Physiological roles insects

Sex pheromone biosynthesis in many moth species is controlled by a cerebral neuropeptide, so-called PBAN. PBAN is a 33 amino acid C-terminally amidated neuropeptide that is produced by neuroendocrine cells of the subesophageal ganglion (SEG), Studies of the regulation of sex pheromone biosynthesis in moths have revealed that this function can be elicited by additional neuropeptides, all of which share the common C-terminal pentapeptide [99-103]. All of these peptides were found to contain the signature C-terminal sequence and have been designated the PK/PBAN family. The PK/PBAN family is a multifunctional family of peptides that plays a major role in the physiology of insects. In addition to their ability to stimulate sex pheromone biosynthesis in moths, they... 

However, it is now becoming increasingly apparent that conjugation reactions may play an important physiological role in the regulation of insect ecdysteroids. Perhaps this possibility will provide the necessary stimulus for more comprehensive studies in the future. 

Histamine, produced in many tissues, is s)mthesized by removing the carboxyl group from the amino acid histidine (Figure 16.8). It has many, often anno)dng, physiological roles. Histamine is released during the allergic response. It causes the itchy skin rash associated with poison ivy or insect bites. It also promotes the red, watery eyes and respiratory s)tmptoms of hay fever. 

While the increased concentration of 20,26-dihydroxyecdysone was anticipated as a result of 20-hydroxyecdysone metabolism, it cannot be ruled out that 20,26-dihydroxyecdysone has a physiological role of its own in insect development (2) This assumption was supported... 

To summarize, dopa quinone imine conversion factors have been detected in cuticle and/or hemolymph from only three species of Lepidoptera. Other kinds of regulatory factors such as dihydroxy-indole blocking factor have not been detected in insect tissues. The precise physiological roles played by conversion factors that generate indoles is unknown. They may be modulators of reactions associated primarily with melanization. 

The sequence of important reactions forming amines from the essential amino-acids phenylalanine and tryptophan is worthy of attention because of the physiological role of these amines in many animals. Little is known of their effects in insects but they have been shown to be present in insects as neurotransmitters. 

Secondary compounds produced by plants may have other significant survival roles, such as signals to attract insects, birds, or other animals to enhance pollination or seed dispersal. In addition to any potential functions, secondary compounds may concomitantly serve a physiologic function, such as protection against ultraviolet (UV) light or frost, or provide a function in nitrogen transport and storage. In several instances, compounds can serve multiple functions in the same plant. Anthocyanins or monoterpenes can be... 

At the physiological level it is well established that vital dyes such as nile blue, neutral red and methylene blue retard larval development under normal lighting conditions (12L/12D with source unspecified) (25 27). Female but not male pupal weights are also reduced. Unfortunately experiments were conducted without dark controls so that it is difficult to evaluate the role of photosensitization in these effects. As house flies and fire ants succumb to photosensitization, they lose motor control and become more excitable (28). This suggested a neurotoxic effect and investigation of fire ant acetylcholinesterase vitro revealed that this enzyme was sensitive to photo-oxidation. vivo results, however, revealed no effect on the enzyme which suggests another mode of action. Epoxldatlon of cholesterol and membrane lysis may be alternative primary sites. If this were the case ecdysone metabolism of insects would probably also be effected. 

The role of allelochemic-nutrient interactions in insect dietetics has been investigated only rarely. Examples of such interactions abound in vertebrate literature (14, 15) and may supply useful leads for researchers working with Insects. Many of the deleterious physiological effects of plant allelochemics may be due primarily to various interactions between these allelochemics and essential nutrients. In other words, it is Important to not only consider the presence of nutrients, but also the "bio-availability" of these nutrients to the phytophagous Insect. 

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