Ovarian development of a river catfish Hemibagrus nemurus (Valenciennes, 1840) in captivity

Hemibagrus nemurus is a riverine catfish with high economic and nutritive values. Investigations on ovarian development of this fish were carried out to determine the mode of ovarian development and describe the oocyte developmental stages. Histological studies were done on ovaries using light microscopy and scanning electron microscopy. Fish were sampled monthly for a period of six months (August 2009 to January 2010). The mean oocyte diameter (OD) ranged from 871 ± 161.41 μm to 1,167 ± 26.77 μm and the highest OD was in November. Oocyte size-frequency distribution showed a polymodal distribution. The mean gonadosomatic index (GSI) ranged from 1.14 ± 0.87% to 7.06 ± 1.40% and highest GSI was in November. The ovaries exhibited three phases of oocyte growth, which were primary growth, secondary growth and maturation phases. Based on histological criteria, the oocyte developmental stages were divided into seven stages as chromatin nucleolar, early perinucleolar, late perinucleolar, cortical alveolar, vitellogenesis, mature oocyte and germinal vesicle migration stages. All the seven stages of oocyte development were observed in the ovaries. Oogonia were always present throughout the developmental stages. The ovaries had more than two stages of oocyte development. This is the first report on the mode of ovarian development of H. nemurus. These findings indicated that H. nemurus has asynchronous mode of ovarian development and is capable of spawning several times in a year under favourable conditions.     

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.     

多马胺能药物对鲇鱼促性腺激素（GtH）分泌活动的影响

以珠江流域鲇鱼（silurus asotus)为实验材料,研究了多巴胺（DA）能药物（DA及其D－2型受体拮抗物 ,DOM）对鲇鱼促性腺激素（GtH)释放的影响,结果表明,在性腺发育的各个时期,单独注射DOM（5ug/g)均不能显著提高鲇鱼血液基础GtH水平,当DOM与LHRH－A联合注射时能显著增强LHRH－A刺激GtH释放的作用;DA只能抑制GnRH诱导的GtH释放,对基础GtH释放无抑制作用,这种生殖内分泌调节方式与鲇形目的革胡子鲇（Clarias gariepinus)和大鳍Hu（Mystus macropterus)相似,而与鲤形目的鲁科（Cyrpindiae)鱼类不同。     

Seasonal changes in the pituitary- gonad axis of feral goldfish, Carassius auratus L., from Ontario, Canada

Apparently healthy, feral goldfish, Carassius auratus L., were collected from a pond in Cambridge, Ontario from March until November 1981, and during April 1982. Based on histological examination, oocyte development was divided into five stages and the reproductive cycle into five periods. The origins of oogonia and the atresia process were examined. The gonadosomatic index (GSI) was found to be an accurate indicator of ovarian activity in the feral population. Based on the GSI, proportion of various oocyte stages and egg size, females older than 2 years appeared to spawn during two periods, May to June and late August; 2-year-old fish spawned in the first period. There was a reduction in the density, abundance and nuclear diameter of presumptive pituitary gonadotrops in early August, after the completion of ovarian development and before the completion of spawning.     

多巴胺能药物对鲤鱼促性腺激素分泌活动的影响

研究多巴胺（ＤＡ）及其激动剂阿扑吗啡（ＡＰＯ）和拮抗剂Ｄｏｍｐｅｒｉｄｏｎｅ（ＤＯＭ）对不同性腺发育时期和不同年龄雌鲤促性腺激素（ＧｔＨ）分泌活动的影响。结果表明：鲤鱼基础ＧｔＨ分泌具有明显的季节性变化,表现为血清ＧｔＨ含量在性腺发育早期较低,性腺成熟期升高,到性腺退化期又降低。ＤＡ和ＡＰＯ对ＧｔＨ分泌的抑制作用及ＤＯＭ对ＧｔＨ分泌的刺激作用在不同性腺发育时期为：性腺发育早期〉性腺成熟期〉性腺退化     

Ovarian activity and plasma sex steroid levels of Distichodus antonii in relation to environmental conditions in the upper basin of the Congo River

Distichodus antonii is an endemic fish species of the Congo River basin in which the stocks of wild populations are threatened by overfishing pressure. Knowledge of its reproductive biology would be useful in consideration of conservation and management options for the species. Therefore, this study investigated changes in ovarian activity and levels of steroid profiles in wild populations in relation to variation in temperature and rainfall. Adult females (n = 101, body weight of 3 183 ± 14.75 g, SE) were captured monthly over one year (2013–2014). Apart from evaluation of oocyte diameters and gonad developmental stages, gonado-, hepato-, lipososomatic indices (GSI, HSI, LSI) and plasma levels of sex steroids (testosterone-T, estradiol-17β-E2) were determined. The results suggested a synchronous development of oocytes with two annual reproductive seasons over the one-year study. Plasma T and E2 levels peaked during spawning periods likely reflecting active oogenesis. The highest values of morphosomatic indices were observed during the longest rainfall period in September, and were associated with high steroidogenic activity evidenced by increased E2 production. In addition, more vitellogenic oocytes (September and October) were observed during the latter season than during the short rainy season (in May).     

雄烯二酮和甲基睾酮诱导雄性日本鳗鲡性腺发育的作用

多次埋植雄激素雄烯二酮（ADSD）或甲基睾酮（MT）均可促进雄性日本鳗鲡（Anguilla japonica)性腺发育成熟,明显提高脑和垂体mGnRH,垂体GtH含量,埋植3次后,MT处理组的GSI及垂体GtH含量显著高于ADSD处理组,MT处理组血清GtH含量在第1次埋植后显著升高,而ADSD处理组在第4次埋植后才显贰高于对照组。这些结果表明：埋植ADSD和MT可反馈作用于雄性日本鳗鲡脑和垂体,促进GnRH和TtH的合成和分泌,进一步诱导精巢发育。而且MT的作用效果较ADSD快。     

Reproductive biology and endocrine regulation of final oocyte maturation of captive white bass

The ovarian development, and plasma levels of gonadotropin II (GtH II) and sex-steroid hormones at the end of vitellogenesis were examined in captive white bass Morone chrysops. The changes in plasma hormone levels and oocyte morphology associated with gonadotropinreleasing hormone agonist (GnRHa)-induced final oocyte maturation (FOM) were studied. Although plasma 17β-oestradiol (E₂) and oocyte diameter increased, there were no changes in GtH II, testosterone (T), 17,20β-dihydroxy-4-pregnen-3-one (17,20β-P) or 17,20β,21-dihydroxy-4-pregnen-3-one (17,20β,21-P) in non-hormone-treated females, and no FOM was observed. Treatment with a sustained-release GnRHa delivery system (GnRHa implant) induced two FOM cycles separated by about 24 h, with the release of approximately equal numbers of eggs in each spawn. Plasma GtH II levels were elevated significantly throughout FOM, reaching a maximum of 9·07 ± 1·55 ng ml^?1 in ovulated fish. Both plasma E₂ and T increased soon after the GnRHa treatment, but E₂ declined in fish undergoing germinal vesicle (GV) migration. Plasma T increased further during FOM (7·55 ± 2·87 ng ml^?1), but declined precipitously at ovulation. A surge in plasma 17,20β-P and 17,20β,21-P (4·11 ± 0·97 ng ml^?1 and 3·10 ± 0·77 ng ml^?1, respectively) was observed in females undergoing GV breakdown (GVBD). Based on the involvement of different sex-steroid hormones, FOM was separated into two stages. Early FOM included lipid-droplet coalescence and GV migration, and was associated with elevations in plasma GtH II and T. Late FOM included GVBD and yolk-globule coalescence, and was associated with elevations in plasma GtH II, 17,20β-P and 17,20β,21-P. The results of this study point to the absence of a surge in plasma GtH II as the missing link in the reproductive axis responsible for the failure of captive white bass to undergo FOM at the end of vitellogenesis. Sustained elevation of plasma GtH II via treatment with a GnRHa implant induced two consecutive spawns with an overall egg production two- to eightfold higher than previously obtained from captive broodstocks, and similar to annual egg production Values reported for wild fish.     

Spawning season, ovarian development and fecundity of female Trichomycterus corduvense (Osteichthyes, Siluriformes)

We studied female reproductive biology of Trichomycterus corduvense. The study was carried out in the Anizacate River (Córdoba, Argentina). Samples were collected throughout one year on a monthly basis. Seven oocyte phases were identified. Five ovarian stages were described based on the macroscopic analysis of the oocyte phases. The spawning season for the species ranges from October to February; it was determined based on variations in GSI and the existence of mature females. The dynamics of oocyte development of T. corduvense, indicated the asynchronism of maturation. The correlation coefficient between fecundity and the individual weight was very low. Therefore, we suggest that this coefficient cannot be used to predict T. corduvense fecundity.     

鳗鲡繁殖生物学研究Ⅴ．性类固醇激素诱导雌鳗促性腺激素(GtH)分泌和卵巢发育的作用

多次注射雌二醇或睾酮对雌鳗促性腺激素(GtH)的合成与分泌活动以及卵巢发育都有明显的促进作用,其中睾酮的作用更较雌二醇显着;多次注射LHRH-A的促进作用则不明显.多次埋植雌二醇或睾酮都能促使脑垂体合成GtH,但所取血清样品中的GtH含量都未见明显增加;多次埋植雌二醇后血清中卵黄蛋白原的含量明显增加,但卵巢GSI增长幅度小,表明埋植雌二醇虽能促使肝细胞合成卵黄蛋白原并释放到血液中,但未能全部渗入卵母细胞内;多次埋植睾酮后血清中的卵黄蛋白原含量虽未见明显增加,但卵巢明显发育长大,这表明埋植睾酮能促使肝细胞合成的卵黄蛋白原迅速地通过血液运送到卵巢,并渗入卵母细胞内.       

Homologous radioimmunoassay and radioreceptorassay of gonadotropic hormone for an Indian carp Catla catla

A homologous radioimmunoassay (RIA) for Indian carp (C. catla) gonadotropin (GtH) was developed by using purified Catla GtH and its specific antiserum. In Ouchterlony agar diffusion, antisera raised against purified Catla GtH (cGtH), showed clear crossreaction. Catla-anti GtH (anti-cGtH) did not cross-reacted with Catla TSH enriched fraction. Immunocrossreaction was further confirmed with competitive binding inhibition studies where displacement of radiolabelled cGtH was precisely linear against increasing concentrations of cGtH, hence this was later used as standard curve for RIA. Competitive binding inhibition was also observed with purified murrel GtH, silver carp GtH and Cyprinus GtH, using varied doses. Both murrel and silver carp GtH showed clear parallelism with cGtH, while Cyprinus GtH inhibition slope was less steeper. Mammalian GtHs (hCG, oLH, oFSH), bTSH and bPRL had no crossreaction with anti-cGtH. Radioreceptorassay (RRA) for cGtH was developed by preparing plasma membranes from Catla oocytes. Binding of 125I-cGtH to oocyte plasma membranes showed saturability with high affinity (Ka = 0.11 X 10(13)M-1) and low capacity (17 fmol/mg protein). Displacement of 125I-cGtH in receptorassay by cold cGtH was linear and therefore served as standard curve. The interassay and intrassay variability in RIA was 7.9% and 3% while that of RRA was 5% and 3% respectively. Sensitivity of RIA was in the picogram level whereas it was in nanogram level by RRA. Determination of carp pituitary and serum GtH content by RIA and RRA showed the consistency, precision and validity of these assays. Although RRA was comparatively less sensitive than RIA, it was convenient, quick and less expensive.     

Differential expression of neural and gonadal aromatase enzymatic activities in relation to gonadal development in Japanese eel, Anguilla japonica

The objectives of the present study were to investigate the enzymatic characteristics of brain aromatase in Japanese eel, Anguilla japonica, as well as the correlations between aromatase activities in various tissues (brain regions, pituitary, and gonads) and ovarian development. Eel brain aromatase exhibited a K(m) of 75 nM and a V(max) of 1.14 fmol/min mg protein (91.5 fmol/h mg protein), indicating an enzymatic activity much lower than in other teleosts but similar to that in mammals. This supports the hypothesis of the occurrence of a single aromatase gene in eels (representative of an ancient group of teleosts, Elopomorphs), as in mammals, but unlike what is observed in more recent teleosts. Aromatase inhibitors could significantly suppress brain and pituitary aromatase activity. There was no significant sex difference in aromatase activity in the forebrain, midbrain, hindbrain, or pituitary, but there was in the gonads, where aromatase could be detected in the ovaries but not in the testes, in accordance with the role of this enzyme in ovarian differentiation. Comparison with another teleost, black porgy (Percomorph), under the same experimental conditions, further confirmed the low activity of aromatase in the eel. We investigated variations in brain, pituitary, and gonad aromatase activity in relation to ovarian development in control female eels (gonadosomatic index, GSI, 0.1-1.6%) as well as in eels treated with pituitary extract (experimental ovarian maturation; GSI up to 25%). Differential expression of neural and gonadal aromatase was observed in relation to the course of gonadal development. Pituitary aromatase activity increased with GSI at all stages. Brain (specially forebrain) aromatase activity significantly increased in early vitellogenic control eels (GSI>0.8%) and in treated eels. The low activity of eel aromatase may be related to the characteristic life cycle of the eel, in which there is a long delay of the onset of puberty before oceanic reproductive migration.     

Influence of testosterone and/or luteinizing hormone releasing hormone analogue on precocious sexual development in the juvenile rainbow trout

The influence of testosterone, luteinizing hormone releasing hormone (LHRH) agonist and combinations of these hormones on gonadotropic hormone (GtH) levels in the sexually immature trout was investigated. Both the steroid and releasing hormone preparations, testosterone in Silastic capsules and cholesterol-pelleted LHRH-A, were formulated for sustained release and long-term biological action following a single hormone implantation. Marked increases in pituitary GtH followed testosterone and/or testosterone and LHRH analogue treatment combined, but the low pituitary GtH level in controls remained unchanged after LHRH analogue administration alone. Plasma GtH titers increased with time after testosterone treatment, indicating a positive steroid feedback effect by androgen on GtH in the juvenile rainbow trout. When combined with testosterone treatment, LHRH analogue augmented plasma GtH levels compared to fish receiving testosterone treatment alone. In males the elevated plasma GtH levels were associated with testes stimulation and onset of spermatogenesis; in females, however, no significant stimulation of the ovaries was observed. It can be concluded from these studies that the testosterone stimulus is sufficient to induce onset of sexual development in immature males but not females. Whereas LHRH analogue releases GtH from the testosterone-primed trout pituitary, LHRH treatment alone under these conditions fails to stimulate the juvenile trout reproductive system.     

Reproductive strategy of the Patagonian catfish Hatcheria macraei

This study describes the reproductive strategy of the stream‐dwelling catfish Hatcheria macraei in the Pichileufu River, Argentina. Gonad maturity phases, classified on the basis of histological analysis, stages of gamete development and the frequency distribution of oocyte size, were correlated with macroscopic features of the gonads. Hatcheria macraei has a cystovarian ovary, asynchronous oocyte development and lobular testes. Five oocyte and four spermatogenic stages were identified and related to macroscopic gonad characteristics, making it possible to divide gonad development into five phases for females and males. Mature oocyte diameter ranged from 922 to 1935 µm. Absolute fecundity in mature females varied from 115 to 480 oocytes. Hatcheria macraei has multiple spawning during a protracted reproductive season that extends from December to April. This, together with its small size, is characteristic of an opportunistic reproductive strategy, commonly found in species that inhabit adverse and unpredictable environments, such as the low‐order rivers of Patagonia.     

Histopathology and helminth parasites of African catfish Clarias gariepinus (Burchell, 1822) in relation to heavy metal pollution in a subtropical river system

In a study aimed to determine the histopathology, component parasite communities and level of selected heavy metals, African catfish Clarias gariepinus from three rivers in Zimbabwe (Gwebi, Manyame and Mukuvisi) were analysed for heavy metals (Cd, Cr, Cu, Fe, Ni, Pb, Zn) in the gills, liver, kidney and muscles. The histopathology of these tissues was assessed by microscopic examination of stained thin sections. Metazoan parasite diversity and species composition in fish along different sites of the rivers were determined and compared. Levels of Cd, Fe, Pb and Zn were lowest in the Gwebi, Cr and Cu in the Manyame, and Ni in the Mukuvisi River. There were significant differences (P < 0.5) in concentration of iron and nickel in the gill and liver tissues of fish among the three rivers while significant differences in concentration of iron and lead were observed in muscle tissue. Gill chronic inflammation and ossification were significantly different (P < 0.5) in fish from among the three rivers. Chronic inflammation, hemosiderin deposits and bile accumulation in the liver were also significantly different (P < 0.5) among the three rivers and so was the extent of chronic inflammation in the kidney tissue. Lamellar fusion was slightly more present in gills of catfish from the Mukuvisi than the Gwebi River. The parasite community of C. gariepinus comprised three monogenean, two cestode and three nematode species. The least polluted Gwebi River had the highest parasite community diversity while the most polluted Mukuvisi River had the lowest diversity. Fish parasite community structure is thus a potential indicator of river pollution, while heavy metal pollution is a potential threat to fish and human health in the system.     

草鱼生长激素非竞争式酶联免疫吸附测定法的建立及鉴定

应用草鱼生长激素（ｇｃＧＨ）单克隆抗体及多价兔抗血清建立了草鱼ＧＨ非竞争式酶’联免疫吸附测定ＥＬＩＳＡ系统。用正辛酸法对腹水单抗进行了分离纯化,获得了高纯度的单抗制备物。聚丙烯酸胺凝胶电泳表明纯化的单抗由分子量分别为５５ｋＤ和２５ｋＤ的两条蛋白带组成。用纯化单抗铺底,用兔抗血清作后续抗体建立了一种测定草鱼ＧＨ的非竞争式双抗夹心ＥＬＩＳＡ方法。交叉试验表明该测定系统只与草鱼ＧＨ和基因重组鲤生长激素（ｒｃＧＨ）具有剂量依存的结合反应,而与大马哈鱼生长激素（ｓＧＨ）、牛生长激素（ｂＧＨ）、大马哈鱼促性腺激素（ｓＧｔＨ）、及黑鲢促性腺激素（ｂｓｃＧｔＨ）等均无交叉反应。该 ＥＬＩＳＡ方法的灵敏度可达０．８ｎｇ／ｍｌ,组内变异系数为 ５．９ ％,组间变异系数为７．６％,回收率达９０％以上。初步应用表明,鲤和团头鲂垂体抽提液、草鱼血清、鲤血清及鲫血清在该测定系统中有剂量依存的反应曲线,而大口鲶、黄颡鱼、中华鲟及黄鳝鱼垂体抽提液及大口鲶、胡子鲶和罗非鱼血清在该测定系统中没有交叉反应。