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.     

Effect of infection with Trichobilharzia ocellata and Schistosoma mansoni on the ultrastructure of the albumen gland of their respective hosts, Lymnaea stagnalis and Biomphalaria glabrata

The albumen gland, a female accessory sex gland of pulmonate snails, produces the perivitelline fluid. The ultrastructure of the albumen glands of control and infected specimens of Lymnaea stagnalis and Biomphalaria glabrata was studied. The albumen gland of L. stagnalis contains two types of secretory cells--light (active) and dark (inactive)--and two types of supporting cells--centroacinar and myoepithelial. The secretory cells apparently represent two activity stages of one type of cell. The gland B. glabrata possesses only one secretory cell type, which alternates with one type of supporting cell. The albumen glands of L. stagnalis and B. glabrata infected at a juvenile stage were studied 4 and 14 weeks (L. stagnalis) and 4 and 9 weeks (B. glabrata) after exposure. After four weeks' infection, B. glabrata produced some egg masses, but in subsequent stages egg mass production completely coased. Infected L. stagnalis never produced eggs. B. glabrata was apparently infected at a "physiologically" more mature stage than L. stagnalis. The morphology of the albumen glands four weeks after exposure (the daughter sporocyst stage) is in agreement with this hypothesis. At this interval the secretory cells of L. stagnalis appeared to be much more severely affected (inactive Golgi bodies and rough endoplasmic reticulum, crinophagy of the secretory granules) than the cells of B. glabrata. In the later stages studied (shedding of the cercariae), the glands of both species appeared to be completely inactive (reduced height of the epithelium, inactive organelles, crinophagy, absence of secretory granules). At this stage of infection, daughter sporocysts containing cercaria embryos were seen in the connective tissue of the albumen gland of B. glabrata, but not of L. stagnalis. The results thus indicate that the development and synthetic activity of the albumen gland are seriously affected by infection. These processes are known to be under the endocrine control of the female gonadotrophic hormones. Since it has been established that these hormones are normally present in the haemolymph of infected snails, the findings can be explained by assuming that the parasite interferes in some way or other with the snail's endocrine system.     

Effects of Castration on Growth and Reproduction of Helisoma duryi (Mollusca: Pulmonata)

Summary

Castration of Helisoma duryi disturbs the balance between growth and reproduction in favour of growth, as is evidenced by the stimulation of body and shell growth and reduction in egg mass production when compared with sham operated controls. Female accessory sex organ wet weight is increased in castrated and virgin snails. Male accessory sex organ wet weight is unaffected and female accessory sex organ wet weight is reduced by dorsal body ablation, suggesting that growth of differentiated female accessory sex organs is stimulated by the endocrine dorsal bodies. Albumen gland synthetic activity is inhibited in the absence of a functioning gonad. This inhibition may be due partly to the accumulation of secretory products within the glands and partly to the inactivation of the endocrine dorsal bodies and neurosecretory caudodorsal cells in the cerebral ganglia. The circulating levels of the vitellogenic protein ferritin are reduced by castration, and increased by injection and implantation of active gonadal tissue into castrates. This may be due to an indirect effect of gonadal factor (s) on the extragonadal synthesis of ferritin.     

Maternal impact on egg development in Lymnaea stagnalis: a growth factor is produced by the albumen gland in the reproductive tract

Summary

In the freshwater snail Lymnaea stagnalis, perivitellin fluid is the main source of nutrition for developing embryos; it contains predominantly galactogen and proteins. The fluid is produced by the albumen gland, a large exocrine organ in the female reproductive tract. To further define the protein products of this gland and provide more information about the maternal contribution to egg development, albumen glands were extracted and the extracts purified by reversed-phase HPLC. One major HPLC peak fraction exhibited neurotrophic activity when bioassayed on identified Lymnaea neurons in vitro; it has been partially sequenced and has the highest degree of sequence identity with epidermal growth factor (EGF). These results demonstrate that a growth factor with neurotrophic activity is produced by the albumen gland, and is packaged along with the eggs to serve a growth-promoting function in the embryo.     

Structure of the female genital glands of the oviduct in the opisthobranch mollusc, Runcina

Runcina is a small hermaphroditic opisthobranch which possesses a monaulic reproductive system. In previous studies the male copulatory apparatus, the structure of the spermatophore and also the process of oogenesis have been described. The present paper gives an account of the ultrastructure of the female genital glands of the oviduct. In Runcina the oviduct comprises three primary regions, the albumen gland, the egg capsule gland and the mucous gland. Eggs enter the fertilization chamber and as they pass the opening of the albumen gland they become surrounded by albumen or perivitelline fluid. The eggs appear to become encapsulated as they traverse the egg-capsule gland and are eventually stuck together by mucus to form an egg mass. The epithelial lining of the three glands consists of alternating ciliated and secretory cells. The characteristics in secretory products of the glandular cells are described, and are discussed with reference to the way they contribute to egg vestment.     

Biochemical Composition of the Eggs of the Freshwater Snail Lymnaea stagnalis and Oviposition-induced Restoration of Albumen Gland Secretion

Summary

Galactogen and protein form the main constituents of the eggs of Lymnaea stagnalis. The amount of galactogen per egg is fairly constant, irrespective of the size of the egg mass or the age of the snail.

The restoration of the albumen gland, which produces the perivitelline fluid for the eggs, was studied in long-day (16 hr light-8 hr dark) snails after spontaneous oviposition. The wet wt of the gland and its galactogen and protein contents are markedly increased within 8 hr and reach a maximum at 32 hr after oviposition. These maxima correspond to the levels determined in snails that did not lay eggs for at least 1 to 2 days. The amounts of galactogen and of protein in the albumen gland are linearly related to the wet wt of this gland.

The restoration period of the albumen gland almost covers the mean egglaying interval. This implies synchronized cycles of albumen storage and egg formation.

The estimated amount of galactogen, released by the albumen gland during egg mass formation, is in accordance with that deposited in the eggs. In contrast, the wet wt of the eggs is 4.6 times higher than that of the released secretory material. Since after oviposition water uptake by the eggs in the egg mass is negligible, the perivitelline fluid, which is released by the albumen gland and surrounds the egg cell, must be diluted in the reproductive tract of the snail prior to oviposition.     

Anatomic,Histologic and Certain Enzymatic Studies on the Male Genital Organs of Hemiechinus auritus collaris Gray,the Indian Long Eared Hedgehog

Anatomically the male reproductive organs of Hemiechinus auritus collaris are of considerable interest and present a unique pattern of arrangement of different glands. The testes are inguinal and a true scrotum is absent. A pair of accessory glands, the seminal vesicles, are situated dorsal to the bladder. A pair of obviously lobulated glands, ventral to the bladder, represent the internal prostate and a pair of compact glands situated outside the pelvis in para-anal position the external prostate. The Cowper's gland and the gland of ampulla are absent. The present studies also concern enzymes of the phosphatase group, including both specific and non-specific phosphatases, in the testes and the sex accessory glands during both active and inactive periods in this insectivore.     

Fine structure of reproductive glands in two primitive marine pulmonates (Basommatophora: Siphonariidae)

Within the clade Euthyneura the marine basommatophorans are particularly neglected. More morphological and molecular studies are needed because their phylogenetic relationships with other pulmonates remain unresolved. The present study examines the most conspicuous reproductive gland, the glandular complex in two marine limpets, Siphonaria capensis and S. serrata (Pulmonata: Basommatophora) at both gross and fine structural levels. These two sympatric species with different developmental modes were selected to compare the structure and function of this enormous glandular structure. In both S. capensis and S. serrata, the glandular complex shows an undifferentiated state composed of an acidophilic albumen gland and a basophilic mucous gland. The glands contain secretory cells and supporting cells (= ciliated cells) that are highly ciliated. When the histochemical properties of the glandular complex were compared with those of siphonariid egg masses (of each species) it could be established that the albumen gland was responsible for the production of perivitelline fluid whereas the mucous gland secreted substances that help in the assembly of mucous layers surrounding the egg capsules. We suggest that the presence of a single glandular complex comprised of two glands is the most primitive organization of reproductive glands in pulmonates. Furthermore, the histology, fine structure and histochemistry of these glands are very similar to those of the reproductive glands of opisthobranchs.     

瘤背石磺产卵前后生殖系统的组织学变化

瘤背石磺(Onchidium struma)是雌雄同体、异体交配的腹足纲贝类,其生殖系统较为复杂,通过解剖学和组织切片技术对成体瘤背石磺的生殖系统及产卵前后的组织学变化进行了系统的研究.结果表明:(1)雄性生殖系统主要南阴茎囊、阴茎、雄性附性腺、两性腺(早期主要产生精于)和储精囊等部分组成,而雌性生殖系统则由两性腺(后期主要产生卵子)、生殖细胞输送管、蛋白腺、黏液腺、受精囊和阴道等组成;(2)雄性生殖系统的组织学结构在产卵前后变化较小,但两性腺、卵蛋白腺和黏液腺的组织学在产卵前后变化显著;(3)产卵后的两性腺由于成熟卵子的排放,整体结构松散,部分腺泡中有少量未排出的成熟卵细胞和卵黄合成早期的卵母细胞;(4)产卵前的卵蛋白腺中含有许多强嗜碱性的小颗粒(组织学结构类似于卵鞘中的胚胎外周蛋白),产卵后腺体中的颗粒相对较大,且呈嗜酸性;(5)产卵前的黏液腺中存在嗜碱性区、嗜酸性区和混杂区三种区域,但是产卵前黏液腺以嗜酸性细胞为主,而产卵后的黏液腺中以嗜碱性细胞区域为主,且分泌管道中有一些嗜碱性物质.由此可见,卵蛋白腺的主要功能是分泌卵蛋白包裹受精卵形成卵外周蛋白层,而黏液腺则在产卵过程中分泌黏液物质形成卵鞘结构及链状的卵带.     

Cloning and characterization of a candidate nutritive glycoprotein from the albumen gland of the freshwater snail, Helisoma duryi (Mollusca: Pulmonata)

Abstract. The albumen gland is a female accessory sex gland that synthesizes and secretes perivitelline fluid around pulmonate eggs. The perivitelline fluid is composed of mainly galactogen and proteins, and is thought to provide nourishment to the embryos during development. We have previously identified the major secretory protein of the albumen gland of the freshwater snail Helisoma duryi as a native glycoprotein of ∼288 kDa, consisting of four 66-kDa subunits. In this study, the major albumen gland protein in H. duryi was purified, cloned, and the full-length cDNA sequence determined. Nucleotide sequence analysis revealed that the albumen gland protein (HdAGP) shared 83% identity with a partial cDNA sequence from a developmentally regulated albumen gland protein in Biomphalaria glabrata . The HdAGP mRNA was detected by RT-PCR in the albumen gland, ovotestis, mantle and digestive gland. SDS-PAGE analysis of the albumen gland protein in egg masses at different stages of development showed that the amount of HdAGP steadily decreased during embryogenesis, suggesting its possible catabolism by the developing embryos. Protein domain searches suggested that the HdAGP shared limited sequence identity, and adopted a similar three-dimensional conformation to the bactericidal, permeability increasing, protein family, raising the possibility of a potential bactericidal function for this important reproductive/developmental protein.     

Female reproductive biology of Platygaster diplosisae (Hymenoptera: Platygastridae) and Aprostocetus procerae (Hymenoptera: Eulophidae), two parasitoids associated with the African Rice Gall Midge, Orseolia oryzivora (Diptera: Cecidomyiidae)

We investigated the female reproductive system of Platygaster diplosisae (Hymenoptera: Platygastridae) and Aprostocetus procerae (= Tetrastichus pachydiplosisae) (Hymenoptera: Eulophidae), two parasitoids associated with the African rice gall midge, Orseolia oryzivora (Diptera: Cecidomyiidae). Both optical and electron microscopy were used. The female reproductive system of P. diplosisae includes two large ovaries of the meristic polytrophic‐type, each composed of several tens of ovarioles. The system includes also a venomous gland that extends to a common oviduct. This gland had a filiform secretory portion, in which the epithelium was thin and surrounded a common evacuation canal. The secretory cells secrete into a large reservoir. Parasitism due to P. diplosisae is gregarious. The female reproductive system of A. procerae includes two ovaries of the meristic polytrophic‐type, and each ovary has a few ovarioles. Each ovariole includes one or two oocytes, which can be seen in the vitellarium. Two accessory glands, which extend to the oviduct, are also visible. The secretory epithelium of the accessory gland is made up of a dense network of secretory cells surrounded by muscle fibers. Females of A. procerae pierce the tissues of the gall and probably deposit one egg on or close to the pupa of the midge. Aprostocetus procerae is a solitary parasitoid of the midge. The two parasitoids exploit the same host at different developmental stages. These findings improve our knowledge of the reproductive biology of these two parasitoids associated with the African rice gall midge, an important pest in Africa.     

Morphology and ultrastructure of the venom glands of the northern pacific rattlesnake Crotalus viridis oreganus

The venom gland of Crotalus viridis oreganus is composed of two discrete secretory regions: a small anterior portion, the accessory gland, and a much larger main gland. These two glands are joined by a short primary duct consisting of simple columnar secretory cells and basal horizontal cells. The main gland has at least four morphologically distinct cell types: secretory cells, the dominant cell of the gland, mitochondria-rich cells, horizontal cells, and “dark” cells. Scanning electron microscopy shows that the mitochondria-rich cells are recessed into pits of varying depth; these cells do not secrete. Horizontal cells may serve as secretory stem cells, and “dark” cells may be myoepithelial cells. The accessory gland contains at least six distinct cell types: mucosecretory cells with large mucous granules, mitochondria-rich cells with apical vesicles, mitochondria-rich cells with electron-dense secretory granules, mitochondria-rich cells with numerous cilia, horizontal cells, and “dark” cells. Mitochondria-rich cells with apical vesicles or cilia cover much of the apical surface of mucosecretory cells and these three cell types are found in the anterior distal tubules of the accessory gland. The posterior regions of the accessory gland lack mucosecretory cells and do not appear to secrete. Ciliated cells have not been noted previously in snake venom glands. Release of secretory products (venom) into the lumen of the main gland is by exocytosis of granules and by release of intact membrane-bound vesicles. Following venom extraction, main gland secretory and mitochondria-rich cells increase in height, and protein synthesis (as suggested by rough endoplasmic reticulum proliferation) increases dramatically. No new cell types or alterations in morphology were noted among glands taken from either adult or juvenile snakes, even though the venom of each is quite distinct. In general, the glands of C. v. oreganus share structural similarities with those of crotalids and viperids previously described.     

Histology and histochemistry of the accessory reproductive glands in the male hairy-nosed wombat (Lasiorhinus latifrons)

Summary The accessory male reproductive glands of the hairy-nosed wombat, Lasiorhinus latifrons, are a prostate and three pairs of Cowper's glands. Component units of all are branched tubular structures of varying epithelial makeup and secretory content. The prostate has the carrotlike shape and three consecutive regions commonly found in marsupials. The regions differ in their tubular histology and histochemistry: all contain secretory globules in glandular lumina. Cowper's glands A and B are histologically identical except for the absence of interstitial mast cells from gland B: gland C is characterized by narrower tubules and larger epithelial cells. Histochemical tests for protein, carbohydrate and iron indicate that glycogen is a major secretory product of the prostate (largely posterior region), iron is also secreted (mainly posterior region) and a small quantity of acid mucin is produced (mainly central region). Glycogen is a feature also of anterior prostatic glandular epithelium and of the capping cells of the urethral transitional epithelium. Cowper's gland A has considerable protein in its secretion, gland B a neutral glycoprotein and gland C a sialomucin: the latter two also exhibit cytoplasmic glycogen in their secretory cells.     

Sex pheromone titre in the glands of Spodoptera litura females: circadian rhythm and the effects of age and mating

The present study investigates the effects of age and mating status on the circadian variations of gland sex pheromone titre in female Spodoptera litura Fabricius. Similar to other nocturnal moths, S. litura females exhibit circadian variations of gland sex pheromone contents, with higher levels during scotophase and lower levels during photophase. The sex pheromone titre in the glands peaks during the first scotophase after eclosion and sharply declines afterwards. Higher pheromone contents during scotophase may facilitate female reproductive activities, and the negative relationship between pheromone titre and female calling is likely the result of pheromone release during female calling. Interestingly, the present study demonstrates that mated S. litura females have significantly higher sex pheromone titre in their pheromone glands (PGs) than virgin females. This finding contrasts with all previous studies of other insect species, in which mating generally reduces the sex pheromone titre in female PGs. In S. litura, mating and male accessory gland fluids can suppress female calling behaviours and re‐matings. These results suggest that the suppression of female calling behaviours by mating and male accessory gland fluids may significantly reduce the release of sex pheromones and thus result in higher sex pheromone titre in the PGs of mated females.     

Reproduction in the genus Limacina (Opisthobranchia: Thecosomata)

Reproductive mechanisms in the seven species of the thecosomatous pteropod genus Limacina are described and compared. All species are protandrous hermaphrodites. Five species– L. bulimoides, L. helicina, L. lesueuri, L. retroversa and L. trochiformis –have a similar reproductive anatomy in which the gonoduct leading from the gonad to the common genital pore functions as a seminal vesicle in the male and is elaborated into mucous and albumen glands in the female. The male system consists of a prostate gland and penis connected to the common genital pore by an external ciliary tract. All five species have a free-swimming veliger stage which hatches from free-floating egg masses. Limacina helicoides has the same reproductive anatomy but is ovoviviparous, with embryos retained in capsules in the mucous gland until they are juveniles of 50 mm in shell diameter. Limacina inflata lacks mucous and albumen glands and a penis; a spermatophore formed by the prostate gland is used in aphallic sperm transfer. This species exhibits brood protection with un-encapsulated embryos retained in the mantle cavity until they are released as veligers measuring 0067 mm in diameter. L. inflata is the most abundant of the seven species despite lowered fecundity; reasons for its ecological success are discussed.     

Seasonal changes in the reproductive anatomy of male Antechinus stuartii (Marsupialia: Dasyuridae)

Male Antechinus stuartii (Marsupialia: Dasyuridae) undergo significant endocrinological changes during their life history. The endocrine changes are associated with complete male mortality. The accessory reproductive tract of males is important for seminal plasma production, and changes associated with the reproductive cycle were not described in detail by earlier studies. The present study sought to describe some of the seasonal changes in structure of the male accessory reproductive tract in relation to the known hormonal changes. The epididymis, prostate, and bulbourethral glands are relatively undifferentiated in February and May, a time when plasma concentrations of testosterone are known to be low. By July, considerable hypertrophy and differentiation of the accessory reproductive tract are observed. This is most obvious in the bulbourethral glands, which change from being indistinguishable from one another in February and May to being three large morphologically and histologically distinct glands in July. The hypertrophy and secretory activity continue into August, the breeding season. These findings correlate with the hormonal profiles found in other studies of A. stuartii. J Morphol 231:261–275, 1997. © 1997 Wiley-Liss, Inc.     

Release of proteins and polysaccharides from the albumen gland of the freshwater snail Helisoma duryi : effect of cAMP and brain extracts

The albumen gland is a compound tubular exocrine gland found in the female reproductive tract of freshwater pulmonate snails such as Helisoma duryi. It secretes a perivitelline fluid, composed of protein and polysaccharide complexes, and coats each fertilized egg. A 288-kDa native glycoprotein, composed of several 66-kDa subunits, was identified in soluble extracts of albumen gland. Forskolin stimulates the release of secretory granules, containing both proteins and polysaccharides, from the cytoplasm of the glandular cells. An acid extract of the central nervous system or the adenosine-3′,5′-cyclic monophosphate (cAMP) analogue 8-bromo cAMP, stimulates protein secretion from the gland. Pretreatment of the albumen gland with cAMP antagonist (R_p isomer of cAMP) inhibits the stimulatory effect of a brain extract. Digestion of brain extract with proteolytic enzymes abolishes its activity, suggesting the factor from the brain is peptidergic. The neuroactive agents serotonin, Phe-Met-Arg-Phe-amide, Tyr-Gly-Gly-Phe-Met-Arg-Phe-amide, small cardioactive peptide B, and caudodorsal cell hormone were also tested for potential secretion-promoting ability. Brain extracts were partially purified with a Sep-Pak C₁₈ reverse-phase cartridge and indicate the peptide is relatively hydrophobic. These results suggest that a brain peptide promotes the secretion of perivitelline fluid, and this is mediated by the adenylate cyclase/cAMP signal transduction pathway. Accepted: 19 December 1997     

Ultrastructure of the male reproductive accessory glands in the medfly Ceratitis capitata (Diptera: Tephritidae) and preliminary characterization of their secretions

The morphology and the ultrastructure of the male accessory glands and ejaculatory duct of Ceratitis capitata were investigated. There are two types of glands in the reproductive apparatus. The first is a pair of long, mesoderm-derived tubules with binucleate, microvillate secretory cells, which contain smooth endoplasmic reticulum and, in the sexually mature males, enlarged polymorphic mitochondria. The narrow lumen of the gland is filled with dense or sometimes granulated secretion, containing lipids. The second type consists of short ectoderm-derived glands, finger-like or claviform shaped. Despite the different shape of these glands, after a cycle of maturation, their epithelial cells share a large subcuticular cavity filled with electron-transparent secretion. The ejaculatory duct, lined by cuticle, has epithelial cells with a limited involvement in secretory activity. Electrophoretic analysis of accessory gland secretion reveals different protein profiles for long tubular and short glands with bands of 16 and 10 kDa in both types of glands. We demonstrate that a large amount of accessory gland secretion is depleted from the glands after 30 min of copulation.