ECOLOGICAL BIOCHEMISTRY - Study Guide - V. M. Isaenko 2005

Chapter 6. ECOLOGICAL AND BIOCHEMICAL INTERACTIONS AMONG ANIMALS

During their vital activity, animals produce A wide variety of BIOLOGICALLY ACTIVE SUBSTANCES. Some of these compounds exert their effects within the same Organism, serving as chemical regulators, stimulants, and modulators of internal physiological processes (such as Hormones and Enzymes). Other substances are released into the environment, where they affect organisms of the same or different species. Compounds perceived by the Senses of smell, Vision, Hearing, and Touch serve as vital signals for animals during feeding, reproduction, defense against predators, and other activities. In a broader sense, these signals act as universal hallmarks of life.

Compounds produced and released into the environment by animals to mediate their interactions are classified by some researchers as telergones. These, in turn, are subdivided into rgones, which affect other individuals of the same species, and heterotelergones, which influence organisms of different species. According to another Classification, which is currently dominant, chemical compounds released by animals for intraspecific communication are referred to, as previously noted (see Chapter 2), as pheromones. Broadly defined, pheromones are single substances or complex combinations of compounds released into the environment by organisms to transmit information that triggers specific responses—such as characteristic behavioral patterns or physiological processes—or, conversely, inhibits certain behaviors and physiological Functions in individuals of the same species that perceive these substances as signals.

Chemicals involved in interactions between different organisms, including animals, are known as allomones (derived from the Greek alios meaning other or foreign, and ornos meaning to set in motion, urge, or prompt) or kairomones (from the Greek kairos meaning advantage or profit). Allomones are substances that confer a benefit or advantage upon the organisms producing them by affecting organisms of other species. Kairomones are substances produced by certain organisms that benefit or advantage other organisms instead.

In insects, pheromones, allomones, and kairomones can either be synthesized within the body from simple precursors or acquired directly from food and used either as is or following specific biochemical modifications. Some animals utilize sequestered plant allomones to protect themselves from being eaten by other predators. At the same time, certain animals produce their own defensive compounds (primarily Alkaloids and terpenoids) using the exact same biochemical pathways found in plants. This phenomenon is observed in ants, millipedes, diving beetles, frogs, and several other animal species.

Chemical signaling substances are also divided into two major groups: releasers and primers. Releaser pheromones elicit an immediate behavioral response in receiving animals; Examples include sex pheromones, alarm pheromones, trail pheromones, and territorial marking pheromones. Primer pheromones, by contrast, induce prolonged physiological effects. These include, for instance, substances that influence the timing of sexual maturation or regulate caste differentiation in social insects.

Yet another classification of chemical signaling substances is based on their biological significance to the animals that produce them (Table 6.1).

Class="center">Table 6.1.

CLASSIFICATION OF CHEMICAL SIGNALING SUBSTANCES IN ANIMALS

according to their biological significance

It should be borne in mind that, depending on specific circumstances, dosage, and the functional state of the organism, the very same substance can elicit quite different biological responses in sensitive animals.