A study on the physical fitness index, heart rate and blood pressure in different phases of lunar month on male human subjects

The gravitational pull of the moon on the earth is not the same in all phases of the lunar month, i.e. new moon (NM), first quarter (FQ), full moon (FM) and third quarter (TQ), and as a result the amplitude of tide differs in different phases. The gravitational pull of the moon may have effects on the fluid compartments of the human body and hence the cardiovascular system may be affected differentially in the different phases of the lunar month. In the present study resting heart rate (HR) and blood pressure (BP), physical fitness index (PFI), peak HR and BP immediately after step test, and recovery HR and BP after step test were measured during different phases of the lunar month in 76 male university students (age 23.7?±?1.7 years). At rest, both systolic and mean arterial BP were ～5 mmHg lower in NM and FM compared to FQ and TQ, but resting HR was not significantly different between phases. Further, peak HR and peak systolic BP after step test were lower (～4 beat/min and ～5 mmHg, respectively) in NM and FM compared to FQ and TQ. PFI was also higher (～5) in NM and FM compared to FQ and TQ. Recovery of HR after step test was quicker in NM and FM compared to that of FQ and TQ. It appears from this study that gravitational pull of the moon may affect the cardiovascular functions of the human body. Moreover, the physical efficiency of humans is increased in NM and FM due to these altered cardiovascular regulations.     

Lunar synchronization of testicular development and steroidogenesis in rabbitfish

Lunar synchronization of testicular development in the golden rabbitfish, Siganus guttatus, was assessed by measuring changes in sperm motility and conditions in the seminal plasma, and by in vitro production of steroid hormones in testicular fragments and sperm preparations. The duration and percentage of sperm motility was low 1 week before spawning (the new moon), but increased significantly on the day of spawning (the first lunar quarter). During the first lunar quarter, the osmolality decreased, but Ca(2+) concentration increased in the seminal plasma. These results suggest that spermiation occurs rapidly towards the specific lunar phase. Testicular fragments and sperm preparations were incubated with human chorionic gonadotropin (hCG) and two precursor steroid hormones, 17alpha-hydroxyprogesterone (17alpha-OHP) and testosterone (T), during the two lunar phases. The production of 11-ketotestosterone (11-KT) increased significantly when the testicular fragments were incubated with hCG at the first lunar quarter, while incubation of sperm preparations with 17alpha-OHP during the same moon phase resulted in a significant increase in 17alpha,20beta-dihydroxy-4-pregnen-3-one (DHP) production in the medium. These results suggest that 11-KT is produced in the somatic cells of the testis under the influence of gonadotropin, and that sperm can convert 17alpha-OHP to DHP. Additionally, steroidogenic activity was considered to increase toward the specific lunar phase. The synchronous increase in testicular activity supports the hypothesis that lunar periodicity is a major factor for the testicular development of S. guttatus.     

Effects of lunar phases on short-term,explosive physical performance among young trained athletes

Beliefs that lunar phases affect human physiology started in ancient times. Research has recently revealed that a physical fitness index increased in sedentary students at the new moon (NM) and full moon (FM) compared to other moon phases. However, the effect of lunar cycle (moon illumination and gravitational pull) on physical performance in athletes was not examined. Therefore, this study aimed to evaluate whether short-term explosive performance can be influenced by the different phases of the lunar cycle. Fourteen young male Taekwondo athletes (age: 16.9 ± 0.7 years, height: 159.7 ± 50.6 cm, body mass: 62.85 ± 7.84 kg) performed the following tests to assess the explosive physical performance during the different phases of the lunar cycle (NM, FQ (first quarter), FM, and LQ (last quarter)): maximal isometric manual contraction (dominant hand (MIMCD) and non-dominant hand (MIMCND)), maximal back isometric contraction (MBIC), squat jump (SJ), countermovement jump (CMJ), and 10-m sprint (10 m). The testing sessions during the different moon phases were performed in a counterbalanced order. The order of tests remained the same (MIMCD, MIMCND, MBIC, SJ, CMJ, and 10 m), and all sessions were performed in the evening (6:00 to 8:00 p.m.) on the first day of each evaluated lunar phase. Each parameter was measured over two consecutive lunar months in the calendar. Analysis of variance tests showed that there was no significant effect of lunar cycle on all explosive test measures, p > 0.05. Our results failed to identify any effect of lunar phase on evening explosive performance (mainly involving phosphagen pathway-based efforts) among young trained athletes. Therefore, it appears that moon phase/illumination does not affect short-term physical performance in young trained adolescents.     

The involvement of sex steroid hormones in downstream and upstream migratory behavior of masu salmon

From May through July when masu salmon, Oncorhynchus masou, commence downstream migration under natural conditions, yearling precocious male masu salmon (resident form) showed higher GSI and plasma levels of testosterone (T) and 11-ketotestosterone (11-KT) in contrast to immature smolts (migratory form). From March through September coinciding with the upstream migration period, 2-year-old male and female adults also showed higher GSI and plasma levels of T, estradiol-17beta (E(2)) 11-KT, 17alpha-hydroxyprogesterone and 17alpha,20beta-dihydroxy-4-pregnene-3-one (DHP). In order to test the effects of steroid hormones on migratory behaviors, silascone tube capsules containing 500 microg of T, E(2), 11-KT, DHP, or a vehicle was implanted into smolts, castrated precocious males, or immature parr, and downstream and upstream behavior were observed in artificial raceways in spring and autumn. Downstream behavior of smolts was inhibited significantly by T, E(2) and 11-KT. Upstream behavior was stimulated by T and 11-KT in castrated precocious males and stimulated by T, E(2) and 11-KT in immature parr. These results indicate that T, E(2) and 11-KT are the factors regulating downstream and upstream migratory behavior. In particular, because of its changing patterns in plasma and significant effects, T, the common precursor hormone of E(2) (female) and 11-KT (male), is considered to play central roles in both types of behavior.     

Reproductive cycles in a reared strain of the mummichog, a daily spawner

Annual, lunar, and diel samplings were taken from a strain of mummichog (Arasaki strain) reared in outdoor tanks under natural conditions, to examine gonadal maturity. Gonads of yearling fish were quite immature in September. During late autumn and winter, a gradual increase in the GSI of both sexes was observed, and the growth of cortical alveolus phase oocytes in females and basal spermatogenesis in males progressed. In late February, a rapid increase in the GSI of both sexes, vitellogenesis in females, and active spermatogenesis in males, occurred. The spawning period of the yearling fish was from late March to August judging from the presence of milt-producing males and ovulated females. The spawning period of the underyearling fish started in the same month as the yearlings, but terminated 1 month earlier. Plasma levels of oestradiol-17 β (E₂) in females and testosterone in males were high during the spawning period in the yearlings. In the underyearlings, however, E₂ levels peaked in early spring, and declined in the latter part of the spawning period. Neither a lunar nor semilunar cycle was evident in the reproductive activity of this fish, which proved to be a typical daily spawner. Females showed an apparent daily reproductive cycle; oocyte maturation commenced at about 1200 hours, germinal vesicle breakdown (GVBD) occurred at about 2400 hours, and ovulation was completed by 2400 hours, 24 h after GVBD. Such clear annual and daily reproductive cycles make this strain of mummichog a suitable model for the study of environmental and endocrine regulation of reproductive cycles in marine and estuarine teleosts.     

Correlation between plasma steroid hormones and vitellogenin profiles and lunar periodicity in the female golden rabbitfish, Siganus guttatus (Bloch)

Characteristics of the lunar reproductive cycle in the golden rabbitfish, Siganus guttatus, were determined by histological observations of ovarian development, and immunological measurements of plasma steroid hormones, estradiol-17beta (E2), testosterone (T), 17alpha,20beta-dihydroxy-4-pregnen-3-one (DHP) and 17alpha,20beta,21-trihydroxy-4-pregnen-3-one (20beta-S), and vitellogenin (VTG). Ovarian and plasma samples were collected every week according to the lunar phases from May to July. Weekly change of gonadosomatic index (GSI) showed two peaks at the first lunar quarter in June and July. Yolky oocytes were also observed around this time. Histological observations revealed that the vitellogenic oocytes appeared again 1 week after spawning and developed synchronously. These results suggest that this species is a multiple spawner and the oocyte development is in a group-synchronous manner. Plasma steroid hormones (E2, T, DHP and 20beta-S) and VTG levels changed in parallel with changes in GSI. The peak of plasma VTG level occurred prior to spawning. These cyclic changes of plasma steroid hormones and VTG support the hypothesis that lunar periodicity is the major factor in stimulating reproductive activity of S. guttatus.     

Circadian changes in serum concentrations of steroids in Japanese char Salvelinus leucomaenis at the stage of final maturation

Circadian changes in serum concentrations of testosterone (T), 11-ketotestosterone (11KT), estradiol-17beta (E2), 17alpha,20beta-dihydroxy-4-pregnen-3-one (DHP), 17alpha-hydroxyprogesterone (OHP), cortisol (F) and progesterone (P) were investigated in the spermiated/ovulated Japanese char Salvelinus leucomaenis for over three days using newly developed time-resolved fluoroimmunoassays. Testosterone and DHP in both sex and 11KT in male showed significantly (P<0.05) higher serum levels just before/after onset of darkness (15:00 or 18:00), and the levels during night and daytime were significantly (P<0.05) lower than those of the peak levels. Serum F levels in both sex during dark phase were significantly (P<0.05) higher than those levels during daytime. A surge of serum OHP concentrations in both sexes was observed at the time of twilight (03:00). The peak time of serum T, 11KT and DHP levels were approximately 6 hours prior to those of serum F and OHP levels. Serum E2 in female and P in both sex fluctuated intensely during sampling period, and did not show remarkable changes. These results strongly suggest the existence of circadian-like diel changes in serum T, DHP, F and OHP levels in both sex and 11KT in male, and no variations in serum E2 in female and P in both sex in spermiated/ovulated Japanese char under the stage of final maturation. Furthermore, relationship between circadian rhythms of steroid hormones and spawning behaviors are discussed in the present study.     

Comparative analysis of milt quality and steroid levels in blood and seminal fluid of Persian sturgeon males, Acipenser persicus during final maturation induced by hormonal treatment

Steroids both in seminal fluid (SF) and blood serum (BS) as well as the milt quality (sperm motility and sperm production) were investigated during final maturation of Persian sturgeon. The BS levels of testosterone (T), 11-Ketotestosterone (11-KT), progesterone (P), 17α,20β,21-trihydroxy-4-pregnen-3-one (20βS), cortisol (C) and 17α,hydroxyprogesterone (OHP) elevated after pituitary preparation (PP) treatment and then decreased during stripping period for spermiating males. Such elevations did not occur for non-spermiating individuals and steroids remained in basal levels after PP treatment until the end of stripping period. For both groups (spermiating and non-spermiating fish), the BS levels of 17α,20β-dihydroxy-4-pregnen-3-one (DHP) did not show significant changes during experiment. During stripping period, the values of all tested steroids were significantly lower in SF than in BS of spermiating males. SF levels of 20βS and 11-KT showed a decreasing trend and the other steroids were unchanged during this period. Significant positive correlations were found between the values of 20βs and 11-KT in BS with their levels in SF. Also, BS and SF levels of 20βs and 11-KT were positively correlated with sperm motility characteristics (percentage and duration of motility) and sperm production (sperm density and milt volume), respectively. The results showed the probable involvement of 20βs, P, OHP, T, 11-KT and C in final maturation of Persian sturgeon, especially 20βs and 11-KT had good correlations with qualitative parameters of milt. The lower levels of steroids in SF than those in BS might also be essential for viability of Persian sturgeon spermatozoa. Probably, there are mechanisms that stabilize the concentrations of a number of hormones in the SF.     

Annual changes in testicular development and plasma sex steroids in the captive male dojo loach <Emphasis Type="Italic">Misgurnus anguillicaudatus</Emphasis>

Testicular development in the captive male dojo loach Misgurnus anguillicaudatus was examined monthly in relation to the levels of plasma sex steroids [testosterone (T), 11-ketotestostrone (11-KT), and 17,20β-dihydroxy-4-pregnen-3-one (DHP)]. On the basis of testicular histology, the annual gonadal cycle was found to be divisible into 3 periods: the recovery and proliferation period, which mainly consists of early spermatogenic testis from August to November (reproductive phase I); the preparation period for the next spawning period, which mainly consists of late spermatogenic testis from December to April (reproductive phase II); and the mature period, characterized by a high proportion of mature testis from May to July (reproductive phase III). Individual variability in testicular development was high, and continuous spermatogenesis was observed throughout the year. High levels of plasma T, 11-KT, and DHP were observed during reproductive phase III. 11-KT began to increase in February, while T was present at low levels in reproductive phase II. These results suggest that the physiologically active season of testis development for breeding in the dojo loach is from May to July, although spermatogenesis occurs throughout the year.     

Timing of final oocyte maturation in Acropora and merulinid corals

Final oocyte maturation is a gametogenic process that occurs at the end of oogenesis, which includes germinal vesicle migration (GVM) and germinal vesicle breakdown (GVBD). This process is essential for oocytes to become competent for fertilization and occurs just before spawning. Timing of GVM and GVBD has been extensively studied to understand reproductive timing in various marine organisms. For corals, however, such information remains scarce. Here, we examined the timing of GVM and GVBD in broadcast-spawning corals: two Acropora and six merulinid species, from around the full moon until spawning day(s), at Lyudao, Taiwan in 2019 and 2020. The proportion of oocytes that had completed GVM around the full moon varied among species (14–64%), while the proportion increased to > 80% by 6–7 d after the full moon when many sampled colonies spawned. By contrast, although data are limited, the timing of GVBD indicated a more uniform pattern among species, and the onset of GVBD in the majority of oocytes occurred within 3–10 h before spawning. As GVM and GVBD are prerequisites for fertilization, and probably the spawning itself, the interspecific variation in the timing of GVM likely reflects an interspecies variation in spawning timing. This hypothesis may partially explain the different spawning timing (days) among coral species observed at the study location. Further research is needed to test such a hypothesis, given the limitation of our study with regard to the number of observations, annual variation, and examined coral taxa.

     

Aromatase inhibitor induces complete sex change in the protogynous honeycomb grouper (Epinephelus merra)

The protogynous hermaphrodite fish change sex from female to male at the certain stages of life cycle. The endocrine mechanisms involved in gonadal restructuring throughout protogynous sex change are not clearly understood. In the present study, we implanted maturing female honeycomb groupers with nonsteroidal aromatase inhibitor (AI), Fadrozole (0, 1, and 10 mg/fish) and examined changes in gonadal structures and serum levels of sex steroid hormones 2(1/2) months after implantation. The ovaries of control females had oocytes undergoing active vitellogenesis, whereas AI caused females to develop into functional males. These males had testes, which were indistinguishable in structure from those of normal males, but bigger in size, and completed all stages of spermatogenesis including accumulation of large amount of sperm in the seminiferous tubules. AI significantly reduced the serum levels of estradiol-17beta (E2) and increased levels of testosterone (T), 11-ketotestosterone (11-KT), and 17alpha, 20beta-dihydroxy-4-pregnen-3-one (DHP). Further, AI suppressed in vitro production of E2, and stimulated the production of T and 11-KT in the ovarian fragments of mature female. In the honeycomb grouper, suppression of both in vitro and in vivo production of E2 and degeneration of oocytes by AI suggests that AI induces complete sex change through inhibition of estrogen biosynthesis, and perhaps, subsequent induction of androgen function.     

Ovarian steroidogenesis and the role of sex steroid hormones on ovarian growth and maturation of the Japanese eel

Three sex steroid hormones, estradiol-17β (E2), 11-ketotestosterone (11-KT), and 17α,20β-dihydroxy-4-pregnen-3-one (DHP), are well established as primary estrogen, androgen, and progestin, respectively, in teleost fish. Japanese eel, Anguilla japonica, would be a suitable candidate to study ovarian steroid physiology of fish because the ovarian growth and steroidogenesis is dormant under laboratory condition but can be induced by administration of exogenous gonadotropic reagents. In this review, we summarized our work on the function and production of sex steroid hormones in the ovary of the Japanese eel during ovarian growth and oocyte maturation artificially induced by treatment with extract of salmon pituitary. In vitro and in vivo assays suggest that 11-KT and E2 play primary roles in previtellogenic and vitellogenic growth of oocytes, respectively, whereas DHP is essential for induction of final oocyte maturation. We also reviewed the correlation between ovarian steroidogenesis to produce these sex steroid hormones, serum titers and gene expression.     

Changes in hormonal profile, gonads and sperm quality of Argyrosomus regius (Pisces, Scianidae) during the first sexual differentiation and maturation

In the present study, sexual gonadal differentiation and first sexual maturation of Meagre (Argyrosomus regius) was studied, based upon the annual changes in gonadosomatic index (GSI), gonadal histology, and the plasma steroid hormones, testosterone (T), 11-ketotestosterone (11-KT), and estradiol (E2). In addition, spermatozoa characteristics were evaluated by measuring sperm motility and morphology. Results demonstrated that Meagre completes sex differentiation at 10 to 12 mo of age, and are group-synchronous spawners, which reach puberty at 2 (mean length 26.8 ± 0.7 cm, mean weight 920 ± 75 g; N = 10) and 3 (mean length 35.8 ± 0.8 cm, mean weight 1610 ± 89 g; N = 10) years of age for males and females, respectively. In males, during the sex differentiation period, T levels were significantly higher with respect to those of 11-KT; this suggests that T has a key role in the early phases of the sex differentiation. During the spawning season an increase in plasma concentrations of all hormones was observed with 11-KT levels being significantly higher that those of T. In females, during the sex differentiation period, there was an increase in E2 plasma levels, while during the first spawning season, a significant increase of T and E2 levels were measured. Regarding sperm characteristics, the measured curvilinear velocity (VCL) and straight-linear velocity (VSL), resulted in the same order of magnitude with respect to those measured in other marine fish, while the average path velocity (VAP) was similar to that measured in the European Eel. The head of Meagre spermatozoa presents as oval shaped with a surface area of approximately 3.66 μm² and a perimeter of approximately 6.65 μm. All these findings represent an important basis for further investigation on the reproductive biology of this specie and may assist the farmers to improve seed production in aquaculture.     

Endocrine correlates of intra-specific variation in the mating system of the St. Peter's fish (Sarotherodon galilaeus)

The Challenge Hypothesis postulates that androgen levels are a function of the social environment in which the individual is living. Thus, it is predicted that in polygynous males that engage in social interactions, androgen levels should be higher than in monogamous animals that engage in parental care. In this study, we tested this hypothesis at the intra-specific level using a teleost species, Sarotherodon galilaeus, which exhibits a wide variation in its mating system. Experimental groups of individually marked fish were formed in large ponds with different operational sex-ratios (OSR) to study the effects of partner availability on blood plasma levels of sex steroids [11-ketotestosterone (11-KT), testosterone (T), and 17,20beta-dihydroxy-4-pregnen-3-one (17,20beta-P)] and gonadosomatic index (GSI). Polygyny mostly occurred in the female biased OSR groups. 17,20beta-P and gonadosomatic index did not differ among OSR groups. However, 11-KT was high in male biased OSR and positively correlated with aggressive challenges, thereby supporting the central postulate of the Challenge Hypothesis. The results of T were the inverse of those of 11-KT, probably because 11-KT is metabolized from T. 11-KT levels of polygynous males did not differ neither from those of monogamous males, nor from those of males that participated in parental care. These results do not support the expected relationships between polygyny, parental care, and androgen levels. The differences from expectations for 11-KT may be related to the fact that in S. galilaeus, the mating and the parenting phase are not clearly separated and thus, males may still fight and court while they are brooding.     

Plasma Sex Steroid Levels and Steroidogenesis in the Gonad of the Self-fertilizing Fish Rivulus marmoratus

Synopsis The mangrove killifish, Rivulus marmoratus, is the only known self-fertilizing vertebrate. This species is sexually dimorphic; sexually mature individuals are either hermaphrodite or primary and secondary males. Although the mangrove killifish has a unique reproductive strategy, there has been no study on the reproductive endocrinology of this species. Thus we investigated plasma sex steroid hormone levels and steroidogenesis in the gonads of R. marmoratus by enzyme linked immunosorbent assay (ELISA). Plasma 17β-estradiol (E2) and 11-ketotestosterone (11-KT) were detected both in hermaphrodite and in primary male. Ovarian follicles (follicle-enclosed oocytes) from hermaphrodites, which were categorized into early yolk stage and late yolk stage, and testis tissue of primary males were cultured with different concentrations of 17α-hydroxyprogesterone (OHP) or testosterone (T) for 24 h. Production of T, E2, 11-KT and 17α-20 β-dihydroxy-4-pregnen-3-one (17α,20β-P) in the medium from tissue culture were measured by ELISA. Early and late ovarian follicles of hermaphrodites and testis pieces of primary males synchronously secreted E2, 11-KT, and 17α,20β-P following incubation with OHP or T. We conclude that both hermaphrodite and primary male of the mangrove killifish secrete estrogen, androgen, and progestin synchronously.     

Hormonal and behavioral correlates of morphological variation in an Amazonian electric fish (Sternarchogiton nattereri: Apteronotidae)

The weakly electric fish from the main channel of the Amazon river, Sternarchogiton nattereri, offers a striking case of morphological variation. Females and most males are toothless, or present only few minute teeth on the mandible, whereas some males exhibit exaggerated, spike-like teeth that project externally from the snout and chin. Androgens are known to influence the expression of sexually dimorphic traits, and might be involved in tooth emergence. In this study we assess the relationship in S. nattereri between morphological variation, 11 ketotestosterone (11-KT) and testosterone (T). We also examine relationships of morphology and androgen levels with electric organ discharge (EOD) frequency, reproductive condition, and seasonality. Our main finding is that male morph categories differed significantly in plasma concentrations of 11-KT, with toothed males showing higher levels of 11-KT than toothless males. By contrast, we did not detect statistical differences in T levels among male morph categories. Reproductive condition, as measured by gonadosomatic indexes (GSI), differed across two sample years, increased as the season progressed, and was higher in toothed males than in non-toothed males. EOD frequency was higher in toothed males than in either toothless males or females. Taken together, our findings suggest that S. nattereri male sexual characters are regulated by 11-KT levels, and that both morphology and androgens interact with reproductive condition and EOD frequency in ways that vary within and across reproductive seasons.     

Apparent semi-lunar spawning rhythmicity in a brackish cardinalfish

The purpose of the present study was to examine the lunar-related spawning rhythmicity of the amboina cardinalfish Apogon amboinensis, which is a euryhaline species inhabiting mangrove creeks in the Indo-Pacific area. During the reproductive season, the gonado-somatic index increased towards and peaked within a week of the first and last quarter moon. Histological observations of the ovaries also showed development of yolk-laden oocytes towards the first and last quarter moon; postovulatory follicles, an indicator of spawning, appeared around these lunar phases. Fish with immature oocytes in the ovary were also collected in the same lunar phases, suggesting that at least two fish populations with different oocyte development stages exist at any given time. The levels of two steroid hormones secreted from the ovarian pieces into a culture medium with human chorionic gonadotropin were measured using enzyme-linked immunosorbent assay (ELISA). The level of oestradiol-17β increased around the new and full moon periods. On the other hand, 17α,20β-dihydroxy-4-pregnen-3-one levels increased around the first and last quarter moon, suggesting that the fish are actively undergoing vitellogenesis and final oocyte maturation around the respective lunar phase. These results suggest that with the 1 month ovarian development process, A . amboinensis exhibits a semi-lunar spawning pattern with peaks around the first and last quarter moon. When A . amboinensis were reared under laboratory conditions without the tidal stimuli, mouth-brooding was initiated in 13 of 20 males within a week of the first and last quarter moon. The possibility of a lunar-related endogenous rhythm in A . amboinensis is discussed.     

Perception and possible utilization of moonlight intensity for reproductive activities in a lunar-synchronized spawner, the golden rabbitfish

Rabbitfishes are known to spawn synchronously around the species-specific lunar phase. It is considered that they perceive and utilize cues from the moon in order to be synchronized gonadal development and spawning with the lunar cycle. Using the golden rabbitfish, Siganus guttatus, which spawns synchronously around the first quarter moon during the reproductive season, we measured the fluctuation of melatonin levels and examined the response of the fish to moonlight intensity. Daily fluctuation of melatonin concentration in the blood of golden rabbitfish showed low levels during daytime and high levels during night-time, suggesting that melatonin functions in the perception and utilization of photoperiod. Plasma melatonin concentration at the new moon was higher than that at the full moon. When the fish were exposed to moonlight at midnight of the both moon phases, the melatonin concentrations decreased to the control levels. These results show that the fish possibly perceive moonlight intensity and plasma melatonin fluctuates according to 'lightness' at a point of night. At the first spawning period (experiment was started one month before the spawning), the fish reared under natural conditions spawned at the expected spawning dates, whereas the fish reared under the constant darkness and lightness of night did not spawn. At the second spawning period (experiment was started 2 weeks before the spawning), the fish reared under the conditions of natural and constant darkness of night spawned but not that of constant lightness of night. It is possible that night conditions are related to synchronous gonadal development and spawning in the golden rabbitfish.     

Androgens stimulate sex change in protogynous grouper,Epinephelus coioides: spawning performance in sex-changed males

We examined the efficacy of androgens (1.0 mg/kg body mass), testosterone (T), 11-ketotestosterone (11-KT), 17alpha-methyltestosterone (MT), testosterone propionate (TP) or androgen mixture (T, MT and TP in an equal ratio), for induction of sex change in protogynous orange-spotted grouper, Epinephelus coioides. The spawning performance in sex-changed males was also investigated. MT and androgen mixture at a dose of 1.0 mg/kg BW induced a sex transition and completion of spermatogenesis up to the functional male phase. The androgen mixture was most effective. Significantly, higher plasma T levels were found in MT and androgen mixture groups compared to control and other androgen implantation (T, TP or 11-KT) groups. We found that plasma levels of estradiol-17beta (E2) or 11-KT were not different among treated groups. Sex-changed males could successfully fertilize mature eggs. Fertilization and hatching rates were of 23.5-70.4% and 8.4-44.6%, respectively. The data demonstrated that induction of sex change by exogenous androgens in groups could apply to the aquaculture field for seed production.