Salt And Water Balance

Osmotic pressure of medium as % NaCI

FIGURE 18.6. The relationship between osmotic pressure of the hemolymph and that of the external medium in some freshwater insects. [After J. Shaw and R. H. Stobbart, 1963, Osmotic and ionic regulation in insects, Adv. Insect Physiol. 1:315-399. By permission of Academic Press Ltd. and the authors.]

In freshwater insects, food is the usual source of ions that are absorbed through the midgut wall. However, in some species ions are accumulated through other parts of the body, for example, the gills of caddisfly larvae, the rectal respiratory chamber of dragonfly, damselfly and mayfly larvae, the anal gills of syrphid larvae, and the anal papillae of mosquito and midge larvae. The role of the anal papillae in ionic regulation has been particularly well studied. In mosquito larvae a pair of papillae is located on each side of the anus (Figure 18.7A). They communicate with the hemocoel and are well supplied with tracheae. Their walls are a one-cell-thick syncytium (perhaps an adaptation to eliminate intercellular leakage) and covered with a thin cuticle (Figure 18.7B). Mosquito larvae can accumulate chloride, sodium, potassium, and phosphate ions against large concentration gradients using the papillae. The ability to accumulate ions varies with the habitat in which an insect is normally found. Thus, Culexpipiens, which is found in contaminated water, is less efficient at collecting ions than Aedes aegypti, which typically lives in fresh rainwater pools. Indeed, normal larvae of the latter species can maintain a constant hemolymph sodium concentration when the sodium concentration of the external medium is only 6 |aM/l. The hemolymph sodium concentration under these conditions is only about 5% below the normal level (Shaw and Stobbart, 1963).

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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