Biology subjects

Toyota, K.

Publications and source records attributed to Toyota, K..

5 recordsLinked to original sources

bioRxiv2025

Insulin-like androgenic gland factor regulates the development of internal and external secondary sexual characteristics in juvenile male kuruma prawn Marsupenaeus japonicus

In decapod crustaceans, insulin-like androgenic gland factor (IAG) is a well-known peptide hormone produced by the androgenic gland, a male-specific endocrine organ. In certain species classified within Pleocyemata, experimental manipulation of IAG signaling has successfully altered both internal and external sexual characteristics, leading to sex reversal. Therefore, IAG is considered a key regulator of male sexual differentiation and maturation and is thought to be a crustacean androgen. In the kuruma prawn Marsupenaeus japonicus (Dendrobranchiata), an important fishery species in Japan, a homologous molecule known as Maj-IAG has been identified. However, its physiological function in males remains poorly understood. In this context, we conducted Maj-IAG knockdown (KD) via RNA interference in juvenile male M. japonicus. Over a 9-week period, Maj-IAG KD significantly inhibited the development of the petasma, male-specific external copulatory structure, and parts of the internal reproductive organs, such as the vas deferens and seminal vesicles. In contrast, somatic growth and testicular development were unaffected by Maj-IAG KD. Histological analysis of the testes revealed no evident abnormalities such as degeneration of testicular structures or abnormal arrest of germ cell differentiation. These findings indicate that Maj-IAG partially governs the development of male secondary sexual characteristics in juveniles and further suggest that once testicular differentiation is initiated, the maintenance and development of the testis proceeds without dependence on Maj-IAG. Our study provides fundamental insights that may contribute to the advancement of functional sex reversal technologies in penaeid shrimps. HighlightsO_LILong-term gene knockdown of the insulin-like androgenic gland factor gene (Maj-IAG) was successfully achieved in Marsupenaeus japonicus. C_LIO_LISomatic growth and spermatogenesis were not affected by Maj-IAG knockdown. C_LIO_LIMaj-IAG is involved in the development of male secondary sexual characteristics in juvenile prawns, including the external male copulatory structures and certain parts of the internal male reproductive organs. C_LI

zoology↗

bioRxiv2025

Characterization of a crustacean hyperglycemic hormone of the horsehair crab Erimacrus isenbeckii

The horsehair crab Erimacrus isenbeckii is widely distributed from Alaska and the Bering Sea through Southern Sakhalin, and in Japan from the coastal areas of Hokkaido to the Sea of Japan. In the Hokkaido area, although strict resource management has been promoted by setting an allowable catch limit, the catch amount has remained at a low level. While knowledge on larval rearing methods is accumulating in relation to seedling production techniques, information on adult growth and molting is limited, due to a deep-sea species that requires a long period for growth. In decapod crustaceans, the sinus-gland/X-organ complex in the eyestalk ganglion synthesizes and secrets various neuropeptides such as crustacean hyperglycemic hormone (CHH) to regulate the homeostasis of blood glucose levels. In this study, combined isolation of sinus gland peptides by reverse-phase high-performance liquid chromatography (RP-HPLC) and amino acid sequencing, and transcriptome analyses using male and female eyestalk ganglion has been successfully identified EiCHHa. The in vivo assays of EiCHHa using the blue swimming crab Portunus pelagicus revealed EiCHHa has a hyperglycemic effect, as well as CHHs in other decapod crustaceans. Additionally, we successfully demonstrated the sexual differences in the transcriptomic profiles between males and females. Especially, two sinus gland-derived neuropeptides (EiCHHb and a crustacean female sex hormone (EiCFSH)) were isolated as female-biased transcripts, suggesting that both hormones may have female-specific roles such as the development of female characteristics and reproduction.

molecular biology↗

bioRxiv2023

Comparative analysis of gonadal transcriptomes between turtle and alligator identifies common molecular cues activated during the temperature-sensitive period for sex determination

The mode of sex determination in vertebrates can be categorized as genotypic or environmental. In the case of genotypic sex determination (GSD), the sexual fate of an organism is determined by the chromosome composition with some having dominant genes, named sex-determining genes, that drive the sex phenotypes. By contrast, many reptiles exhibit environmental sex determination (ESD), whereby environmental stimuli drive sex determination, and most notably temperature. To date, temperature-dependent sex determination (TSD) has been found in most turtles, some lizards, and all crocodilians, but commonalities in the controlling processes are not well established. Recent innovative sequencing technology has enabled investigations into gonadal transcriptomic profiles during temperature-sensitive periods (TSP) in various TSD species which can help elucidate the controlling mechanisms. In this study, we conducted a time-course analysis of the gonadal transcriptome during the male-producing temperature (26L) of the Reeves turtle (Chinese three-keeled pond turtle) Mauremys reevesii. We then compared the transcriptome profiles for this turtle species during the TSP with that for the American alligator Alligator mississippiensis to identify conserved reptilian TSD-related genes. Our transcriptome-based findings provide an opportunity to retrieve the candidate molecular cues that are activated during TSP and compare these target responses between TSD and GSD turtle species, and between TSD species. Highlights- A time-course gonadal RNA-seq was conducted using Mauremys reevesii. - Sexual differentiation genes in males were activated at an earlier stage than the ones in females. - Turtle-alligator comparative analysis revealed novel candidate TSD genes.

developmental biology↗

bioRxiv2023

Dual roles of crustacean female sex hormone during juvenile stage in the kuruma prawn Marsupenaeus japonicus

The crustacean female sex hormone (CFSH) has been identified as a female-specific hormone that plays a crucial role in female phenotype developments in the blue crab Callinectes sapidus. To date, its homologous genes have been reported in various decapod species. Additionally, unlike the blue crab, several species have two different CFSH subtypes. The kuruma prawn Marsupenaeus japonicus is a representative example species of this phenomenon, having two CFSH subtypes identified from the eyestalk (MajCFSH) and ovary (MajCFSH-ov). Eyestalk-type MajCFSH is expressed predominantly in the eyestalk at the same level in both sexes, indicating no female-specificity. Here, we conducted gene knockdown analysis of eyestalk-type MajCFSH using sexually immature juveniles of kuruma prawn (average body length: [~]10 mm) to elucidate its physiological functions. As a result, MajCFSH-knockdown did not affect the development of sex-specific characteristics such as external reproductive organs, while it induced apparent growth suppression in male juveniles, implying that MajCFSH may play a male-specific juvenile growth role. Moreover, MajCFSH-knockdown female and male juveniles changed their body color to become brighter, indicating that MajCFSH has the ability to change body color by dispersing the pigment granules in the chromatophore. Overall, our present study improved our understanding of the physiological roles of CFSH using kuruma prawn. Highlights- MajCFSH-knockdown was conducted using sexually immature juveniles of kuruma prawn. - MajCFSH-knockdown male juveniles showed significant growth suppression. - MajCFSH-knockdown female and male juveniles changed their body color to become brighter.

physiology↗

bioRxiv2021

Laterally biased diffusion of males of the water flea Daphnia magna

The water flea Daphnia magna is a representative example of zooplankton living in freshwater environments. They primarily propagate via asexual reproduction under normal and healthy environmental conditions. Environmental stimuli that signal a shift to disadvantageous conditions induce D. magna to change their mode of reproduction from asexual to sexual reproduction. During the sexual reproduction phase, they produce special tough eggs (resting eggs), which can survive severe environmental conditions. Despite our increased understanding of their mating behaviours, the sex-specific characteristics of swimming behaviours among daphnid species are poorly understood. In this study, we analysed the swimming patterns and dynamics of female and male adult D. magna. First, we found laterally biased diffusion of males in contrast to the homogeneous, nondirectional diffusion of females. Second, computer modelling analysis using a discrete-time Markov chain simulation, in which the frequencies of turning behaviour were evaluated as probability distributions, explained the greater diffusion of males in the horizontal direction. Under the presumption that high diffusion in the horizontal direction increases the probability of encountering a distant mate, these findings led us to hypothesise that male D. magna increase genotype heterogeneity by effectively selecting the probability distributions of certain motion parameters. Summary statementsWe analysed the swimming behaviours of adult water flea Daphnia magna, and found apparent sexual differences: laterally biased diffusion of males in contrast to the nondirectional diffusion of females.

animal behavior and cognition↗