褛裳夜蛾的交配行为及雄蛾对性腺提取物的反应节律

详细观察了褛裳夜蛾成虫的交配行为,利用风洞、触角电位技术研究了雄蛾对性腺提取物的反应节律,通过林间诱蛾试验进行了验证,旨在为褛裳夜蛾性信息素的精确提取及性信息素组份分离、鉴定提供依据。研究结果表明:成虫的求偶、交配行为均发生在暗期,有一定的节律性:雌蛾在羽化3d以后开始求偶,1周左右表现最为强烈,3-4日龄雌蛾在暗期4-6h开始求偶,最大求偶率在暗期6-8h;5-9日龄在进入暗期就开始求偶,最大求偶率出现在暗期4-6h。风洞试验表明,3-7日龄的雄蛾对性腺提取物均有明显的性行为反应,5日龄雄蛾在暗期4-6h对性腺提取物的反应最为强烈。3-6日龄的成虫在暗期4-6h开始交配,而7-8日龄的成虫于暗期2-4h开始交配,6日龄的成虫交配率最高,交配高峰在暗期4-8h。雄蛾对性腺提取物的触角电位反应也有一定的节律性:雄蛾对4日龄雌蛾性腺提取物开始有电生理反应,对6-7日龄暗期5h性腺提取物反应最为强烈。林间诱蛾试验测定了性腺提取物的引诱活性,7日龄雌蛾性腺提取物林间诱蛾量最高,引诱高峰在暗期4-6h,该结果也验证了褛裳夜蛾雄蛾对性腺提取物的反应节律。     

松墨天牛是否存在雌性接触信息素?

将松墨天牛MonochamusalternatusHope的身体不同部位切除之后的交配试验显示,分别剪去头部、鞘翅以及前胸部后仍然可以正常交配,用雄虫的腹部代替雌虫的腹部后,仍然能够引起雄虫的交配趋势动作,但不能完成真正交配,因此推测雌性接触信息素如果存在,主要集中在雌虫身体后半部,尤其是中后胸部位。但是冻死后的雌虫不再引起雄虫的交配行为,而且冻死的雌虫与活雌虫同时放入培养皿中,雄虫喜欢与活雌虫交配,不选择冻死的雌虫,因此推测视觉在其松墨天牛的交配过程中扮演着重要的角色,而接触性信息素有可能并不存在。将雄虫的触角分别从第5~6节和第1节剪去的试验结果显示,雄虫仍然可以很快地找到雌虫,发生交配行为。这有2种可能的解释一是雄虫不仅仅靠触角来感受雌虫的接触信息素,头部下颚须和下唇须上或者足上也有可以感受信息素的感受器;二是雌虫不存在接触信息素,雄虫通过视觉就可以找到对方,完成交配过程。浸泡致死的雌虫不再引起雄虫的交配行为,并且将正己烷和乙醚的浓缩液滴加在浸泡致死的雌虫以及玻璃棒和鹅卵石的生测试验结果显示,都没有引起雄虫的交配行为。这进一步说明,松墨天牛可能并不存在体表接触信息素。性成熟后的松墨天牛雌雄成虫是靠衰弱寄主的强烈的挥发性气味聚集到寄主树干上,在树干这个较为狭小的环境里,有可能是通过视觉找到配偶,完成交配过程。     

Juvenile hormone titre and egg production in Tenebrio molitor infected by Hymenolepis diminuta: effect of male and/or female infection,male age and mating

Infection of Tenebrio molitor with Hymenolepis diminuta induces curtailment of female fertility. We examined ovulation and oviposition, and associated titres of juvenile hormone (JH), in relation to parasitism and mating. Oviposition was significantly increased in infected mated and virgin beetles by days 6 and 9 post-emergence. Ovulation was not changed by infection; by the end of the 18-day experiment, the total number of laid eggs was not significantly altered. On day 6, JH levels were significantly higher in virgin infected insects, compared to non-infected controls (236+/-37.7 and 107+/-9.62 pg/g wet weight). Oviposition increased after mating, but total eggs ovulated remained the same. JH levels were higher in mated females on days 12 and 18 post-emergence, for infected and control insects. Previous studies suggested that male reproductive potential might rise following infection, because uninfected females lay more eggs when mated to infected males. We tested whether this caused an increase in female JH. Males were mated on days 5 or 12, when significant changes in their reproductive physiology begin to be observed, and are maximal, respectively. However, male age was of greater significance in promoting JH levels in females (p=0.001), than infection status of either partner (p=0.33).     

蜀柏毒蛾生殖行为及性信息素产生与释放节律

为了探索蜀柏毒蛾Parocneria orienta Chao性信息素产生和释放规律, 为利用性信息素监测和防治蜀柏毒蛾奠定基础, 本研究在野外及室内温度22±1℃、 相对湿度75%~80%、 光周期14L∶10D条件下观察研究了蜀柏毒蛾成虫的羽化、 求偶、 交尾、 产卵行为, 触角电位反应测定处女雌蛾性信息素产生与释放的时辰节律。结果表明： 蜀柏毒蛾羽化行为全天可见, 主要集中在1:00-5:00, 占总羽化量的44.94%, 7:30-11:00进行婚飞和交尾, 交尾高峰期出现在8:30左右, 交配时间少则2 h, 多则8 h, 求偶、 交配均发生在光期。随着日龄的增加, 召唤时间前移并且延长, 1日龄的处女雌蛾交尾时间较短; 雌蛾羽化当天就可交尾, 2日龄雌蛾交尾率最高, 达36.67%。雌蛾分多处产卵, 雌蛾一生最高产卵量达402粒, 最低产卵量为78粒。羽化当天的雌蛾体内性信息素含量较低, 第2天最高, 以后逐日下降; 2日龄蜀柏毒蛾处女雌蛾性信息素的产生量从7:00起逐渐增加, 8:30-9:30时最高, 9:30后逐渐减小。雄蛾对处女雌蛾腺体提取物的触角电位反应在8:30-9:00最强, 说明8:30-9:00是雌蛾产生和释放性信息素的高峰期。蜀柏毒蛾的羽化、 求偶、 交尾及性信息素的产生与释放存在一定的时辰节律, 野外处女雌蛾诱蛾试验证实了性信息素释放与交配行为在时辰节律上的一致性。     

Impact of a novel species of Nosema on the southwestern corn borer (Lepidoptera: Crambidae)

A study was undertaken to elucidate the impact of an undescribed Nosema sp. on the southwestern corn borer (SWCB; Diatraea grandiosella Dyar). The Nosema sp. (isolate 506) included in the study was isolated from an overwintering SWCB larva in Mississippi. It was highly infectious per os, with a median infective dose of 2.0 x 10(3) spores per larva. Even at the highest dosage tested (10(7) spores per larva), minimal mortality (< or = 3%) was observed in infected larvae, pupae, and adults reared in the laboratory on an artificial diet. However, infected pupae (0- and 7-d-old) were smaller, and the time to adult eclosion from pupation was slightly increased. Furthermore, the number of eggs produced by infected SWCB female moths substantially decreased (32%), and this effect was most pronounced on day 2, when the greatest number of eggs were oviposited by infected and noninfected moths. For eggs produced by infected females mated with infected males, hatch was slightly decreased by 16 and 15% for eggs laid on days 2 and 3, respectively. In addition, egg hatch was reduced in eggs oviposited by noninfected females mated with infected males on day 3. A low prevalence of infection (< 6%) was observed in the F1 generation originating from infected females mating with noninfected males, from noninfected females mating with infected males, and from infected females mating with infected males. Nosema 506 spores were observed in the proximity of reproductive tissues of infected female and male moths. Spores also were detected on the chorion surface and within eggs laid by infected females. Furthermore, 1-11% of larvae hatching from surface-sterilized eggs were infected by Nosema 506 indicating a transovarial mechanism of transmission.     

日龄和交配状态对二化螟雄蛾内生殖器特征的影响

【目的】性信息素群集诱杀应用于二化螟Chilo suppressalis测报和防治。本研究旨在明确性信息素群集诱杀二化螟的机理及诱集雄蛾的交配状态。【方法】利用行为学和生殖器解剖技术,研究不同日龄和交配状态二化螟雄蛾内生殖器特征,并将其与田间性信息素诱集获得的雄蛾进行比较。【结果】二化螟雄蛾单射精管非角质化区可分为7段;生殖器内含物主要为白色,紧实程度可以分为5级(0-4级),存在充满和未充满生殖器两种状态。随着日龄增加,雄蛾附腺以及第3和4段非角质化区内含物等级降低,第5和7段非角质化区内含物未充满比例升高,内含物为白色的比例下降。交配后1 h之内二化螟雄蛾第5和7段非角质化区和复射精管内含物等级显著低于未交配雄蛾,而第1-4段非角质化区内含物等级显著高于未交配雄蛾。交配后24 h,所有内含物等级和未交配雄蛾无显著差异;交配后36 h,第5和7段非角质化区内含物未充满比例高于未交配雄蛾。性信息素诱集和未诱集雄蛾生殖器内含物等级无显著差异。田间性信息素诱集雄蛾附腺端半部内含物等级显著高于2-6日龄未交配二化螟,第3和4段非角质化区内含物等级显著低于刚羽化(0日龄)雄蛾。【结论】本研究结果表明,利用生殖器内含物特征可以区别交配后12 h内的已交配和未交配二化螟雄蛾,性信息素群集诱杀的可能大部分是羽化1 d的未交配雄蛾。本研究结果为二化螟雄蛾交配状态判定和蛾类害虫性信息素测报和防治的有效性提供了一定依据。     

豆野螟成虫行为学特征及性信息素产生与释放节律

豆野螟Maruca vitrata (Fabricius)是一种严重的泛热带豆类蔬菜害虫。本文在（29±1）℃、相对湿度75%～80%、光周期14L∶10D条件下研究了豆野螟成虫的羽化、交尾行为以及雌蛾性信息素的释放节律。结果表明：其羽化行为全天可见,在雌蛾中,86%于暗期羽化; 在雄蛾中,73%于暗期羽化。雌雄蛾羽化行为在暗期第4、5和8 h差异达到显著 (t>4; P<0.05)。交尾活动发生在暗期19：00到5：00之间,交尾持续时间最短约为20 min,最长约为90 min,3日龄进入暗期第5 h具有最高的交尾率。1、6和7日龄成虫具有单个交尾高峰,2到5日龄成虫具有两个交尾高峰。同一日龄成虫交尾在暗期前半段平均花费的时间要明显高于在后半段花费的时间。低龄和高龄的成虫用于交尾的时间明显高于中龄的性成熟成虫。成虫的开始交尾时间随着日龄的增加逐渐前移。雄蛾对进入暗期后第5 h和第9 h处女雌蛾的性腺提取物和空气收集性信息素的触角电位反应最强,对 3日龄处女雌蛾的性腺提取物和空气收集性信息素的触角电位反应最强。处女雌蛾田间诱蛾试验表明：23：00-01：00为诱蛾高峰期,3日龄处女雌蛾的诱蛾效果最好。该蛾的羽化、交尾及性信息素产生与释放均存在节律上的一致性。雌蛾的性信息素释放的时间较长,见于整个暗期,然而交尾行为发生时间较短,主要发生于两个交尾高峰之间。     

Assortative Mating in Two Pheromone Strains of the Cabbage Looper Moth, Trichoplusia ni

The evolution of animal communication systems is an integral part of speciation. In moths, species specificity of the communication channel is largely a result of unique sex pheromone blends produced by females and corresponding specificity of male behavioral response. Insights into the process of speciation may result from studies of pheromone strains within a species in which reproductive isolation is not complete. Toward this end we investigated assortative mating based on female pheromone phenotypes and male response specificity between mutant and normal colonies of the cabbage looper moth, Trichoplusia ni. There was no evidence of assortative mating in small cages in which the density of moths was high. In larger cages with lower densities of moths, assortative mating was evident. In these larger cages, matings between normal males and normal females and mutant males and mutant females were more frequent than interstrain matings. Wind tunnel tests indicated that normal males responded preferentially to pheromone released by normal females, whereas mutant males did not discriminate between normal and mutant pheromone blends. In large field cages, pheromone traps baited with normal females caught equal numbers of mutant and normal males, while pheromone traps baited with mutant females caught primarily mutant males. The overall pattern of assortative mating could be explained primarily based on the normal males' preference for the pheromone blend released by normal females.     

Sexual selection in an isopod with Wolbachia‐induced sex reversal: males prefer real females

A variety of genetic elements encode traits beneficial to their own transmission. Despite their ‘selfish’ behaviour, most of these elements are often found at relatively low frequencies in host populations. This is the case of intracytoplasmic Wolbachia bacteria hosted by the isopod Armadillidium vulgare that distort the host sex ratio towards females by feminizing the genetic males they infect. Here we tested the hypothesis that sexual selection against Wolbachia‐infected females could maintain a polymorphism of the infection in populations. The infected neo‐females (feminized males) have lower mating rates and received less sperm relative to uninfected females. Males exhibited an active choice: they interacted more with uninfected females and made more mating attempts. A female behavioural difference was also observed in response to male mating attempts: infected neo‐females more often exhibited behaviours that stop the mating sequence. The difference in mating rate was significant only when males could choose between the two female types. This process could maintain a polymorphism of the infection in populations. Genetic females experimentally infected with Wolbachia are not exposed to the same sexual selection pressure, so the infection alone cannot explain these differences.     

Spermatophore production and spermatheca content in Tenebrio molitor infected with Hymenolepis diminuta

Male and female Tenebrio molitor act as intermediate hosts for metacestodes of the rat tapeworm, Hymenolepis diminuta. It is known that the bean-shaped accessory glands of infected males exhibit an extended growth period and are significantly larger than those from noninfected males by day 10 after emergence. We wished to determine whether more material is transferred from these glands into the spermatophores. Here we report that the protein content and trehalase activity of spermatophores produced by bean-shaped accessory glands from infected males is elevated. However, protein transferred to the female spermatheca during mating was not affected by the infection status of the male. No evidence of transfer of trehalase to the spermatheca was detected but spermatheca from virgin, infected females contained significantly greater trehalase activity than those from noninfected females.     

Rhythmicity of sex pheromone content in female Heliothis virescens: impact of mating

Abstract Pheromone production in virgin females of Heliothis virescens (F.) (Lepidoptera: Noctuidae) peaked between the fourth and seventh hours of scotophase on the second, third, fourth and fifth days following eclosion. The highest peak (186 ng) occurred on day 3 after eclosion. Z-11-Hexadecenal comprised the highest proportion of seven components in the pheromone glands. Disproportionately higher amounts of hexadecanal and Z-11-hexadecenol occurred during photo-phase and other periods when low quantities of total pheromone were recorded.
Mating suppressed pheromone production which remained low until 48 h after mating. Coupling females with males mated three times previously or with 6-day-old males was less effective in causing a drop in pheromone content which peaked again 24 h after mating. This suggests the transfer of a male factor, a pheromonostatic factor, that suppresses pheromone production in mated females and that the factor from older and previously mated males is less effective.     

Calling behavior of the female german cockroach,Blattella germanica (Dictyoptera: Blattellidae)

Virgin German cockroach females, Blattella germanica(L.), were observed, for the first time, to exhibit a characteristic calling behavior during which females emit a volatile sex pheromone. Under a photoperiod of 12L12D, the percentage of 7-day-old virgin females that exhibited this behavior peaked before the end of the scotophase in a similar pattern to the diel periodicity of mating. A clear relationship was evident between calling and stages of sexual receptivity during successive gonotrophic cycles. Females initiated calling 5–6 days after the imaginal molt, when their basal oocytes were 1.6 mm long. If not mated, females continued to exhibit bouts of calling during the next 3–4 days until 24 h before ovulation. Calling was completely suppressed by mating as well as the presence of an egg case in the genital atrium in both virgin and mated gravid females. We suggest that calling and the emission of a volatile sex pheromone serve to attract males from a distance as well as to potentiate responses to contact sex pheromone in aggregations.     

Effect of the entomopathogenic fungus,Entomophthora muscae (Zygomycetes: Entomophthoraceae), on sex pheromone and other cuticular hydrocarbons of the house fly,Musca domestica

House fly (Musca domestica) males are highly attracted to dead female flies infected with the entomopathogenic fungus Entomophthora muscae. Because males orient to the larger abdomen of infected flies, both visual and chemical cues may be responsible for the heightened attraction to infected flies. Our behavioral assays demonstrated that the attraction is sex-specific-males were attracted more to infected females than to infected males, regardless of cadaver size. We examined the effect of E. muscae on the main component of the house fly sex pheromone, (Z)-9-tricosene, and other cuticular hydrocarbons including n-tricosane, n-pentacosane, (Z)-9-heptacosene, and total hydrocarbons of young (7 days old) and old (18 days old) virgin females. Young E. muscae-infected female flies accumulated significantly less sex pheromone and other hydrocarbons on their cuticular surface than uninfected females, whereas the cuticular hydrocarbons of older flies were unaffected by fungus infection. These results suggest that chemical cues other than (Z)-9-tricosene, visual cues other than abdomen size, or a combination of both sets of cues might be responsible for attraction of house fly males to E. muscae-infected females.     

Concurrent modulation of neuronal and behavioural olfactory responses to sex and host plant cues in a male moth

Mating has profound effects on animal physiology and behaviour, not only in females but also in males, which we show here for olfactory responses. In cotton leafworm moths, Spodoptera littoralis, odour-mediated attraction to sex pheromone and plant volatiles are modulated after mating, producing a behavioural response that matches the physiological condition of the male insect. Unmated males are attracted by upwind flight to sex pheromone released by calling females, as well as to volatiles of lilac flowers and green leaves of the host plant cotton, signalling adult food and mating sites, respectively. Mating temporarily abolishes male attraction to females and host plant odour, but does not diminish attraction to flowers. This behavioural modulation is correlated with a response modulation in the olfactory system, as shown by electro-physiological recordings from antennae and by functional imaging of the antennal lobe, using natural odours and synthetic compounds. An effect of mating on the olfactory responses to pheromone and cotton plant volatiles but not to lilac flowers indicates the presence of functionally independent neural circuits within the olfactory system. Our results indicate that these circuits interconnect and weigh perception of social and habitat odour signals to generate appropriate behavioural responses according to mating state.     

Sex‐dependent infection causes nonadditive effects on kissing bug fecundity

The influence of parasites on host reproduction has been widely studied in natural and experimental conditions. Most studies, however, have evaluated the parasite impact on female hosts only, neglecting the contribution of males for host reproduction. This omission is unfortunate as sex‐dependent infection may have important implications for host–parasite associations. Here, we evaluate for the first time the independent and nonindependent effects of gender infection on host reproductive success using the kissing bug Mepraia spinolai and the protozoan Trypanosoma cruzi as model system. We set up four crossing treatments including the following: (1) both genders infected, (2) both genders uninfected, (3) males infected—females uninfected, and (4) males uninfected—females infected, using fecundity measures as response variables. Interactive effects of infection between sexes were prevalent. Uninfected females produced more and heavier eggs when crossed with uninfected than infected males. Uninfected males, in turn, sired more eggs and nymphs when crossed with uninfected than infected females. Unexpectedly, infected males sired more nymphs when crossed with infected than uninfected females. These results can be explained by the effect of parasitism on host body size. As infection reduced size in both genders, infection on one sex only creates body size mismatches and mating constraints that are not present in pairs with the same infection status. Our results indicate the fitness impact of parasitism was contingent on the infection status of genders and mediated by body size. As the fecundity impact of parasitism cannot be estimated independently for each gender, inferences based only on female host infection run the risk of providing biased estimates of parasite‐mediated impact on host reproduction.     

Infection increases the value of nuptial gifts, and hence male reproductive success, in the Hymenolepis diminuta-Tenebrio molitor association

During copulation, male insects pass accessory gland components to the female with the spermatophore. These gifts can affect female reproductive behaviour, ovulation and oviposition. Here, we show that female mealworm beetles, Tenebrio molitor, mated with males infected with metacestodes of the rat tapeworm, Hymenolepis diminuta, produced significantly more offspring than those mated with uninfected males. There is a significant positive relationship between parasite intensity in the male and reproductive output in the female. Infection results in a significant increase in bean-shaped accessory gland (BAG) size. We suggest that infected males pass superior nuptial gifts to females and discuss the confounding effects of infection in male and female beetles upon overall fitness costs of infection for the host and the likelihood that the parasite is manipulating host investment in reproduction.     

榆木蠹蛾生殖行为及性信息素产生与释放节律

通过室内饲养与野外观察榆木蠹蛾Holcocerus vicarius (Walker)成虫的羽化、交尾、产卵行为,触角电位反应测定处女雌蛾性信息素产生与释放节律,旨在为榆木蠹蛾性信息素的鉴定和合成奠定基础。结果表明：榆木蠹蛾羽化行为全天可见,主要集中在15:00－19:00。成虫羽化当日即可交尾,21:30－0:30进行婚飞和交尾,交尾高峰出现在晚23:00左右,光期未见交尾。随着日龄的增加,召唤时间前移并且延长,2～3日龄处女雌蛾召唤时间早于1日龄雌蛾,交尾时间较短;雌蛾在羽化1 d后达到性成熟,2日龄雌蛾交尾百分率最高,达41.8%。雌蛾将产卵器伸出寻找缝隙处产卵,分多处产卵,雌虫最高产卵量达720粒,最低产卵量为105粒,卵期为12～22 d不等,孵化率为72%～88%。羽化当晚的雌蛾体内性信息素含量较低,第2天最高,以后逐日下降;2日龄榆木蠹蛾处女雌蛾性信息素的产生量从晚17:00起逐渐增加, 21:30－22:00时最高, 22:00后逐渐减小。雄蛾触角电位反应在22:30最强。21:30－23:00是雌蛾产生和释放性信息素的高峰期。榆木蠹蛾的羽化、交尾存在一定的时辰节律,通过处女雌蛾的野外诱集试验证实了性信息素释放与交配行为在时辰节律上的一致性。     

Control of attractivity and receptivity in female red-sided garter snakes

Female red-sided garter snakes emerge from their hibernacula in the spring attractive and receptive to males. Attractivity is communicated by a pheromone released through the female's skin and is a consequence of ovarian recrudescence the previous summer. Receptivity, on the other hand, is stimulated by ovarian estrogen secretion during emergence itself. Mating renders females both unattractive and unreceptive. Another "mating" pheromone of male origin is important in making females unattractive after mating. To investigate the role of cloacal stimulation in the loss of attractivity and receptivity we injected a local anesthetic (lidocaine or tetracaine) in the cloacal region of females before mating. This does not prevent mating, although it blocks neural transmission of copulatory sensory stimuli. The time course of transition from attractive and receptive states was then observed. Females treated with local anesthetic as well as control females were unattractive within 15 min of mating. However, when retested 2-3 and 24 h after mating, a significantly higher proportion of treated females regained their attractivity, while mated control females remained unattractive. This restorative effect was transient, though, as treated females retested 48 h after mating were as unattractive as the controls. Both anesthetized and control females were unreceptive when tested following mating and did not regain receptivity with time. Last, the mating-induced surge in circulating concentrations of prostaglandin was diminished in females that received a local anesthetic prior to mating. Taken together these results indicate that the loss of attractivity and receptivity following mating in the red-sided garter snake is due to combined effects of a mating pheromone and a physiological, neurally mediated response to the sensation of stimuli associated with the act of mating.     

Investigations on the Olfactory Discrimination Exhibited by the Females in the Male-induced Implantation Failure (the Bruce Effect) in Laboratory Mice

Direct contact with the alien male pheromone for 7 days before mating significantly decreased the rate of male-induced implantation failure (the Bruce effect) in newly inseminated female mice. By contrast, females housed with alien males for 7 days before mating so that physical contact with the latter was prevented exhibited a high rate of implantation failure following exposure to alien males after mating. Exposure to an air-borne pheromone produced by alien males induced oestrus (the Whitten effect) in a significant number of grouped females. The results do not support the suggestion that the inability of the stud male to block implantation is due to his original induction of oestrus. The results also do not support the view that the key factor in the induction of the Bruce effect is the ability of the female to identify the stud as an individual which prevents her from responding to him but allows her to react to a new male with hormonal changes leading to implantation failure and return to oestrus. It is suggested that the olfactory discrimination exhibited by the female in the Bruce effect is influenced by her overall olfactory experience before and after mating. The results are consistent with the view that the male-originating pheromone involved in the Bruce effect is distinct from the one involved in the Whitten effect.     

In vivo and in vitro study of the action of dopamine on oocyte growth and juvenile hormone production in Blattella germanica (L.) (Dictyoptera; Blattellidae)

In vivo, within the first ovarian cycle of B. germanica, dopamine (1 microgram/cockroach) enhanced oocyte growth when injected on day 1 or 2, just before vitellogenesis, whereas it induced the inverse effect on day 6-7, at the end of vitellogenesis. In vitro, dopamine (10(-4) M) stimulates juvenile hormone production by incubated corpora allata from 2-day-old females, and inhibited it on 6-day-old glands. The physiological significance of these effects is discussed.