Ultrastructure of the vitelline follicles of Gorgoderina vitelliloba (Trematoda: Gorgoderidae)

An electron microscope study of the vitelline follicles of Gorgoderina vitelliloba indicates that they contain vitelline cells in various stages of development. Juvenile cells are small and characterised by a little cytoplasm. During differentiation a large amount of granular endoplasmic reticulum develops. In more mature cells, indistinct Golgi complexes give rise to globules of shell protein which migrate to form clusters at the periphery of the cell. Further maturation results in the appearance of large lipid bodies in the vitelline cell cytoplasm.Developing vitelline cells are ensheathed by nurse cell cytoplasm containing numerous small vacuoles which appear to be derived from smooth endoplasmic reticulum. It is suggested that nurse cells may have a role in selection and transport of nutrient material for vitelline cells and that they manufacture precursors of lipid which is subsequently stored as a food reserve in mature vitelline cells. Possible transport sites between parenchymal cells and nurse cells were identified.     

东方杯叶吸虫卵黄腺和卵巢的超微结构研究

本文应用透射电镜观察了东方杯叶吸虫卵黄腺和卵巢的超微结构,并与体外培养成虫进行比较。根据形态特征和内含物的存在情况,将卵黄细胞和卵母细胞的发育均分为不同时期,详细描述了各期的形态特征,探讨了卵黄球和皮质颗粒等内含物的生理功能。体外培养成虫成熟卵黄细胞中有散在的卵黄物质,成熟卵母细胞中线粒体囊泡化,这些可作为体外培养的评价指标。     

Development and roles of vitelline cells in eggshell formation in Fasciola gigantica

Summary

In Fasciola gigantica, vitelline cells are the major contributors to the formation of the eggshell. The vitelline cells develop in vitelline follicles that are located in the posterior third of the adult parasite's body, in the areas lateral to the uterus and the testis. Mature vitelline cells are released and transported to the Mehlis' gland-ootype complex via a series of vitelline ducts. Based on ultrastructural features, the developing vitelline cells are classified into four stages: stem cell, protein-synthetic, carbohydrate-synthetic and mature cell stages. At the protein-synthetic stage, the eggshell globules are formed, whereas during the carbohydrate-synthetic stage glycogen particles and glycan vesicles are synthesized. The mature vitelline cells are detached from the nurse cells, and pass successively into the intrafollicular, interfollicular, longitudinal and transverse vitelline ducts, to be stored in the vitelline reservoir before being transported to the ootype via the median vitelline duct. At the same time, ova are transported from the ovary through the oviduct into the ootype lumen where each becomes surrounded by a number of vitelline cells. Vitelline cells secrete eggshell globules to surround a group of vitelline cells and an ovum in the ootype lumen, and these globules coalesce into the definitive eggshell. In the middle part of the uterus fertilization occurs, after which the eggshell is completely formed. Within the egg proper, vitelline cells break down, releasing glycogen and other products to nourish the developing embryo.     

The female gonad in two species of Microplana (Platyhelminthes,Tricladida, Rhynchodemidae): Ultrastructural and cytochemical investigations

The female gonad of the land planarians Microplana scharffi and Microplana terrestris consists of two small germaria located ventrally in the anterior third of the body and of two ventro‐lateral rows of oblong vitelline follicles distributed between the intestinal pouches. Both these structures are enveloped by a tunica composed of an outer extracellular lamina and an inner sheath of accessory cells. Oocyte maturation is characterized by the appearance of chromatoid bodies and the development of endoplasmic reticulum and Golgi complexes. These organelles appear to be correlated with the production of egg granules with a fenestrated/granular content of medium electron density, about 4–5 μm in diameter, which remain dispersed in the ooplasm of mature oocytes. On the basis of cytochemical tests showing their glycoprotein composition, and their localization in mature oocytes, these egg granules have been interpreted as yolk. In the vitelline follicles, vitellocytes show the typical features of secretory cells with well‐developed rough endoplasmic reticulum and Golgi complexes involved in the production of eggshell globules and yolk. The eggshell globules, which appear to arise from repeated coalescences of two types of Golgi‐derived vesicles, contain polyphenols and, when completely mature, they measure about 1–1,2 μm in diameter and show a meandering/concentric content pattern as is typical of the situation observed in most Proseriata and Tricladida. Mature vitellocytes also contain a large amount of glycogen and lipids as further reserve material. On the basis of the ultrastructural features of the female gonad and in relation to the current literature the two species of rhynchodemids investigated appear to be closely related to the freshwater planarians belonging to the family Dugesiidae. J. Morphol. 2009. © 2009 Wiley‐Liss, Inc.     

Observations on the origin of two substances produced by the vitellaria in Gorgoderina attenuata

The vitelline cells in Gorgoderina attenuata produce two qualitatively distinct substances. One substance assumes the form of individual, dense, osmiophilic globules. Many globules are contained in a single vesicle. The other substance is an amorphous mass of medium density that completely fills a vesicle. Observations indicate that the dense, osmiophilic globules develop in association with a system of small, contiguous, ribosome-free vesicles. It is suggested that this system of vesicles constitute a Golgi apparatus for these cells. The amorphous mass substance develops in vesicles which appear to be derived from endoplasmic reticulum. Close association between the amorphous mass vesicle and mitochondria are commonly observed.     

Ultrastructural and cytochemical aspects of the female gonad of Geoplana burmeisteri (Platyhelminthes, Tricladida, Terricola)

The ultrastructure of the female gonad of the land planarian Geoplana burmeisteri was investigated by means of electron microscopy and cytochemical techniques. It consists of two small germaria located ventral to the intestine and of two irregular, lateral rows of vitelline follicles, both enveloped by a tunica composed of an extracellular lamina and an inner sheath of accessory cells. Accessory cell projections completely surround developing oocytes and vitellocytes. The main feature of oocyte maturation is the appearance of chromatoid bodies and the development of the rough endoplasmic reticulum (RER) and Golgi complexes. These organelles appear to be correlated with the production of egg inclusions of medium electron density, about 1.5-1.8 microm in diameter, which remain scattered in the ooplasm of mature oocytes. On the basis of cytochemical tests demonstrating their glycoprotein composition, these inclusions were interpreted as residual yolk globules. Vitellocytes are typical secretory cells with well-developed RER and Golgi complexes that are mainly involved in the production of yolk globules and eggshell globules, respectively. Eggshell globules appear to arise from repeated coalescence of small Golgi-derived vesicles and, at an intermediate stage of maturation, show a multigranular pattern. Later, after vesicle fusion, they reach a diameter of 1.3-1.6 microm when completely mature and show a meandering/concentric pattern, as is typical of the situation seen in most Proseriata and Tricladida. The content of yolk globules is completely digested by pronase, while the content of eggshell globules is unaffected. Mature vitellocytes contain, in addition, a large quantity of glycogen and lipid droplets as further reserve material. On the basis of the ultrastructural characteristics of the female gonad described above and in relation to the current literature, we conclude that G. burmeisteri appears to be more closely related to the freshwater triclads, in particular to members of the Dugesiidae, than to the marine triclads.     

Fasciola hepatica: A light and electron autoradiographic study of shell-protein and glycogen synthesis by vitelline follicles in tissue slices

The incorporation of tritiated amino acids and monosaccharides by the vitelline cells of F. hepatica slices maintained in vitro was studied by light and electron microscope autoradiography.A “pulse-chase” labeling technique was used with tritiated tyrosine, phenylalanine, leucine, and methionine, of which H³-tyrosine was the most readily incorporated into shell-protein globules of immature vitelline cells. The mechanism of protein synthesis appeared to resemble the GER-Golgi mediated mechanism of vertebrates. Young vitelline cells were the most active in protein synthesis, and they matured considerably during the 60 min chase period. Maturing cells, which were carrying out glycogenesis, incorporated no amino acids.An “accumulation” labeling technique was used with H³-galactose and H³-glucose. Both monosaccharides were readily incorporated into glycogen by vitelline cells which had reached the stage of glycogenesis, but mature cells, which were already packed with glycogen, incorporated little monosaccharide. Labeling appeared in the nurse cells of follicles containing many mature vitelline cells. No evidence was found for the involvement of any cell organelle in glycogenesis, but preformed glycogen may have acted as a “template” for further synthesis.     

Differential expression of Paragonimus westermani eggshell proteins during the developmental stages

Eggs of trematode parasites are comprised of numerous vitelline cells and one fertilized ovum, and are encapsulated within a protein shell provided by the vitellocytes. In this study, we isolated two full-length cDNA clones that showed substantial levels of sequence identity with trematode-specific eggshell precursor proteins from the human lung fluke, Paragonimus westermani. These cDNAs, designated Pw-Vit20 (868-bp-long) and Pw-Vit36 (883-bp-long), shared a 76% identity with one another at the nucleotide level, and each encoded a 261-amino acid (aa) polypeptide. The deduced aa sequences contained a N-terminal hydrophobic segment, as well as a sequence motif of Gly-Gly-Gly-Tyr-Asp-Asn/Thr-Tyr-Gly-Lys/Gln, which is highly homologous with the eggshell proteins of Fasciola hepatica. With the high frequencies of tyrosine, glycine and lysine, the positions occupied by tyrosine, which has been proved to be converted into dihydroxyphenylalanine, were well preserved. Pw-Vit20 and Pw-Vit36 were found to be monoexonic genes with variably diverged variants scattered into multiple genomic loci. Their protein products were localized in the vitelline follicles and eggshells. Expression of Pw-Vit20 was restricted to the egg and adult stages, thus suggesting a critical involvement of Pw-Vit20 in the parasite's fecundity activity. Conversely, Pw-Vit36 was constitutively expressed in the metacercariae and juvenile stages in the vitelline follicles and ducts, which suggested that the prepositioning of stem or primordial vitelline cells within the juveniles prior to sexual maturation. Pw-Vit36 might acquire a unique or additional function relevant to the maturation and/or development of the vitelline cells/follicles during the evolutionary period of P. westermani. Differential biological implications of multiple eggshell precursor proteins may provide insight into the molecular mechanism of eggshell formation and the developmental process of the vitelline follicles in the parasitic trematode.     

Fasciola hepatica: Morphological changes in vitelline cells following treatment in vitro with the deacetylated (amine) metabolite of diamphenethide (DAMD)

Fasciola hepatica: morphological changes in vitelline cells following treatment in vitro with the deacetylated (amine) metabolite of diamphenethide (DAMD). International Journal for Parasitology 18: 1061–1069. The effect of the deacetylated (amine) metabolite of diamphenethide (DAMD, 10 μg ml⁻¹) on the vitelline cells of Fasciola hepatica over an 18 h period in vitro has been determined by transmission electron microscopy. DAMD acts preferentially on the undifferentiated stem cells and the intermediate cells in the early stages of protein synthesis; it appears to prevent their continued development. In the stem cell the nucleolus is absent after 6 h. During the rest of the drug treatment period considerable clumping of heterochromatin takes place, the cells round up and become electron-dense. Signs of autophagy are also evident, and the mitochondria become swollen and disorganized. From 6 h onwards there are progressive changes in the It1 (intermediate type 1) cells, including clumping of the heterochromatin in the nucleus, a decrease in the number of egg-shell globules (and consequently a reduction in the number and size of the shell globule clusters), and a decrease in the number of ribosomes on the GER cisternae, although the GER system remains well-developed. By 18 h the nucleolus is absent, and the cells are very rounded and electron-dense; the mitochondria are swollen and disorganized. Similar changes are evident in the It2 (intermediate type 2) cells, so that by 18 h it is difficult to distinguish between the It1 and It2 cells. In the mature cells there is a progressive decrease in the number and size of the shell globule clusters from 9 h onwards. Glycogen synthesis and ‘yolk’ formation may also be impaired and lipid droplets are present. Spaces begin to appear between the nurse cell cytoplasm and the vitelline cells after 9 h, and disruption of the nurse cell cytoplasm is evident after 12 h, becoming very severe by 18 h. By this time the follicle is very disorganized and empty-looking. In more severely affected follicles the mature cells are seen to be breaking down. Over the 18 h drug treatment period, a change in the cell population of the follicle takes place, with relatively more stem, early It1 and mature cells being present, whilst few if any characteristic It1 and It2 cells remain. The results are interpreted as being due to an inhibition of protein synthesis in the vitelline cells by DAMD.     

Ultrastructure of Pharyngostomoides procyonis Harkema 1942 (Diplostomatidae). II. The female reproductive system

Several components of the female reproductive system of Pharyngostomoides procyonis, including the vitellaria and vitelline duct, ovary and oviduct, Laurer's canal, and Mehlis' gland and associated ducts, were observed with the electron microscope. Vitelline follicles contain cells in various stages of development. Mature vitelline cells contain membrane-delimited clusters of vitelline globules near the plasma membrane. Cilia are present in the vitelline duct. The ovary contains germ cells in various stages of maturation. Oogonia are found in the peripheral region. Mature oocytes contain numerous dense bodies near the plasmalemma. Also included in the cytoplasm of mature oocytes are "nucleolus-like bodies," myelin-like bodies, and mitochondria containing dense granules and few cristae. The epithelium of the oviduct is ciliated. Sperm are present in the oviduct and in Laurer's canal. Two types of secretory cells found in Mehlis' gland are described.     

Trematode embryology: a new method for whole-egg analysis by confocal microscopy

Trematode worms have the neoophoran mode of development in which several specialized vitelline cells surround the zygote. This vitelline cell mass appears just before the zygote passes through the ootype, a thickening of the oviduct, where the egg shell is formed. The great amount of vitelline material blurs the visualization of embryo development in whole egg seen by brightfield microscopy. The eggshell is difficult to cut into thin or ultrathin sections and acts as a barrier to fixation and infiltration with embedding media. The egg shell is also brightly fluorescent when analyzed by fluorescence microscopy. To overcome these technical disadvantages a simple staining protocol widely used in adult helminth morphological analysis was adapted for the study of the embryonic development of two different trematode species. The effects of potassium hydroxide as bleach and ethylene glycol as mounting medium were also evaluated. Confocal microscopy allowed virtual sectioning of whole-mounted eggs and made possible internal morphological detailed analysis of different embryonic stages. This method could contribute to the study of helminth egg embryology.     

日本血吸虫卵黄培养细胞超微结构动态的研究

从超微结构水平研究日本血吸虫卵黄细胞培养的动态。在体外培养过程中,卵黄细胞对外界环境的改变比日本血吸虫的其它体细胞更加敏感。随着培养时间的延长,卵黄细胞发生不同程度的变性,成熟卵黄细胞比未成熟卵黄细胞发生变性。变性主要表现在核和胞质的电子密度降低;卵黄球相互融合,或卵黄球与膜之间的空隙逐步增大,最终卵黄球从中释放出来,变成裸露体;脂滴数目增多,体积增大;粗面内质网扩大和囊泡变,其上的核糖体脱颗粒等     

The ovaries and changes in their structural components at the end of vitellogenesis and during vitelline membrane formation in the butterfly, Calpodes

The eight ovarioles of Calpodes ethlius are meroistic and polytrophic with seven nurse cells per follicle. The follicles consisting of oocyte, nurse cells and surrounding follicular cells are connected by interfollicular bridges, whose cells are characterized by bundles of microtubules which appear, with some fine filaments, to terminate on or near to the plasma membrane at hemidesmosomes. The ovariolar sheath consists of tightly knit circular and longitudinal muscles which are heavily tracheated. The ovariolar duct consists of more loosely arranged circular and longitudinal muscles and an inner epithelial layer, also tracheated. The vitelline membrane appears to be secreted largely by the oocyte first as an electron-lucent layer which becomes gradually more electron-dense, probably as a result of addition of material from the follicular cells. Overlapping plate-like structures on the outer surface of the fully formed vitelline membrane may provide waterproofing.     

Oogenesis in pig ovaries during the prenatal period: ultrastructure and morphometry

Oogenesis in fetal pig ovaries comprises the successive changes from the primordial germ cells to the dictyotene oocytes in primordial ovarian follicles. In this study the observations were carried out with an electron microscope and stereological analysis was performed. At the ultrastructural level there are no differences between the primordial germ cells and oogonia, but oogonia are connected with the intercellular bridges. The onset of the dictyotene phase was accompanied by the changes in the cytoplasm of oocytes. Near the nucleus, the yolk nucleus is formed containing numerous Golgi bodies, endoplasmic reticulum (ER), mitochondria and granules. ER proliferates in contact with the external leaflet of the nuclear envelope forming the narrow ER cisterns. Between the nuclear envelope and ER cisterns, the vesicles with grey content are visible. The proliferating ER forms numerous concentric cisterns around the nucleus. Next, the most external cisterns fragment, detach, and then form the cup-like structures. These structures separate the distinct areas of cytoplasm-compartments, which contain mitochondria, ribosomes and lipid droplets. The cells of cortical sex cords of the ovary, which encloses the oocyte, form the follicles. The volume of oocytes in forming follicle increases due to the increase in the number of the cell inclusions: lipid droplets, vacuoles and yolk globules. In the oocytes of primordial ovarian follicles, the compartments are transformed into the yolk globules, which are encountered by a sheath of ER cisterns and the grey vesicles; they contain the mitochondria, lipid droplets and light vacuoles. The role of the compartments and yolk globules as metabolic units is discussed in comparison with similar structures of the mature eggs of pigs and other mammal species.     

Electron microscope studies of Fasciola hepatica. X. Egg formation

Evidence obtained would suggest that the processes involved in egg formation in Fasciola hepatica occur in the following sequence. The egg constituents, namely an ovum and some vitelline cells, pass through the proximal ootype and as they do so they are smeared by the secretions of Mehlis' gland which have accumulated there. A temporary interface is set up between the Mehlis' gland secretion and the fluid which surrounds the egg constituents. Shell globules are released by the vitelline cells and coalesce on the inner aspect of the interface. At the same time some of the Mehlis' secretion diffuses across the interface, thereby bringing about the dissociation of the interface. It is suggested that Mehlis' gland secretion brings about the fusion of the shell layer. During the initial stages of the process the developing egg is supported by the cells of the ootype epithelium. Later the egg passes into a wider, more distal part of the ootype where the process of shell deposition is continued. When complete, or almost complete, the egg passes into the uterus where changes indiciating the initial process of tanning are seen to take place. A thin, very uniform layer of Mehlis' gland secretion can still be identified on the surface of mature eggs.     

Vitellogenesis of basal trematode Aspidogaster limacoides(Aspidogastrea: Aspidogastridae)

The vitellogenesis of the trematode Aspidogaster limacoides (Aspidogastrea: Aspidogastridae), a parasite of cyprinid fishes, is described here using transmission electron microscopy. Four different stages of vitellocytes are differentiated: immature vitellocytes, early maturing vitellocytes, advanced maturing vitellocytes and mature vitellocytes. The process follows the same general pattern already described in other free-living neoophorans and parasitic flatworms (i.e. Trematoda, Monogenea and Cestoda): differentiation into mature vitelline cells involves the development of mitochondria, granular endoplasmic reticulum, Golgi complexes, lipid droplets and shell-globules. Mature vitellocytes of A. limacoides are composed of numerous shell-globule clusters, few lipid droplets and glycogen granules. They differ from those of another aspidogastrean Rugogaster hydrolagi in that they possess numerous globules tightly packed and by the presence of only one type of vitelline material. The interstitial tissue of vitelline follicles of A. limacoides contains a peripheral nucleus and long cytoplasmic projections extending between vitelline cells. Since aspidogastreans are considered as an archaic group of parasitic flatworms and thus have a strategic phylogenetic position, future works needs to pay special attention to the ultrastructural and chemical composition of mature vitellocytes within this basal group of trematodes.     

Schistosoma haematobium: oxidoreductase histochemistry and ultrastructure of niridazole-treated females

Administration of niridazole to Saccostomus campestris produced changes in enzyme activity in Schislosoma haematobium females as indicated histochemically by a decrease in the activity of cytochrome oxidase (EC 1.9.3.1), malate (NAD) dehydrogenase (EC 1.1.1.37), malate (NADP) dehydrogenase (EC 1.1.1.40), succinate dehydrogenase (EC 1.3.99.11), isocitrate (NAD) dehydrogenase (EC 1.1.1.41), isocitrate (NADP) dehydrogenase (EC 1.1.1.42), lactate dehydrogenase (EC 1.1.1.27), glucose-6-phosphate dehydrogenase (EC 1.1.1.49), NADH: tetrazolium oxidoreductase, NADPH: tetrazolium oxidoreductase, and a disappearance of both the activity of phenolase (EC 1.10.3.1) and the reactivity of vitelline phenols. These changes were associated with the following alterations in the ultrastructure of the parasites: a decrease in number of immature vitelline cells of gonial type, a disruption of the tegument surface, a swelling of mitochondria in vitelline cells, a disappearance of the regular structure of the endoplasmic reticulum and a vaeuolization of the cytoplasm in vitelline cells, an appearance of areas of focal cytoplasmic degradation in vitelline cells, and a disruption of shell globules. The degree of changes in enzyme activity and ultrastructure increased both with increase in the dose of niridazole administered to the hosts, and with length of time after treatment.Preincubation of control sectioned material in a buffered niridazole-sucrose solution produced total inhibition of succinate dehydrogenase activity, whereas the activity of other enzymes examined remained unchanged.     

Effects of low-protein diet on Schistosoma mansoni morphology visualized by morphometry and confocal laser scanning microscopy

Previous studies have shown that protein deficiencies can hamper both the course of experimental schistosomiasis and normal development of adult worms. To further investigate this relationship, we compared adult male and female Schistosoma mansoni from malnourished and well-fed mice through morphometric and confocal laser scanning microscopy analysis. Swiss mice were fed protein-deficient diets (8%) and infected subcutaneously with approximately 80 S. mansoni cercariae (BH strain, Brazil). Control mice were fed a standard rodent diet (23% protein). The nutritional status was evaluated by body weight gain and albumin values. Mice were sacrificed 63 days post-infection. Recovered worms were stained with hydrochloric carmine and preserved as whole-mounts for bright-field examination and confocal microscopy. The body weight gain and serum albumin concentrations were significantly lower (P < 0.05) in malnourished mice than in controls. In general, all morphometric values of specimens grown in malnourished mice were lower than those of control mice. Schistosome worms grown in malnourished mice had statistically significant differences (P < 0.05) in the reproductive system and tegument than those grown in mice fed standard diets. In female worms, vitelline glands showed few remaining follicles and ovaries lacked mature oocytes. In male parasites, tubercles were fewer in number on the dorsal surface and testicular lobes presented fewer differentiated germinal cells. In summary, we describe novel data supporting the view that low-protein diets may influence the development of adult worms.     

Histochemical studies on eggshell formation in Paramphistomum cervi (Digenea: Paramphistomatidae)

The formation of the egg mass in the ootype, containing the oocyte, vitelline cells, numerous spermatozoa and Mehlis' gland secretion marks the beginning of eggshell formation. Mehlis' gland cells pour their lipoprotein secretion into the ootype; this secretion forms a thin template around the egg mass and upon this template the shell globules are deposited. Eggshell formation begins in the proximal uterus and is completed in the middle uterus. The eggshells are devoid of phenols and phenolase indicating that hardening is not by quinone tanning. The eggshells contain keratin and are stabilized by disulphide linkages.     

Ultrastructural and cytochemical aspects of the germarium and the vitellarium in Syndesmis patagonica (Platyhelminthes,Rhabdocoela, Umagillidae)

The cytoarchitecture of the female gonad of the endosymbiont umagillid Syndesmis patagonica has been investigated using electron microscopy and cytochemical techniques. The female gonad consists of paired germaria and vitellaria located behind the pharynx in the mid‐posterior region of the body. Both the germaria and the vitellaria are enveloped by an outer extracellular lamina and an inner sheath of accessory cells which contribute to the extracellular lamina. Oocyte maturation occurs completely during the prophase of the first meiotic division. Oocyte differentiation is characterized by the appearance of chromatoid bodies and the development of endoplasmic reticulum and Golgi complexes. These organelles appear to be involved in the production of round granules, about 2–2.5 μm in diameter, with a homogeneous electron‐dense core surrounded by a granular component and a translucent halo delimited by a membrane. These egg granules migrate to the periphery of mature oocytes, are positive to the cytochemical test for polyphenol detection, are unaffected by protease and have been interpreted as eggshell granules. The mature oocytes also contain a small number of yolk granules, lipid droplets, and glycogen particles scattered throughout the ooplasm. The vitellaria are branched organs composed of vitelline follicles with vitellocytes at different stages of maturation. Developing vitellocytes contain well‐developed rough endoplasmic reticulum and small Golgi complexes involved in the production of eggshell and yolk globules. Eggshell globules are round, measure 4–5 μm in diameter, and have a mosaic‐like patterned content which contains polyphenols. The yolk globules, 2–3 μm in diameter, show a homogeneous protein content of medium electron density, devoid of polyphenols, and completely digested by protease. The mature vitellocytes also contain glycogen as further reserve material. The presence of polyphenolic eggshell granules in the oocytes and of polyphenolic eggshell globules with a mosaic‐like pattern in the vitellocytes have been considered apomorphic features of the Rhabdocoela + Prolecithophora. J. Morphol. 275:703–719, 2014. © 2014 Wiley Periodicals, Inc.