Endocrine System

Insects, like vertebrates, possess both epithelial endocrine glands (the corpora allata and molt glands, derived during embryogenesis from groups of ectodermal cells in the region of the maxillary pouches) and glandular nerve cells (neurosecretory cells), which are found in all ganglia of the central nervous system and in parts of the visceral nervous system. Their axons terminate in storage and release sites (neurohemal organs) or run directly to their target organ. In addition, the gonads and some other structures of certain species produce hormones.

The functions of hormones are many, and discussion of these is best treated in conjunction with specific physiological systems. In this chapter, therefore, only the structure of the glands, the nature of their products, and the principles of neuroendocrine integration will be examined.

3.1. Neurosecretory Cells and Corpora Cardiaca

The best-studied neurosecretory cells are the median neurosecretory cells (mNSC) of the protocerebrum. They occur in two groups, one on each side of the midline, and their axons (which form the NCC I) pass down through the brain, crossing over en route, and normally terminate in a pair of neurohemal organs, the corpora cardiaca, where neurosecretion is stored (Figure 13.4). In some species, for example, Musca domestica, some neurosecretory axons do not terminate in the corpora cardiaca but pass through them to the corpora allata. In many Hemiptera-Heteroptera, the axons bypass the corpora cardiaca and, instead, terminate in the adjacent aorta wall. In aphids, some neurosecretory axons transport their product directly to the target organ. And the axons of the m NSC which produce bursicon terminate in the fused thoracoabdominal ganglion of higher Diptera and in the last abdominal ganglion of cockroaches andlocusts (Highnam and Hill, 1977). The corpora cardiaca are closely apposed to the dorsal aorta into which neurosecretion and intrinsic products of the corpora cardiaca are released when the neurosecretory cell membranes are depolarized. The NCC I also

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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