Annual change of the gonadal development of the amphioxus in Xiamen

The study was made by observing the annual change of the gonadal development of amphioxus in Xiamen cohtinuously for two years from November, 1986 to November, 1988. We determined the gonadal diameter, gonadosomatic index of each amphioxus, and observed the histological characteristic of the gonadal development of the female and male by cut section, which provided the basis for dividing the stages gonads and the determining level of the gonadal development of amphioxus in each month.

Morphological and histological changes in the brains of turbot(Scophthalmus maximus)with gonadal development

The brain plays a critical role in controlling reproduction through the hypothalamus-pituitary-gonadal(HPG)axis in vertebrates.Turbot(Scophthalmus maximus)has become an economically important marine fish in Europe and North China.Previous research investigating turbot reproduction has focused on the role of the HPG axis in regulating egg and sperm production.However,the morphology and histology of the organs in the HPG axis have not been studied.In this study,we investigated the morphology and histology of brains in female and male turbot at different stages of gonadal development.The results showed that the brains of both female and male turbot were composed of seven parts that are typical of advanced teleosts:the telencephalon,diencephalon,cerebellum,hypothalamus,pituitary gland,myelencephalon,and olfactory bulbs.The telencephalon was well-developed and contained five distinct lobes,with the contiguous diencephalon at the caudal portion.The torus longitudinales and rostral torus semicircularis of the mesencephalon flattened along the dorsal surface,and the rostral corpus cerebellum was located in the dorsal portion.The actual total brain volume in mature males was significantly greater(p<0.05)than that of females with gonadal development.Notably,the pituitary volume in male turbot significantly increased(p<0.05)from immature to mature stage,but this difference did not occur in females.The data together illustrate a distinct sex difference in the turbot brain during gonadal development,providing insight into their HPG axes.

Hypothalamic-Pituitary-Gonadal(HPG)Axis and Transcriptional Regulatory Elements Regulate piwil2 Gene Expression During Gametogenesis and Gonadal Development in Japanese Flounder(Paralichthys olivaceus)

The P-element induced wimpy testis(Piwi)proteins,which are associated with PIWI-interacting RNAs(piRNAs),play important roles in meiosis,germ cell division,and germline maintenance.In this study,we identified and characterized the Paralichthys olivaceus piwil2 gene,a constituent factor of the piRNA pathways involved in the biogenesis of reproductive development.The biological analysis indicated that piwil2,which contains PAZ and PIWI domains,was highly conserved between teleosts and tetrapods.The piwil2 distribution profile in different tissues confirmed a sexually dimorphic expression pattern,with a higher expression level in testis.In situ hybridization demonstrated that piwil2 was expressed in the oogonia and oocytes of the ovaries as well as in the Sertoli cells and spermatocytes of the testes.Gene piwil2 showed a maternally inherited expression pattern during embryonic development,and was highly expressed during the early embryonic development.Different luciferase reporters were constructed to determine the transcriptional regulatory mechanisms of piwil2.The piwil2 core promoter region was located at−360 bp to−60 bp.Furthermore,some representative sex hormones,including human chorionic gonadotropin,17α-methyltestosterone,and estradiol-17βhad distinct regulatory effects on piwil2.In a summery,these results indicate that piwil2,regulated by sex hormones and transcriptional elements,has vital functions in the reproductive cycle and gonadal development.

Impacts of different feeding modes on the gonadal development, total edible yield, and nutritional composition of male Chinese mitten crab (Eriocheir sinensis)

This study analyzed the tissue indices,proximate composition,fatty acid and amino acid composition of edible tissues of male E.sinensis under three feeding modes(formulated diets(FD),natural diets(ND),and traditional diets(TD)).The results showed that different feeding modes had no impacts on the overall gonadal development,as no significant difference was found in gonadsomatic index among three treatments.For edible yield,three modes all had similar levels of the meat yield,hepatosomatic index,and total edible yield.Although different feeding modes did not affect the individual edible yield and gonadal development,significant differences were detected in the nutritional composition of males from three modes.For proximate composition,significant differences were found in the total lipids of gonads and the carbohydrate of hepatopancreas and meat.For fatty acids,crabs from ND had a higher proportion of monounsaturated fatty acids.In gonads and hepatopancreas,FD had a higher proportion of long-chain polyunsaturated fatty acids.For amino acids,FD had higher amino acid contents,while ND had the lowest.Except tryptophan,the essential amino acids scores of the meat were all greater than 100.As there was no significant difference on meat quality and meat yields between three feeding modes,this study suggests that the formulated diet could replace the natural diet and traditional diet towards sustainable crab farming in future.

Environmental hypoxia:A threat to the gonadal development and reproduction in bony fishes

Vast stretches of open water bodies are gradually becoming hypoxic as a result of depletion of oxygen levels mainly due to various human anthropogenic activities.This problem of hypoxic stress on the fish population is likely to be exacerbated soon since the aquatic hypoxic environment is continuously spreading over vast areas worldwide.In recent years,various harmful effects of hypoxia to bony fishes have been reported,such as the restriction of energy-consuming metabolic processes,arrest of the growth of ovary and testes that are associated with endocrine disruption,loss of sperm and egg quality,inhibition of fertilization,hatching success,and also the reduction of larval survivability,thereby impairment of overall reproductive and developmental processes in fish.Disruption of the brain-pituitary-gonad axis,and certain enzymes related to steroidogenesis and vitellogenesis in fish have also been reported as the primary targets for an endocrine malfunction during hypoxia.Hypoxia-sensitive downregulation of key genes responsible for controlling sex hormones’synthesis has been documented in certain bony fishes.Further,continuous exposure to hypoxia was reported to induce early expression of pro-apoptotic/tumor suppressor p53 genes,thereby causing immense cell death in hypoxic embryos.However,the cellular responses to long-term hypoxia exposure and the degree of reproductive impairments in bony fishes are still not adequate to figure out the actual underlying mechanisms.The present review intends to highlight the current knowledge about the detrimental impact of chronic/acute hypoxia at different stages of fish reproduction and the associated underlying molecular mechanisms.

Gonadal development and silvering of the Japanese Eel(Anguilla japonica)in the Yangtze River during downstream migration

The Yangtze River and its branches are important habitats for the Japanese Eel(Anguilla japonica),however,there are few data on gonadal development and silvering indices of eels during the downstream spawning migration.This study investigates gonadal development in 121 Japanese eels caught downstream from the Jingjiang Reach of the Yangtze River in October 2012.We found that in females the ovaries of most of the out-migrating population developed earlier than the testes in males,that is,the ovaries reached stage 3(F3)or early stage 4(eF4),while the testes were at stage 2(M2)or stage 3(M3).Gonadal development in eels collected in 2012 was earlier than that of samples caught from the same region in 2007e2008 and from the Pearl River Estuary in 1972e1973.The average age,body size and gonadal-somatic index of females were significantly greater than those in males.For both females and males,there were no significant differences between the two stages of gonadal development in any of the morphological indices,which indicates that gonadal development of the Japanese Eel is independent of body size.These results help us to understand the spawning population of Japanese Eels in the Yangtze River.

Advances in Growth and Development in Crustaceans Induced by Eyestalk Ablation

Eyestalk ablation has been widely used in artificial breeding of crustaceans due to its significant promotion effect on gonadal development, which plays a certain role by directly affecting neuroendocrine function of X-organ sinus gland （XO-SG） complex in eyestalks. As an important endocrine organ, XO-SG complex of the eyestalk has become a hot issue in crustacean endocrinology. This paper introduced the biological structure and physiological functions of XO-SG complex and summarized the molecular mechanism of eyestalk neuroendocrine, which provided theoretical references for further revealing the regulatory mechanism of eyestalk neuroendocrine system.

Molecular Characterization, Expression Pattern and Transcriptional Regulation of Figla During Gonad Development in Japanese Founder (Paralichthys olivaceus)

The factor in the germline alpha(figla), as a member of the basic helix-loop-helix family, has been reported to be involved in ovary development in mammals and teleosts. However, the regulatory mechanisms of figla in teleosts remain unclear. Here,figla in P. olivaceus(Pofigla) was characterized with encoding a 202 amino acid protein that contains a conserved basic region and helix-loop-helix(HLH) domain. Amino acids alignment and synteny analysis revealed that Pofigla was conserved with the orthologous gene sequences in other vertebrates. The results of qRT-PCR showed Pofigla was maternally inherited during embryonic development. For tissue distribution, Pofigla showed a sexually dimorphic gene expression in the gonad of different genders, with a higher expression in ovary than in testis. In situ hybridization(ISH) results demonstrated Pofigla was specifically expressed in germ cells including oocytes, spermatogonia and spermatocytes. By screening and analyzing two proximal regions(-2966/-2126 and-772/-444) with high promoter activity, we found SOX5, LEF1, FOXP1 and GATA1 may play important roles in the transcriptional regulation of Pofigla. Furthermore, we observed the co-localization between Figla and LEF1 in HEK 293T cells. And the significant up-regulation effect of the canonical Wnt signaling pathway on the expression of Pofigla was found in cultured ovarian cells. This study provided the first evidence that figla not only has an important function in ovary development, but also plays some potential roles in testis development and/or male germ cell differentiation during early testis development in P. olivaceus. The results provide valuable reference in exploring the regulatory network of figla in teleost.

Gonad traits and age structure of the sea urchin Heliocidaris crassispina in central range:a comparison with rangeextenders

The sea urchin Heliocidaris crassispina has northern expanded in geographic range to Toga Bay,Oga Peninsula in the Sea of Japan due to the global warming.To demonstrate the gonad traits and age structure of H.crassispina in the central range and compare the difference with those in northern extended range,we collected 100 H.crassispina individuals from a barren off Shitsumi,Fukui(central range),in August 2018.Their growth,gonad traits(size,development and color),and sex ratio were investigated and compared with those in Toga Bay,in August 2014(extended range).The successive 2012–2016 year classes of H.crassispina indicated successive juvenile recruitment in the central range,as found in the extended range.The individuals at three years old in central range were obviously larger than those in the extended range,showing large test diameter and body weight,possibly due to the higher temperature in central range than that in northern extended range.In addition,a balanced sex ratio in the central range was found,in contrast to the female-skewed sex ratio found in the extended range.Gonadal development was sex-and site-dependent.The testicular development in the central range was not only delayed in comparison to ovarian development,but also less delayed than those in the extended range,which possibly attribute to the higher water temperature in the central range.A significantly lower male gonad index and L*(lightness)value was recorded in central ranges compared to that in extended range,possibly due to the releasement of sperm of H.crassispina in central ranges.

Study on Early Propagation Technology of Yellow Catfish (Pelteobagrus fulvidraco)

[Objectives] This study was conducted to study early reproduction techniques of yellow catfish(Pelteobagrus fulvidraco) in Jianghan Plain. [Methods] Parents of P. fulvidraco were cultured by the methods of artificial temperature control and nutrition enhancement. [Results] After culture, the body weight, gonad weight, maturity coefficient and egg diameter of P. fulvidraco increased gradually. Up to April 30, the gonad weight of the female parents of P. fulvidraco cultured in greenhouses was significantly higher than that of the parents under natural conditions(P<0.05), 54% higher than that of the parents naturally cultured at the same period;the maturity coefficient of the parents cultured under strengthened conditions was also significantly higher than that of the parents under natural conditions at the same period(P<0.05);and the ovaries of the strengthened parents were orange yellow and full of eggs, and the number of eggs per fish was relatively high. In early May, the parents cultured under strengthened conditions were induced to spawn artificially. The average induced spawning rate and fertilization rate reached 86.7% and 71.6%, respectively, reaching the respective normal level. The gonad maturity of P. fulvidraco cultured under strengthened conditions was 15 d earlier than that under natural conditions, resulting in mass production of early-propagated larvae of P. fulvidraco. [Conclusions] In Jianghan plain area, artificial propagation can be achieved in early May by means of artificial temperature control and strengthened culture, which is 20 d ahead of natural conditions.

Full sexual maturity-cycle exposure to environmentally relevant concentrations of 17β-estradiol decreases reproductive capacity of zebrafish

17β-Estradiol(E2)has been widely detected in natural water and treatment with E2 induces potential endocrine disrupting effects in fish.However,effects on fish fecundity and steroid system after treatment with environmentally relevant concentrations of E2 for the full sexual maturation cycle remain unclear.In this study,zebrafish were treatment with 0,10 or100 ng/L E2 from embryo to adult stage,and effects on gonadal development and differentiation,steroid hormone levels,transcription of genes associated with the hypothalamic-pituitary-gonadal-liver(HPG)axis in adults and fertilization rate of offspring were assessed.The results showed that treatment with E2 lead to increased number of feminization in zebrafish.In females,E2 decreased cumulative amount of spawning and inhibited the maturation of oocyte.In males,E2 inhibited the maturation and motility of sperm,as well as decreased the movement speed of sperm.These adverse effects on sperm might be responsible for the reduced fertilization observed in offspring.In addition,treatment with E2 changed the levels of steroid hormones in zebrafish gonad and altered the transcriptional levels of genes associated with HPG axis,which is responsible for the regulation of germ cells maturation and gonadal development in zebrafish.Overall,these results suggested that treatment with environmentally relevant concentrations of E2 for the full sexual maturity cycle resulted in adverse effects on reproduction in zebrafish.

A critical role of foxp3a-positive regulatory T cells in maintaining immune homeostasis in zebrafish testis development

Suppressive regulatory T cells(Treg cells)play a vital role in preventing autoimmunity and restraining excessive immune response to both self-and non-self-antigens.Studies on humans and mice show that the Forkhead box p3(Foxp3)is a key regulatory gene for the development and function of Treg cells.In zebrafish,Treg cells have been identified by using foxp3a as a reliable marker.However,little is known about the function of foxp3a and Treg cells in gonadal development and sex differentiation.Here,we show that foxp3a is essential for maintaining immune homeostasis in zebrafish testis development.We found that foxp3a was specifically expressed in a subset of T cells in zebrafish testis,while knockout of foxp3a led to deficiency of foxp3a-positive Treg cells in the testis.More than 80%of foxp3a^(-/-)mutants developed as subfertile males,and the rest of the mutants developed as fertile females with decreased ovulation.Further study revealed that foxp3a^(-/-)mutants had a delayed juvenile ovary-to-testis transition in definite males and sex reversal in about half of the definite females,which led to a dominance of later male development.Owing to the absence of foxp3a-positive Treg cells in the differentiating testis of foxp3a^(-/-)mutants,abundant T cells and macrophages expand to disrupt an immunosuppressive milieu,resulting in defective development of germ cells and gonadal somatic cells and leading to development of infertile males.Therefore,our study reveals that foxp3a-positive Treg cells play an essential role in the orchestration of gonadal development and sex differentiation in zebrafish.

Higher dietary protein increases growth performance,anti-oxidative enzymes activity and transcription of heat shock protein 70 in the juvenile sea urchin(Strongylocentrotus intermedius)under a heat stress

This study was conducted to investigate the effect of dietary protein concentration(12%,18%,24%,30% and 36%)on the growth performance,activity of anti-oxidative enzymes and heat shock protein 70(HSP70)transcription in the sea urchin(Strongylocentrotus intermedius)under a heat stress.After 112 days of feeding trial the sea urchins were heat stressed(26
C)and the coelomic fluid and intestine sampled at time 0 and 15 min,2 h and 6 h.The results showed that an increase in dietary protein(12%-24%),significantly increased(p<0.05)the sea urchin weight gain rate(WGR).As dietary protein increased(from 18% to 36%),the gonadosomatic index(GI)of juvenile sea urchins also significantly increased(p<0.05)from 18.0%to 22.6%.Superoxide dismutase(SOD)activity increased with dietary protein increase(12%-30%)and the enzyme activity was significantly higher(p<0.05)in the coelomic fluid of sea urchins that were fed with 30% diets when compared to 12% and 36% protein diets at all time points after the heat stress.Catalase(CAT)activity showed a similar tendency with the increase in dietary protein concentration at time 0 and 15 min after the heat stress(p<0.05).Transcription of HSP70 in the intestine also showed a similar trend to SOD and was highest in the animals that were fed with 30% protein diets(p<0.05).Our results suggest that 24% protein diets could meet the requirements for growth performance but a 30% protein diet resulted in improved gonad development and anti-heat stress capacity in this sea urchin species.

Thermosensitive period for sex determination of the tropical freshwater turtle Malayemys macrocephala

Many egg-laying reptiles possess temperature-dependent sex determination(TSD)in which outcome of gonadogenesis is determined by incubation temperature during a temperature-sensitive period of development.Prior studies on Malayemys macrocephala showed that incubation temperatures influence gonadal development and suggested that M.macrocephala exhibits TSD.However,information on the temperature-sensitivity period in this species was unknown until the current study.Turtle eggs were collected from rice fields in central Thailand from December 2016 to February 2017.In the laboratory,eggs were incubated at male-biased temperature(26°C)and shifted to female-biased temperature(32°C),or vice versa.Single shift experiments were performed systematically during embryonic stages 13–21.After hatching,sex of individual turtles was determined by histological analysis.We found that the sex determination of M.macrocephala is affected by temperature up to stage 16 of embryonic development.

Effects of pituitary extract,ovaprim,and bitter leaf(Vernonia amygdalina)on the histopathology of African catfish(Clarias gariepinus)

The development of aquaculture in Nigeria is constrained by the inadequate supply of high quality of fingerlings of African catfish(Clarias gariepinus).There are conflicting reports on the reproductive efficacy of Vernonia amygdalina when compared with the synthetic hormone Ovaprim(OV)and Pituitary Extract(PE)on C.gariepinus.The histopathology of select organs in catfish treated with generic Ovaprim(OV),Pituitary Extract(CPE),and aqueous extract of Vernonia amygdalina(VAE)were evaluated.Sixteen female C.gariepinus(average weight of 1 kg)wereevenly and randomly distributed to four groups.Fish in groups A,B,C,and D were injected intramuscularly with aqueous solutions of OV(0.5 mL/kg),PE(5 mg/kg),VAE(10 mg/kg),and distilled water(DW;0.5 ml),respectively.Histological examinations of the ovary,liver,kidney,and spleen were carried out.Histopathology revealed that OV-and PE-treated groups showed synchronous and synchronous ovarian development,vacuolar change of hepatocytes,thinning of hepatic cords,reduced renal haemopoietic compartments,tubular degeneration and necrosis,and decrease in splenic periarteriolar lymphoid sheaths(PALS).VAE-treated groups had asynchronous ovarian development with atretic ovarian follicles,widespread vacuolar change of hepatocytes,intact renal tubular and hemopoietic compartments,and preponderance of large and coalescing splenic PALS.We conclude that VAE is an ineffective spawning agent,especially when compared with OV and PE,as VAE could not induce synchronous gonadal development.However,VAE may have immunopotentiating,nephroprotective,and haemopoietic properties.

Characterization and expression analysis of sox3 in medaka gonads

Numerous studies have showed that sox3 is involved in neurogenesis and sex differentiation in vertebrates.However,the accurate expression pattern is still unclear in fish.In this study,medaka sox3 was isolated and its expression patterns were compared with germ cell gene vasa in adult gonads.By reverse transcription-polymerase chain reaction(RT-PCR)analysis,sox3 RNA expression was detected in the brain,eyes and gonads.By chromogenic and fluorescent in situ hybridization,sox3 was present in the oogonia and early stages of oocytes as well as granulosa cells and theca cells in the later stages;in the testis,sox3 was occurred in the Sertoli cells and sperm with a specific signal in the location of chromatid body of sperm;in the embryos,sox3 was expressed in the central nervous.These results suggest that medaka sox3 gene was occurred in somatic and germ cells in adult gonads of both sexes,involved in the process of spermatogenesis,as well as the development of the nervous system.This study provides a precise expression pattern of sox3 and suggests that sox3 may be involved in gonadal and nervous system development of fish.

Variation of lipids and fatty acids composition in the tissues of wild devil stinger(Inimicus japonicas)during sexual maturation

The present study was conducted to characterize the lipid and fatty acid profiles in different tissues(gonad,liver and muscle)of the wild-caught devil stinger during sexual maturation.Wild-caught devil stinger were divided into six groups according to gonad development and gender.Total lipid content was up to 40%dry weight in liver and was significantly higher than in other tissues(ovary,testis and muscle)in both male and female stinger during sexual maturation.During maturation,total lipid content in the female stinger liver decreased,but in males significantly increased in all tissues.Higher proportions of neutral lipids(NL)were observed in the stinger liver,while polar lipids(PL)were mainly quantified in the gonad and muscle of both male and female stinger.The PL content of the ovary significantly decreased with sexual maturation,but NL were significantly increased.The fatty acids composition of the stinger broodstocks were tissue-and lipid class-specific.In the stinger gonad high-unsaturated fatty acids(HUFA),such as ARA,DHA and EPA,are selectively transferred and conserved,indicating the crucial role of these fatty acids during sexual maturation of this fish species.