Alarm, pheromones involved

Phenomena of alarm. The pheromones involved here are usufdly emitted by attacked or injured individuals, and represent a system of defence within the species against predators (Atema and Stenzler, 1977). With the cyprinoid Phoxinus phoxinus, the fright substance, identified as isoxanthopterin (Pfeiffer and Lemke, 1973), is actively secreted by the skin of alarmed individuals and induces flight in other individuals of the same species. It is interesting to note that this pterin is also produced by copepods and ascidians (Momzikoff, 1973). 

Pheromones are often described by function, by the effect they have. For example, sex pheromones describe those involved in mate-finding or attraction. Others include aggregation, alarm, and trail pheromones. Some responses are context-specific - for example in some ant species alarm pheromones cause ants to disperse if released far from the nest but to attack if released close to the nest. In a way, these descriptors allow us simply to describe the range of behaviors mediated by pheromones and then generalize from these to describe patterns in use, say, of sex pheromones across taxa. 

In this chapter, we review the ways whereby lobsters chemically communicate with each other and the contexts in which they do it. We make a distinction between different types of chemicals. Based on the terminology of Wyatt (Chap. 2), we use semiochemicals as chemicals involved in animal interactions and pheromones as a subset of semiochemicals used in intraspecific contexts. We also use cues as chemicals that benefit the receiver and not necessarily the sender, with a prime example being alarm cues released in the blood of injured conspecifics. 

Wilson (3) and Wilson and Bossert (4) divided pheromones into release pheromones (if the stimulus triggers an immediate behavioral response in the receiving organism) and primer pheromones (if the response is a long lasting one). Substances involved in alarm, territorial marking, trail, social status, sexual attraction and reproductive isolation are release pheromones while the odors involved in puberty acceleration, pregnancy block, estrus synchronization or suppression are primer pheromones. 

The term recruitment , like the term alarm has become diffuse as the diversity and complexity of social insect behavior has emerged. In this review we will take recruitment to mean the inducement of workers to move from one area to another, either to retrieve food or to move to new territory or a new nest site. The chemical signals involved are usually, but not always, deposited on the substratum, and may therefore also constitute an orientation signal. The two possible functions of trail pheromones , recruitment of nest mates and orientation to food or nest, need to be carefully separated to estimate the importance of these chemical signals in the ecology of each species. 

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