The role of the accessory reproductive glands and genital ducts in egg pod formation in female Schistocerca gregaria

Removal of the accessory reproductive glands in female Schistocerca gregaria does not prevent the formation of eggplugs as expected. The egg pods formed are incomplete, with froth in the egg plug partially lacking. The extent of collapse is dependent on the time of removal of the glands. These results suggest that the genital ducts (egg calyces and lateral oviducts) play a significant role in the production of egg pod material, and the accessory glands probably participate in the process. Ligation of the glands has the same effect on egg pod structure; secretion accumulates in the glands indicating that, although the contribution made to the egg pod by the glands is small, they are not vestigial and are not acting simply as reservoirs for secretions produced distally. Cautery of the Comstock-Kellogg glands produces no visible change in egg pod structure or in method of formation, and thus their function remains undetermined. In the absence of the ventral median pouch egg masses are laid without the plug. A thin layer of nonvacuolated material is smeared over the walls of the oviposition hole, suggesting that the secretions produced in the upper regions of the genital ducts are added to or modified by an additional secretion from this gland, before being released to the exterior.     

The hormonal control of accessory reproductive gland development in female Schistocerca gregaria

Allatectomy of adult female Schistocerca gregaria prevents the normal development of the accessory reproductive glands and no secretion is produced. Development of the glands can be restored by the administration of synthetic juvenile hormone and the response is dose-dependent. A continuous supply of hormone is required for maintenance of secretory activity. In the normal developmental sequence the total protein content of the glands remains constant until the time at which vitellogenesis occurs in the terminal oöcytes. As maturation proceeds there is a linear increase in protein content of the glands. The initial increase occurs as a result of cellular changes in the glands and is then followed by an increase due to an accumulation of secretion in the lumina.     

The ultrastructure of the male accessory reproductive glands of the colorado beetle

Summary The accessory reproductive glands of Leptinotarsa decemlineata males are simple epithelial tubular glands. They are surrounded by a network of slow acting muscle cells. All the gland cells have a very extensive granular endoplasmic reticulum, a prominent Golgi apparatus, but few secretory granules. The secretory product in the lumen, which is a neutral mucopolysaccharide-protein complex, appears as a granular material in which fibrillar structures occur. Neither in the gland cells nor in the lumen were regional differences observed. After allatectomy the gland cells degenerate in a remarkable way. A zone containing microvillous structures appears between the outer and inner cells. While the inner cells degenerate completely, the outer ones do not but become organised for minimal consumption of energy, necessary to survive diapause.Grateful acknowledgment is made for a mandate as Aangesteld Navorser of the National Foundation of Scientific Research in Belgium.We wish to thank Ing. W. Bohijn for operating the EM and Mr. G. Maes for photography.     

Male insect accessory glands: Functions and control of secretory activity

Summary

Paralleling the diversity of the class Insecta, the male accessory glands (MAG) exhibit a wide range of form, and their secretion serves a variety of functions, including spermatophore and mating plug formation, sperm activation, provision of nutrients to females, and, through production of fecundity-enhancing and/or receptivity-inhibiting substances, modification of female reproductive behavior. In most insects, juvenile hormone (JH) is important in the regulation of MAG secretory activity; specifically, JH controls the production of particular proteins in the secretion. However, the production of some proteins appears not to be influenced by JH; rather, their synthesis is regulated by ecdysteroids. During sexual maturation, JH and ecdysteroids seem to interact to bring about a specified temporal sequence of protein synthesis in the MAG.     

The Comstock-Kellogg glands in female Schistocerca gregaria: Their eversion and haemocoelic pressure

The glandular pouches of Comstock and Kellogg on the genital chamber of females of Schistocerca gregaria can be everted and displayed by exerting firm pressure on the tip of the abdomen. The glands evert when the ovipositor values are extended and the gland apertures pass the posterior border of the sub-genital plate. This process has not been observed to occur spontaneously in females in this colony. Increasing the pressure in the haemocoel by means of a saline reservoir is effective in causing gland eversion only when pressures in excess of 75 mm mercury are used: these pressures cause abnormal distortion in the insect. Haemolymph pressure monitored in digging and egg-laying females varies only slightly from atmospheric pressure and never approaches the pressures required to enforce gland eversion. Gland eversion is not observed in digging females, but is difficult to observe in females in the act of laying, due to the presence of egg-pod secretion.These observations are discussed in relation to the structure of the pouches and other information concerning their possible functions in the female desert locust.     

Phase polymorphism in Schistocerca gregaria: Assessment of juvenile hormone synthesis in relation to vitellogenesis

Juvenile hormone (JH) synthesis by the corpora allata of gregarious and solitarious phase females of Schistocerca gregaria was determined in vitro during the penultimate and last stadia as well as during the first gonotrophic period of adults. Generally, the corpora allata of solitarious females showed higher rates of JH synthetic activity. In addition, in adult females there was a temporal difference between the corpora allata activities of gregarious and solitarious locusts, the latter exhibiting relatively higher rates of JH synthesis early in the first gonotrophic period. The corpus allatum volumes of solitarious females were also generally larger than those of their gregarious counterparts; there was no synchrony between fluctuations in JH synthetic activity and changes in corpus allatum volume in either phase.The early onset of relatively high JH synthetic rates in solitarious females was correlated with the early detection, by rocket immunoelectrophoresis, of vitellogenin in the haemolymph and vitellin in the oöcytes. Vitellogenin appeared in the haemolymph on day 4 in solitarious females and on day 6 in gregarious females and vitellin appeared in the oöcytes on days 6 and 8 respectively. Oöcyte length at which vitellogenesis was first detected was 1.8 mm for gregarious and 1.3 mm for solitarious females. However, despite the accelerated onset of both vitellogenin synthesis and uptake, oöcyte maturation time of solitarious females was longer. In both gregarious and solitarious females, vitellogenin titres increased until oöcytes reached a length of about 4 mm and declined thereafter. Vitellin content of ovaries increased proportionately to oöcyte growth until they attained a length of 5.0 mm. The subsequent increase in length of oöcytes to maturity is attributed to postvitellogenic growth, possibly by hydration.     

Development of the genital ducts in Telmatodrilinae (Tubificidae, Clitellata)

In Tubificidae, the male genital duct comprises a funnel in the testes segment, followed by a vas deferens, an atrium, and, frequently, a copulatory structure in the adjacent ovarian segment. There may also be a diffuse or compact prostate gland in association with the duct. The morphology and position of the genital ducts are important for the classification of the oligochaetous Clitellata. Different parts of the male duct, however, have been named without regard to whether they are homologous or not. One way to establish better hypotheses of homology is to study the detailed morphology and/or the development of the genital ducts. The morphogenesis of the genital ducts in Alexandrovia onegensis (Telmatodrilinae) is described. The male funnel originates by multiplication of peritoneal (mesodermal) cells in the posterior septum in the testes segment. A cord of these cells breaks through the septum and grows backwards into the next segment, where it connects to the epidermis. This cord gives rise to the vas deferens, and is therefore mesodermal in origin. The atrium in A. onegensis develops from a primary epidermal (ectodermal) invagination. The vas deferens and atrium connect and a continuous duct from the testes segment to the exterior is formed. Several compact prostate glands develop along the atrium, each being formed from cells in the atrial epithelium. The spermatheca develops from an invagination of the epidermis in the testes segment. The female duct is formed from peritoneal (mesodermal) cells in the posterior septum in the ovarian segment. These developmental findings strengthen the hypothesis about a closer relationship between the Telmatodrilinae and Tubificinae (both Tubificidae).     

Ultrastructure of the accessory glands of gene's organ in the cattle tick, Boophilus

The organization and ultrastructure of the accessory glands of the cattle tick, Boophilus microplus, are described. The glands consist of two groups of acinar cells situated on either side of Gene's organ. A single acinus consists of from eight to 12 cells and each cell is connected via an individual duct to pores on the dorsal surface of the mouthparts. The position of these pores is such that the secretion of the accessory glands is incorporated into the egg wax during oviposition. Each gland cell has striking quantities of smooth endoplasmic reticulum and numerous Golgi dictyosomes and appears to produce a secretion that is lipoidal in nature. Each cell secretes into its own individual lumen and is connected to a cuticular pore by a duct cell.     

The effects of starvation and subsequent feeding on juvenile hormone synthesis and oöcyte growth in Schistocerca americana gregaria

The effect of starvation on the synthesis of C₁₆ juvenile hormone (JH) and the growth of terminal oöcytes was assessed in Schistocerca americana gregaria at two times during adult life: before activation of the corpora allata and during the first gonotrophic cycle. In both groups, starvation resulted in a decline in JH synthesis within 2–3 days and rates of synthesis remained low throughout the experimental period. The growth rate of oöcytes which were not vitellogenic at the time of starvation was depressed whereas the percentage of resorption of vitellogenic oöcytes increased dramatically with starvation. Although the percentage of resorption increased in animals with vitellogenic oöcytes, some mature oöcytes were produced, particularly in animals in which the oöcytes were greater than 5 mm in length at the time of starvation. This suggests that oöcyte maturation can be divided into two distinct phases—an early phase of vitellogenesis associated with high rates of JH synthesis and a late phase, in oöcytes greater than 5 mm, associated with much lower rates of JH synthesis.Stimulation of JH synthesis by farnesenic acid in 5-day starved animals resulted in high rates of JH synthesis, indicating that starvation did not appreciably alter the enzymic activities of the final two stages in JH synthesis. Thus rate limitation did not occur at these stages.Feeding of 5-day starved animals resulted in a transient increase in the rate of JH synthesis. However, rates of JH synthesis and oöcyte growth remained subnormal throughout the observation period, suggesting that the effects of starvation cannot be entirely reversed by feeding. Thus starvation may decrease the reproductive potential of the females.     

A histochemical study of the secretions of reproductive glands and of the egg envelopes of Achatina fulica (Pulmonata: Stylommatophora)

Histochemical investigations of the secretions of reproductive glands—albumen gland, apical uterus, basal uterus and prostate gland—indicate the presence of galactogen in the albumen gland, acid mucopolysaccharide in the apical uterus, and lipoprotein in the basal uterus and prostate gland of A. fulica. The proteinaceous secretions produced by the glands do differ in their terminal reactive sites. Intense alkaline phosphatase reaction is found in albumen gland and apical uterus; carbonic anhydrase activity could be detected mainly in the uterine glands. The cyclical secretory activity of the reproductive glands has been studied preparatory to egg-laying and in the spent phase. Histochemical characteristics of the egg envelopes—albumen, shell membrane and egg-shell—suggest a possible sequential deposition of glandular products during the descent of eggs through the repv. ductive tract. The factors contributing to the stability and resistant nature of the egg envelopes, and the possible role of nutritive materials contained in reproductive gland secretions in the development of the embryo (even while the eggs are inside the uterus), are discussed.     

Variations in ecdysteroid levels in 5th instar larvae of Schistocerca gregaria in gregarious and solitary phases

Moulting hormone levels in whole bodies of 5th instar S. gregaria were determined throughout the 5th larval instar using gas chromatography with electron capture detection of the derivatized hormone. No differences were found between hormone levels in insects in the gregarious and solitary phase. No evidence for the existence of polar ecdysteroid conjugates used for storage or transport of these hormones was found. Approximately one tenth of the 20-hydroxyecdysone observed in the gregarious insects was detected in the faeces, almost equally divided between free hormone and polar conjugates of it.     

Ultrastructure of the male accessory ducts and prostate gland of Diclidophora merlangi (Monogenoidea)

The vas deferens, seminal vesicle, penis and common genital atrium of the monogenean, Diclidophora merlangi are lined by a very flat, lamellate epithelium. The structure is apparently syncytical, although nuclei or perikaryons have not been observed. The epithelium extends to just inside the gonopore where a septate desmosome marks the union with body tegument. There is minor regional variation in structure. The terminal portion of the seminal vesicle and the penis lumen are lined in part by the luminal cytoplasm of the prostate gland which surrounds this part of the reproductive tract. The prostate gland cells are synthetically active and produce a characteristic secretory body that is released either singly by exocytosis, involving membrane fusion, or in bulk via apocrine secretion. The secretion is acidophilic, PAS-positive and reactive for protein. The penis is sucker-like in structure and armed with a ring of 16 genital hooklets. Cilia have not been observed in any part of the male reproductive tract, and sense receptors are not apparent in the tegument surrounding the gonopore.     

Accumulation of secretory proteins in the accessory reproductive glands of the male migratory grasshopper, Melanoplus sanguinipes: A developmental study

Production of secretion in the accessory reproductive glands of male Melanoplus sanguinipes has been examined by electrophoresis and radiolabelling. The secretion of each group of tubules (long hyaline glands, white glands, short hyaline glands, and seminal vesicles) can be resolved into more than 20 protein bands and includes several glycoproteins and, in the long hyaline and white glands only, lipoproteins. Each group of tubules has a characteristic pattern of synthesis and accumulation of proteins; that is, specific proteins appear in the secretion at particular times during sexual maturation. In allatectomized insects, the long hyaline glands accumulate very little secretion; the white glands and short hyaline glands accumulate about one-third the normal amount; and accumulation in the seminal vesicles is not affected by the operation. Allatectomy exerts its effect by inhibiting the synthesis of particular proteins. The observations are discussed in terms of juvenile hormone-specific protein synthesis in the accessory reproductive glands.     

Composition,synthetic and cytolytic activities of Galleria mellonella silk glands during the last-larval instar under the action of juvenile hormone

Within the first 48 hr of the last-larval instar of Galleria mellonella the silk glands grow but silk production is restrained. This ‘preparatory phase’ of the glands is probably maintained by juvenile hormone. Silk production and accumulation are stimulated in the ‘accumulation phase’ between 60 and 132 hr by unknown factors in the absence of juvenile hormone. The rate of RNA synthesis culminates at 84 hr but the RNA content increases until the end of cocoon spinning at 144 hr. In the following ‘regression phase’ (144–160 hr), when the glands exhibit high activities of acid and alkaline DN-ases and of acid phosphatase, the RNA and protein contents rapidly decrease, but that of DNA remains high. This phase is typical of moulting insects, is independent of juvenile hormone, and seems to be caused either by an increase in ecdysteroids or by lack of nutrients. The following ‘degeneration phase’ occurs when the surge of ecdysteroids terminates the larval-pupal transformation. Disintegration of silk glands by autolysis and phagocytosis is completed after pupal ecdysis (180 hr). Treatment of larvae with a juvenoid (ZR 512) at 48 or 132 hr in the last instar dramatically alter the composition, synthetic and cytolytic activities of silk glands. At the next ecdysis the glands attain a state very similar to that of the preparatory phase. They are capable of intensive silk production and completion of developmental cycle when the supernumerary larvae prepare for pupation. The results indicate that juvenile hormone can reverse the development of the silk glands.     

Nuclear binding sites for juvenile hormone III in the male accessory reproductive glands of Melanoplus sanguinipes

Summary

We have identified a potential nuclear juvenile hormone (JH) receptor in the long hyaline tubules (LHT), part of the male accessory reproductive gland (MARG) of M. sanguinipes. The MARG was incubated in vitro with [³H]JH III, and the distribution of the [³H]JH III among the cellular fractions of the LHT was determined. Some 37±4% of the radioactivity was associated with the crude nuclear pellet, while the cytosolic, microsomal and mitochondrial fractions contained 30±3%, 23±2% and 10±1%, respectively. The bound JH III was measured in nuclear extracts of LHT from males up to 15 days post-eclosion. These results revealed that JH binding increased in an age-dependent manner up to day 7, then levelled off to day 12, to increase again on day 14. The nuclear-binding component in the LHT had a very strong affinity for JH III, with a K_D value of 0.8 nM. Our observations are considered in relation to the potential site and mode of action of JH.     

Ultrastructural changes accompanying secretion and cell death in the molting glands of an insect (Oncopeltus)

During the fifth (last) larval instar of Oncopeltus fasciatus, morphological changes in the molting glands associated with ecdysone secretion include an increase in cytoplasmic volume relative to that of the nucleus, increased amounts of rough endoplasmic reticulum and mitochondria, and the formation of deep infoldings of the plasma membrane. On the sixth day of the fifth instar large electron-lucent areas become apparent beneath the basement membrane; however, the glands remain intact until the seventh (last) day of the instar when a dramatic fragmentation of the cytoplasm, and condensation and fragmentation of the nucleus are observed. It is likely that such changes occur rapidly, just prior to the time of ecdysis to an adult. Cell death in the molting glands of Oncopeltus is markedly different from that described for the molting glands of other insect species in that autophagic vacuoles are not observed prior to a complete loss of cellular integrity.     

Giant spermatozoa and a huge spermatheca: A case of coevolution of male and female reproductive organs in the ground louse Zorotypus impolitus (Insecta,Zoraptera)

The male and female genital apparatus of the recently discovered ground louse Zorotypus impolitus were examined using light and electron microscopy. The rounded testes and a large seminal vesicle are connected with a complex of four accessory glands by a long tapering ejaculatory duct. Two accessory glands have the same whitish coloration, whereas the third one is pale blue, and the elongated and cylindrical fourth one translucent. The sperm are the largest known in Hexapoda, 3 mm long and 3 μm wide, with a volume of ca. 21,000 μm³; the ratio between the diameter of the axoneme and the width of the main body of the sperm ranges between 1:10 and 1:13. The exceptional width of the spermatozoa is due to an extreme enlargement of the mitochondrial derivatives and accessory bodies. A single sperm is contained in a small globular spermatophore (100 μm). The highly unusual external transfer correlates with an atypical mating behavior. The male produces several to many spermatophores during the mating process. As in other zorapterans the ovaries are panoistic and the eggs bear two micropyles. An exceptionally large apical spermathecal receptacle is present; it is connected with the vagina by a long spermathecal duct, which varies structurally along its course. A correlation between the sperm size and the size of the spermatheca is likely. Ultrastructural features of different species support two strikingly different models of male and female reproductive apparatus in the small order Zoraptera. This is in stark contrast to the extreme uniformity of their external morphology. It is likely that sexual selection played a decisive role in the evolution of the reproductive system.     

Structure of the male reproductive accessory glands of Pterostichus nigrita (Coleoptera: Carabidae), their role in spermatophore formation

Accessory gland secretions of male insects have many important functions including the formation of spermatophores. We used light and electron microscopy to investigate the structure of the accessory glands and posterior vasa deferentia of the carabid beetle Pterostichus nigrita to try to determine where spermatophore material is produced. Each accessory gland and posterior vas deferens had an outer layer of longitudinal muscle, beneath which was a layer of connective tissue and a thin band of circular muscle, all of which surrounded a layer of epithelial cells lining the lumen of the ducts. Based on the ultrastructure of the epithelial cells, and their secretory products, we identified two epithelial cell types in each region (distal and proximal) of the accessory glands and four types in the posterior vas deferens. Most secretory products, which stained positively for proteins and some mucins, were released into the lumen of the ducts by apocrine secretion. The accessory glands produced one type of secretory product whereas in posterior vasa deferentia, four types of secretory products were found layered in the lumen. Our results suggest that most of the structural material used to construct a spermatophore is produced by the cells of the posterior vasa deferentia.     

The inhibition of milk synthesis by juvenile hormone in the viviparous cockroach, Diploptera punctata

The brood sac of the viviparous cockroach, Diploptera punctata, synthesizes a protein rich milk which nourishes developing embryos. Milk is first detected in the brood sac (by immunoelectrophoresis) when the embryos begin drinking and continues to increase in parallel with total protein of the brood sac. When embryos cease drinking, both total protein and milk decline in the brood sac. Premature decline in protein and milk content of the brood sac has been observed after treatment with juvenile hormone (from implanted active corpora allata) or a juvenile hormone analogue (ZR 512 applied topically). The fine structure of the brood sac 7 days after corpora allata implant is consistent with that of gland cells which are not actively synthesizing milk. The effect of ZR 512 is detected in decreased milk content of the brood sac after 24 hr of treatment.     

Juvenile hormone III produced in male accessory glands of the longhorned beetle,Apriona germari,is transferred to female ovaries during copulation

We report on juvenile hormone (JH) biosynthesis in vitro by male accessory glands (MAGs) in the longhorned beetle, Aprionona germari, accompanied by the transfer of JH from males to females during copulation. JH was extracted from the MAGs and separated by reversed‐phase high‐performance liquid chromatography. JH III was identified as the major JH by gas chromatography–mass spectrometry. A radiochemical assay and a non‐radioactive method were used to measure the in vitro rate of JH biosynthesis by the MAGs. After 4 h of incubation with ³H‐methionine in the medium, the radioactivity in the MAGs substantially increased. In a separate assay, incubation of the MAGs with non‐radioactive methionine for 4 h resulted in a 39% increase in JH III. Seven‐day‐old males were injected with medium 199 containing ³H–methionine and 24 h later they were mated with virgin females. Hemolymph and the MAGs were collected from the mated males and hemolymph, ovaries and eggs were collected from the mated females for assaying radioactive JH. The radioactivity incorporated into JH in the MAGs was transferred to the females during copulation and later transferred into their eggs. Assayed 1 h after copulation, JH III level in the MAGs decreased 42% and the content of JH III in the male hemolymph did not change, whereas the content of JH III in the female hemolymph and ovaries both increased. © 2010 Wiley Periodicals, Inc.