Monosex Culture Research Articles

Crustacean endocrinology: Sexual differentiation and potential application for aquaculture

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.

Molecular mechanisms of sex determination and differentiation in decapod crustaceans for potential aquaculture applications: An overview

AbstractCrustacean aquaculture, especially monosex culture, requires a comprehensive knowledge of the mechanisms regulating sex determination and differentiation. Decapod crustaceans display either female heterogamety (ZW/ZZ) or male heterogamety (XY/XX) as their mode of genotypic sex determination. However, some decapod species exhibit sexual plasticity via removing the androgenic gland, knockdown insulin receptor transcripts, administrating exogenous sex steroids, and altering environmental factors. Although the master sex‐determining gene in decapods remains elusive, various sexual genes, hormones, and neurotransmitter are emerging as important factors in sex differentiation. This review looks into recent advancements in studies related to the genetic sex determination system and factors that trigger sex reversal. Moreover, the elucidation of the role of genetic factors in sex differentiation in both females and males, as well as their underlying interrelated regulatory mechanisms, provides justification for three levels of application: the induction of monosex populations, detection of precocious sex and genotype, and prevention of uncontrolled reproduction. Finally, we proposed future directions of bioinformatics analysis and genome editing coupled with sex control to increase the yield for economic decapods. In conclusion, this review provides a foundation for future research on the reproductive biology and sexual regulation of decapods, with the aim of aiding practitioners in advancing the crustacean aquaculture industry.

Production of neomale and neofemale large yellow croaker (Larimichthys crocea) and establishment of all-female populations

The large yellow croaker (Larimichthys crocea), with an XX/XY sex-determining system, is a key mariculture fish in China. The monosex culture of this species has economically advantageous due to distinct sexual growth dimorphism, requiring sex control technologies. This study aimed to produce neomale (XX♂) and neofemale (XY♀) fish by inducing sex-reversal in large yellow croaker and utilize neomales (XX♂) to create all-female populations. Letrozole (LTZ; 10 mg/kg) and 17β-estradiol (E2; 2 mg/kg) were orally administered to the fish (45 days post-hatching, dph) for 80 days to induce sex-reversal. LTZ treatment resulted in 91.1% masculinization and E2 treatment resulted in 93.5% feminization. E2 treatment significantly inhibited the growth while no significant difference was observed in the the LTZ group and the control. Furthermore, Sex-reversal in large yellow croaker was confirmed by distinct expression patterns of two sex-related genes, dmrt1 and cyp19a1a. Subsequently, neomales were crossed with control females upon reaching sexual maturity, facilitating the large-scale production of all-female populations. These results underscore the viability of sex-reversal methods in large yellow croaker and the potential for mass-production of all-female populations, thereby establishing a groundwork for monosex culture in this species.

Early Sex Differentiation of Climbing Perch (Anabas testudineus Bloch.): A Pathway to Feminization

The phenomenon of sexual dimorphism in climbing perch, which shows that female fish grow faster than males, underlies the development of mono-sex culture. Female mono-sex culture is more applicable for farmers by crossing neo-male fish with normal females. The timing of sexual differentiation in climbing perch is still unknown. It is very useful in sex reversal procedures to produce neo-male climbing perch. This study revealed the time and status of climbing perch sexual differentiation. Ten samples of climbing perch from the spawning of five pairs of parents were taken from the nursery pond at 10–29 days post-hatching (dph). Samples were prepared through a histology preparation procedure. Observations of the structure and characteristics of the gonads were carried out using a light microscope and analyzed histologically. The results indicated that gonad samples aged 10, 11, 12, 13, 15, and 16 dph showed primordial germ cells surrounded by somatic tissue forming genital ridges and mitotic division. Meanwhile, the gonads begin to differentiate as ovaries found at 18 dph with the presence of oogonia and ovarian cavities. Gonads aged 20–21 dph increasingly showed single oogonia cells (size 20–37.5 µm), germ cell cysts, genital ridges, oocytes undergoing the vitellogenesis process, perinucleolar oocytes, and the formation of the ovarian cavity. Sex differentiation of climbing perch was predicted from 18–21 dph. This conclusion underlies that the sex reversal procedure in climbing perch must be carried out before 18 dph.

Role of Mn-LIPA in Sex Hormone Regulation and Gonadal Development in the Oriental River Prawn, Macrobrachium nipponense.

This study investigates the role of lysosomal acid lipase (LIPA) in sex hormone regulation and gonadal development in Macrobrachium nipponense. The full-length Mn-LIPA cDNA was cloned, and its expression patterns were analyzed using quantitative real-time PCR (qPCR) in various tissues and developmental stages. Higher expression levels were observed in the hepatopancreas, cerebral ganglion, and testes, indicating the potential involvement of Mn-LIPA in sex differentiation and gonadal development. In situ hybridization experiments revealed strong Mn-LIPA signaling in the spermatheca and hepatopancreas, suggesting their potential role in steroid synthesis (such as cholesterol, fatty acids, cholesteryl ester, and triglycerides) and sperm maturation. Increased expression levels of male-specific genes, such as insulin-like androgenic gland hormone (IAG), sperm gelatinase (SG), and mab-3-related transcription factor (Dmrt11E), were observed after dsMn-LIPA (double-stranded LIPA) injection, and significant inhibition of sperm development and maturation was observed histologically. Additionally, the relationship between Mn-LIPA and sex-related genes (IAG, SG, and Dmrt11E) and hormones (17β-estradiol and 17α-methyltestosterone) was explored by administering sex hormones to male prawns, indicating that Mn-LIPA does not directly control the production of sex hormones but rather utilizes the property of hydrolyzing triglycerides and cholesterol to provide energy while influencing the synthesis and secretion of self-sex hormones. These findings provide valuable insights into the function of Mn-LIPA in M. nipponense and its potential implications for understanding sex differentiation and gonadal development in crustaceans. It provides an important theoretical basis for the realization of a monosex culture of M. nipponense.

Production of neofemale by 17β-estradiol and YY super-male breeding in mandarin fish (Siniperca chuatsi)

It is well known that mono-sex culture has the advantages of a more rapid growth rate, more uniform size and lower energy consumption of gonadal development in fish. In production practice, male mandarin fish (Siniperca chuatsi) show great aquaculture value after the overwintering stage. As a species with an XY-type sex determination system, feminizing genetically male fish into physiological female fish and breeding YY supermales is a common method used to produce all-male populations. In this study, we systematically investigated feminization of mandarin fish by indirect feeding of 17β-estradiol (E2) at different doses (200, 400 and 600 mg/kg). Neo-females were successfully yielded in all E2-treated concentrations. The sex-reversed ratios of the 200, 400 and 600 mg/kg E2-treated groups were 40%, 87% and 100%, respectively. From 45 to 135 dat (days after treatment), the gonads in the 600 mg/kg E2-treated group consisted of oogonium and previtellogenic oocytes. At 165 dat, early vitellogenic oocytes were observed in the gonads of the 600 mg/kg E2-treated group. Regarding the expression of sex-related genes, 600 mg/kg E2-treated mandarin fish presented a different gene expression pattern from that of normal males. Moreover, the growth and development status were also analysed in XY normal males and YY supermales at 360 dph, and YY supermales showed a higher number of lumina and significantly lower growth performance than XY normal males. In conclusion, we have established a technique for efficiently inducing male to female sex reversion and YY supermale breeding of mandarin fish, which provides a great foundation for the production of all-male mandarin fish.

CRISPR/Cas9-mediated gene mutation of EcIAG leads to sex reversal in the male ridgetail white prawn Exopalaemon carinicauda.

In the culture of crustaceans, most species show sexual dimorphism. Monosex culture is an effective approach to achieve high yield and economic value, especially for decapods of high value. Previous studies have developed some sex control strategies such as manual segregation, manipulation of male androgenic gland and knockdown of the male sexual differentiation switch gene encoding insulin-like androgenic gland hormone (IAG) in decapods. However, these methods could not generate hereditable changes. Genetic manipulation to achieve sex reversal individuals is absent up to now. In the present study, the gene encoding IAG (EcIAG) was identified in the ridgetail white prawn Exopalaemon carinicauda. Sequence analysis showed that EcIAG encoded conserved amino acid structure like IAGs in other decapod species. CRISPR/Cas9-mediated genome editing technology was used to knock out EcIAG. Two sgRNAs targeting the second exon of EcIAG were designed and microinjected into the prawn zygotes or the embryos at the first cleavage with commercial Cas9 protein. EcIAG in three genetic males was knocked out in both chromosome sets, which successfully generated sex reversal and phenotypic female characters. The results suggest that CRISPR/Cas9-mediated genome editing technology is an effective way to develop sex manipulation technology and contribute to monosex aquaculture in crustaceans.

Stocking density affects culture performance and economic profit of adult all-female Chinese mitten crabs (Eriocheir sinensis) reared in earthen ponds

As female Chinese mitten crab (Eriocheir sinensis) generally offer the higher edible yield, greater nutritional value, and consequently, higher market price compared to males, therefore all-female monosex culture has been popularized for the farming E. sinensis. However, the optimal stocking density remains unknown for all-female culture of E. sinensis. The present study was conducted to evaluate the effect of different stocking densities (D1.3: 1.3 inds/m2, D1.9: 1.9 inds./m2, D2.5: 2.5 inds./m2 and D3.8: 3.8 inds./m2) on growth performance, gonadal development, and economic profits of all-female E. sinensis during nine months culture period. The results showed that all growth parameters including mean body weight, body weight gain (BWG) and specific growth rate (SGR), exhibited an inverse relationship with stocking density. However, stocking density did not have a significant effect on the percentage of puberty molting, gonadosomatic index (GSI) and hepatosomatic index (HSI). At the end of the experiment, the survival rate significantly decreased with the increasing stocking density, while both final production yield and economic feed conversion ratio (eFCR) significantly increased with stocking density (P < 0.05). Profitability analysis showed that total cost and total return increased significantly with the stocking density, but the highest net profit (129.68 × 103 CNY/ha) and return-on-investment (ROI, 87.65%) were achieved at the D2.5 group. Overall, these results suggested that the optimal stocking density might range from 1.9 to 2.5 individuals/m2 in grow-out ponds for all-female mono-culture of E. sinensis.

Recent Developments in Aquaculture and Future Prospects: A Comprehensive Review

In the pursuit of promoting sustainable aquaculture production, numerous cutting-edge technologies have emerged in recent years. The utilization of effective microbes (EM) in managing water quality, the implementation of biofloc technology, aquamimicry, the inclusion of Black Soldier Fly (BSF) as an additional protein source, the use of triploidy and polyploidy, vaccines, probiotics, and prebiotics, the integration of Internet of Things (IoT) for monitoring water quality in the farm operation, the practice of monosex culture, and the application of neo-female techniques are all being employed in aquaculture operations. The advancements in these cutting-edge technologies have been focused on promoting sustainable aquaculture production, mitigating the risk of disease outbreaks, enhancing crop yields, and contributing to eco-friendly environmental initiatives. This review paper highlights the cutting-edge technologies that have emerged in the field of aquaculture in recent years, up until the present time, with a focus on advancements in fish nutrition. The advancements in aquaculture technology have been instrumental in promoting the achievement of sustainable development goals, particularly SDG-1 (no poverty) and SDG-2 (zero hunger). These goals are aimed at reducing poverty and eliminating hunger by utilizing the enhanced aquaculture production facilitated by the latest technological innovations. In the arena of aquaculture, this review paper has the potential to nourish the minds of aquaculturists and aquafarmers with a bountiful feast of knowledge. It unveils the latest technologies and developments in the realm of aquaculture, serving as a nutritious resource that can enhance the operation of cultures and promote a fruitful increase in production in the not-so-distant future.

Recent developments in aquaculture – A review

Abstract Towards the sustainable aquaculture production, more recent technologies have been developed in the past few years. The application of effectives microbes (EM) in controlling water quality, the application of biofloc technology, aquamimicry, black soldier fly (BSF) as supplemental protein feed, application of triploidy, polyploidy, vaccines, probiotic and prebiotic, Internet of Things (IoT) in monitoring the water quality in the farm operation, monosex culture and neo-female application also being applied in the aquaculture operation. The developments of these recent technologies were towards achieving the sustainable aquaculture production, prevention of the disease outbreak, help in increasing the yield of crops harvested as well as towards the green environmental developments. This review paper emphasizes the most recent technologies developed in aquaculture in the past few years until these days. The developments of the new technology in aquaculture also in order to support the sustainable development goals (SDGs) proposed by the United Nation focused on SDG1 (no poverty) and SDG2 (zero hunger) from the increase of aquaculture production achieved through the recent developed technology. Ultimately, this review paper can generate new knowledge and information to the aquaculturist and aquafarmers on the new technologies and developments in aquaculture which could help benefit in the cultures operation and increase production in the near future.

Comparative gonad transcriptome analysis in cobia (Rachycentron canadum).

Background: Cobia (Rachycentron canadum) is a species of fish with high commercial potential particularly due to fast growth rates. The evidence of sexual size dimorphism favoring females indicate potential benefits in having a monosex culture. However, the involvement of genetic factors responsible for sexual development and gonadal maintenance that produces phenotypic sex in cobia is largely unknown. Methods: In the present study, we performed transcriptome sequencing of cobia to identify sex-biased significantly differentially expressed genes (DEGs) in testes and ovaries. The reliability of the gonad transcriptome data was validated by qPCR analysis of eight selected significantly differential expressed sex-related candidate genes. Results: This comparative gonad transcriptomic analysis revealed that 7,120 and 4,628 DEGs are up-regulated in testes or ovaries, respectively. Further functional annotation analyses identified 76 important candidate genes involved in sex determination cascades or sex differentiation, including 42 known testis-biased DEGs (dmrt1, amh and sox9 etc.), and 34 known ovary-biased DEGs (foxl2, sox3 and cyp19a etc.). Moreover, eleven significantly enriched pathways functionally related to sex determination and sex differentiation were identified, including Wnt signaling pathway, oocyte meiosis, the TGF-beta signaling pathway and MAPK signaling pathway. Conclusion: This work represents the first comparative gonad transcriptome study in cobia. The putative sex-associated DEGs and pathways provide an important molecular basis for further investigation of cobia's sex determination, gonadal development as well as potential control breeding of monosex female populations for a possible aquaculture setting.

A refined roadmap to decapod sexual manipulation

AbstractMany decapod crustaceans with sexual dimorphism in body size are economically significant species for fisheries and aquaculture, making monosex culture a desirable practice to increase farmers' yield and profits. It is well established that the male‐specific androgenic gland (AG) mediates masculinization in decapods by producing and secreting the insulin‐like AG hormone (IAG). However, IAG is not a sex‐determining factor; hence, iag silencing in decapods does not always lead to successful sex change. Since the establishment of monosex populations in the giant freshwater prawn Macrobrachium rosenbergii, the same AG/iag manipulation approach has been attempted in economically significant penaeid shrimps, crabs, crayfish and spiny lobsters, to no avail. There are many factors at play with species‐specific intricacies which require close examination when addressing monosex production. This review provides a refined roadmap to successful sexual manipulation in decapod crustaceans, highlighting the key caveats to be considered and critical gaps in knowledge such as the timing of iag expression compared to the development of sexual characteristics, the relationship between iag and a master regulator, as well as silencing capacity. Lastly, this review examines what the future might hold for monosex aquaculture in decapods, taking into consideration novel technologies such as gene editing.

An Overview of the Major Constraints in Scylla Mud Crabs Grow-out Culture and Its Mitigation Methods

Scylla mud crabs are economically important portunid species for aquaculture in many countries. However, mass production of mud crabs as a supply of seafood is still difficult up-to-date. This review aimed to provide an overview of the major constraints faced in the grow-out farming of mud crabs, and the potential solutions were discussed. The major constraints in the Scylla mud crabs' grow-out culture are (1) inadequate seed supply, (2) cannibalism, (3) disease outbreaks, and (4) no commercial formulated feed that is specifically designed for mud crabs. The inadequate wild mud crabs seed supply can be solved through artificial seed production seed in the hatcheries, but the knowledge of mud crab requirements at early life stages is needed to improve the rearing techniques and production. Cannibalism in the grow-out culture of mud crabs is manageable, provided that the farmers are knowledgeable about the basic prevention methods (shelter provision, size grading, monosex culture) and they are practicing it. On the disease outbreaks, research into discovering new alternatives to antibiotics and prevention methods should be prioritized. Finally, the commercial formulated grow-out diet that is specific for the Scylla mud crabs should be developed to replace the use of natural products for feeding.

Effect of dosage of orally administered 17α-methyltestosterone on sex reversion of the yellowtail tetra Astyanax lacustris (Lütken, 1875).

The females of yellowtail tetra (Astyanax lacustris), known as the freshwater sardine, are approximately 1.33 times larger than males, and thus, all-female monosex culture would increase production and reduce size variability. The present work aimed to identify the optimal dose of 17α-methyltestosterone (MT) to be used in the masculinization of A. lacustris for indirect sex reversal. Three different concentrations of MT (20, 40, and 60 mg/kg of feed in the diet) were fed to the fry for 30 days. Thirty adult individuals from each treatment, including the control (0 mg MT/kg), were evaluated for gonadal development, morphological and histological sexual identification, zootechnical performance, and the possible genotoxic effect caused by prolonged exposure to MT. MT significantly (P<0.01) affected the differentiation of the gonads, with the presence of possible inhibitory effects in all treatments. Intersex individuals were present in the 20 and 60 mg MT/kg treatments. All treatments were able to masculinize A. lacustris and the treatment with the lowest hormone concentration produced the highest percentage of males 76.7%, while the control had 46.7% males. The presence of erythrocyte nuclear alterations indicated a possible cytotoxic effect of MT in treatments 40 and 60 mg MT/kg, however, the use of the hormone did not affect the growth and the survival of the individuals. Thus, the use of MT is a viable option for obtaining neomales as a first step into the production of all-female progenies.

Sex Reversal of the Giant Freshwater Prawn Macrobrachium dacqueti through Androgenic Gland Ablation

The male Macrobrachium species (giant freshwater prawn) typically achieve better growth and a larger harvest size than females. Hence, it is clear that the monosex culture of all-male prawn populations would be inexpensively advantageous. This study aimed to determine whether androgenic gland (AG) ablation induces sex reversal of giant freshwater prawn Macrobrachium dacqueti. The AG of the prawn was ablated through bilateral microsurgery (AG ablation) and let them recover for two months. The weight and length were also measured every 15 days. Results revealed that the removal of AG from the males of immature M. dacqueti resulted in sex reversal, with 70% female differentiation. Successful neo-female prawns exhibited the development of an ovary with orange coloration as it matures. Andrectomized M. dacqueti did not develop the appendix masculina in the second pleopod, an indicator of a suspected neo-female prawn. A significant increase in weight and length was observed within two months compared to the control. Based on the result of the study, sex reversal of M. dacqueti is possible through AG ablation. Therefore, sex-reversed (neo-females) M. dacqueti can be used to breed with normal males to produce all-male progenies since both parents possess male hormones, thereby rendering a huge advantage for prawn culture.

Comparative Transcriptome Analyses Characterize Expression Signatures Among Males, Females, Neo-Males, and Gynogenetic Females in the Yellow Drum (Nibea albiflora)

The yellow drum (Nibea albiflora) is one of the most important marine economic fish in China, and its sexually dimorphic growth makes it preferable for mono-sex culture. Although gynogenesis and neo-male induction techniques have been established, the molecular pathways and regulatory mechanisms of sex determination and maintenance in gynogenetic females and neo-males remains far from fully understood. In this study, the gene expression profiles were investigated in the gonads and brains of wild-type male, wild-type female, neo-male, and gynogenetic female yellow drum using comparative transcriptome analyses. Generally, a total of 52,999 novel transcripts were obtained in RNA-seq, of which 45,651 were isoforms of known protein-coding genes, 1,358 novel protein-coding genes, and 5,990 long non-coding RNAs. We found that the differences between wild-type males and neo-males and between wild-type females and gynogenetic females were relatively small at both the histological and transcriptomic levels, indicating that artificial gynogenesis or hormonal sex reversal may have minimal effects on normal female or male life function, respectively. In the brain, pathways such as “Oocyte meiosis”, “Cell cycle”, and “Riboflavin metabolism” were found to be significantly enriched. In the gonads, pathways such as “Prolactin signaling pathway”, “PPAR signaling pathway”, “Cholesterol metabolism”, and “Jak-STAT signaling pathway” were found to play important roles in maintaining the regular proliferation and differentiation of females and males in yellow drum. In particular, we found that zp4 might be an effective molecular marker to differentiate between gynogenetic and normal females owing to its unique expression pattern. The results of this study may help to elucidate the molecular mechanisms involved in sex maintenance in the gonads and brain and provide basic data for genetic breeding of the yellow drum.

Transcriptomic profiling and novel insights into the effect of AG ablation on gonad development in Macrobrachium rosenbergii

Androgenic glands (AGs) regulate male sexual differentiation in M. rosenbergii, and AG ablation may induce sex-reversal and male-to-neofemale transformation. However, information on gonad development following AG ablation is scarce. To investigate the effects of gonad development and sex reversal after AG ablation, we utilized transcriptomic profiling, RT–qPCR, and histological and morphological observation. Transcriptomic profiling generated 42.32–42.92 million clean reads. A total of 94,747 unigenes were assembled with a total length, average length, N50, and GC content of 160,460,655 bp, 1693 bp, 3438 bp, and 39.86%, respectively. Hsp70, IGFBP7, Mar-Mrr, Serpin, TUBA3, CREB, EF1a, and BMP7 were identified as differentially expressed by gonad transcriptome profiling after AG ablation. Interestingly, the Rap1, Hippo, PI3K, oxytocin, thyroid hormone, and apoptosis signalling pathways were all found to be involved in the sex-reversal process by regulating cell proliferation and gonad development and maintaining homeostasis. Sexual morphology features and histological changes following AG ablation validated the sex reversal from male to neofemale. Sexual manipulation permits monosex culture while considerably improving output yield. Taken together, these findings provide insight into the sexual reversal mechanism of M. rosenbergii after AG ablation. The findings in this study may aid in the future investigation of the sex-reversal mechanisms in other decapod species and offer a new breeding and culture strategy for M. rosenbergii aquaculture industry.

The influence of monosex rearing on gonad maturation and reproductive behavior of Indian white prawn, Penaeus indicus broodstock

Monosex culture was proven to be an effective rearing method for grow-out, but in a closed-cycle hatchery, males and females are usually reared communally in tanks until maturation. This study determined the effect of communal rearing (CR) and separate rearing (SR) on male and female Penaeus indicus broodstock gonad maturation. This study also evaluated the influence of the rearing method on reproductive behavior and mating success. The results showed that CR female broodstock had higher maturation rates at 77.78 ± 5.31% (p = 0.061) and a shorter latency period at 6.71 ± 2.54% than SR females (p = 0.211), but the differences were not statistically significant. Similarly, maturation rates for both male groups were 40.62 ± 3.12% and were not significantly different (p = 1.00). The interspermatophore period (p = 0.044), spermatophore weight (p = 0.878), count (p = 0.780), viability (p = 0.257), and percent abnormality (p = 0.257) did not vary between males. In terms of the effect of rearing method on reproductive behavior, males from the SR group initiated more chase (p = 0.018) and fight with other males (p = 0.022) than CR males did, and the differences were significant. SR males also touched the discarded molt (p = 0.167) and advanced to the probe position (p = 0.525) more times than CR males, but the differences were not significant. The sum of all the reproductive behaviors was also significantly higher in the SR (54.00 ± 1.20) than in the CR (24.20 ± 0.86) groups (p = 0.017). Initial results showed that successful mating in the SR (80%) was higher than that recorded in the CR group (20%). These findings suggest that monosex rearing of male and female P. indicus will not negatively affect gonad maturation and will enable sex-specific nutritional manipulations, which can even possibly promote higher mating success.

A Review of Sexual Determination and Differentiation in Crustacean

The prerequisite for monosex culture is to elucidate the molecular mechanism of sex determination and differentiation in crustaceans, as well as to explore the key genes that play a role in this process. Monosex culture technology based on crustacean economic species is of great importance in terms of genetic breeding and economic benefits of aquaculture. As a result, study into the mechanisms of sex determination and differentiation in crustaceans not only contributes to the current absence of basic theories of crustacean sexual mechanism, but also encourages technical innovation in aquaculture to increase overall economic efficiency. This study synthesizes and evaluates available research on sex determination and differentiation in crustaceans, and then provides recommendations for future research objectives and priorities in the field.

Comparative analyses of growth parameters of pure Clarias gariepinus and its hybrid in monosex culture

This study compared sexual differences in growth parameters of pure and hybrid African catfishes (Clarias gariepinus and Clariabranchus) raised in a monosex culture. The two species were obtained from 281 fishes comprising 150 pure breed and 131 hybrids in an earlier study and grouped by sex separately as male and female in four separate plastic tanks, representing two replicates per sex. Ten each of the pure clarias and its hybrid were reared in each tank. In all, 40 male and 40 female fish comprising 20 each of the pure clarias and its hybrid for each sex were evaluated for the growth parameters. A total of 80 fish were included in this study and the study lasted nine (9) weeks. The fish were fed commercially compounded feed twice daily throughout the period of the experiment. Length-weight relationship and growth parameters such as Mean Growth Rate (MGR), Specific Growth Rate (SGR), Absolute Growth Rate (AGR), Relative Growth Rate (RGR), Condition Factor (CF) were computed and evaluated for sex effect. All statistical analyses involving descriptive, general linear model analysis of variance (ANOVA) and post hoc test were done using Minitab® 17 Statistical Software. Sex had significant (P&lt;0.05) effects on all growth parameters except Absolute Growth Rate (AGR) albeit at different levels, but specie only had significant (P&lt;0.05) effect on Mean Growth Rate (MGR), while the interaction of sex x specie exerted significant (P&lt;0.05) effects on all growth parameters except Condition Factor (CF). This study revealed that growth performance is significantly (P&lt;0.05) affected by sexual dimorphism and also by interaction of sex and specie.