Electron microscopical and cytochemical study of vitelline cells in the fresh water Triclad Dugesia lugubris s. l.

Gremigni, Vittorio; Domenici, L.

doi:10.1007/bf00222174

Cited by 40 publications

(11 citation statements)

References 16 publications

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“…Confirming the descriptions of previous authors (le Moigne 1963; Marinelli and Vagnetti 1973;Gremigni and Domenici 1974), we identified two types of yolk cells in eggs at around the stage when cleavage begins: large and lipid-rich spherical yolk cells and motile, RNA-rich fusiform yolk cells. The latter type aggregates around the cleaving zygotes and forms the yolk syncytium that surrounds the early embryo.…”

Section: Origin and Function Of Yolk Cellssupporting

confidence: 89%

Early embryogenesis of planaria: a cryptic larva feeding on maternal resources

2006

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The early planarian embryo presents a complete ciliated epidermis and a pharynx and feeds on maternal yolk cells. In this paper, we report on all the elements involved in the formation of such an autonomous embryo, which we name cryptic larva. First, we provide a description of the spherical and fusiform yolk cells and their relationship with the blastomeres, from the laying of the egg capsule up to their final fate in mid embryonic stages. Then, we describe the early cleavage and the subsequent development of the tissues of the cryptic larva, namely, the primary epidermis, the embryonic pharynx, and a new cell type, the star cells. Finally, we discuss the possibility that the cryptic larva either constitutes a vestigial larva or, more likely, is the evolutionary result of the competition between multiple embryos for the limited and shared maternal resources in the egg capsule.

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Section: Origin and Function Of Yolk Cellssupporting

confidence: 89%

Early embryogenesis of planaria: a cryptic larva feeding on maternal resources

2006

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“…4). Yolk cells inside the developing capsule are thought to secrete proteins rich in 3,4-dihydroxyphenyl-L-alanine (DOPA) and enzymes that oxidize DOPA into o -quinone, which ultimately polymerizes with other proteins to harden and pigment the shell (Gremigni and Domenici, 1974; Ishida and Teshirogi, 1986; Marinelli, 1972; Nurse, 1950). Indeed, all four genes found to contribute to the tanning process are expressed in yolk glands, providing additional evidence for the contribution of yolk cells to shell development.…”

Section: Discussionmentioning

confidence: 99%

Genetic dissection of the planarian reproductive system through characterization of Schmidtea mediterranea CPEB homologs

Rouhana

Tasaki

Saberi

et al. 2017

Developmental Biology

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Cytoplasmic polyadenylation is a mechanism of mRNA regulation prevalent in metazoan germ cells; it is largely dependent on Cytoplasmic Polyadenylation Element Binding proteins (CPEBs). Two CPEB homologs were identified in the planarian Schmidtea mediterranea. Smed-CPEB1 is expressed in ovaries and yolk glands of sexually mature planarians, and required for oocyte and yolk gland development. In contrast, Smed-CPEB2 is expressed in the testes and the central nervous system; its function is required for spermatogenesis as well as non-autonomously for development of ovaries and accessory reproductive organs. Transcriptome analysis of CPEB knockdown animals uncovered a comprehensive collection of molecular markers for reproductive structures in S. mediterranea, including ovaries, testes, yolk glands, and the copulatory apparatus. Analysis by RNA interference revealed contributions for a dozen of these genes during oogenesis, spermatogenesis, or capsule formation. We also present evidence suggesting that Smed-CPEB2 promotes translation of Neuropeptide Y-8, a prohormone required for planarian sexual maturation. These findings provide mechanistic insight into potentially conserved processes of germ cell development, as well as events involved in capsule deposition by flatworms.

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“…Smith & Clegg, 1959 ;Locke & Krishnan, 1971) . In the Platyhelminthes, the detection of diphenol and protein in the composite eggs of Trematoda, Cestoidea, and Turbellaria suggests the existence of sclerotin, and the presence of sclerotin precursors in yolk cells has been reported (Nurse, 1950 ;Burton, 1963 ;Nollen, 1971 ;Bunke, 1972Bunke, , 1981Gremigni & Domenici, 1974;and others) . In polyclads, which oviposit endolecithal eggs, Vialli (1934), Domenici et al (1975) and others observed that previtellogenic oocytes contain granules with di-or polyphenols and protein which are distributed in the cortex of mature oocytes .…”

Section: Hardening Of the Eggshell And Epgmmentioning

confidence: 99%

Eggshell formation in polyclads (Turbellaria)

Ishida

Teshirogi

1986

Hydrobiologia

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Eggshell formation in polyclads was studied by means of transmission electron microscopy and histochemistry. Shell-forming granules (SFG) in the egg, as well as secretions of shell glands (SGS), play roles in eggshell formation. As the oocytes pass through the portion of the female tract where the shell glands open, they are surronded by a two-layered envelope of SGS . This envelope prevents the dispersion of SFGs discharged after oviposition, and its inner layer participates in eggshell formation with the SFGs . In Pseudostylochus sp ., most SFGs consist of five parts . Similarities in staining between the parts of the SFGs and the parts of the eggshell indicate that discrete parts of the shell are derived from specific SFG components . Hardening of the eggshell and egg-plate matrix takes place through primary tanning of a sclerotin-like protein .

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Electron microscopical and cytochemical study of vitelline cells in the fresh water Triclad Dugesia lugubris s. l.

Cited by 40 publications

References 16 publications

Early embryogenesis of planaria: a cryptic larva feeding on maternal resources

Early embryogenesis of planaria: a cryptic larva feeding on maternal resources

Genetic dissection of the planarian reproductive system through characterization of Schmidtea mediterranea CPEB homologs

Eggshell formation in polyclads (Turbellaria)

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