General and comparative endocrinology最新文献

Gonad maturation is critical for the reproductive success of any organism, and in fish, captivity can significantly affect their reproductive performance, leading to maturation incompetence and spawning failure. The greater amberjack (Seriola dumerili), a fish species recently introduced to aquaculture fails to undergo oocyte maturation, ovulation, and spawning when reared in aquaculture facilities. Since confinement has been shown to influence gonad maturation and completion of the reproductive cycle, investigations into epigenetic mechanisms may shed light on the reasoning behind the reproductive dysfunctions of fish under captivity. Among the known important epigenetic regulators are small non-coding RNAs (sncRNAs), and in particular microRNAs (miRNAs). In this study, immature, maturing (late vitellogenesis), and spent ovaries of captive greater amberjack were collected, and the differential expression of miRNAs in the three different ovarian development stages was examined. Expression patterns of conserved and novel miRNAs were identified, and potential targets of highly differentially expressed miRNAs were detected. Additionally, read length distribution showed two prominent peaks in the three different ovarian maturation stages, corresponding to miRNAs and putative piwi-interacting RNAs (piRNAs), another type of ncRNAs with a germ-cell specific role. Furthermore, miRNA expression patterns and their putative target mRNAs are discussed, in relevance with the different ovarian maturation stages of captive greater amberjack. Overall, this study provides insights into the role of miRNAs in the reproductive dysfunctions observed in fish under captivity and highlights the importance of epigenetic mechanisms in understanding and managing the reproductive performance of economically important fish species.

Crustaceans, which represent a significant subset of arthropods, are classified into three major classes: Ostracoda, Malacostraca, and Branchiopoda. Among them, sex manipulation in decapod species from the Malacostraca class has been extensively researched for aquaculture purposes and to study reproductive physiology and sexual plasticity. Some decapods exhibit sexual dimorphism that influences their biological and economic value. Monosex culture, in which only one sex is cultivated, increases production yields while reducing the risk of invasiveness, as genetic leakage into natural waters is less likely to occur. Differences in yield are also observed when cultivating different sexes, with all-male cultures of Macrobrachium rosenbergii being more profitable than both mixed and all-female cultures. Research on decapod sexual differentiation has led to a better understanding of sex determination and sexual differentiation processes in arthropods. Similar to most mammals and other vertebrate classes, Malacostraca crustaceans, including decapods, exhibit a cell-non-autonomous mode of sexual development. Genetic factors (e.g., sex chromosomes) and endocrine factors (e.g., insulin-like androgenic gland factor and crustacean female sex hormone) play pivotal roles in the development of sexually dimorphic traits. This review synthesizes the existing understanding of sex determination mechanisms and the role of sex hormones in decapod species. Additionally, it provides an overview of the methyl farnesoate, which has been suggested to be involved in male sex differentiation in some crab species, as well as the phenomenon of male-to-female sex reversal in host decapods caused by parasitic crustaceans.

The Krüppel-like factors (KLFs) have emerged as important transcriptional regulators of various cellular processes, including neural development. Some of them have been described as intrinsic factors involved in axon regeneration in the central nervous system (CNS) of vertebrates. Zebrafish are known for their ability to regenerate several tissues in adulthood, including the CNS, a capability lost during vertebrate evolution and absent in adult mammals. The role that KLFs could play in this differential ability remains unknown. Therefore, in this study, we analyzed the endogenous response of certain KLFs implicated in axon regeneration (KLFs 6, 7, 9, and 13) during retina development and after axon injury. The results showed that the expression of Klfs 6, 7, and 13 decreases in the developing retina of mice but not in zebrafish, while the mRNA levels of Klf9 strongly increase in both species. The response to injury was further analyzed using optic nerve crush (ONC) as a model of lesion. Our analysis during the acute phase (hours) demonstrated an induction of Klfs 6 and 7 expression exclusively in the zebrafish retina, while Klfs 9 and 13 mRNA levels increased in both species. Further analysis of the chronic response (days) showed that mRNA levels of Klf6 transiently increase in the retinas of both zebrafish and mice, whereas those of Klf7 decrease later after optic nerve injury. In addition, the analysis revealed that the expression of Klf9 decreases, while that of Klf13 increases in the retinas of zebrafish in response to optic nerve injury but remains unaltered in mice. Altogether, these findings support the hypothesis that KLFs may play a role in the differential axon regeneration abilities exhibited by fish and mice.

Thyroid stimulating hormone (TSH), a glycoprotein synthesized and secreted from thyrotrophs of the pituitary gland, is composed of a glycoprotein hormone common alpha subunit (CGA) and a specific beta subunit (TSHB). The major biological function of TSH is to stimulate thyroidal follicles to synthesize and secrete thyroid hormones through activating its cognate receptor, the thyroid stimulating hormone receptor (TSHR). In the present study, polyclonal antisera against ricefield eel Tshb and Tshr were generated respectively, and the expression of Tshb and Tshr was examined at mRNA and protein levels. RT-PCR analysis showed that tshb mRNA was expressed mainly in the pituitary as well as in some extrapituitary tissues including the ovary and testis. Tshr mRNA was also expressed in a tissue-specific manner, with transcripts detected in tissues including the kidney, ovary, and testis. The immunoreactive Tshb signals in the pituitary were shown to be localized to the inner areas of adenohypophysis which are close to the neurohypophysis of adult ricefield eels. Tshb-immunoreatvie cells in the pituitary of ricefield eel larvae were firstly observed at hatching. The expression of immunoreactive Tshb and Cga was also detected in ricefield eel ovary and testis together with Tshr. In the ovary, immunoreactive Tshb, Cga, and Tshr were observed in oocytes and granulosa cells. In the testis, immunoreactive Tshb was mainly observed in Sertoli cells while immunoreactive Cga and Tshr were detected in germ cells as well as somatic cells. Results of the present study suggest that Tsh may be synthesized both in the ovary and testis locally, which may play paracrine and/or autocrine roles in gonadal development in ricefield eels.

Parental care is regulated by multiple endocrine mechanisms. Among these hormones, prolactin (PRL) is involved in the expression of parental behaviors. Despite the consensus that PRL mediates variation in parental effort with age and body condition, its role in the adjustment of parental effort to fluctuating environmental conditions, including changing predation pressure, still awaits further investigation. To shed light on this knowledge gap, we relied on a long-term monitoring of female common eiders Somateria mollissima (n = 1277 breeding attempts, 2012–2022) incubating under fluctuating predation risk to investigate the link between baseline PRL levels and female minimum age, body condition, clutch size, environmental parameters (predation pressure, climate, nest microhabitat) and hatching success. We predicted that PRL would be higher in older females, those in better condition or incubating larger clutches. We also predicted that females would reduce parental effort when nesting under challenging environmental conditions (high predation pressure or poor climatic conditions), translated into reduced baseline PRL levels. We also explored how variation in PRL levels, female characteristics and environmental parameters were related to hatching success. Following our predictions, PRL levels were positively associated with body condition and female age (before showing a senescent decline in the oldest breeders). However, we did not observe any population-level or individual-level reduction in PRL levels in response to increasing predation pressure. Population-level baseline PRL levels instead increased over the study period, coincident with rising predation threat, but also increasing female body condition and age. While we did not provide evidence for a direct association between baseline PRL levels and predation risk, our results support the idea that elevated baseline PRL levels promote hatching success under internal constraints (in young, inexperienced, breeders or those incubating a large clutch) or constraining environmental conditions (during years of high predation pressure or poor climatic and foraging conditions). Finally, the low repeatability of baseline PRL levels and high interannual variability highlight considerable within-individual flexibility in baseline PRL levels. Further research should explore flexibility in parental effort to changing environmental conditions, focusing on both baseline and stress-induced PRL levels.

The physiological processes in animal production are regulated through biologically active molecules like peptides, proteins, and hormones identified through the development of the fundamental sciences and their application. One of the main polypeptides that plays an essential role in regulating physiological responses is the pituitary adenylate cyclase-activating polypeptide (PACAP). PACAP belongs to the glucagon/growth hormone-releasing hormone (GHRH)/vasoactive intestinal proteins (VIP) family and regulates feed intake, stress, and immune response in birds. Most of these regulations occur after PACAP stimulates the cAMP signaling pathway, which can regulate the expression of genes like MuRF1, FOXO1, Atrogin 1, and other ligases that are essential members of the ubiquitin system. On the other hand, PACAP stimulates the secretion of CRH in response to stress, activating the ubiquitin signaling pathway that plays a vital role in protein degradation and regulates oxidative stress and immune responses. Many studies conducted on rodents, mammals, and other models confirm the regulatory effects of PACAP, cAMP, and the ubiquitin pathway; however, there are no studies testing whether PACAP-induced cAMP signaling in poultry regulates the ubiquitin pathway. Besides, it would be interesting to investigate if PACAP can regulate ubiquitin signaling during stress response via CRH altered by HPA axis stimulation. Therefore, this review highlights a summary of research studies that indicate the potential interaction of the PACAP and ubiquitin signaling pathways on different molecular and physiological parameters in poultry species through the cAMP and stress signaling pathways.

Reproductive hormones are essential to mating systems, behavior, fertility, gestation, parturition, and lactation in mammals and understanding the role of hormones in these processes is essential for species conservation. Sirenia is a unique order of marine mammals that include manatees, dugongs, and the extinct Steller’s sea cow. Extant Sirenian species are all listed as vulnerable due to habitat loss, cold stress, boat strike trauma, harmful algal bloom toxicity, entanglements, and illegal hunting. Therefore, successful reproduction is essential to maintaining and increasing Sirenian populations. Understanding Sirenian reproductive behavior, endocrinology, and mating strategies will aid conservation and management efforts to protect and provide the proper conditions for successful reproduction. The objectives of this review were to synthesize the current knowledge regarding reproductive cycles and endocrinology of Sirenians and identify knowledge gaps for future investigation. The current literature on Sirenian reproductive physiology reports reproductive seasonality, sexual maturation, estrous cyclicity and acyclicity, pregnancy, and sex differences. However, there remain significant knowledge gaps on the cyclicity and pulsatile release of gonadotropins, maturation in females, and characterization of pregnancy hormone profiles throughout gestation. To date, there is no explanation for confirmed pattern for ovarian acyclicity, nor understanding of the function of the numerous accessory corpus luteum described in manatees. Research including a greater number of longitudinal and postmortem studies on a wider variety of wild manatee populations are important first steps. Taken together, understanding the reproductive endocrinology of these vulnerable and threatened species is critical for policy and management decisions to better inform protection initiatives.

Spodoptera litura commonly known as the cutworm, is among the most destructive lepidopteran pests affecting over 120 plants species. The powerful destructive nature of this lepidopteran is attributable to its high reproductive capacity. The testicular fusion that occurs during metamorphosis from larvae to pupa in S.litura positively influences the reproductive success of the offspring. In contrast, Bombyx mori, the silkworm, retains separate testes throughout its life and does not undergo this fusion process. Microscopic examination reveals that during testicular fusion in S.litura, the peritoneal sheath becomes thinner and more translucent, whereas in B.mori, the analogous region thickens. The outer basement membrane in S.litura exhibits fractures, discontinuity, and uneven thickness accompanied by a significant presence of cellular secretions, large cell size, increased vesicles, liquid droplets, and a proliferation of rough endoplasmic reticulum and mitochondria. In contrast, the testicular peritoneal sheath of B.mori at comparable developmental stage exhibits minimal change. Comparative transcriptomic analysis of the testicular peritoneal sheath reveals a substantial difference in gene expression between the two species. The disparity in differential expressed genes (DEGs) is linked to an enrichment of numerous transcription factors, intracellular signaling pathways involving Ca²⁺ and GTPase, as well as intracellular protein transport and signaling pathways. Meanwhile, structural proteins including actin, chitin-binding proteins, membrane protein fractions, cell adhesion, extracellular matrix proteins are predominantly identified. Moreover, the study highlights the enrichment of endopeptidases, serine proteases, proteolytic enzymes and matrix metalloproteins, which may play a role in the degradation of the outer membrane. Five transcription factors-Slforkhead, Slproline, Slcyclic, Slsilk, and SlD-ETS were identified, and their expression pattern were confirmed by qRT-PCR. they are candidates for participating in the regulation of testicular fusion. Our findings underscore significant morphological and trancriptomic variation in the testicular peritoneal sheath of S.litura compared to the silkworm, with substantial changes at the transcriptomic level coinciding with testicular fusion. The research provides valuable clues for understanding the complex mechanisms underlying this unique phenomenon in insects.