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The cleavage pattern of a vertebrate's embryo is either holoblastic (complete) or meroblastic (partial). Sturgeon and other basal bony fishes represent a transition of the cleavage pattern. To understand the transition, it is essential to develop an effective technique for the inhibition of specific blastomere cleavage. So far, various studies have demonstrated that diatom-derived polyunsaturated aldehyde (PUA), 2,4-decadienal (DD)—a model aldehyde for experimental studies—adversely affects the developing embryos of several aquatic species. In this study, we employed DD for inhibition of cleavage of a definite blastomere in sturgeon embryos under various conditions. The effective treatment was found to be a combination of DD injection (0.01 v/v) and visible light (44.86–91.15 W m−2). Notably, DD injection or light irradiation alone cannot inhibit cleavage. Furthermore, spatial RNA localization analysis using quantitative polymerase chain reaction (qPCR)-tomography revealed that the localized pattern of selected maternal messenger ribonucleic acids (mRNAs) remained constant along the animal–vegetal (A-V) axis, which suggests that RNA localization is completed by the end of oogenesis and that early embryonic cleavage is not required for A-V asymmetry preservation. [ABSTRACT FROM AUTHOR]

Generally, holoblastic cleavage in embryos (as in amphibians) in which all blastomeres contribute to one of the germ layers, are preserved as a stem lineage of vertebrates, and meroblastic cleavage has evolved independently in each vertebrate lineage. The increasing egg size: yolk volume is the key factor for transition from holoblastic to meroblastic cleavage patterns. Sturgeon (Acipenser) eggs are two times larger than those of the African clawed frog Xenopus laevis (amphibian); despite the varying size, sturgeon embryos retain nearly the same developmental characteristics as X. laevis. Comparatively, the fate of blastomeres derived from the vegetal pole (VP) of a sturgeon embryo is unspecified. Thus, the goal of this study was to determine whether the VP of the embryo contributes to embryonic development, or is simply extra-embryonic. This may also reveal whether the transition of the cleavage pattern (holoblastic to meroblastic) in the actinopterygian lineage is correlated with the egg size: yolk volume. Here, we found that sturgeon vegetal blastomeres formed only primordial germ cells, and the rest were made up of cellular yolk (yolk cells; YCs). Morphological and phenotypic characteristics revealed that after the 1 k-cell / mid-blastula transition, YCs became transcriptionally inactive and served only to provide nutrition to larvae as they developed. Furthermore, inhibition of vegetal blastomeres revealed that sturgeon can utilize their yolk in an acellular form, similar to teleosts, implying that meroblastic cleavage in the actinopterygians, like teleosts, might have evolved by the fusion of the vegetal blastomeres. • The vegetal blastomeres of sturgeon embryos produce primordial germ cells and cellular yolk mass (yolk cells; YCs). • After the mid-blastula transition, YCs became transcriptionally inactive and serve only to provide nourishment. • Inhibiting vegetal blastomeres revealed that sturgeons can utilize their yolk in an acellular form rather than as YCs. • YCs from vegetal blastomeres present a distinct transition from holoblastic to meroblastic cleavage in ray-finned fishes. [ABSTRACT FROM AUTHOR]

Nanoparticles are finding increasing applications in diagnostics, imaging and therapeutics in medicine. Iron oxide nanoparticles (IONs) have received significant interest of scientific community due to their distinctive properties. For the first time, we have delivered IONs into germ cells in any species. Our results showed that sturgeon primordial germ cells (PGCs) delivered with IONs could be detected until seven days post fertilization (dpf) under fluorescent microscope and at 22 dpf by micro-CT. Delivery of IONs into cells could be helpful for studying germ cell biology and the improvement of germ cell-based bio-technologies as isolation of PGCs using magnetic activated cell sorting or application of hyperthermia for a host sterilization purpose. Intriguingly, in our study, we did not find any toxic effects of IONs on the survival and hatching rates of sturgeon embryos when compared with embryos injected with FITC-dextran only. [ABSTRACT FROM AUTHOR]