. Comparative animal physiology. Physiology, Comparative; Physiology, Comparative. CHAPTER 12. Chemoreceotion INTRODUCTION ANY ORGANISMS Utilize sensitivity to the chemical consti- tuents of the environment in the detection of food, initiating the necessary orientation to food, and in regu- lating the feeding habits and the ingestion of foods, and in the avoidance of chemically unfavorable environments. Among insects and some other animal groups chemoreception plays an important part in reproductive behavior, , attraction of male to female, and in regulating deposition of the fertilized eg
. Comparative animal physiology. Physiology, Comparative; Physiology, Comparative. CHAPTER 12. Chemoreceotion INTRODUCTION ANY ORGANISMS Utilize sensitivity to the chemical consti- tuents of the environment in the detection of food, initiating the necessary orientation to food, and in regu- lating the feeding habits and the ingestion of foods, and in the avoidance of chemically unfavorable environments. Among insects and some other animal groups chemoreception plays an important part in reproductive behavior, , attraction of male to female, and in regulating deposition of the fertilized eggs, Chemoreception is, therefore, an important adjunct to the other sensory activi- ties of organisms, all of which are essential for survival and propagation of the species. The sense organs responsible for chemoreception have not been completely identified, but all the evidence seems to indicate three types which differ in sensitivity as well as in the role they play in animal orientation. The proto- zoans and sponges exhibit no specific chemoreceptors and it is generally agreed that, in these phyla, chemosensitivity is a consequence of the general property of irritability inherent in living matter. This general chemical sensitivity has been retained by the higher metazoans, including the vertebrates, al- though among the latter Parker^^ has suggested that specific receptors, free nerve endings in the skin or mucous membranes, are involved in general chemical sensitivity.'- The outstanding characteristics of this general chemi- cal sense are its low order of sensitivity and the negative avoiding reaction which is typically elicited. In free living planaria, in insects, and in the vertebrates, there is excellent evidence for the existente of specialized chemoreceptors whose sensitivity is greater and whose role in organismic orientation differs from that of the gen- eral chemical sense. Koehler"*" has published evidence indicating the exist- ence of chemoreceptors lo
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