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The physiological state of mature brood fish is a determining factor for achieving and stimulating a successful spawning process in captivity. In this 2- year investigation, the physiology of mature Liza ramada females was examined throughout the day at various times (24 hours) to ascertain the most suitable time for obtaining mature females raised in both saline water and fresh water in addition to handling them during the spawning season. In addition, blood concentrations of hormones involved in growth, acclimatization, and response to stress, as well as the levels of glucose, total protein, albumin, and the albumin: globulin ratio of L. ramada mature females were all investigated with respect to the factor of time during a period of 24hours. The highest levels of growth hormone, thyroxine, triiodothyronine, prolactin, cortisol, total protein and albumin were recorded at 12 midday and 6 in the morning for mature L. ramada females raised in both saline water and fresh water, respectively. These recorded levels were suitable for attaining a successful spawning and concurrently stimulating the process for L. ramada raised in captivity. Average levels of glucose were recorded for these fish at the aforementioned times. Low levels of the mentioned hormones, total protein, and albumin were observed at 6PM in fish raised in both saline and fresh waters. These hormones play a significant role in growth, acclimatization, stress response during handling, and stimulating spawning of L. ramada. In conclusion, it was proved that the optimal times for obtaining and handling mature L. ramada females during spawning induction are at 12PM for fish raised in saline water and 6AM for fish raised in fresh water. [ABSTRACT FROM AUTHOR]

Hypophyseal homogenate of common carp is considered one of the different hormonal sources for spawning induction in the teleosts. The present work aimed to measure the hormonal concentration of the hypophysis in different carp species, which can be used as a source of hormones for spawning induction in teleosts. The hypophysis of different mature carp species (both males and females); namely, common carp (Cyprinus carpio), grass carp (Ctenopharyngodon idella) and silver carp (Hypophthalmichthys molitrix) were evaluated biochemically to discuss their hormonal source. Five hormones in the pituitary gland, including: adrenocorticotropin hormone (ACTH), prolactin hormone (PRL), growth hormone (GH), luteinizing hormone (LH), and follicle-stimulating hormone (FSH) were analyzed using electrochemiluminescence immunoassay (ECLIA). Compared to female carps, the hypophysis homogenate of male carps recorded lower levels of the measured hormones. The biochemical results showed that the hypophysis homogenate of H. molitrix showed higher levels of 426±13, 118±6, 2355±47, and 1005±35 ng/mg for PRL, GH, LH, and FSH, respectively. Whereas, lower level of ACTH (5±0.5 ng/mg) was recorded compared to those obtained in C. carpio and C. idella. However, the concentrations of those hormones recorded the lowest values in male carpfish, while the concentration of ACTH hormone was higher in male common carp, recording 13±1.2 ng/mg. The present biochemical observations revealed the suitability and effectiveness of the cheap silver carp hypophysis as a spawning inducer in fishes. [ABSTRACT FROM AUTHOR]

Like females of many commercially important fishes, Liza ramada fail to complete ovarian development and do not undergo final maturation (FOM), ovulation or spawning when reared in captivity. The aim of the present work was to investigate the histological and physiological changes during the reproductive cycle of Liza ramada reared in freshwater fish ponds and during induction of spawning in saline water. In the present study, the levels of total thyroxine (T4), triiodothyronine (T3) and cortisol in the plasma of Liza ramada in a complete reproductive cycle were measured in correlation with the seasonal histological changes in gonads. During the reproductive cycle of females, serum triiodothyronine (T3), thyroxine (T4) and cortisol decreased during ovarian early-vitellogenesis and increased during mid-vitellogenesis to reach a peak for both T4 and cortisol. Then, these hormones declined to low levels during late-vitellogenesis. At the prespawning stage, all mentioned hormones re-increased to high levels and finally declined during induction of spawning. There was a decrease in serum levels of thyroid and cortisol hormones coincided with an increase in testicular activity of the fish. T3 and T4 increased during testis ripening to reach a peak during spawning, while cortisol reached a peak during ripe stage and decreased to low levels during spawning. In conclusion, the seasonal changes in thyroid hormones and cortisol concomitant with gonadal maturation and spawning of Liza ramada support role for these hormones in reproduction and stress response of this fish. [ABSTRACT FROM AUTHOR]

Introduction Eggs of the silver carp (Hypophthalmichthys molitrix) absorb water after release from the female, causing them to become turgid and increase substantially in size. Prior observations have suggested that silver carp eggs may swell and burst in soft waters. Identifying water hardness threshold values is needed for the successful incubation of silver carp (H. molitrix) eggs. Aim of the work The present experiments were designed to determine the effect of water quality on the reproductive performance of the silver carp. Material and methods In this study, we tested the effect of water hardness from three sources – tap, El-Serw Fish Farm, and Lake Manzalah – on silver carp egg enlargement and hatching success. Results Water chemistry variables, including temperature, dissolved oxygen, and pH, were consistent among tests. The observed results, during induction of spawning, indicated that the application of human chorionic gonadotropin, at a dose of 1500 IU/kg, was effective for inducing the final stages of maturation, ovulation, and spawning in silver carp in ripe spawners. Water hardness during egg hardening had a significant effect on the hatching success of eggs originating from the same parent fish. Hatching success rates were highest for eggs hardened in the hardest water treatment (132 mg/l) and lowest for eggs hardened in the softest water treatment (45 mg/l). Both embryonic and larval development have been described, and there was no difference in the tested waters. Conclusion Our research suggests that water hardness of 45–132 mg/l is suitable for the reproduction of silver carp. [ABSTRACT FROM AUTHOR]

An excess of mucus has been observed in the water during induction of mullet spawning. Few data are available on the physiology of mullets during the induced spawning, especially data on the response of mucous-secreting cells in the gills and intestine.The aims of the present studies were to evaluate the effects of stress on the mucous-secreting cells in the gills and intestine during induced spawning of Mugil cephalus (Teleostei).Quantification of possible cell hyperplasia (or depletion) and the chemical composition of the mucous cells during induction of M. cephalus spawning was carried out using histochemical techniques.The majority of mucous cells were concentrated at the edge of the gill filaments. The mucous cell density in the gills was significantly increased during spawning, but it was significantly decreased during preoviposition mortality. However, the mucous cell density in the mucosal layer of the intestine was significantly decreased during spawning and at preoviposition mortality. The size of mucous cells in both the gills and the intestine was significantly decreased during spawning and at preoviposition mortality, whereas its size was significantly increased in the gills after spawning. Two types of glycoproteins (GPs) (acid and neutral) were identified in the mucous cells of the gill and intestine epithelium of M. cephalus. During induction of spawning, the amount of GPs in the mucous cells altered. The amount of each variety of the carbohydrate (intensity of reaction) differed at the different stages during spawning. In general, the secretion of acidic mucous was increased during spawning.The decrease in the GP contents in mucous cells of M. cephalus, as a result of their hypersecretion in response to stress early during handling and acclimation, decreased the production of mucus and reduced its protective role against desiccation of gill and intestine tissue when the ion concentration changed in water during acclimation and induced spawning. This may be considered one of the possible reasons for mortality. Therefore, caution must be exercised not only in acclimation of fish but also in minimization of exposure of fish to stress during induction of spawning. [ABSTRACT FROM AUTHOR]

The reproductive cycle can be controlled by either placing the fish in an appropriate environment or by changing the internal regulating factors of the fish with injected hormones or other substances.The present work was designed to determine the suitable environmental and hormonal requirements for induced spawning of thin-lipped grey mullet, reared in freshwater fish farms.The application of a high-potency synthetic analogue of luteinizing hormone-releasing hormone agonists (LHRH-a) and human chorionic gonadotropin (HCG) for inducing the final stages of maturation, ovulation, and spawning in mullets was investigated in ripe spawners, reared in freshwater fish farms, with average egg diameters of 0.600 mm or more, in suitable water temperature and salinity.Two hormonal injection strategies were used. The first involved the use of HCG as a priming injection, followed, 24 h later, by a resolving injection of HCG. The second strategy followed the same time frame but the priming injection was HCG and the resolving injection was luteinizing hormone-releasing hormone agonists alone or in combination with HCG. The use of pregnyl (HCG) as a priming injection at a dose of 20 000 IU/kg body weight, followed by a second injection of 40 000 IU HCG/kg body weight 24 h later proved to be effective in inducing final oocyte maturation, ovulation, and spawning in Liza ramada at 44-50 h after hormonal injection. The optimum water temperature and salinity was 19oC and 35%, respectively. Translucent ovulated eggs had coalesced lipid and yolk masses. The fertilized eggs had one or more oil globules gathered in the upper space of the egg. The blastodisc was situated on the bottom side of the floating egg.HCG is very useful for inducing and synchronizing spawning in L. ramada ripe spawners, reared in freshwater fish farms, in combination with suitable environmental factors. [ABSTRACT FROM AUTHOR]

ABSTRACT The present experiments were designed to determine the effect of different stress factors; handling, seawater acclimation, confinement, and induced spawning on plasma cortisol, hydro mineral balance as well as changes in size, number and integrated intensity of somatolactin (SL)-expressing cells in Liza ramada mature females confined to fresh water ponds. The plasma levels of cortisol, PO43−, Na+, and K+ were higher, while Ca2+ and Mg2+ were lower than controls during transportation without anesthesia. By using clove oil (5 mg L−1) as an anesthetic during transportation, the plasma cortisol, PO43−, Na+, and K+ were similar to controls, while Ca2+ and Mg2+ were higher. During seawater acclimation, the plasma cortisol and minerals were significantly higher except Na+ which was lower than controls. In addition, during induction of spawning, the plasma levels of cortisol, PO43−, Na+, K+, and Mg2+ were significantly higher than controls. The SL-producing cells are located in the pars intermedia (PI) bordering the neurohypophysis. The stress affected the number, size, and immunostaining of SL-expressing cells. During seawater acclimation, the size and the integrated intensity of SL immunoreactivity were lower, but the number of these cells was higher than controls. Furthermore, the number, size, and the integrated intensity of SL immunoreactivity were significantly lower than controls during handling and after spawning, which was opposite to confinement. The response of SL-expressing cells in PI in parallel with changes in cortisol and hydro mineral balance induced by stress support the possible role of SL in the adaptive response of fish to stress. J. Exp. Zool. 00A:1-15, 2012. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Understanding the physiological picture of fish during the reproductive cycle, seawater acclimation, and induced spawning is of essential value to know the possible reasons of preoviposition mortality and to develop successful hatchery technology.Determination of the effect of different stress factors on hydro-mineral balance as well as changes in somatolactin (SL) immunoreactive cells in mature Liza ramada females.Water chemistry and the different plasma ion levels were measured. Immunocytochemical staining for the sections of the pituitary gland was performed to describe the activity of SL immunoreactive cells.The plasma levels of PO43-, Na+, K+, Ca2+, and Mg2+ showed a slight increase during transportation without anesthesia. The concentrations of these minerals returned to the initial levels by using clove oil (5 mg/l) as anesthetic. However, their levels decreased during seawater acclimation and gradually increased with confinement to reach the initial values. Furthermore, the levels of PO43-, Na+, K+, Ca2+, and Mg2+ were significantly (P0.05) elevated during spawning and preoviposition mortality of ovulated females. SL immunoreactive cells in the pars intermedia of the pituitary showed a dramatic increase in their secretory activity during handling, seawater acclimation, preoviposition mortality, and induced spawning. However, the synthetic activity of these cells was enhanced during confinement. The activation of SL-secreting cells was in parallel with changes in hydromineral balance induced by stress, supporting the possible role of this hormone in the adaptive response of fish to stress.Clove oil effectively suppresses the response of electrolytes to stress, and may prove to be a useful anesthetic for reducing the adverse effects of stress. [ABSTRACT FROM AUTHOR]

Abstract: In the present study, we investigated the distribution and activities of corticotropin-releasing factor (CRF) and adrenocorticotropic hormone (ACTH) immunoreactive (ir) cells in the brain and pituitary of Liza ramada during ovarian maturation, seawater acclimation, and induction of spawning. Using immunohistochemistry, we detected that CRF-ir cell bodies exist in different brain regions: medulla oblongata (MO), midbrain tegmentum, habenula, nucleus preopticus (NPO), and in a ventral hypothalamic region corresponding to the nucleus lateralis tuberis (NLTP). In the pituitary gland, we detected some ACTH-producing cells in the rostral pars distalis (RPD) containing CRF immunoreactivity. The synthetic and secretory activity of CRF-ir cells in the NPO and MO as well as ACTH-ir cells in the pituitary were enhanced during ovarian maturation. During seawater acclimation, CRF-ir cells in the NPO and MO and ACTH-ir cells in the pituitary showed dramatic increases in their synthetic activity. These cells showed dramatic increase in their secretory activity during spawning induced by human chorionic gonadotropin (HCG) injection in L. ramada. Finally, hormonally induced ovulation was accompanied with elevation of plasma cortisol and depletion of CRF and ACTH immunoreactivity within the brain and the pituitary gland, respectively. Taken together, our findings suggest that mature breeders of L. ramada may respond to stress resulting from ovarian maturation, and seawater acclimation as well as induced spawning. Mechanisms include enhancement of the synthetic and/or secretory activity of CRF-ir cells in the NPO and MO as well as ACTH-ir cells in the pituitary gland along with a rise in plasma cortisol during ovulation, supporting the possible role of these hormones during stress and reproduction in L. ramada. [Copyright &y& Elsevier]