Sensory Hairs

The simplest form of mechanosensillum is seen in sensory hairs (sensilla trichodea) (Figure 12.1), which occur on all parts of the body but are in greatest concentration on those that frequently come into contact with the substrate, the tarsal segments of the legs, antennae, and mouthparts. Typically, they are single structures but on occasion they are found in large groups known ashairplates (Figure 12.2). In its simplest form a sensillum comprises arigid, poreless hair set in a membranous socket and four associated cells; these are the inner sheath cell (also known as the trichogen or generative hair cell), outer sheath cell (tormogen or membrane-producing cell), neurilemma cell, which ensheathes the cell body and axon of the sensory neuron, and the sensory neuron whose dendrite often is cuticularized and includes a terminal cuticular filament (scolopale) (McIver, 1985; Keil, 1997, 1998). In addition to their generative function, the outer sheath cells have an important physiological role in maintaining the appropriate ionic and molecular environment for stimulus transduction and conduction by the dendrites. Specifically, they pump K+ ions into the space that surrounds the tip of the sensory dendrite to facilitate generation of the receptor current (Section 2.3). A characteristic feature of the tip of sensory neurons are large numbers of microtubules. Because of their position and experiments with antimicrotubule drugs, it has been suggested that the microtubules may play a role in transduction. However, French's (1988) assessment of the evidence led him to conclude that their more likely roles are in the development and structural maintenance of the sensilla.

Within the above-generalized structure, hairs may differ widely in their detailed morphology, physiology, and function (Section 2.3). Nevertheless, they are all designed such

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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