Coordination of Events

It is essential that the complex series of events comprising a molt cycle be coordinated. Central to this coordination are hormones (Chapter 13, Section 3), though the expression of their effects can be modified by other factors, for example, nutrition and injury. Many events withinamolt cycle are influenced by hormones, but still unclear is whether this influence is direct or indirect; that is, do hormones directly regulate all of these events or merely initiate a cascade of reactions? The picture is further complicated because more than one hormone may influence the same event.

p-Ecdysone affects many events throughout a molt cycle. It initiates apolysis, stimulates epidermal cell mitosis, increases chitinase activity, promotes the synthesis of select epidermal cell proteins, triggers release of tyrosine from its conjugates, and induces the synthesis of several enzymes involved in tanning. Further, the development and activity of the epidermal feet are correlated with changing hemolymph ecdysone levels in the final larval instar. Among the earliest studies of the site of action of ecdysone were those of Karlson et al. (see references in Neville, 1975), specifically in relation to tanning. Ecdysone stimulates synthesis of dopa decarboxylase mRNA. Karlson's group suggested that ecdysone acted on the epidermal cells and this is supported by in vitro studies on isolated epidermis. However, for some species, it also seems likely that the hemocytes are a target organ. More recently, the ability of p -ecdysone to induce the expression of genes for other key molecules in the molt cycle has been shown, for example, for chitinase (Zheng et al., 2003). It appears that genes associated with the molt cycle differ in their sensitivity to the hormone, some being switched on at low (or decreasing) concentrations, others requiring higher (or increasing) titers for their expression. In this way, varying amounts of p-ecdysone throughout

Beekeeping for Beginners

Beekeeping for Beginners

The information in this book is useful to anyone wanting to start beekeeping as a hobby or a business. It was written for beginners. Those who have never looked into beekeeping, may not understand the meaning of the terminology used by people in the industry. We have tried to overcome the problem by giving explanations. We want you to be able to use this book as a guide in to beekeeping.

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