PGE2 functions in ovoviviparous teleost black rockfish (Sebastes schlegelii): evolutionary status between parturition and ovulation†.

Fish have evolved various reproductive strategies including oviparity, viviparity, and ovoviviparity, which undoubtedly affect the survival of the whole species continuity. As the final step in reproduction, parturition in viviparous vertebrate and ovulation in oviparous teleost seem to share a similar mechanism, when prostaglandins (PGs) act as the trigger to launch the whole process. In the present study, ovoviviparous teleost black rockfish (Sebastes schlegelii) is employed as the research object. Intraperitoneal injection showed that PGE2 (500 µg/kg) could activate the delivery reactions in perinatal black rockfish. RNA-seq data of ovary in perinatal period revealed transcriptional change in cell junction, inflammation, and apoptosis, which is related to mammal parturition and teleost ovulation. Further results proved the positive correlation between ptger EP2 and previous mentioned pathways. Subsequent experiment proved that PGE2 was able to induce the ovulation and spawning in unfertilized individuals, which had a bilayer follicular structure compared to monolayer follicular in perinatal period black rockfish. Both unfertilized and perinatal ovary matrix could response to PGE2 stimulation. In conclusion, the function of PGE2 in activating both parturition and ovulation in a relatively different pathways conserved with viviparity or oviparity provided novel evidence of the evolutionary status of ovoviviparous vertebrates.

The initiation and maintenance of a differentiated state in development.

Proper function of the body is maintained by an intricate interaction and communication among cells. during the animal development how these cells are formed and maintained is an important yet elusive. Understanding of how cells such as muscle and nerve cells maintain their identities would enable us to control the diseases which include malfunctioning in cellular identities such as cancer. In this article, we describe how the concept of formation and maintenance of cell identities has changed over the last 100 years. We will also briefly describe our current experimental work which includes transcriptional dynamics, and protein-protein interaction and how they are bringing new molecular insights. We also describe liquid-liquid phase separation as a potential new mechanism for the stability of gene expression in the non dvididng specialised cells of Xenopus oocytes.

Gonadal lipidomics profile of an ovoviviparity teleost, black rockfish, during gonadal development.

In order to study the variation of gonad lipidomics during reproductive cycle, black rockfish was employed as the research model in the present study. Using histology, lipidomics, and qPCR, the profile of gonad lipidomics and the expression levels of related genes during different developmental stages were detected and analyzed to show the potential regulatory network of lipid metabolism. Based on Ultra High-Performance Liquid Tandem Chromatography Quadrupole Time of Flight Mass Spectrometry (UHPLC-QTOFMS), four significant differential glycerophospholipid metabolic pathways including phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS), and phosphatidic acid (PA) were enriched by KEGG. Pathway-related enzyme-coding genes, including phosphatidylserine decarboxylase (pisd), phosphatidylserine synthase (ptdss1, ptdss2), and phospholipase D (pld1, pld2) were identified from the whole genome data and confirmed by cloning. The expression profiles of these genes were tested by qPCR in the tissues and gonads in developmental stages, and we found that pisd, pld, and ptdss genes were all downregulated through the developmental process in the brain of male, and the latter two genes were upregulated in the liver and testis at stage IV, which were the opposite trend observed in the female. Thus, our findings would be helpful in further understanding the substance metabolism and regulation during gonad development in ovoviviparity teleosts.

Reproductive performance in successive generations of the brine shrimp Artemia salina (Crustacea: Anostraca) from the Sebkha of Sidi El Hani (Tunisia).

Artemia salina cysts collected from the Sebkha of Sidi El Hani hatched and cultivated in the laboratory were investigated. Nauplii were acclimated to laboratory conditions until reproductively mature (Generation 1; G1). Reproductive performance in terms of total cysts and nauplii offspring, days between brood production, and cyst and nauplii numbers was evaluated. Nauplii produced by specimens in the G1 were defined as those of G2 with there also being third (G3) and fourth (G4) generations. The aims were to evaluate Artemia salina in aquaculture conditions with the long-term aim of developing a system for "artemiculture". There was a larger number of cysts or nauplii per brood between G1 (60.7 ±â€¯10.9 nauplii or cysts/female) and subsequent generations, notably G2 (122 nauplii or cysts/female, P <  0.05). The mean number of cysts and nauplii per female increased from the first and last brood. Number of cysts produced per female increased markedly (P <  0.05) from G1 (54.5 ± 14.2) to G3 (128.9 ± 39.2). Percentage of females producing nauplii increased from G1 (20 %) to G4 (100 %). There was, therefore, an increase in percentage of ovoviviparous offspring (nauplii) per female (P <  0.05) from G1 (7%) to G4 (71 %). There were no differences, however, between mean numbers of broods per female, and numbers of days between broods. The results indicate there are variations in reproduction from oviparity to ovoviviparity as consecutive generations of Artemia salina are cultivated. In summary, there was a rapid adaptation of Artemia salina of Sidi El Hani to laboratory conditions.

Reversals in complex traits uncovered as reticulation events: Lessons from the evolution of parity-mode, chromosome morphology, and maternal resource transfer.

Complex traits include, among many others, the evolution of eyes, wings, body forms, reproductive modes, human intelligence, social behavior, diseases, and chromosome morphology. Dollo's law states that the evolution of complex traits is irreversible. However, potential exceptions have been proposed. Here, we investigated whether reticulation, a simple and elegant means by which complex characters may be reacquired, could account for suggested reversals in the evolution of complex characters using two datasets with sufficient genetic coverage and a total of five potential reversals. Our analyses uncovered a potential reversal in the evolution of parity mode and a potential reversal in the evolution of placentotrophy of fish (Cyprinodontiformes) as reticulation events. Moreover, in a reptile that exhibits a potential reversal from viviparity to oviparity (Zootoca vivipara), reticulation provided the most parsimonious explanation for sex chromosome evolution. Therefore, three of the five studied potential reversals were unraveled as reticulation events. This constitutes the first evidence that accounting for reticulation can fundamentally influence the interpretation of the evolution of complex traits, that testing for reticulation is crucial for obtaining robust phylogenies, and that complex ancestral characters may be reacquired through hybridization with a lineage that still exhibits the trait. Hybridization, rather than reappearance of ancestral traits by means of small evolutionary steps, may thus account for suggested exceptions to Dollo's law. Consequently, ruling out reticulation is required to claim the evolutionary reversal of complex characters and potential exceptions to Dollo's rule.

Genomic evidence for local adaptation in the ovoviviparous marine fish Sebastiscus marmoratus with a background of population homogeneity.

Advances in next-generation sequencing techniques have allowed for the generation of genome-wide sequence data, to gain insight into the dynamics influencing genetic structure and the local adaptation of marine fish. Here, using genotyping-by-sequencing (GBS) technique, we identified 31,119 single nucleotide polymorphisms (SNPs) for Sebastiscus marmoratus in 59 individuals from three populations in Chinese coastal waters. Based on all SNPs, there was little evidence of genetic differentiation among populations. However, outlier tests revealed 329 SNPs putatively under divergent selection across populations. Structural and phylogenetic topology analyses based on the outliers showed clear genetic differentiation among populations. Gene Ontology (GO) annotation results revealed that most of these outliers are known or hypothesized to be involved in metabolic process. Together with previous work using mitochondrial cytochrome b sequences, the present results further suggest that the population structure is strongly influenced by locally adaptive pressure. Overall, adaptive evolution in a heterogeneous environment plays an important role in inducing genetic differentiation among local populations. This study increases understanding of the factors (including gene flow and local adaptation) promoting and constraining population genetic differentiation in marine organisms.

Lack of population genetic differentiation of a marine ovoviviparous fish Sebastes schlegelii in Northwestern Pacific.

Sebastes schlegelii is one of the fishes that aggregate around drifting seaweed during early development. To examine the population genetic structure of S. schlegelii, a 452-bp fragment of the mtDNA control region was sequenced and used to interpret life history characteristics and larval dispersal strategy. Two-hundred and twenty-one individuals from 13 sites across the entire range of S. schlegelii in China, Japan and Korea were analyzed. A neighbor-joining tree and network showed that there were no significant genealogical structures corresponding to sampling locations. AMOVA, pair-wise FST and exact test revealed no significant genetic differentiation among locations. The migration rate among locations was high based on the result of LAMARC. We conclude that larval dispersal with drifting seaweed and the current environmental factors may play an important role in shaping the contemporary phylogeographic pattern and genetic homogeneity of S. schlegelii.

The Evolution of Ovoviviparity in a Temporally Varying Environment.

Environments that vary within a generation of an organism provide opportunities for adaptation if the level of variation is severe and predictable. We describe a model of evolution in such environments with genotypes that show trade-offs in viability and fecundity. One genotype develops rapidly and has superior viability but reduced fertility relative to the alternative genotype. Conditions that allow the evolution of the rapidly developing genotypes are explored. We show how the evolution of ovoviviparity and resource specialization in Drosophila sechellia shares many important features of this model. We suggest that our model may capture many of the evolutionary forces responsible for the evolution of niche specialization and ovoviviparity seen in D. sechellia.

Determination in oocytes of the reproductive modes for the brine shrimp Artemia parthenogenetica.

The brine shrimp, Artemia, reproduces either oviparously, producing encysted embryos (diapause cysts), or ovoviviparously, producing free-swimming nauplii. Environmental factors, such as photoperiod, have been applied to control the reproduction mode of Artemia, but when the determination of a reproductive mode occurs remains unknown. We analysed the differential gene expression between oocytes from oviparous and ovoviviparous Artemia reared under different photoperiods. A total of 692 qualified cDNA clones were obtained by subtractive hybridization, 327 of which matched GenBank® Nucleotide Sequence Database entries. Gene expressions of 44 cDNAs (representing 56 clones) were analysed in oocytes using real-time PCR. Among these genes, 11 (21 clones) were significantly (P<0.05) up-regulated and 7 (9 clones) down-regulated in Artemia oocytes that subsequently enter diapause. Remarkably, known diapause-related proteins such as ArHsp22 (Artemia heat-shock protein 22) and chitin-binding proteins are found to be already differentially expressed. Furthermore, RNAi (RNA interference) knockdown of a differentially expressed gene, polo-like kinase 1, in oocyte of ovoviviparous Artemia led to the production of white embryos rather than free-swimming nauplii. In summary, our results provide evidence at the molecular level that the reproductive mode of Artemia is already determined at the oocyte stage of their life cycle.