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Sexual selection drives rapid evolution of morphological, physiological, and behavioral traits, especially in males, and it may also drive the rapid evolution of hybrid male sterility. Indeed, the faster male theory of speciation was once viewed as a major cause of Haldane's rule in male-heterogametic XY taxa, but is increasingly being replaced by the genetic conflict hypothesis partly because it cannot explain the faster evolution of hybrid female sterility in female-heterogametic ZW taxa. The theory nonetheless predicts that there should be more genes for hybrid male sterility than for hybrid female sterility even in such taxa, but this remains untested. Thus, finding evidence for the faster male theory of reproductive isolation beyond the F1 generation in ZW systems still represents a challenge to studying the impact of sexual selection. In this study, we examined F2 hybrids between the domesticated silkworm Bombyx mori and the wild silk moth Bombyx mandarina , which have ZW sex determination. We found that although only females showed reduced fertility in the F1 generation, the F2 hybrid males had a significant reduction in fertility compared with the parental and F1 males. Importantly, 27% of the F2 males and 15% of the F2 females were completely sterile, suggesting the presence of recessive incompatibilities causing male sterility in female-heterogametic taxa. [ABSTRACT FROM AUTHOR]

Background. Corallium japonicum, a prized resource in Japan, plays a vital role in traditional arts and fishing industries. Because of diminished stock due to overexploitation, ongoing efforts are focused on restoration through transplantation. This study aimed to enhance our understanding of the reproductive biology of these valuable corals and find more efficient methods for sex determination, which may significantly contribute to conservation initiatives. Methods. We used 12 three-month aquarium reared C. japonicum colony fragments, conducted histological analysis for maturity and sex verification, and performed tran- scriptome analysis via de novo assembly and mapping using the C. rubrum transcrip- tome to explore gene expression differences between female and male C. japonicum. Results. Our histological observations enabled sex identification in 33% of incompletely mature samples. However, the sex of the remaining 67% of samples, classified as immature, could not be identified. RNA-seq yielded approximately 21-31 million short reads from 12 samples. De novo assembly yielded 404,439 highly expressed transcripts. Among them, 855 showed significant differential expression, with 786 differentially expressed transcripts between females and males. Heatmap analysis highlighted 283 female-specific and 525 male-specific upregulated transcripts. Transcriptome assembly mapped to C. rubrum yielded 28,092 contigs, leading to the identification of 190 highly differentially expressed genes, with 113 upregulated exclusively in females and 70 upregulated exclusively in males. Blastp analysis provided putative protein annotations for 83 female and 72 male transcripts. Annotation analysis revealed that female biological processes were related to oocyte proliferation and reproduction, whereas those in males were associated with cell adhesion. Discussion. Transcriptome analysis revealed sex-specific gene upregulation in incom- pletely mature C. japonicum and shared transcripts with C. rubrum, providing insight into its gene expression patterns. This study highlights the importance of using both de novo and reference-based assembly methods. Functional enrichment analysis showed that females exhibited enrichment in cell proliferation and reproduction pathways, while males exhibited enrichment in cell adhesion pathways. To the best of our knowledge, this is the first report on the gene expressions of each sex during the spawning season. Our findings offer valuable insights into the physiological ecology of incompletely mature red Japanese precious corals and suggest a method for identifying sex using various genes expressed in female and male individuals. In the future, techniques such as transplantation, artificial fertilization, and larval rearing may involve sex determination methods based on differences in gene expression to help conserve precious coral resources and ecosystems. [ABSTRACT FROM AUTHOR]

• 16,461 annotated transcripts were estimated in the eyestalk transcriptome. • XO/SG-derived neuropeptides were identified from males and females of M. japonicus. • MjapDsx1 and MjapDsx2 with no sex-specific splicing isoforms were identified. • MjapDsx1 was biasedly expressed in male eyestalk ganglion. Kuruma prawn (Marsupenaeus japonicus) is a benthic decapod crustacean that is widely distributed in the Indo-West Pacific region. It is one of the most important fishery resources in Japan, but its annual catches have declined sharply since the 1990s. To increase stocks, various approaches such as seed production and aquaculture were attempted. Since the demand for important fishery species, including kuruma prawn, is expected to increase worldwide in the future, there is a need to develop new technologies that will make aquaculture more efficient. Historically, the eyestalk endocrine organ is known to consist of the X-organ and sinus gland (XO/SG) complex that synthesizes and secrets various neuropeptide hormones that regulate growth, molt, sexual maturation, reproduction, and changes in body color. In the current study, eyestalk-derived neuropeptides were identified in the transcriptome. In addition, most orthologs of sex-determination genes were expressed in eyestalks. We identified two doublesex genes (MjapDsx1 and MjapDsx2) and found that MjapDsx1 showed male-biased expression in the eyestalk ganglion with no sex-specific splicing, unlike insect species. Therefore, this study will provide an opportunity to advance the research of neuropeptides and sex determination in the kuruma prawn. [ABSTRACT FROM AUTHOR]

This study uses data from the 1918–1920 influenza pandemic in Japan along with newly digitized and complete census records on births and infant deaths to analyze mortality selection in utero. I find that fetal exposure to the influenza pandemic during the first trimester of the pregnancy decreases the proportion of males at birth. The results from mechanism analysis suggest that this decline in male births is associated with the deterioration of fetal and infant health. This result supports a wide range of existing literature on the long-run adverse effects of pandemic influenza. • The study tests the prenatal selection mechanism behind fetal influenza exposure. • Newly digitized census records on births and infant deaths are used. • Fetal flu exposure between 1918 and 1920 decreased the proportion of males at birth. • The reduction in the relative male births was associated with a scarring mechanism. [ABSTRACT FROM AUTHOR]

In the isopod Armadillidium vulgare , many females produce progenies with female-biased sex ratios, owing to two feminizing sex ratio distorters (SRD): Wolbachia endosymbionts and the f element. We investigated the distribution and population dynamics of these SRD and mitochondrial DNA variation in 16 populations from Europe and Japan. Confirming and extending results from the 1990s, we found that the SRD are present at variable frequencies in populations and that the f element is overall more frequent than Wolbachia . The two SRD never co-occur at high frequency in any population, suggesting an apparent mutual exclusion. We also detected Wolbachia or the f element in some males, which probably reflects insufficient titer to induce feminization or presence of masculinizing alleles. Our results are consistent with a single integration event of a Wolbachia genome in the A. vulgare genome at the origin of the f element, which contradicts an earlier hypothesis of frequent losses and gains. We identified strong linkage between Wolbachia strains and mitochondrial haplotypes, but no association between the f element and mitochondrial background. Our results open new perspectives on SRD evolutionary dynamics in A. vulgare , the evolution of genetic conflicts and their impact on the variability of sex determination systems.

Fishes of the genus Seriola are widely farmed and highly valued in global aquaculture production. To further understand their economically important traits and help improve aquaculture product quality and sustainability, we performed a chromosome-level genome construction for Seriola aureovittata. Combining two technologies, PacBio and BGISEQ-500, we assembled 649.86 Mb S. aureovittata genome sequences with a contig N50 of 22.21 Mb, and 98% of BUSCO genes were detected in total. The initial assembly was then further scaffolded into 24 pseudochromosomes using Hi-C data, indicating the high quality of the genome. Genome evolution analysis showed that many genes related to fatty acid metabolism and oxygen binding, or transport were expanded, which provided insights into the metabolic characteristics of fatty acids and efficient oxygen transport. Based on the genome data, we confirmed the evolutionary relationship of S. aureovittata, S. dorsalis and S. lalandi and identified chr12 as the putative sex chromosome of S. aureovittata. Our chromosome-level genome assembly provides a genetic foundation for the phylogenetic and taxonomic investigation of different Seriola species. Moreover, the genome will provide an important genomic resource for further biological and aquaculture studies of S. aureovittata., (© 2022 John Wiley & Sons Ltd.)

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The Japanese frog, Rana rugosa, has two distinct sex chromosome types, XX/XY and ZZ/ZW. These two types are found in localized groups, separated geographically by a boundary area predicted to lie somewhere around Lake Biwa in central Japan. To determine this precise boundary, the heterogametic sex of 18 populations around Lake Biwa was examined by genotyping sex-linked genes. Phylogenetic relationships between the populations were also analyzed using mitochondrial 12S rRNA gene. Results showed that the Suzuka-Kii mountain range located east of Lake Biwa separated the XX/XY populations from the ZZ/ZW populations. Unexpectedly, from a phylogenetic perspective, the ZZ/ZW populations around Lake Biwa belonged not to the main ZW group but to the XY group. The authors propose that the ZZ/ZW populations around Lake Biwa diverged secondarily from the XX/XY group through a change of heterogametic sex, eventually forming a new group. This group was thus named the ‘Neo-ZW group’. As the main ZW group inhabiting northwestern Japan is known to have a different male heterogametic origin, this finding shows that change of heterogametic sex from male to female may have occurred twice, and independently, during the frog speciation.Heredity (2008) 100, 92–99; doi:10.1038/sj.hdy.6801068; published online 14 November 2007 [ABSTRACT FROM AUTHOR]

Objective: In the field of forensic science, sex discrimination of skeletons is an important identification item for personal identification. The individual sex discrimination method using skeletons includes a determination method using measurement values and a macroscopic form observation method. Both methods have advantage and disadvantage. In this study, we used the homologous model technique and principal component (PC) analysis to determine gender difference from morphology of the mandible., Methods and Materials: 45 patients (23 males and 22 females) of CT imaging for tooth extraction from January 2018 to March 2019 at department of oral surgery, Osaka Medical College. The mean age was 43.1 ± 14.6. Patients with less than 14 remaining teeth were excluded because the number of remaining teeth may affect the shape of the mandible. 3D images were constructed, and 20 landmarks plotting on the 3D model surfaces. We generated template models of the mandible consisting of approximately 8434 polygons. The template model automatically fitted into the individually scanned point cloud of the mandible by minimising external and internal energy functions. As described above, the mandibles were constructed for each sample by using the Homologous Body Modeling software (HBM, Digital Human Technology, Inc.) and the mHBM-Rugle (Medic Engineering Corporation). The mandibles were analysed using the PCA., Results: The contribution of the most important PC was found to be 27.2%. 12 PCs explained over 75% of the total variance. That is, it was able to express 75% or more of the mandible expression with 12 PCs. A significant difference between male and female was observed in the first PCs (Wilcoxon test, p < 0.05). Visualising the result of the first PC showed that the mandibular branch of male was larger than that of female, and the mandible angle was overhanging outside., Conclusion: This method is a combination of the determination method using the previous measurement values and the determination using macroscopic observation, and is considered to be innovative method.

1. Selective harvesting is acknowledged as a serious concern in efforts to conserve wild animal populations. In fisheries, most studies have focused on gradual and directional changes in the life-history traits of target species. While such changes represent the ultimate response of harvested animals, it is also well known that the life history of target species plastically alters with harvesting. However, research on the adaptive significance of these types of condition-dependent changes has been limited. 2. We explored the adaptive significance of annual changes in the age at sex-change of the protandrous (male-first) hermaphroditic shrimp and examined how selective harvesting affects life-history variation, by conducting field observations across 13 years and a controlled laboratory experiment. In addition, we considered whether plastic responses by the shrimp would be favourable, negligible or negative with respect to the conservation of fishery resources. 3. The age at sex-change and the population structure of the shrimp fluctuated between years during the study period. The results of the field observations and laboratory experiment both indicated that the shrimp could plastically change the timing of sex-change in accordance with the age structure of the population. These findings provide the first concrete evidence of adult sex ratio adjustment by pandalid shrimp, a group that has been treated as a model in the sex allocation theory. 4. The sex ratio adjustment by the shrimp did not always seem to be sufficient, however, as the supplement of females is restricted by their annual somatic growth rate. In addition, adjusted sex ratios are further skewed by the unintentional female-selectivity of fishing activity prior to the breeding season, indicating that the occurrence of males that have postponed sex-change causes sex ratio adjustment to become unfavourable. 5. We conclude that the plastic responses of harvested animals in selective fishing environments must be considered in efforts to conserve wild animal resources, because such responses can become maladaptive., (© 2012 The Authors. Journal of Animal Ecology © 2012 British Ecological Society.)