Accessory Gland Substances Research Articles

Male accessory gland substances activate egg development in nutritionally stressed Aedes aegypti mosquitoes

The effect of mating on egg development in starved Aedes aegypti mosquitoes was examined. Mated females that were maintained on water for 4 days before ingesting blood were more likely to develop eggs than were unmated females. The implantation of a single male accessory gland from either A. aegypti or A. albopictus males increased the proportion of unmated females that developed eggs, but glands from A. bahamensis or A. taeniorhynchus did not. Male accessory gland homogenates from A. aegypti were also active when injected at concentrations of 0.02 gland equivalents or greater, but heating them destroyed their activity. When a small blood meal was supplemented with saline to increase abdominal distention, only mated females responded to the distention with increased egg development. Juvenile hormone topically applied to sugar-deprived, blood-fed unmated females also enhanced egg development. If males were starved for 3 days before they mated, they were less likely to stimulate oögenesis in sugar-deprived blood-fed females than if the males were maintained on sucrose before mating.

Effects of male accessory gland substances on the pre-oviposition behaviour of Aedes aegypti mosquitoes

Secretions of the male accessory glands of Aedes aegypti (L.) induce gravid virgin females to engage in pre-oviposition behaviour. Normal mating, the implantation of whole glands, or the injection of male accessory gland homogenates, all induced pre-oviposition behaviour in gravid virgin females, but implants of testes did not. Injection of male accessory gland extracts from other mosquito species, including A. albopictus, A. sierrensis, A. taeniorhynchus and Anopheles nr. salbaii into gravid virgin A. aegypti females did not induce pre-oviposition, suggesting that the male components were species-specific. Male accessory gland substances retained their biological activity when stored at 4°C for 24 h or when maintained at −10°C for 2 weeks, but lost their activity after longer periods and were inactivated by heating.

Male accessory gland substances and the control of sexual receptivity in female Culex tarsalis

ABSTRACT. Homogenates of accessory glands from male Culex tarsalis Coquillet (Diptera; Culicidae) were fractionated using gel filtration column chromatography. A component of low molecular weight capable of suppressing female sexual receptivity was obtained and partially characterized. Proteins present in homogenates of isolated accessory glands formed aggregates with other proteins in extracts of whole mosquitoes. Consequently, previous reports of the molecular weight of biologically active components in homogenates from accessory glands from other mosquito species may be inaccurate.When female Cx. tarsalis were mated with 3H‐leucine labelled males. radioactivity could be found throughout the body of the female 24 h after mating. Autoradiography showed that the radioactivity was incorporated into the cells of various organs, and was not specifically localized in a particular target tissue. Approximately 30% of the total radioactivity transferred to the female was found in the head and thoracic regions, and proteins from the head had a specific activity twice that of the thoracic proteins. Bioassay of isolated body parts from mated and virgin females showed that injections of head tissues from mated females into virgin females suppressed sexual receptivity. These results suggest that the head is involved in the physiological mechanisms resulting in refractory mating behaviour.

Anopheles stephensi (Diptera: Culicidae): changes in male mating competence and reproductive system morphology associated with aging and mating.

Laboratory observations on the mating behavior of the Khano-Harni ( KH ) strain of Anopheles stephensi indicated that females and males become sexually mature by their 2nd night of life. Some females (10%, n = 67) mated on their night of emergence when crossed with 3-day-old males. At 28–30 °C maximum male mating activity occurred between 3 and 7 days of age. Comparisons between the percentage of laboratoryadapted KH females inseminated by KH males and wild-caught ( WC ) males indicated that little change in group mating occurs during colonization, while the ability of males to mate singly improves with laboratory selection. Dissections of KH males of known age and mating history indicated that the number of spermatocysts decrease and the proportion of the testes occupied by the sperm reservoir increases with age, while the quantity of spermatozoa present in the sperm reservoir and postgonadal system and the degree of repleteness of the male accessory glands with secretory material decreases with successive matings. The male reproductive system was found to rejuvenate after mating, with the replenishment of male accessory gland substance in the accessory glands and spermatozoa in the sperm reservoir and postgonadal system. Males that multiplymated during an abbreviated interval took longer to rejuvenate their reproductive systems than did males mating once. Morphological changes associated with age and mating were used to develop a method to determine age and the reproductive history of male An. stephensi

Evidence of neuroendocrine relationships between mating and ovulation in the tsetse fly, Glossina morsitans morsitans

Although mating is a necessary prerequisite for the induction of ovulation in the tsetse fly, Glossina morsitans morsitans, neither the accessory gland substance from the male nor any testicular component is responsible for causing ovulation. Experimental evidence suggest that two neural factors, one originating from the uterus during mating act as an afferent stimulus, and the other originating from the ovary during oocyte maturation regulate a cerebral hormonal factor which controls the event of ovulation. It is probable that one successful copulation removes an inhibition for the release of an ovulation stimulating hormone from the neurohemal organ into the circulation. The rate of synthesis and/or transport of the hormone from the neurosecretory cells to the neurohemal organ is probably regulated by the rate of oocyte development.

Modification of female circadian flight‐activity by a male accessory gland pheromone in the mosquito, Culex pipiens quinquefasciatus

ABSTRACT. The pattern of circadian flight activity in female Culex pipiens quinquefasciatus was modified after insemination or injection with an extract of male accessory glands. The changes were linked with an apparent alteration in the timing of one of the major components of the rhythm. In LD 12:12, virgin females were highly active at ‘dusk’ and ‘dawn’ and in the latter part of the dark phase; inseminated females were less active at ‘dusk’ and ‘dawn’ and were active in the first half of the dark phase. In DD, there were two peaks in each cycle, the initial (evening) peak occurring at the same time after all treatments; the peaks were approximately 12 h apart in virgin females, but only 6–7 h apart in females which had been inseminated or injected with accessory gland extract. The accessory gland substance (pheromone) also appeared to cause a progressive increase in activity. These induced changes are consistent with a switch to host‐seeking behaviour, which, under natural conditions, leads to a peak of biting in the middle of the night.

Autogeny in saltmarsh mosquitoes induced by a substance from the male accessory gland

OVARIAN maturation by mosquitoes and other haematophagous Diptera without a prior blood meal is called autogeny, while the term anautogeny applies to those cases where blood is necessary. Many populations of the saltmarsh mosquito, Aedes taeniorhynchus, contain both autogenous and anautogenous females1–2. Moreover, within this species there are two types of autogenous females : (1) those that need a stimulus from mating to produce eggs autogenously and (2) those that lack this requirement3. We report that autogenous egg production associated with mating is triggered by a substance from the male accessory gland. The stimulation of normal oviposition behaviour and the termination of sexual receptivity in the female mosquito are also caused by a male accessory gland substance which is introduced into the female during mating4,5. Both of these responses are uniformly exhibited by all females of several species6.

Rôle of male accessory gland substance in the regulation of blood intake by mosquitoes

The presence of male accessory gland substance during mating is shown to increase the blood intake in the adult female Aedes aegypti and Culex pipiens fatigans. Females mated with males whose accessory glands were surgically removed took significantly less blood than females mated with normal males. However, females mated with males whose seminal vesicles were surgically removed took as much blood as the controls.

Involvement of male accessory gland substance in the fertility of mosquitoes

The male accessory gland substance is shown to be involved in the fertility of eggs for the first time in Aedes aegypti and Culex pipiens fatigans. Surgical removal of the paired accessory glands of males did not impair their mating ability. However, the eggs laid by the females after mating with operated males were found to be sterile. This condition could be reversed if the accessory gland substance was later received by the females. Evidence suggests that the accessory gland substance is essential for fertilization.

Neuro-hormonal control of sexual behavior in insects.

In the life of a sexually reproducing organism there is no single act more important in an evolutionary sense than copulation. An unmated individual is an evolutionary dead-end whose genes are lost to future generations of its species. Approximately the same outcome lies in store for the genes of indi­ viduals which mate inappropriately and leave offspring of reduced fitness or no offspring at all. This opening statement serves to emphasize the strength of the selective forces acting on behaviors and physiological mechanisms related to the act of copulation. It may be assumed that each behavior or physiologi­ cal mechanism influencing mating has an adaptive significance in promoting reproductive success. In insects, location and selection of a suitable mate de­ pends primarily on inherited mechanisms owing to limitations of time, neural circuitry, and lack of parental care. Even though internally controlled, the development and performance of mating behavior must be sensitive to envi­ ronmental conditions if for no other reason than that successful copulation demands the cooperation of a member of the opposite sex. Mutual stimula­ tion of mating partners seems to be the predominant pattern in insects; there­ fore, it seems appropriate to look for control mechanisms in the area of coor­ dination of sensory input and motor responses, i.e. in the central nervous sys­ tem. The efficiency of the reproductive effort will be increased if there is some method of synchronizing the act of copulation with the presence of mature or nearly mature gametes and, in the case of the male, the ability to produce the secretions necessary for sperm transfer. Oocyte development and the produc­ tion of accessory gland substances are dependent on the synthesis of specific proteins. This protein synthesis is stimulated in most cases by hormones re­ leased into the blood, of which the hormonal product of the copora allata predominates. Both nervous and hormonal mechanisms are important in coordinating reproductive processes. The neuroendocrine system is the essen­ tial connecting link between the two coordinating systems, operating so that behavior can be coordinated with gamete maturation. There exists a consider­ able body of literature which concerns itself with the identification and de-

The effect of matrone on oviposition in the mosquito, Aedes aegypti

Male Aedes aegypti produce a substance made or stored in their accessory glands, which when passed on to females via mating, will prevent subsequent insemination. In addition to becoming refractory with regard to further insemination, mated females also oviposit far more eggs than virgins. The male accessory gland substance, called matrone, has been highly purified and when injected into virgin females, prevents any initial insemination, and will also stimulate oviposition. Matrone can be fractionated into two protein fractions both of which are needed to prevent insemination. However, only one of the fractions will stimulate oviposition; the other has no discernible biological effect when administered by itself.

Reproductive Behavior and Effects of the Male Accessory Gland Substance in the Cabbage Maggot, Hylemya brassicae

Adults of Hylemya brassicae (Bouche) were observed in the laboratory to obtain data on mating behavior and fertility. Most mating occurred early in the day, and this rhythm was influenced only slightly by exposure to continuous light. Males mated throughout their lives with the peak activity period at age 3 days. There was some loss of fertility in the males with age and mating frequency. The occurrence of a mating pheromone seemed unlikely. Oviposition and inhibition of further matings, normally triggered by copulation, were produced in nonmated females by injections of the male accessory gland substance.

Mosquitoes: female monogamy induced by male accessory gland substance.

Male accessory glands were implanted in virgin females of Aedes aegypti. When exposed to males, females copulated readily but were not inseminated; they remained sterile for life. Extract from one male could sterilize more than 64 females. The active principle may be a protein or peptide. Intraspecific transplant prevented insemination in 12 species, including Aedes, Anopheles, and Culex; interspecific transplant gave partial protection.