about 25% of trehala manna, the cocoons of a parasitic beetle. Trehalose also occurs in fungi, e.g. Amanita muscaria, generally replacing sucrose in plants lacking chlorophyll and starch. 

Fibers (see Fibers, survey) used in textile production can have a wide variety of origins plants, ie, ceUulosic fibers (see Fibers, cellulose esters) animals, ie, protein fibers (see Wool) and, in the twentieth century, synthetic polymers. Depending on the part of the plant, the ceUulosic fibers can be classified as seed fibers, eg, cotton (qv), kapok bast fibers, eg, linen from flax, hemp, jute and leaf fibers, eg, agave. Protein fibers include wool and hair fibers from a large variety of mammals, eg, sheep, goats, camels, rabbits, etc, and the cocoon material of insect larvae (sUk). Real sUk is derived from the cocoon of the silkworm, Bombjx mori and for a long time was only produced in China, from which it was traded widely as a highly valuable material. 

Secondary Structure. The silkworm cocoon and spider dragline silks are characterized as an antiparaHel P-pleated sheet wherein the polymer chain axis is parallel to the fiber axis. Other silks are known to form a-hehcal (bees, wasps, ants) or cross- P-sheet (many insects) stmctures. The cross-P-sheets are characterized by a polymer chain axis perpendicular to the fiber axis and a higher serine content. Most silks assume a range of different secondary stmctures during processing from soluble protein in the glands to insoluble spun fibers. 

Crystallinity. Generally, spider dragline and silkworm cocoon silks are considered semicrystalline materials having amorphous flexible chains reinforced by strong stiff crystals (3). The orb web fibers are composite materials (qv) in the sense that they are composed of crystalline regions immersed in less crystalline regions, which have estimates of 30—50% crystallinity (3,16). Eadier studies by x-ray diffraction analysis indicated 62—65% crystallinity in cocoon silk fibroin from the silkworm, 50—63% in wild-type silkworm cocoons, and lesser amounts in spider silk (17). 

Commercial and Artificial Processing. Commercially, silkworm cocoons are extracted in hot soapy water to remove the sticky sericin protein. The remaining fibroin or stmctural sdk is reeled onto spools, yielding approximately 300—1200 m of usable thread per cocoon. These threads can be dyed or modified for textile appUcations. Production levels of sdk textiles in 1992 were 67,000 metric tons worldwide. The highest levels were in China, at 30,000 t, foUowed byJapan, at 17,000 t, and other Asian and Oceanian countries, at 14,000 t (24). Less than 3000 metric tons are produced annually in each of eastern Europe, western Europe, and Latin America almost no production exists in North America, the Middle East, or Africa. 1993 projections were for a continued worldwide increase in sdk textile production to 75,000 metric tons by 1997 and 90,000 metric tons by 2002 (24). 

Films or membranes of silkworm silk have been produced by air-drying aqueous solutions prepared from the concentrated salts, followed by dialysis (11,28). The films, which are water soluble, generally contain silk in the silk I conformation with a significant content of random coil. Many different treatments have been used to modify these films to decrease their water solubiUty by converting silk I to silk II in a process found usehil for enzyme entrapment (28). Silk membranes have also been cast from fibroin solutions and characterized for permeation properties. Oxygen and water vapor transmission rates were dependent on the exposure conditions to methanol to faciUtate the conversion to silk II (29). Thin monolayer films have been formed from solubilized silkworm silk using Langmuir techniques to faciUtate stmctural characterization of the protein (30). ResolubiLized silkworm cocoon silk has been spun into fibers (31), as have recombinant silkworm silks (32). 

Thermal Properties. Spider dragline silk was thermally stable to about 230°C based on thermal gravimetric analysis (tga) (33). Two thermal transitions were observed by dynamic mechanical analysis (dma), one at —75° C, presumed to represent localized mobiUty in the noncrystalline regions of the silk fiber, and the other at 210°C, indicative of a partial melt or a glass transition. Data from thermal studies on B. mori silkworm cocoon silk indicate a glass-transition temperature, T, of 175°C and stability to around 250°C (37). The T for wild silkworm cocoon silks were slightly higher, from 160 to 210°C. 

Gespenstf n. specter, ghost, phantom. Gesperr(e), n. locking device, catch, ratchet, gespieen, p.p. (of speien) spat vomited. Gespinst, n. spun yarn spun goods thread (textile) fabric web cocoon, -faser, /. textile fiber, -pflanze,/. textile plant fiber plant. 

Kokon, m. cocoon, -faden, m. cocoon fiber, cocoon thread. 

Pupillenerweiterung, /. dilation of the pupil. Puppe,/. pupa cocoon doll puppet dummy. Puppenkokon, n. cocoon. 

Substance Abuse and Mental Health Services Administration Treatment episode data set (TEDS), 1999. Available at http //www.icpsr.umich.edu/cocoon/ICPSR STUDY/03314.xml. Accessed Feburary 13, 2004... 

The feeling of a spider web may be unsettling, but a similar natural material has been used for centuries to make silk fabric that is prized for its smooth texture. Silkworms produce the silk fibers used to make clothing. They feast on mulberry leaves and convert the molecules from these leaves into silk, from which they spin cocoons. 

The ancient Chinese discovered how to harvest silkworm cocoons, boil them to loosen the tangle, and unravel the silk into a fiber from which elegant clothing could be produced. A single silkworm cocoon can yield nearly a mile-long filament of silk, but the filament is so fine that it takes around 30 mulberry trees to yield enough cocoons to make one kilogram of silk. 

Silk. Silk, the only natural fiber that comes in filament form, has been and still is one of the most appreciated and valued textile fibers. Silk filaments are secreted by the larvae of several types of silk moths to make their cocoons. Most silk is derived, however, from the larvae of the Bombyx mori moth, which has been widely cultivated in China for over 5000 years. Fragments of silk fabric dated to the late fourth millennium b.c.e. were found at Qianshanyang, in the province of Zhejiang, in China. There are, however, even earlier indications of the use of silk silk remains were found together with an eleventh-century b.c.e. mummy in Egypt, probably also providing evidence of ancient trading routes between the Far and Middle East. 

The larvae of Bombyx mori, the cultivated moth from which most silk has long been and still is made, feed on leaves of mulberry trees. In addition to cultivated silk, small quantities of "wild silk," also known as nonmulberry silk, have been derived in many parts of the world from the cocoons of moths other than Bombyx mori. Table 90 lists wild silks and the insect species that produce them (Peigler 1993 Jolly et al. 1979). 

F 6-34.7 Making yellowish flesh cocoon in combination with Yand +1... 

Ymc Making light yellow cocoon in combination with YA, an allele of Y... 

FIGURE 24.4 Silkworm genetic loci responsible for carotenoid transport, (a) List of the genetic loci. + indicates a recessive allele of I. (b) Schematic illustration of the function of the F, I, and C genes. Only larvae with the genotype Y + C] transport carotenoids into the silk gland and create yellow cocoons. 

Besides its biological significance, the silkworm has economic value. Silk has been a major natural fiber used in textile production for millennia. By utilizing CBP, coloration of a natural fiber by transport of a natural pigment based on molecular genetic engineering has been achieved (Sakudoh et al. 2007). Determination of other genes for cocoon color may lead to the ability to produce custom-colored silks, which may have an impact on the textile industry. 

Tabunoki, H., Higurashi, S., Ninagi, O. et al. 2004. A carotenoid-binding protein (CBP) plays a crucial role in cocoon pigmentation of silkworm (Bombyx mori) larvae. FEBS Lett., 567(2-3) 175-178. 

Tsuchida, K., Katagiri, C., Tanaka, Y. et al. 2004b. The basis for colorless hemolymph and cocoons in the Y-gene recessive Bombyx mori mutants A defect in the cellular uptake of carotenoids. J. Insect Physiol., 50(10) 975-983. 

---