Structural organization of ovarian follicle cells in the cotton bug (Dysdercus intermedius) and the honeybee (Apis mellifera)

Summary The somatic epithelia of Dysdercus and Apis follicles were analyzed by electron microscopy, and the patterns of F-actin and microtubules were studied by fluorescence microscopy. The epithelia in both species differ considerably in shape and in the organization of the cytoskeleton. During previtellogenic stages, the epithelium consists of columnar-shaped cells with small (Dysdercus) or no (Apis) lateral intercellular spaces. During vitellogenesis, the follicle cells round up; the intercellular spaces increase in size in Dysdercus follicles, whereas in Apis follicles they remain small. Along the basal surface of the follicle cells, there are conspicuous parallel bundles of microfilaments perpendicular to the anteroposterior axis of the follicles. In the honeybee, these microfilament bundles are present in long filopodia, most of which are embedded in thickenings of the basement membrane and extend over the surfaces of neighbouring cells. In the cotton bug, the basal surface of the follicle cells is thrown into parallel folds. The microfilament bundles are located just underneath the cell membrane where the folds contact the basement membrane. In the polar regions of the Dysdercus follicle, the epithelial cells become flat and adhere to each other without forming intercellular spaces. The basement membrane is particularly thick in the polar areas; this has also been observed in Apis follicles around the intercellular bridge connecting oocyte and nurse cells.     

The spatial arrangement of germ line cells in ovarian follicles of the mutantdicephalic inDrosophila melanogaster

Summary The pattern of intercellular connections between germ line cells has been studied in follicles of the mutantdicephalic (dic), which possess nurse cell clusters at both poles. Staining of follicles with a fluorescent rhodamine conjugate of phalloidin reveals ring canals and cell membranes and thus allows us to reconstruct the spatial organization of the follicle. Each germ line cell can be identified by the pattern of cell-cell connections which reflect the mitotic history of individual cells in the 16-cell cluster. The results indicate that in both wild-type anddicephalic cystocyte clusters one of the two cells with four ring canals normally becomes the pro-oocyte. However, in some follicles (dicephalic and wild-type) oocytes were found with fewer or more than four ring canals. Indic follicles, one or several nurse cells may become disconnected from the other cells during oocyte growth at stage 9–10. Such disconnected cells cannot later on empty their cytoplasm into the oocyte. This, in turn, might be of consequence for the determination of axial polarity of the embryo.     

Follicles in the Endocrine Pancreas of Myxine glutinosa Studied by Scanning Electron Microscopy

Abstract Scanning electron microscopic studies of the inner surfaces of the follicular cavities in the endocrine pancreas of Myxine glutinosa have revealed two types of follicles. The predominant type of follicles is lined by cells bearing microvilli, while the rare second type has smooth surfaced cavities. It is postulated, that the microvillous cells absorb material stored in these follicles, while the smooth surfaced follicles are disintegrating.     

Influence of cortisol along the pituitary‐ovary axis in the cichlid fish Oreochromis mossambicus

Cortisol is the principal glucocorticoid released due to various forms of environmental as well as aquacultural stressors in fish. The aim of the present investigation was to determine cortisol‐induced alterations along the luteinizing hormone (LH)‐secreting cells–ovary axis in the tilapia Oreochromis mossambicus. Administration of cortisol to stripped O. mossambicus for a period of 22 days during the ovarian cycle caused significantly higher number of follicles with chromatin nucleoli (stage I) compared to those of initial controls and controls. Whereas the number of follicles at perinucleolar (stage II) and vitellogenic (stage IV) stages did not differ significantly between controls and cortisol‐treated fish, the number of follicles at cortical alveolar stage (stage III) was significantly lower in cortisol‐treated fish than in controls. While the stage V follicles (maturation stage) were absent in initial controls, their presence in controls was concomitant with intensely labelled LH‐secreting cells in the proximal pars distalis (PPD) region of the pituitary gland during prespawning phase. However, cortisol‐treatment resulted in complete absence of stage V follicles associated with weakly immunoreactive LH‐content in the PPD region of the pituitary gland during prespawning phase. These results suggest that chronic cortisol‐ treatment causes suppression of LH‐secreting cells activity and blocks progression of vitellogenic follicular development process in O. mossambicus.     

The fine structure of blood follicles in the earthworm genera Amynthas and Lumbricus (Annelida: Oligochaeta)

Blood follicles of the earthworm Amynthas are hemoglobin-containing, sac-like dilatations of blood vessels which connect to the general circulation. Grape-like clusters of follicles are found posterior to the pharynx, among tufts of micronephridia, and single follicles are located among cells of the pharyngeal gland. In Lumbricus, follicles take the form of simple swellings and irregular-shaped diverticula of nephridial capillaries. The fundamental structure of the wall of follicles and of vessels in both genera is the same and consists of two layers: an extracellular vascular lamina and an outer (coelomic) covering of smooth muscle-like myoperithelial cells. Hemocytes may be free and circulating or they may facultatively attach to the vascular lamina as littoral cells, constituting an incomplete endothelium-like surface. Hemocytes that appear to be in the process of attaching or detaching are rounded, while adherent cells are flattened and elongate. Free and littoral hemocytes actively endocytose packets of circulating extracellular hemoglobin. Hemocytes within follicles possess radiating cell processes which also endocytose hemoglobin. Although these cells were presumed to secrete hemoglobin, staining with 3,3′-diaminobenzidine confirms the presence of hemoglobin only within pinosomes and not within protein-synthesizing or packaging organelles. The presence of hemosiderin-like bodies suggests that follicular hemocytes catabolize hemoglobin. Blood follicles apparently provide a means of significantly increasing cell-surface area for hemoglobin processing, without substantially increasing the volume and pumping load of the circulatory system.     

On the ultrastructure of follicles and isolated follicular granulosa cells of porcine ovary

Summary The endoplasmic reticulum in granulosa cells of primary, secondary, and small tertiary follicles of the porcine ovary is sparse and largely of the granular type.In granulosa cells of large tertiary follicles the endoplasmic reticulum shows distinct signs of proliferation. Some cells even contain whorls of endoplasmic reticulum membranes, essentially of the agranular variety.Direct continuity between endoplasmic reticulum membranes of the granular and agranular type as well as the continuous increase in agranular membranes suggest that these membranes may originate from the granular membranes.Granulosa cells isolated from large tertiary follicles by microdissection and keptin vitro show essentially the same ultrastructure as granulosa cells of intact large tertiary follicles.Some lipid droplets appear to be localized in cavities of the endoplasmic reticulum. It is suggested that the droplets contain precursor material for steroid hormone synthesis.Finally, the development of the agranular endoplasmic reticulum including the appearance of whorls in some granulosa cells of large tertiary follicles indicates that steroid synthesis may occur in such follicular granulosa cells.Read at the Meeting of the Swedish Society for Pathology in Umeå, September 25, 1965 (Bjersing, 1966).This investigation was supported by grants from the Swedish Medical Research Council (Projects No. 13 X-78-01, 12 X-78-02, and 12 X-78-03).     

Histogenesis of atretic ovarian follicles in a seasonally breeding bird

Histologic examination of ovaries from a non-migratory population of scrub jays (Aphelocoma coerulescens) disclosed a marked annual cycle in the incidence of atresia. Atretic follicles became more common as the nesting season progressed and were most abundant immediately after the cessation of breeding. Atresia involved a dissociation of granulosa cells and movement of these cells into the follicle. Subsequently, granulosa cells showed steatogenesis and ultimately disappeared simultaneously with the invasion of the follicle by ex-thecal gland cells. The data suggest that the diverse histology of avian atretic follicles reflects different stages in the process of atresia rather than multiple origins. Ovarian stromal glands apparently arise both from ex-thecal gland cells of atretic follicles and stromal connective tissue. A possible secretory role of atretic follicles is considered.     

Aberrant oogenesis in the patterning mutant dicephalic of Drosophila melanogaster: time-lapse recordings and volumetry in vitro

Summary Drosophila females homozygous for the mutation dicephalic occasionally produce ovarian follicles with a nurse-cell cluster on each oocyte pole (dic follicles). Most dic follicles contain 15 nurse cells as in the normal follicle, but the total nurse-cell volume is larger in dic follicles; this is in keeping with the increase in DNA content recently described. However, the relative increase in oocyte volume during nurse-cell regression (from stage 10B onward) is not significantly larger in dic than in normal follicles. Time-lapse recordings in vitro show that, as a rule, both nurse cell clusters in a dic follicle export cytoplasm to the oocyte but nurse-cell regression remains incomplete at both poles and the persisting remnants of the nurse cells cause anomalies in chorion shape. The kinematics of cytoplasmic transfer are less aberrant at that oocyte pole which harbours the germinal vesicle. Possible links are discussed between these anomalies of oogenesis and the double-anterior embryonic patterns observed in the majority of developing dic eggs.     

Expression of cell cycle regulatory proteins in epithelial components of dental follicles

Dental follicle is a component of tooth germs, which remain adjacent to the crown of unerupted or impacted teeth. Under the influence of pathologic changes, however, dental follicles that possess reduced epithelium can proliferate into stratified squamous epithelium as far as originate dental cysts. In order to clarify the role of apoptosis and cellular proliferation herein, expression of p53 and PCNA was examined in epithelial components of dental follicles associated with impacted third molars by means of immunohistochemistry. A total of 40 cases was included in this study being 22 cases with reduced epithelium and 18 cases with stratified epithelium. Expression of p53 expression was weak or not detected in dental follicles with reduced and stratified squamous epithelium. By contrast, PCNA positive cells were evidenced in basal and supra basal layers of the stratified squamous epithelium and in reduced epithelium of dental follicles, but without any significant statistically differences between them (P > 0.05). In conclusion, these data suggest that dental follicles possess proliferative activity as depicted by PCNA-positive nuclei in some epithelial cells. However, the biological behavior of dental follicles during the late stage of dental eruptive process may not be associated with deregulation of death and/or cell proliferation.     

Estrogen receptor protein and mRNA expression in the ovary of sheep

Using immunohistochemistry and in situ hybridization, we attempted to identify the estrogen receptor (ER) protein and messenger RNA (mRNA) in sheep ovaries during the follicular phase of the estrous cycle. Monoclonal anti-ER antibodies H222 and 1D5 were used for localizing estrogen receptor on ovarian cryo-sections. Labeling for ER was found over the nuclei of surface epithelium, interstitial tissue, and granulosa cells of small as well as large ovarian follicles. In the preantral and small antral follicles, intense nuclear ER labeling was observed in mural granulosa cells and particularly in cumulus/granulosa cells surrounding the oocyte. In the large healthy looking follicles, greater diversity in labeling for ER was observed, which is characterized by mixed populations of granulosa cells expressing positive and more or less negative nuclear labeling. Such a pattern of labeling was particularly evident in follicles showing the signs of atresia. Generally, more intense nuclear staining was localized in granulosa cells proximal to basal membrane. In situ hybridization studies revealed the presence of ER mRNA in ovarian tissue. Autoradiographic visualization localized ER mRNA expression over the granulosa cells of healthy follicles of all sizes. Level of hybridization signal was comparable in mural and cumulus granulosa cells. In atretic follicles, the level of hybridization signal in granulosa cells was comparable to that of healthy follicles. A relatively weaker level of labeling was observed in granulosa cells dispersed in follicular antrum in follicles with advanced atretic lesions. Theca cells expressed a lower level of labeling than granulosa cells. Specificity of labeling for both ER protein and mRNA in ovary was proved by parallel probing the ovine uterus. Ovine ER recognition by both H222 and 1D5 antibodies was also proved by immunoblotting. These studies demonstrate the presence of the estrogen receptor and its messenger RNA in the sheep ovary and suggest an autocrine/paracrine role of estradiol and its receptor in the regulation of ovarian follicle development in sheep. Mol. Reprod. Dev. 48:53–62, 1997. © 1997 Wiley-Liss, Inc.     

Secretion of cumulus expansion-enabling factor (CEEF) in porcine follicles

The objective of this study was to find out whether porcine cumulus and mural granulosa cells can secrete cumulus expansion-enabling factor (CEEF). Culture drops of M-199 medium were conditioned with denuded porcine oocytes (1 oocyte/μl), cumulus cells from oocytectomized complexes (1 OOX/μl), pieces of mural granulosa isolated from preantral to preovulatory follicles (1000 cells/μl), or oviductal cells (1000 cells/μl) for 24 hr. The production of CEEF was assessed by the addition of mouse OOX and follicle-stimulating hormone (FSH) (1 μg/ml) to microdrops of the conditioned medium. After 16–18 hr, expansion of the mouse OOX was scored on a scale of 0 to 4 by morphologic criteria. Mouse OOX did not expand in nonconditioned FSH-supplemented medium. Immature porcine oocytes produced +3 to +4 expansion of the mouse OOX. Granulosa cells isolated from preantral and early antral follicles and cumulus cells isolated from all stages of follicle development constitutively secreted CEEF under in vitro conditions. Mural granulosa cells of small, medium, and preovulatory (PMSG) follicles also secreted CEEF in vitro; however, FSH or leutenizing hormone (LH) stimulation was essential for this secretion. Hormonally induced secretion of CEEF was accompanied by expansion of the mural granulosa itself. Granulosa cells isolated from follicles of gilts 20 hr after PMSG and human chorionic gonadotropin (hCG) administration did not produce CEEF and did not expand in response to FSH and LH in vitro. CEEF activity also was found in the follicular fluid of small antral follicles, was reduced in medium follicles, and was not detectable in PMSG-stimulated follicles. However, CEEF activity was reestablished in the follicular fluid of preovulatory follicles by hCG injection, conceivably due to increased production of CEEF by cumulus cells. We conclude that (1) porcine cumulus and mural granulosa cells are capable of CEEF production in vitro and (2) autocrine secretion of CEEF by cumulus cells is involved in regulation of porcine cumulus expansion both in vitro and in vivo. Mol. Reprod. Dev. 49:141–149, 1998. © 1998 Wiley-Liss, Inc.     

Follicle cell development is partly independent of germ-line cell differentiation in Drosophila oogenesis

Summary The developmental potential of the cells of the somatic follicular epithelium (follicle cells) was studied in mutants in which the differentiation of the germ-line cells is blocked at different stages of oogenesis. In two mutants, sn ^36a and kelch, nurse cell regression does not occur, yet the follicle cells around the small oocyte continue their normal developmental program and produce an egg shell with micropylar cone and often deformed operculum and respiratory appendages. Neither the influx of nurse cell cytoplasm into the oocyte nor the few follicle cells covering the nurse cells are apparently required for the formation of the egg shell. In the tumor mutant benign gonial cell neoplasm (bgcn) the follicle cells can also differentiate to some extent although the germ-line cells remain morphologically undifferentiated. Vitelline membrane material was synthesized by the follicle cells in some bgcn chambers and in rare cases a columnar epithelium, which resembled morphologically that of wild-type stage-9 follicles, formed around the follicle's posterior end. The normal polarity of the follicular epithelium that is characteristic for mid-vitellogenic stages may, therefore, be established in the absence of morphologically differentiating germ-line cells. However, the tumorous germ-line cells do not constitute a homogeneous cell population since in about 30% of the analyzed follicles a cell cluster at or near the posterior pole can be identified by virtue of its high number of concanavalin A binding sites. This molecular marker reveals an anteroposterior polarity of the tumorous chambers. In follicles mutant for both bgcn and the polarity gene dicephalic the cluster of concanavalin A-stained germ-line cells shifts to more anterior positions in the follicle.     

Effect of Actinomycin D and Cycloheximide on Gonadotropin-Induced 17α, 20β-Dihydroxy-4-pregnen-3-one Production by Intact Ovarian Follicles and Granulosa Cells of the Amago Salmon,Oncorhynchus rhodurus*

The effect of actinomycin D and cycloheximide on gonadotropin (partially purified chum salmon gonadotropin, SGA)-induced 17α, 20β-dihydroxy-4-pregnen-3-one (17α, 20β-diOHprog, a maturation-inducing steroid in amago salmon) production was examined in intact ovarian follicles and granulosa cells of postvitellogenic amago salmon, Oncorhynchus rhodurus. Both actinomycin D and cycloheximide blocked gonadotropin-induced 17α, 20β-diOHprog production by intact follicles. In contrast, gonadotropin-induced 17α-hydroxyprogesterone production by intact follicles was not abolished by actinomycin D, but was abolished by cycloheximide, suggesting that postvitellogenic amago salmon ovarian follicles already contain the RNAs necessary for the synthesis of 17α-hydroxyprogesterone. In isolated granulosa cells, chum salmon gonadotropin was able to stimulate 17α, 20β-diOHprog production only when a precursor, 17α-hydroxyprogesterone was provided in the incubation medium, indicating that gonadotropin acts directly on granulosa cells to enhance the activity of 20β-hydroxysteroid dehyrogenase (20β-HSD). Total inhibition of 20β-HSD enhancement in granulosa cells, judged by 17α, 20β-diOHprog production, was achieved when actinomycin D was added between 1 hr before the start of incubation with 17α-hydroxyprogesterone and gonadotropin to 6 hr after. With cycloheximide total inhibition was observed when added in the period of 1 hr before to 9 hr after the start of the incubation. These results suggest that chum salmon gonadotropin acts on granulosa cells to enhance the de novo synthesis of 20β-HSD by a mechanism involving RNA synthesis.     

DNA degradation in mural granulosa cells of non- and slightly atretic follicles of fresh and cold-stored domestic cat ovaries

Apoptosis of granulosa cells is associated with follicular atresia and may occur before atresia becomes morphologically evident. Detection of DNA fragmentation by in situ end-labeling (ISEL) with terminal transferase allows the histological assessment of apoptotic cells on conventional histological sections. Degradation of DNA also may occur after prolonged cold storage of ovaries caused by the release of lysosomal enzymes. The objectives of this study were to assess follicle atresia and the impact of cold storage for 8, 12, 24, and 48 hr after ovarian excision by assessing DNA degradation in mural granulosa cells of cat ovaries. Follicles were distinguished by morphological criteria as nonatretic (NA), slightly atretic (SA), or atretic, and the mean number (±SEM) of granulosa cells labeled by ISEL was determined. About 50% of follicles showed some sign of atresia independent from the stage of the reproductive cycle of the ovarian donor. Number of ISEL-stained granulosa cells for NA and SA, freshly collected follicles was 7.5 ± 0.6 and 9.3 ± 0.8 cells/field, respectively, compared to 16.2 ± 0.8 cells/field in the wall of atretic follicles (P < 0.001). Fresh NA follicles from luteal phase ovaries had more (P < 0.05) labeled granulosa cells (9.2 ± 0.7 cells/field) than measured in follicles of cats in a follicular phase (5.7 ± 0.7). During cold storage, DNA degradation began within 12 hr (NA, 12.2 ± 0.7 cells/field; SA, 13.3 ± 0.5), both values being different (P < 0.05) from fresh controls. By 24 hr, DNA degradation was at the level of a positive control subjected to DNAse treatment. In summary, results reveal that granulosa cell DNA degeneration precedes the loss of developmental capacity of cat oocytes during atresia and postexcision storage. Finding irreversible changes in granulosa cell DNA after storage of cat ovaries for >12 hr may be important for developing oocyte rescue protocols for rare felids in cases where prolonged storage and transport may be required. Mol. Reprod. Dev. 48:350–355, 1997. © 1997 Wiley-Liss, Inc.     

Studies on morphological features of foetal and adult ovaries in Kano brown goats

In this work we studied the structures of 51 foetal and 14 adult ovaries obtained from slaughtered Kano brown does in Nsukka abattoir. The ages of the adult does were determined by dentition and foetuses by crown rump length method. The foetal and adult ovaries were divided into five different groups using specific age intervals as Gestation day (GD) 50–65, 66–95, 96–125 and 126–145 and adults. For histological studies the ovaries were fixed, processed and routinely stained with H&E. The ovarian follicles were classified into 5 types according to granulosa cell layers surrounding the oocytes. The number of ovarian follicles per microscopic field, number of granulosa cells surrounding type 1 and 1A follicles and diameter of the ovarian follicles were determined for each group at 400× magnification. Grossly the foetal ovaries were like pin head, oval in shape, uniformly smooth and creamy in colour. The adult ovaries had follicles with different sizes. The adult mean ovarian weights were significantly higher (P < 0.01) than those of the foetuses. Microscopically, the GD 50–65 ovaries had no distinct cortex and medulla. Oogonia were numerous among other stromal cells toward the periphery of the ovary. By GD 66–95 the ovaries contained types 1, 1a, 2 and 3 follicles. GD 96–125 ovaries contained type 4 follicles with early antrum formation and those of GD 126–145 comprised type 5 among other follicles. The adult ovaries comprised all the ovarian follicle types. The number of type 1 follicles increased significantly (P < 0.01) with foetal age. It was least in the adults. The diameter of adult follicles was significantly higher (P < 0.01) than those of the foetuses. This result provides baseline information on the morphological development of ovaries in Kano brown goats.     

Morphology of the X-irradiated testes of Dermestes frischii Kugelann (Coleoptera: Dermestidae). I. Somatic cells and pre-spermatid germ cells

During the development of a sterile male control method for Dermestes frischii Kugelann, testis follicles exposed to an X-ray dose of 3.0 krad were investigated using light and electron microscopy.

There was considerable variation in the radiation sensitivity of the various somatic and germ cells. The cyst wall cells seemed particularly resistant while the inner layer of the bilayered follicle sheath was destroyed. The general resistance and versatility of the outer sheath layer maintained the integrity of the follicles. The only outer sheath and apical cells observed to decay were those in close proximity to degenerating germ cells. In some follicles all primary spermatogonia were destroyed, in others their numbers were only depleted. The surviving cells all underwent mitotic delay for 7–14 days. Their subsequent offspring were frequently found to break down and sometimes were proliferated so that germarial polarity was lost. All secondary spermatogonia but only a few primary spermatocytes were destroyed. The decay of germ cells within the same cyst did not necessarily proceed synchronously.     

Yolk synthesis in ovarian follicles ofDrosophila

Summary The autonomous synthesis of yolk proteins in ovarian follicles ofDrosophila melanogaster was analyzed. Vitellogenic follicles were labelled with³⁵S-methionine in vitro and the newly synthesized yolk proteins were separated by SDS-polyacrylamide gel electrophoresis. Possible contamination of the follicle preparations caused by adhering fat body cells could be excluded by culturing follicles in males prior to labelling in vitro. When labelled follicles were cut at the nurse cell/oocyte border the three yolk proteins (YP1, YP2, YP3) were found only in posterior fragments containing ooplasm and follicle cells, whereas two radioactive protein bands (A and B) were detected in nurse cells (anterior fragments). The yolk proteins of these five bands were characterized by peptide mapping. Band A protein, migrating a little more slowly than YP2, is closely related to both YP1 and YP2 while band B contains a yolk protein which is very similar to YP3. Hence, the nurse cells have been identified as a site of vitellogenin synthesis within the ovary ofDrosophila.Supported by the Deutsche Forschungsgemeinschaft, SFB 46     

Immunohistochemical observations of the endocrine pancreas during metamorphosis of the sea lamprey,Petromyzon marinus L.

Summary Light-microscopic immunohistochemistry was used to localize insulin- and somatostatin-immunoreactive cells within developing endocrine pancreatic tissue of metamorphosing lampreys, Petromyzon marinus. The extrahepatic common bile duct and a portion of the intrahepatic bile duct develop into the caudal portion of the endocrine pancreas. The cranial pancreas is composed of follicles originating in the intestinal and diverticular epithelia, thus following the method of formation of pancreatic follicles from gut epithelium in larvae. In both the cranial and caudal portions, and in an intermediate cord of isolated follicles which connect these two major masses, insulin-immunoreactive cells appear first and are followed by cells showing somatostatin-immunoreactivity. In all stages of metamorphosis individual endocrine cells demonstrate immunoreactivity to a single hormone. Biliary atresia in lamprey may have some adaptive significance in providing cells that produce a caudal endocrine pancreas.Supported by NSERC of Canada grant No. A5945 and MRC of Canada grant No. MA8629 to JHY     

Morphological and quantitative evaluation of the ovarian recrudescence in Nile tilapia (Oreochromis niloticus) after spawning in captivity

The Nile tilapia is one of the most important fish species for aquaculture worldwide. Understanding their reproductive biology is essential for improving their aquaculture methods. The morphological and quantitative dynamics of ovarian recrudescence of Oreochromis niloticus was studied for 21 days postspawning. To accomplish this, breeding females were kept in controlled conditions and ovarian samples were collected weekly for histological, ultrastructural and morphometric analyses. Ovarian follicle morphology revealed an intense synthesis activity of the follicular cells, which actively contributed to formation of the zona radiata and oocyte development following spawning. Recently spawned ovaries contained follicles at all developmental stages, but they were predominantly early primary growth (～42%) and full‐grown follicles (～20%). Remnants of spawning, postovulatory follicle complexes represented approximately 5% of the former ovarian follicles immediately after spawning, and less than 1% after 7 days. Atretic follicles accounted for approximately 2% of the follicles studied during the period. The stock of primary growth follicles was stable during ovarian recrudescence, indicating their availability for continuous recruitment. Only the frequency of full‐grown follicles significantly increased in the ovaries during recrudescence, representing approximately 35% of the follicles 21 days postspawning. The diameters of all follicles were significantly different between the periods analyzed. The ovaries' morphological characteristics, the maintenance of young follicles stocks and the gradual and significant increase in the proportion and diameter of full‐grown follicles showed a rapid ovarian recovery and follicular growth of O. niloticus, in 21 days at 29.5°C, necessary for the next spawning. J. Morphol. 275:348–356, 2014. © 2013 Wiley Periodicals, Inc.     

Microscopic structures of the ovary and female genital ducts of Supachai's caecilian,Ichthyophis supachaii Taylor, 1960 (Amphibia: Gymnophiona)

The structures of the female reproductive system (ovary, oviduct and cloaca) of Ichthyophis supachaii were investigated by dissection, histology and light microscopy. Paired, elongated, sac‐like ovaries are parallel to the gut and fat bodies. Follicle stages include germinal nests of oogonia and primary oocytes, early and late previtellogenic follicles, early and late vitellogenic follicles and atretic follicles. Germinal nests of oogonia comprise oogonia and prefollicular cells. Nests of primary oocytes contain clusters of synchronously developing primary oocytes enclosed by connective tissue. Primary oocytes are associated with follicular cells. Previtellogenic follicles initially form the vitelline envelope, theca cell layers and patches of ooplasmic glycoproteins. Vitellogenic follicles contain heterogeneously sized spherical yolk granules. Atresia is present in several stages of developing follicles. The oviduct is divided into the anterior, middle and posterior parts. All oviductal parts are lined by non‐ciliated epithelium. A small number of mucous cells are present in the middle part. The cloaca of female I. supachaii is divided into the anterior and posterior chambers. The anterior chamber is lined by glandular stratified columnar epithelium, while the posterior chamber has stratified cuboidal epithelium with less mucus production. Our results contribute to useful information on the reproductive biology of caecilians.