Insects silkworms

Breithaupt, Chap. 13, Denissenko et al. 2007 stomatopods Mead and Caldwell, Chap. 11 copepods Moore et al. 1999). Generation of microcurrents to obtain chemical information may be a strategy to enhance olfaction, as also described for some insects (silkworm moth Loudon and Koehl 2000). While such activities that enhance odor transmission are limited to only few examples in insects and mammals, they are common strategies in crustaceans involving specific fanning appendages. 

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. 

Toyama, K. 1906. Studies on the hybridology of insects. I. On some silkworm crosses, with special reference to Mendel s law of heredity. Bull. Coll. Agr. Tokyo Imp. Univ., 7 259-393. 

Uchino, K., Imamura, M., Sezutsu, H. et al. 2006. Evaluating promoter sequences for trapping an enhancer activity in the silkworm Bombyx mori. J. Insect Biotechnol. Sericology, 75 89-97. 

The sex pheromone communication system basically involves the release of specific chemicals from a pheromone producer (emitter), the transmission of these chemicals in the environment to a receiver, and the processing of these signals to mediate appropriate behavioral responses in the receiver. The chemicals transmitted downwind have been the most obvious targets for characterization. The code was first broken with the publication in 1959 (3) of the sex pheromone for the domesticated silkworm Bombyx mori after extraction of a half million female silkworm pheromone glands and 30 years of classical chemical analyses. The pheromone was found to be (E10, Z12)-hexadecadien-l-ol, which was called bombykol. This work showed that there was nothing magical about the communication system, and chemists around the world were "attracted" to this area of research on insect pheromones. 

Ommochromes belong to the naturally occurring pigments present in many members of the animal kingdom mainly in insects. Their presence in the central nervous system of the silkworm Bombyx mori was proved by using cellulose and silica stationary phases. The Rp values of standards and the isolated pigments are compiled in Tables 2.107 and 2.108. 

Because the chemical signals (semiochemicals) are normally produced in minute amounts and diluted in the environment with a complex mixture of chemical compounds derived from a myriad of sources, the olfactory system in insects evolved as a remarkably selective and sensitive system, which approaches the theoretical limit for a detector. For example, it has been estimated that the male silkworm moth is able to distinguish within 1 s 170 nerve impulses generated by the female silkworm moth s sex pheromone from 1700 spontaneous nervous impulses [ 1 ], thus, operating on a remarkably low S/N ratio ... 

Karlson and Luscher first introduced the term pheromone in 1959 in a publication about chemical communication in insects in the scientific journal NatureP A pheromone was viewed as a substance that is secreted or excreted into the environment by one individual that elicits some behavioral, developmental, or endocrine response when received by another individual of the same species. The behavioral change in the male silkworm moth in response to bombykol secreted into the environment by the female of the same species fits this mold, for example. 

While the above observation is interesting and could possibly have some implications for the control of the pink bollworm, the complexity of the steroid nucleus of ponasterone A and other molting hormone analogs and their weak insecticidal effect when applied topically or administered orally to most species of economically important insects may preclude their commercialization. The only commercial use of the molting hormone analogs thus far has been in the sericultural industry for the synchronization of cocoon spinning of silkworm colonies (17). 

Figure 2. A molting cycle failure of the silkworm, Bombyx mori, caused by ingestion of the crude methanol extract of Ajuga remota root. The insect underwent normal apolysis, but failed to complete ecdysis. Thus, it could not remove its head capsule or its trunk exuviae. Magnification X11.

Adipokinetic hormones control metabolism of insects during long-distance flight.359 363 In the migratory locust these hormones consist of a pair of related octapeptides and a decapeptide (Table 30-5). The hormones stimulate triacylglycerol lipase in the insects fat bodies, induce release of carbohydrates from body stores, and affect many other aspects of metabolism.363 Insects also have hormones of the insulin family, proteins consisting of disulfide-linked A and B chains as in insulin. The silkworm Bombyx mori has 38 genes for the insulinlike bombyxins, which are synthesized in the brain.364... 

Insects also produce polymers. For example, silk is made by a caterpillar called a silkworm. One silkworms cocoon can contain as much as 900 to 3,000 feet (300 to 900 m) of silk thread. An insect called the Laccifer lacca—or just Lac, for short—lives on trees in India and Southeast Asia. The insects drink the sap from the trees they are living on and produce a polymer that is used to make lacquer and shellac. People use these varnishes to coat and protect ships, houses, wood floors, furniture, and other objects made of wood. 

Figure 1.1 The three major types of hormones that regulate pheromone production in insects. A Juvenile Hormone III (C16 JH), B 20-Hydroxyecdysone and C PBANs from the corn earworm, Helicoverpa zea (Raina et al., 1989), the silkworm moth Bombyx mori (Kitamura et al., 1989) and the gypsy moth, Lymantira dispar (Master et al., 1994). The minimum sequence (pentapeptide) required for activity is indicated.

Ando T., Kasuga K., Yajima Y., Kataoka H. and Suzuki A. (1996) Termination of sex pheromone production in mated females of the silkworm moth. Arch. Insect Biochem. Physiol. 31, 207-218. 

Suwan S., Isobe M., Yamashita O., Minakata H. and Imai K. (1994) Silkworm diapause hormone, structure-activity relationships indispensable role of C-terminal amide. Insect Biochem. Mol. Biol. 24, 1001-1007. 

Bette S., Breer H. and Krieger J. (2002) Probing a pheromone binding protein of the silkworm moth Antheraea polyphemus by endogenous tryptophan fluorescence. Insect Biochem. Mol. Biol. 32, 241-246. 

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