Annual cyclic variations in some biochemical constituents of seminal vesicle and testis of the catfish Heteropneustes fossilis (Bloch): a study correlating plasma testosterone level

In Heteropneustes fossilis, significant annual variations were observed in seminal vesicle-somatic index (SVSI), gonadosomatic index (GSI), concentrations of total proteins, hexosamines, fructose and glucose in both SV and testis, and in plasma testosterone with high values in late prespawning-early spawning phases (June-July) and low or undetectable levels in resting phase (December-January) except for glucose. There is an inverse relationship between the annual patterns of fructose and glucose with fructose dominant in the prespawning and early spawning phases (June-July), and glucose in the resting phase (November-January). The increase in the concentrations of SV and testicular protein, hexosamine and fructose can be correlated with the increase in testosterone concentration on one hand and with the increase of SVSI and GSI, on the other. The decrease in glucose level in the recrudescent phase may be due to its increased conversion into fructose, the main seminal sugar in this species.     

Sex-specific metabolic changes in the annual reproductive cycle of a freshwater catfish

Sex-specific enzymatic and other biochemical changes were studied in the annual reproductive cycle of the freshwater catfish, Clarias batrachus. Citrate synthase (CS) activity of brain, liver and skeletal muscle was maximum in spawning and minimum in postspawning showing a sharp decline in aerobic capacity after spawning. Similar CS activity in remaining phases of the annual reproductive cycle reflects similar energy need during regressed, preparatory and prespawning phases. Glucose 6-phosphate dehydrogenase (G6-PDH) activity declined in spawning and postspawning indicating a possible decrease in lipid and nucleic acid syntheses. The subsequent increase in G6-PDH activity with onset of resting and maintenance of the increased level throughout preparatory and prespawning phases shows restoration of biosynthetic activity. Higher activity of G6-PDH in female than male may be to satisfy a greater biosynthetic need of female reproduction and breeding. The decreased RNA content of tissues showed reduction in protein synthesis capacity during spawning and subsequent increase through postspawning until resting phase. The RNA content of brain and liver was higher in female than male during preparatory and prespawning, which may be associated with higher protein synthesis requirement of female for preparation of reproductive activities. The requirement based sex related changes in metabolism of catfish may be enzyme, tissue or reproductive phase-specific.     

Variation in biochemical composition during gonad maturation of the tropical abalone Haliotis varia Linnaeus 1758 (Vetigastropoda: Haliotidae)

Biochemical changes in the body components during gonad maturation of the tropical abalone Haliotis varia were investigated using wild collected specimens from the Gulf of Mannar, on the southeast coast of India. The gonadosomatic index (GSI) and the hepatosomatic index (HSI) showed negative correlations throughout the study period as well as during the progression of gonad maturation stages. The highest GSI for both the sexes were in the ripe stages followed by late maturing stages. The HSI ranged from 2.97 to 6.71 in females, and 3.55 to 5.09 in males. Among the biochemical components analysed, lipid and carbohydrate contents showed significant variations in the different tissues of H. varia during the progress of gonad maturation. The highest protein content was in the foot muscle and the lowest was in the digestive gland. Total lipids in the ovary were always higher compared with that of the testis and the values ranged from 12.60 to 26.49%, registering the highest value in the ripe ovary. Gonad carbohydrate content was lower when the lipid content was higher, suggesting the conversion of carbohydrate to lipids. The present study demonstrates the role of nutrient translocation between body parts as an essential part of the reproductive physiology of abalone.     

Annual reproductive cycle of a bitterling, Tanakia tanago, reared in an outdoor tank

From June 2000 to September 2001, we investigated the presence of eggs spawned in Margaritifera laevis and the seasonal changes in the gonads of Tanakia tanago. Eggs were observed from mid-March to mid-September. In females with a shrunken ovipositor, as the GSI gradually increased, most ovaries were in the prespawning phase (Oct-Mar). As the GSI increased further, most ovaries were in the early spawning phase (Mar-Jun). As the GSI gradually deceased, ovaries in the late spawning phase appeared (Jun-Sep). When the GSI was very low, most ovaries were in the postspawning phase (Sep-Oct). In males, when the GSI was low, most testes were in the early prespawning phase from Oct-Dec. As the GSI gradually increased, most testes were in the late prespawning phase (Dec-Jan). As the GSI increased further, testes were in the early spawning phase (Jan-Jun). As the GSI gradually decreased, amost testes were in the late spawning phase (Jun-Sep). When the GSI was very low, most testes were in the postspawning phase (Sep-Oct). These results indicate that T. tanago has a distinct annual reproductive cycle and is a spring-autumn spawner. Based on the relationship between reproductive activity and environmental factors, the spawning season of T. tanago appears to be initiated by increasing temperature and / or longer days in spring and to be terminated by shorter days in autumn.     

Seasonal correlative changes between sex steroids and lipid levels in the freshwater female catfish, Heteropneustes fossilis (Bloch)

Circannual variation in plasma levels of testosterone (T), oestradiol-17β(E₂) and 17α-hydroxy-progesterone (17α-OHPg) were measured in female, Heteropneustes fossilis . T and E2 levels increased during the preparatory phase, reached their peak in the early prespawning phase and fell during the late prespawning phase to reach their lowest levels post-spawning. 17a-OHPg was detected from the late preparatory to the late spawning phase showing its peak during the early spawning phase. The levels of free fatty acids (FFA), monoglycerides (MG), diglycerides (DG), triglycerides (TG), phospholipids (PL), free cholesterol (CF)and esterified cholesterol (CE) were estimated in liver, plasma and ovaries. The preparatory phase showed hepatic lipogenic activity while during the prespawning phase TG lipolysis was increased by FFA. Ovarian CF was depleted by enhancing plasma E, levels during the prespawning phase. The gonadosomatic index reached its peak during spawning.     

Seasonal cycles in total chemical composition of two Lake Baikal benthic-pelagic sculpins (Cottocomephorus, Cottoidei)

Annual cycles in chemical composition of the body, liver, gonads, red and white muscles were determined for two medium fat sculpins, Cottocomephorus grewingki and C. inermis , endemic to Lake Baikal. Their total lipid content ranged from 3 to 9% during the year. The content of defatted dry substance was 14–17%, similar to the protein content of the other Baikalian cottoid fishes. The prespawning period was characterized by a positive lipid and protein balance in both species. In C. grewingki the liver performed largely a metabolic function, whereas in C. inermis it served also as a storage site for lipid reserves. During spawning, total body lipids of females of both species showed a two- to threefold decrease. Males of C. grewingki guarding nests deplete greatly their total body lipids, which decrease seven- to ninefold by the time of larval hatching in comparison with the prespawning period, and constitute 1–2%. After spawning, lipid reserves of C. grewingki were quickly restored to the initial level (from about 3 to 9%) and maintained during the long sexual maturation period. In C. inermis total body lipids increased only twofold in comparison to those observed during the spawning period.     

Lipid dynamics and plasma level changes of 17beta-estradiol and testosterone during the spawning season of gilthead seabream (Sparus aurata) females of different ages

The present study was undertaken to evaluate whether the age of brood stock females of Sparus aurata affects the mobilization of lipids from muscle and liver towards the gonads to aid in oocyte development. Taking into account the role some hormones play in lipid mobilization the production of 17beta-estradiol (E2) and testosterone (T) was also measured throughout the spawning season. Four groups of fish were established consisting of 3-, 4-, 5- and 6-year-old females (1.3, 1.5, 2.3 and 2.8 kg average weight, respectively), maintained in separate tanks together with a number of two-year-old males. The results for all four groups showed no variations in fish total length between the beginning and end of the experimental period. However, losses were recorded both of body weight and condition factor. In general terms, there were no significant differences in the plasma levels of E2, T and the gonadosomatic (GSI) and hepatosomatic (HSI) index among the four groups throughout the spawning season. In all groups, the plasma levels of E2, T, GSI and HSI were at their lowest at the end of spawning. Between December (pre-spawning) and March (mid-spawning), all groups suffered depletion of the lipid content of liver and muscle, while gonad lipid content remained constant. The mobilization of lipids from liver and muscle to contribute to the upkeep of the gonadal lipid involved the mobilization of all the fatty acid groups, saturates, monoenes, n-6, n-3, and n-3 HUFA. A good correlation existed between the percentage of the various fatty acid groups transferred from muscle and the age of the reproductive females. However, the greater lipid mobilization from muscle matching the greater age of the reproductive females did not result in greater lipid gonadal reserves or greater body size, suggesting that reproduction on the part of older females requires greater effort. Despite this, the results as a whole indicated that lipogenic capacity, considered as the mobilization of lipids from muscle and liver towards the gonad for the development of oocytes, is unaffected by age in reproductive 3- to 6-year-old gilthead seabream females.     

Sexual cycle and seasonal changes in the ovary of the red mullet, Mullus surmuletus, from the southern coast of Brittany

The reproductive cycle of the red mullet is described on a macroscopic scale in terms of the GSI, HSI and K , and on a microscopic scale in terms of histological changes in the ovary and changes in the oocyte size frequency distribution. On the southern coast of Brittany the red mullet breeds in May and June. During oogenesis, the previtellogenic period lasts 6 months and the secondary phase of vitellogenesis no more than 3 months. When spawning commences the process of vitellogenesis ceases and up to 20% of the vitellogenic oocytes become atretic. Prior to spawning a single batch of oocytes can be seen to be entering secondary vitellogenesis. During the immediate prespawning and spawning periods the existing vitellogenic oocytes mature but there is no recruitment from the stock of previteilogenic oocytes. This results in a gap or hiatus in the oocyte size frequency distribution between previtellogenic and vitellogenic oocytes within which there are very few resting or maturing oocytes. The red mullet appears to be a determinate spawner, in which egg loss through atresia considerably reduces the potential fecundity.     

Annual Variations of Gonadotropin Content and Ovarian Development of Feral Female Catfish, Silurus asotus, in Central China

The Japanese catfish Silurus asotus is widely distributed throughout the freshwaters reservoirs, lakes and rivers of China, Korea and Japan, and is a commercially valuable aquaculture fish in some regions of China and Japan. We studied seasonal variations of gonadotropin (GtH) content of the plasma and pituitary as well as ovarian development. Plasma GtH titres increase in April in the Pearl River and in May in the Liao River in central China. Annual cycles of plasma GtH levels in both rivers are the same, with a gradual decrease after ovulation with the lowest values observed in September (in the Liao River) or October (in the Pearl River). Plasma GtH levels increase gradually in the early stages of ovarian development, with the highest values observed during the late stages of development, and with the lowest GtH titres observed during ovarian regression in both rivers. GtH content of the pituitary remained very high through the spawning period, with the highest titres observed in March in the Liao River, and in July in the Pearl River. As with plasma GtH, the lowest concentrations of pituitary GtH were observed during stages when the ovary was regressed. We analyzed the relationships between plasma and pituitary GtH and reproductive conditions, such as gonadosomatic index (GSI), hepatosomatic index (HSI), oocyte diameter (OD) and oocyte weight (OW). The results indicate that annual changes of GtH content of the plasma and pituitary paralleled GSI, OD and OW, but were negatively correlated with HSI in feral female catfish.     

Spawning and season affect lipid content and fatty acid composition of ovary and liver in Japanese catfish (Silurus asotus)

The influences of spawning and season on lipid content, lipid classes, and fatty acid composition were assessed in ovary and liver of wild and cultured Japanese catfish (Silurus asotus). The lipid content (7.3+/-1.6 g/100 g wet wt.) of ovary from wild catfish at spawning was higher than that at post-spawn. However, no influence of spawning on the lipid content of liver was observed. Docosahexaenoic acid [DHA, C22:6(n-3)] in ovary lipids was 12.3+/-0.5% of total fatty acids. The percentage of n-7 monounsaturated fatty acids in triacylglycerol from the ovary and liver in the spawning season was high. Percentages of C22:6(n-3) in phosphatidylcholine and phosphatidylethanolamine from ovary were higher during spawning than after spawning. No significant differences were observed in the lipid content of ovary and liver from cultured catfish between seasons (summer vs. winter). Content of arachidonic acid (C20:4n-6) in ovary and liver from cultured catfish was higher in summer than in winter. There were differences in lipid classes of ovary and liver by spawning and season. These results suggest that the lipid metabolism in Japanese catfish is greatly influenced by spawning and season.     

Importance of photoperiods in the regulation of ovarian activities in indian major carp Catla catla in an annual cycle

The present study attempted for the first time to explore the importance of photoperiod in the regulation of seasonal ovarian functions in any subtropical major carp. Adult Indian major carp Catla catla were transferred to a long photoperiod (LP; LD 16:8) or a short photoperiod (SP; LD 8:16) for 30 days on 4 dates corresponding to the beginnings of 4 reproductive phases in an annual cycle, and responsiveness of the ovary was evaluated by comparison with the gonadal weight (I(G)), relative number of developing oocytes, serum levels of vitellogenin, and the activity of 2 important steroidogenic enzymes, that is, Delta(5)3beta-hydroxysteroid dehydrogenase and 17.beta-hydroxysteroid dehydrogenase, in the ovary of fish in a natural photoperiod. Exposure of fish to LP during the preparatory phase (February-March) resulted in a significant (p < 0.001) increase in the values of vitellogenin and in the activity of both the steroidogenic enzymes but not in the ovarian weight and in the relative number of different stages of oocytes. A more stimulatory influence of LP was noted during the prespawning phase (April-May), when precocious maturation of ovary was evident from a significant (p < 0.001) rise in the values of each studied features of ovarian functions. However, no ovarian response was found when the fish were transferred to LP during the spawning (July-August) and the postspawning (September-October) phases. On the other hand, the SP was found to have an inhibitory influence on ovarian growth and maturation during the prespawning and the spawning phases or to have no influences on ovarian functions during the preparatory and the postspawning phases of an annual cycle. The results of our study provide the first evidence that photoperiod per se plays an important role in the seasonal maturation of ovary in a subtropical freshwater major carp.     

Seasonal changes in some blood chemistry parameters and in relative liver and gonad weights of pike (Esox lucius L.) from the River Danube

Samples from a natural population of pike (Esox lucius L.) from the River Danube were used in a 12-month study to determine seasonal variations in biochemical parameters of pike blood sera, hepatosomatic index (HSI) and gonadosomatic index (GSI). The ranges of enzyme activities for sample means were: aspartate aminotransferase (ASAT) 252.0–583.8 U 1⁻¹, alanine aminotransferase (ALAT) 4.9–11 -2 U1 and alkaline phosphatase (AP) 39.5–91.8 U1⁻¹. The ranges of other parameters analysed in serum were total protein 27.7–40.1 g 1 ¹, urea 0.57–l.52 mmol 1 ¹ and creatinine 21.2–118.6 μmol 1 ¹. The range of sample means for HSI and GSI were 1.28–4.16 and 0.07–20.2 respectively. Temperature ranged from 4.5 to 23.5°C. The activity of serum AP was positively correlated to water temperature in males only, while urea and creatinine showed a positive correlation to water temperature in individuals of both sexes. GSI was correlated significantly with HSI in females. Total protein reached the lowest values during the spawning period, while creatinine levels depended on both the sex and season.     

Seasonal effects of melatonin on ovary and plasma gonadotropin and vitellogenin levels in intact and pinealectomized catfish, Clarias batrachus (Linn)

Effects of daily administration of melatonin for 15 days were evaluated with respect to ovarian activities and plasma gonadotropin (GtH II) and vitellogenin (Vg) levels in intact (INT) and pinealectomized (Px) female catfish, C. batrachus, during preparatory (April), prespawning (May and June), spawning (July) and post-spawning (September) periods. Px (saline control groups) caused a stimulatory effect during preparatory (with respect to Vg synthesis and incorporation) and prespawning (with respect to Vg synthesis) periods whereas no effect was observed during spawning and post-spawning periods with respect to the reproductive parameters studied. During April, melatonin-treatment significantly decreased plasma GtH II levels and percentage of vitellogenic oocytes without any significant changes in plasma Vg levels and gonadosomatic index (GSI). During early prespawning period, in May, 50microg melatonin brought about a significant reduction in plasma GtH II levels in INT group, whereas 100microg caused a decrease in all parameters; on the other hand, in Px groups both dose levels proved to be inhibitory. In June (late prespawning period) melatonin-treatment could not bring about any change in GSI and plasma Vg levels compared to the control groups regardless of Px but plasma GtH II and mean number of yolky oocytes were significantly reduced in melatonin-treated INT group. During spawning period (July) melatonin inhibited the GSI, mean number of yolky oocytes and plasma GtH II levels without affecting plasma Vg levels. In September (post-spawning period), melatonin did inhibit both GSI and plasma GtH II levels. The results, thus, indicate that melatonin showed variable effects (inhibitory and/or no effect) to GSI, mean number of yolky oocytes and plasma Vg levels but a consistent inhibiton of plasma GtH II levels indicating that melatonin may control the reproduction by blocking the GtH II release from the pituitary via affecting the hypothalamo-hypophysial axis.     

Plasma sex steroids and gonadosomatic index variations during ovarian development of female wild yellowfin seabream (Acanthopagrus latus)

The yellowfin seabream (Acanthopagrus latus) has a good potential for mariculture in Iran, so studies on various aspects of its culture has been carried out. In this study, the characteristic of reproduction in this species was investigated. The involvement of steroid hormones in the development of gonads was assayed by sampling blood and gonad tissue in 85 females of A. latus in fish caught from the Musa Creek, north-west Persian Gulf from October 2010 to May 2011. Gonadosomatic index (GSI) and hepatosomatic index (HSI) were recorded. Developmental stages were associated with changes in sex steroids, GSI and HSI. GSI and HSI began to increase in November (immature stage) and reached the highest value in March (ripe stage), decreasing sharply in April (spent stage). Plasma values of 17β-estradiol (E2) levels reached their highest levels in spawning females in March and then decreased in April. Progesterone levels were low through ovarian development, reached a maximum simultaneously with testosterone in February (mature stage) and then decreased in March (ripe stage). The seasonal changes observed in plasma steroid levels and GSI reflected the pattern of oocyte development and the spawning behavior of yellowfin seabream and were typical of the patterns described in most multiple spawners studied to date.     

Seasonal migrations and reproductive patterns in the lake sturgeon, Acipenser fulvescens, in the vicinity of hydroelectric stations in northern Ontario

This study was conducted in order to evaluate seasonal migratory behaviour and reproductive pattern of lake sturgeon in a confined region of the Mattagami River system in northern Ontario where river flow is regulated by hydroelectric works. Radio tracking and the systematic sampling of lake sturgeon using gill nets indicated that the distribution of fish throughout the study site varied on a seasonal basis. This distribution was related to the migration of individuals to potential spawning sites in the spring, a post-spawning dispersal to feeding areas and late summer migration to an area of concentration on the Groundhog River which is a tributary of the Mattagami River. There was a high proportion of fish (about 50%), within the size range of reproductively active fish, found in the vicinity of suitable spawning habitat during early May. Measurement of the gonadosomatic index (GSI) and plasma sex steroid hormone levels revealed a divergent pattern of reproductive development between the sexes. Female sturgeon exhibited a prolonged period of ovarian regression following spawning. Resumption of ovarian development was not evident until September and was characterized by an increased GSI and plasma levels of testosterone and 17β-estradiol. In contrast, male lake sturgeon began testicular recrudescence within one month of spawning with the GSI reaching prespawning levels by September; reproductive hormones were at prespawning levels by the end of June. It seems that hydroelectric works has complex effects on sturgeon in the Mattagami system. The extensive migratory behaviour of lake sturgeon within the study area make it prone to impingement or entrainment whereas the altered river flow appears to enhance reproductive development. This revised version was published online in August 2006 with corrections to the Cover Date.     

Lipid and fatty acid content in wild white seabream (Diplodus sargus) broodstock at different stages of the reproductive cycle

The lipid and fatty acid content of the gonads, liver and muscle of wild white seabream males and females was studied at different stages of the reproductive cycle. Samples were taken from mature white seabream at pre-spawning (November), mid-spawning (March) and post-spawning (June) stages. The results showed that lipid accumulates in gonads and muscle from November to March. The gonadosomatic index (GSI) was also increased during this period. Male gonads showed a greater increase in polar lipid (PL) than neutral (NL), while female gonads displayed the reverse. The increase in both neutral and polar lipid was higher in the muscle of males than in females. In the same period, male livers showed no changes either in lipid content or the hepatosomatic index (HSI), while female livers registered an increase in both lipid content and HSI. Between March and June, in both males and females, total, neutral and polar lipid decreased sharply in the gonads and muscle. Muscular lipid content reduction was more pronounced in males than females. On the other hand, the lipid content of the liver in males and females remained relatively constant. In general terms, the amounts of major fatty acids (16:0, 18:1n-9, 20:5n-3 and 22:6n-3) in gonadal and muscular polar and neutral lipid in both males and females increased from November to March and declined thereafter. Variations of the liver fatty acid content were less extreme. In the period from mid-spawning to post-spawning, the presence of 20:4n-6 in polar and neutral lipid increased to a notable extent in all organs studied.     

Oogenesis in the bluefin tuna,Thunnus thynnus L.: a histological and histochemical study

Histology and histochemistry are useful tools to study reproductive mechanisms in fish and they have been applied in this study. In the bluefin tuna, Thunnus thymus L., oocyte development can be divided into 4 principal phases based on the morphological features of developing oocytes and follicles. The primary growth phase includes oogonia and basophilic or previtellogenic oocytes classified as chromatin-nucleolus and perinucleolus stages. The secondary growth phase is represented by vitellogenic oocytes at early (lipid globule and yolk granule 1), mid (yolk granule 2) and late (yolk granule 3) vitellogenesis stages. The maturation phase involves postvitellogenic oocytes undergoing maturation process. During the spawning period, both postovulatory follicles, which indicate spawning, and atretic follicles can be distinguished in the ovary. Carbohydrates, lipids, proteins and specially those rich in tyrosine, tryptophan, cystine, arginine, lysine and cysteine, as well phospholipids and/or glycolipids and neutral glycoproteins were detected in yolk granules. Moreover, affinity for different lectins (ConA, WGA, DBA and UEA) was detected in vitellogenic oocytes (yolk granules, cortical alveoli, follicular layer and zona radiata), indicating the presence of glycoconjugates with different sugar residues (Mannose- Man- and/or Glucose -Glc-; N-acetyl-D-glucosamine- GlcNAc- and/or sialic acid- NANA-; N-acetyl-D-galactosamine- GalNAc-; L-Fucose -Fuc-). Histochemical techniques also demonstrated the presence of neutral lipids in globules (vacuoles in paraffin sections) and neutral and carboxylated mucosubstances in cortical alveoli. By using anti-vitellogenin (VTG) serum, immunohistochemical positive results were demonstrated in yolk granules, granular cytoplasm and follicular cells of vitellogenic oocytes. Calcium was also detected in yolk granules and weakly in follicular envelope. In females, the gonadosomatic index (GSI) increased progressively from May, during early vitellogenesis, until June during mid and late vitellogenesis, where the highest values were reached. Subsequently, throughout the maturation-spawning phases (July), GSI decreased progressively reaching the minimal values during recovering-resting period (October).     

Pituitary-gonadal Relationship in the Catfish Clarias batrachus (L): A Study Correlating Gonadotrophin-II and Sex Steroid Dynamics

A heterologous radioimmunoassay was developed for measuring gonadotrophin-II (GTH-II) in the catfish Clarias batrachus. Serum and/or pituitary levels of GTH-II showed significant annual/seasonal variations in male and female catfish, which could be correlated with both gonadosomatic index and/or serum testosterone level. GTH-II was not detected in resting phase, increased during gonadal recrudescence to peak values in late prespawning /spawning phases, and declined to low values in postspawning phase. During gonadal recrudescence, the pituitary and serum levels of GTH-II maintained positive or inverse relationships implying differential rates of hormone release and synthesis/storage. Gonadectomy resulted in increased release of GTH-II; the release pattern varied in females and hemi-castrated or completely castrated males. In females, the GTH-II increase followed a distinct biphasic pattern with the peak rise at week 4 of ovariectomy. In males, castration resulted in significant rise of serum GTH-II levels at all duration except week 5, but the magnitude of the rise was higher in completely castrated fish (weeks 1, 2 and 3). Testosterone replacement in 3-week hemi-castrated fish restored the GTH-II level to that of the sham control vehicle group. In intact fish, administration of testosterone elicited an increase in serum GTH-II levels in the low dose (0.25 and 0.5 mug / g BW) groups and no change in the high dose (1.0 mug / g BW) group. Methallibure treatment inhibited GTH-II levels in a dose-dependent manner. The reduction was greater in males. Withdrawal of the drug treatment restored the GTH-II and testosterone levels after 15 days in the low dose group (2 mug / g BW). The results indicate that there exists a dynamic positive or negative feedback relationship between gonadal steroids and GTH-II, which is essential to control the release and availability of circulating GTH-II.     

Changes in ovarian development and plasma levels of sex steroid hormones in the wild female Japanese sardine (Sardinops melanostictus) during the spawning period

In order to clarify the spawning pattern of Japaneses sardine ( Sardinops melanostictus ) during the spawning period, changes in ovarian histology, frequency distributions of oocyte diameter and plasma levels of oestradiol-17β (E₂) and 17 a ,20β-dihydroxy-4-pregnen-3-one (17 a ,20β-diOH-P) were examined in female fish captured in the region off Kyushu and Shikoku in Japan. With the development of the ovary, the gonadosomatic index (GSI) increased gradually and the size of oocytes became larger. When the GSI exceeded 13, the translucent hydrated eggs began to dominate and ovulation subsequently occurred. After ovulation, GSI decreased to less than 3. Post-ovulatory follicles were found only in the lower GSI ranges and atretic oocytes were always observed in the ovary. Plasma E₂ levels increased along with ovarian development but decreased after completion of yolk accumulation. On the other hand, 17 a ,20β-diOH-P showed the highest level just before and after ovulation. Ovarian histology and hormonal profiles suggest that the sardine spawns repeatedly during the spawning period. Based on the concentration of 17a,20β-diOH-P, the female Japanese sardine was estimated to ovulate before the middle of the night.     

In vivo and in vitro effects of oestradiol-17β on lipid metabolism in Notemigonus crysoleucas

The effects of oestradiol-17β on the gonosornatic index, liver size, hepatic and body lipid levels in the cyprinid teleost, Notemigonus crysoleucas , were investigated. Administration of oestradiol to female TV. crysoleucas during the gonadal preparatory and prespawning seasons stimulates increases in ovarian size. During the early spawning season oestradiol therapy results in a reduction of ovarian gonosomatic index. Oestrogen treatment of males causes a suppression of testicular growth. In female fish exposed to long (15-5L/8-5D) or intermediate (12L/12D) photoperiods oestradiol increases body fat reserves. At short photoperiods (9L/15D) oestrogen treatment of females results in body fat store depletion Low doses deplete and high doses of oestradiol increase body lipid reserves in male fish. The hepatosomic index increases in both male and female fish following oestrogen treatment. Oestradiol therapy during the gonadal preparatory season, but not during the prespawning season, increases total liver lipids. The in vitro effects of oestradiol on liver lipid and carbohydrate metabolism were also examined. Under the conditions used in these experiments, lipid depletion was observed in liver slices incubated with or without oestradiol. Pretreatment of fish with oestradiol before liver tissue was removed drastically reduced in vitro lipid depletion. Oestradiol retards the gluconeogenesis and glycogenesis seen in liver slices incubated in a hormone-free medium.