Reproductively Active Chemicals

Lewis, R. J., Reproductively Active Chemicals A Reference Guide (New York Van Nostrand-Reinhold, 1991). 

For our purposes, oaks are important because they drop the acorns that determine how many white-footed mice successfully withstand the harsh winter months. Before winter arrives, however, a multitude of other factors has influenced the number of mice available to gather the acorns. One of these factors is the mice s reproductive activity, and this happens to be under the influence of some peculiar pheromones. Because they contribute to determining the number of mice, these chemicals also enter our story. They are airborne signals present in adult-mouse urine that affect the maturation and reproductive success of young female mice. 

The VNO is extremely important in mediating endocrine responses to primer pheromones. Puberty acceleration in female rats by male urine odors can be prevented by electrolytic damage to the vomeronasal nerve. Also, effects of male urine odor such as shortening of the estrus cycle (see Ch. 8) can be eliminated by section of the vomeronasal nerve, or bilateral electrocoagulation of the accessory olfactory bulb (Sanchez-Criado, 1982). In rats, the odor of males stimulates ovulation in females, an effect that is lost if the VNO is extirpated (Johns etal., 1978). Female prairie voles, M. ochrogaster, respond to odors from males with reproductive activation. Surgical removal of the VNO from adult females impedes this reproductive activation by the stud male. The weights of the uterus and the ovaries of these females were lower than those of normal or sham-operated individuals. However, the females without a VNO were still able to locate food by chemical cues (Lepri and Wysocki, 1987). 

Apart from chemicals that act directly as pheromones in the reproductive activity of higher animals, there are many other associated materials, sometimes coming from animal excrement, that cause an arousal of interest and act as innate recognition factors between animals within a species, or as a warning to others. Some of these, as we will see later, have an important function in perfumery. 

The challenge remains to identify more precisely the specific surface chemical arrays on a foreign material which, when it is inserted into the uterine cavity, might trigger reactions that produce these adverse effects as well as inhibit reproductive activities (23). 

In a cell, the total number of molecules is limited. If there are a huge number of chemical species that catalyze each other, the number of some molecules species may go to zero. Then molecules that are catalyzed by them no longer are synthesized. Then, other molecules that are catalyzed by them cannot be synthesized, either. In this manner, the chemical compositions may vary drastically, and the cell may lose reproduction activity. 

Gregarious behavior might have various advantages ranging from resource exploitation to mate finding or reproductive synchronization. For example in some terrestrial isopods, reproductive activity of females appears to be synchronized through chemical cues transmitted via feces (Mead and Gabouriaut 1988 Caubet et al. 1998), which are common in communal shelters. 

In this terrestrial salamander system, chemical signals are broadcast in the environment by reproductively active females and are detected by the males as they tap... 

Solomon, N. G., Vandenbergh, J. G., Wekesa, K. S. Barghusen, L. 1996. Chemical cues are necessary but insufficient for reproductive activation of female pine voles Microtus pinetorum). Biol. Reprod., 54, 1038-1045. 

Exp. 3. Is the Chemical Signal Stimulus-Sex Specific To test if the chemical stimulus is specifically produced and/or secreted by females, males were tested individually with two models. Female-scented models were prepared immediately before testing by soaking clean models for 2 hours in 350 ml water that had held 35 females for about 12 hrs. Male-scented models were prepared similarly except that the water (250 ml) had held 25 freshly caught, reproductively active males. 

In males of a number of teleost species, chemical stimuli from conspecific females have been shown to attract males or to cause an increase in male reproductive activities (Liley, 1982). In contrast to the situation in females, it is clear that in many cases the responses of males to female... 

Snakes, as a group, are visually cryptic and auditorially impoverished. Therefore, it is probable that chemical cues are quite important in mate location. The utilization of pheromone trails in the reproductive activity of snakes has been examined to some extent in temperate zone colubrids. In these snakes, sexual behavior occurs primarily in the spring. Males leave the hibernacula first and remain in the vicinity to court the females when they emerge. At this time, female snakes leave trails for the males to follow. The pheromone involved is likely the same lipoprotein (vitellogenin) which the females produce in the liver and secrete through the skin to stimulate male courtship activity (Garstka and Crews, 1981, this volume), although the only evidence for this is that the sexual pheromone trails are also produced by skin secretions and, like a lipoprotein, are non-volatile and persistent (Ford and Low, 1984). 

In several species of rodents, the rate of sexual maturation and density of natural populations are negatively correlated (Krebs and Myers, 1974), Chemical signals discharged by females could be one of the important factors limiting reproductive activity. 

Compared with aggressive and recruitment behavior, literature on the involvement of chemical signals in sexual behavior and reproduction in ants is scarce. This is probably because sexual activity in ants is normally restricted to a few days in the year, and is not easily induced in the laboratory. Two aspects will be discussed here, the bringing together of the sexes prior to mating, and the control of reproductive activities by queens. 

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