Agonistic effect of imidazole and triazole fungicides on in vitro oocyte maturation in rainbow trout (Oncorhynchus mykiss)

The purpose of the present study was to assess the in vitro effect of some imidazole (prochloraz, imazalil) and triazole (epoxiconazole) agricultural fungicides on gonadotropin-induced oocyte maturation in rainbow trout. Results show that prochloraz, epoxiconazole and imazalil strongly potentiated the induction of oocyte maturation by gonadotropin in a dose-dependent manner. Furthermore, 10(-5) M prochloraz and epoxiconazole alone induced oocyte maturation. The mRNA biosynthesis inhibitor, actinomycin d, completely inhibited oocyte maturation induced by fungicides, suggesting that the gonadotropin-like effect of these chemicals is at least dependent on de novo gene expression.     

Using oocyte size to assess seasonal ovarian development in Solea solea (L.)

Maximum oocyte size was used to assess seasonal ovarian development in sole. Fish age, especially the adolescent period, appeared to affect the start of vitellogenin-dependent oocyte development in the annual reproductive cycle and the subsequent oocyte growth rate. The majority of oocyte growth occurred between September and March. Several other aspects of ovarian development were also age-dependent, including the increase in ovary condition factor (ovary weight/fish length³) and the size of oocytes commencing nuclear migration. Evidence is presented that in the recruiting year class of sole abortive maturation occurs where oocytes develop yolk but spawning does not take place. The implications of this study on the estimation of female spawning stock biomass are discussed.     

Effects of BPA and DES on longchin goby (Chasmichthys dolichognathus) in vitro during the oocyte maturation

This study was performed in order to assess whether bisphenol (BPA) and diethylstilbestrol (DES) had agonistic or antagonistic effects on oocyte maturation using marine fish. We tested the effects of these chemicals on in vitro maturation, germinal vesicle breakdown (GVBD), assay using oocytes from the longchin goby, Chasmichthys dolichognathus. During the maturation process, low concentrations of BPA and DES triggered GVBD depending on the stage of oocyte development; BPA at 0.044 nM and DES at 0.037, 0.37, and 3.73 nM induced GVBD in 0.82-0.88 mm diameter oocytes (germinal vesicle located near the center of oocytes). In 0.76-0.80 mm diameter oocytes (fully vitellogenic oocytes), BPA induced GVBD at relatively higher concentrations (4.38, 43.8, and 438 nM). In 0.86-0.90 mm diameter oocytes, BPA and DES had no observable effect on GVBD at the concentrations tested. Oocytes with diameters between 0.82 and 0.88 mm appeared to be more sensitive to these chemicals. Moreover, our results showed that BPA and DES did not inhibit GVBD.     

激素在诱导鲻鱼卵母细胞成熟中的作用机制

本文报道了在注射促性腺激素和促黄体素释放素类似物诱导鲻鱼卵母细胞成熟过程中,其胞质中高尔基体、油球数量和核的形态均发生显著变化,并据此分析了这两种激素在诱导鲻鱼卵母细胞成熟中的作用机理。     

氨海水与5-羟色胺对栉孔扇贝解剖卵的体外促熟作用

研究氨海水与5-羟色胺(5-HT)对栉孔扇贝解剖获得卵母细胞的促熟作用。通过体外浸泡的方法处理栉孔扇贝卵母细胞使其成熟,并完成人工受精。结果表明一定浓度的氨海水可显著促使栉孔扇贝卵母细胞生发泡破裂,但经过氨处理的卵母细胞受精率却不高;5-羟色胺不能诱导栉孔扇贝卵母细胞生发泡破裂,但可有效地使已经发生生发泡破裂的卵母细胞进一步成熟。先用氨海水处理然后用5-羟色胺处理可以得到最佳诱导效果,受精率可达(40.02±2.73)%。     

Sonophotocatalysis of endocrine-disrupting chemicals

Sonolysis and photolysis often exhibit synergistic effects in the degradation of organic molecules. An assay of fish oocyte maturation provides an appropriate experimental system to investigate the hormonal activities of chemical agents. Oocyte maturation in fish is triggered by maturation-inducing hormone (MIH), which acts on receptors on the oocyte surface. A synthetic estrogen, diethylstilbestrol (DES), possesses inducing activity of fish oocyte maturation, and a widely used biocide, pentachlorophenol (PCP), exhibits a potent inhibitory effect on fish oocyte maturation. In this study, the effects of the combined treatment by sonolysis with photolysis (sonophotocatalysis) to diminish the hormonal activity of DES and the maturation preventing activity of PCP was examined. By sonophotocatalysis, hormonal activity of DES was completely lost within 30min and the inhibiting activity of PCP was lost within 120min. These results demonstrated that sonophotocatalysis is effective for diminishing the endocrine-disrupting activity of chemical agents.     

促性腺激素释放素类似物（GnRH—A）对文昌鱼卵细胞成熟及产卵的诱发

在繁殖季节，给正在成熟的文昌鱼体腔注射ＧｎＲＨ－Ａ，结果表明，注射激素后３６ｈ时，有５０％文昌鱼产卵，未产动物成熟卵母细胞达９５．５％。而对照组无任何动物产卵，成熟卵母细胞为５５％，我们由引首次直接证实文昌鱼脊椎动物一样，ＧｎＲＨ－Ａ是调控其卵母细胞成熟和产卵的重要激素。     

Reproductive biology of horse mackerel Trachurus capensis and Trachurus trecae in Namibia and Angola

Harvest control measures for Namibia and Angola are defined using reference points for spawning biomass, which requires knowledge of spawning potential and dynamics of fishery stocks. The reproductive biology of two species of horse mackerel, Trachurus capensis and Trachurus trecae, in these waters was investigated for spawning distribution in time and space. Samples were collected during two scientific cruises conducted in February and July/August 2007 off the coast of Namibia and Angola. A total of 396 fish ovaries was examined to determine the spawning dynamics of the two species. The ovaries were histologically analysed and their oocyte distributions mapped. The length (TL)–weight relationships of the two species differed significantly. The observed development of oocyte recruitment and absence of a hiatus in the oocyte distribution indicated that these species are indeterminate spawners. Analyses of the data from the NatMIRC database (2001–2004) indicated annual changes in gonadosomatic index (GSI) for T. capensis at different latitudes, but these changes were small. GSI also fluctuated between years and areas, but there were no clear spatial or temporal trends, with averages ≤4.0% at all stations. The GSI of both species was not indicative of the histologically determined development of gonad maturity. Oocyte maturation for T. capensis indicated that smaller and younger fish spawn first. Batch fecundity (F) for T. trecae was best described by F = 4 986 TL (cm) – 99 645 (r ² = 0.83). This study provided the first analyses of oocyte development in time and space for the two species in the region.     

Vitellogenin-associated maternal transfer of exogenous and endogenous ligands in the estuarine fish, Fundulus heteroclitus

Sequestration of large quantities of vitellogenin (VTG) is critical for proper oocyte development in most oviparous vertebrates. While previous studies have shown a general correlation between oocyte growth and the accumulation of various exogenous and endogenous ligands, few studies have attempted to elucidate the role VTG plays in this maternal transfer. In the present study, we have demonstrated that oocytic accumulation of [³H]-2,3,7,8-tetrachlorodibenzo-p-dioxin (³H-TCDD) and [¹⁴C]-benzo(a)pyrene (¹⁴C-BaP) by gravid Fundulus heteroclitus is directly correlated with oocyte maturational status. A positive correlation was observed between oocyte maturational state (size) and both total quantity (total pmoles) as well as concentration (pmoles/g tissue) of TCDD and BaP. Further, the bi-phasic accumulation of both TCDD and BaP mirrors that previously observed for protein sequestration by cultured Fundulus oocytes. Additionally, both TCDD and BaP were associated with VTG in vivo. HPLC analysis of serum extracts has shown that VTG associates with both parent BaP and BaP metabolites. Studies with ¹²⁵I-T₄ (thyroxine) also suggest that this critical hormone also associates with VTG in vivo. Ongoing studies are examining the VTG-associated transport and oocytic sequestration of ¹²⁵I-T₄ in gravid Fundulus.     

中华绒螯蟹卵巢发育周期的组织学细胞学观察

于1989－1990年，用组织切片技术，结合外观特征，在光镜水平对浙北地区的中华绒螯蟹卵巢发育周期进行组织学、细胞学观察，并对从卵原细胞增殖到卵母细胞生长、卵子成熟及卵巢退化、重新发生等进行系统观察研究。研究表明，中华绒螯蟹可以观察到第一次成熟分裂中期相为成熟卵的标志，并以此标志将卵子发生分成四期、卵巢发育分成VII期。结果还表明，中华绒螯蟹雌蟹的成熟时间因所处的地理纬度不同而有所差异，浙北地区雌蟹促产怀卵的最佳时间是3月份并延至4月上旬；卵子必须借助海水及交配活动刺激才能达到成熟；因故无法产卵或一直生活在淡水中的成熟雌蟹其整个卵巢即退化，退化卵巢亦能重新发生，新生卵子的形态、发育时序与首次等待青春期蜕壳的蟹一致；孵后母蟹不仅能继续蜕壳生长，其卵巢也能重新发生，新生卵子的形态、发育时序如前一致；但在卵巢结构上彼此又有明显的区别。     

Reproductive life history stages sensitive to oil and naphthalene in Atlantic croaker

The reproductive effects of chronic exposure to water-soluble fractions (WSF) of diesel fuel oil and naphthalene in female Atlantic croaker during critical periods of their reproductive life history were investigated. Fish were repeatedly exposed to WSF of oil (2.5 or 5%) or naphthalene (0.5 or 1.0 ppm) for 5 or 8 weeks. Both pollutants blocked sexual maturation in some fish and impaired ovarian recrudescence in others. The majority of the oocytes in exposed fish were undeveloped and widespread oocyte atresia was evident at higher concentrations of these polycyclic aromatic hydrocarbons (PAH). The disruption of ovarian growth and oocyte development in croaker after PAH exposure was associated with alterations in reproductive endocrine function at multiple sites on the hypothalamus-pituitarygonadal axis. A third period of increased sensitivity to xenobiotics was observed during final oocyte maturation.     

Reproduction of the giant jellyfish, <Emphasis Type="Italic">Nemopilema nomurai</Emphasis> (Scyphozoa: Rhizostomeae), in 2006–2008 as peripherally-transported populations

This study investigated the sexual maturation process, release of spermatozoa or eggs and oocyte diameter of the rhizostomid medusae Nemopilema nomurai using samples collected from August 2006 to June 2008 from the waters around Korea and Japan, including peripheral areas outside the species’ usual habitat. Immature medusae were observed from June to October only in the western sector of the study area. The onset of spermatozoa and egg release occurred in September and October, respectively, and peaked in December and January. Medusae migrated eastward from source areas with the Tsushima Warm Current, where they formed gametes and spawned. Peak position and maximum oocyte diameter increased as the gonads developed according to the size-frequency distribution of oocytes. No fertilized eggs or embryos were found in the gonads. The correlation was analyzed with bell diameter, maximum oocyte diameter, sampling date, surface water temperature and gonad color to estimate which environmental factors and maturation indices were related to the maturation stage of females. Maturation stage correlated well with maximum oocyte diameter, which correlated negatively with surface water temperature. There was no significant correlation between bell diameter and maturation stage. Therefore, bell diameter was inappropriate for determining maturation index. Sex could not be distinguished clearly by gonad color. However, light pink gonads were more prevalent in males and various deep colors such as orange and brown were more frequent in female medusae.     

大弹涂鱼卵细胞发育的显微和超微结构

运用光镜和电镜观察了大弹涂鱼卵细胞发育各时相的形态结构。结果表明，卵细胞发育可分为6个时相，即（1）卵原细胞、（2）卵母细胞单层滤泡、（3）卵母细胞出现脂滴和卵黄、（4）卵母细胞卵黄充满、（5）卵母细胞核极化和（6）卵母细胞退化时相。发现颗粒细胞之间的滤泡小泡。成熟卵中的皮质泡在受精以前就开始释放其内含物到卵周期。对滤泡小泡和滤泡腔、皮质泡的作用以及卵膜结构变化作了讨论。     

光裸星虫体腔液中卵子发生的超微结构

为探究光裸星虫卵子发生的细胞学特点,利用电镜技术观察了光裸星虫体腔液中卵子发生过程的超微结构变化。结果表明:(1)光裸星虫体腔液中存在游离的卵原细胞和卵母细胞,卵母细胞的发育分为卵黄形成前期、卵黄形成初期、卵黄旺盛合成期和成熟期4个阶段。(2)卵原细胞的细胞器少,核质比大。卵黄形成前期,卵母细胞的细胞器有所增加,大量核仁外排物进入胞质中;出现卵黄膜和胶质膜,卵黄膜遍布微孔。卵黄形成初期卵母细胞核有较多突起,细胞器大量增加,出现分散分布的卵黄粒。卵黄旺盛合成期卵母细胞迅速增大,卵黄大量积累。成熟期卵母细胞核膜突起回缩,胶质膜易于脱落。(3)卵黄分为2种。Ⅰ型卵黄电子密度高,不发生融合,为内源性卵黄;II型卵黄中等电子密度,可融合为无定形卵黄块,为外源性卵黄。(4)成熟卵母细胞卵黄膜为三层,外层为颗粒层,表面具有粒状突;中层初始为均质结构,不断增厚并纤维化;内层致密,厚度不均。胶质膜电子密度极低。(5)卵子外有滤泡细胞,其核质比很大,细胞器少,在卵母细胞成熟期发生凋亡。文章还探讨了胶质膜、卵黄膜、滤泡细胞的功能,以及细胞器在卵黄形成中的作用。研究结果积累了光裸星虫卵子发生细胞学资料,为光裸星虫生殖调控与人工繁育研究提供理论参考。     

Life history strategies in zooplankton communities: The significance of female gonad morphology and maturation types for the reproductive biology of marine calanoid copepods

The present review addresses the reproductive strategies of marine calanoid copepods, as affected by their physiological preconditioning, and aims to enhance understanding of their adaptations to specific environmental conditions.Knowledge about oocyte development and internal gonad structure, especially in relation to feeding conditions, is essential for a complete understanding of the reproductive strategies of the copepods. Therefore, the foci of the review are to identify general patterns in oocyte and gonad development in calanoid copepod species from marine ecosystems worldwide and to elucidate the significance of gonad structures for reproductive strategies.Oogenesis is similar in all copepod species. During maturation, the morphology of the oocytes changes distinctly and, according to oocyte size and appearance of ooplasm and nucleus, five oocyte developmental stages are distinguished. In contrast, the gonad structure and its changes during the spawning cycle differ considerably among species, and these differences are related to specific reproductive traits.Four gonad morphology types can be distinguished: the Calanus-type, found in species from all over the world with distinctly different life history traits, is apparently most common in calanoid copepods. In this gonad type, most oocyte developmental stages are present simultaneously, and usually many oocytes mature synchronously, all of which are released in one clutch. The gonad structure allows frequent spawning and large clutches, hence, high egg production rates. This may be a preconditioning for exploiting seasonally high food supply. However, the Calanus-type was also found in species producing eggs at lower rates. In the diverticula of Pseudocalanus-type gonads, only two oocyte developmental stages are present and usually fewer oocytes mature synchronously. Accordingly, the egg production rate is generally lower as compared to the Calanus-type, and apparently only this gonad-type is structurally suitable for ovigerity. Species with Pseudocalanus-type gonads are present from polar seas to the tropics, some of them being key species. The Acartia-type was scarce, found in only one species, Acartia clausi. Here all oocyte developmental stages are present, including intermediate stages, but only a few oocytes mature synchronously and are released together. High spawning frequency compensates for the small clutches, and hence egg production rate may be as high as in Calanus-type gonads. In the Aetidius-type gonad, the total number of oocytes in the diverticula is low as is the number of oocytes maturing synchronously. Less is known about the reproductive biology of species with Aetidius-type gonads; however, their distribution and feeding patterns suggest that this type is common in species inhabiting environments of low food availability.The differences in gonad structures also lead to differences in the egg size:female size ratio, as the space available for each mature oocyte depends on the total number of oocytes. Independent from gonad-type, the eggs are relatively large in species in which the gonads contain only few oocytes, whereas small eggs are produced by species with gonads filled with many oocytes. Since all species carrying their eggs in external sacs until hatching (ovigerous species) have Pseudocalanus-type gonads, the scatter in their egg size:female size ratio is low. The broadcast spawning species are of all gonad-types, and consequently the scatter among them is high.A major factor affecting the timing and magnitude of spawning of calanoid copepods is the energy supply for gonad development. Therefore, part of the review elucidates the role of internal and external resources in fuelling egg production. In many species, freshly assimilated food is transferred into egg material within a short period of time, and clutch size and spawning frequency are the two parameters that allow adjustment of egg production to food availability and temperature. However, internal body reserves may also fuel oocyte development. The extent to which oogenesis depends on ambient feeding conditions varies considerably among species and even within species, apparently reflecting their adaptation to specific environmental conditions. All copepod species continue to release eggs for a short period after the onset of starvation, indicating that a short-term nutrient pool fuels final oocyte maturation. Some species, especially from polar and subpolar regions, are capable of reproducing on internal reserves, either solely or in addition to freshly ingested food, hence, decoupling the reproduction to some extent from the spring bloom. The reproductive strategy of Calanus finmarchicus, which responds with extreme flexibility to variations in food supply, is presented here as an example for the complexity of the reproductive processes in a calanoid copepod.In accordance with their physiological pre-conditioning, the calanoid copepod species exhibit distinctly different reproductive patterns. Polar and sub-polar environments are characterized by strong seasonality in light regime, and hence, phytoplankton concentration. The reproductive activity of many dominant (herbivorous) species peaks during the spring bloom. However, species that utilize internal reserves or food resources other than phytoplankton, reproduce before and after the bloom, or even year-round. In the North Atlantic, presented here as an example for a boreal marine ecosystem, maximum reproduction of the dominant copepod species Calanus finmarchicus occurs during the spring bloom. However, the timing of peak spawning varies between areas, as the onset of the bloom varies with hydrography and climate. The subtropical Gulf of Aqaba, in contrast to other subtropical systems, is characterized by seasonal phytoplankton succession driven by thermal winter convection. These changing environmental conditions, however, did not affect the reproduction of two of the dominant species, Clausocalanus farrani and C. furcatus. In contrast, other calanoid species exhibit reproductive cycles, either related to temperature (Ctenocalanus vanus) or to ontogenetic migration (Rhincalanus nasutus).The information gained from studies of morphology and reproductive traits contributes to standardization of methods in reproductive studies. Based on detailed knowledge of gonad morphology and its changes during maturation and due to food supply, classification schemata have been developed allowing the identification of females ready to spawn. In a next step, egg production may be estimated from preserved females by assessing clutch size through the number of maturing oocytes in the gonads. This approach, however, is as yet applicable only to the species best studied, Calanus finmarchicus.The present review shows that morphological studies on gonad maturation processes may provide significant contributions to fundamental ecological questions. Thus, they extend our knowledge of reproductive ecology from simply relating reproductive traits to abiotic and biotic factors toward a mechanistic understanding of how reproduction is regulated in calanoid copepods.     

Induced Maturation and Spawning by Sex Pheromones in Female Mudskipper (Boleophthalmus pectinirostris)

1 IntroductionMudskipper ( Boleophthalmus pectinirostris ) inhabits muddy burrow in the intertidal mudflats of the temperature zone, feeding mainly on benthic diatoms and adapting to a wide range of salinity[1~3]. Although it is small in size, the mudskipper is delicious, nutritious and has a high market value. Fish farmers in Southeastern Mainland China are eager to culture this species. However, at present the natural resource of the fish has been decreasing or disappearing in some area…     

Factors in the distribution of intertidal,estuarine polychaetes: a field experiment with Nereis (Hediste) diversicolor and Nephtys hombergi in the Tamar at Plymouth

A field experiment was conducted over 10 weeks from July to mid-September, 1984, on a mudflat in the lower reaches of the Tamar Estuary at Plymouth, to test the relative importance of environmental factors and species interactions in controlling the distribution of two polychaete species. Nereis (Hediste) diversicolor from an upper shore site were transplanted into a lower shore site nearby which was characterized by the presence of Nephtys hombergi. 65–71% of N. diversicolor which were transplanted in their own sediments, with no contact with N. hombergi, survived the experimental period. The appearance of some small stages of N. diversicolor in these treatments was attributed in part to recruitment from the overlying water. N. diversicolor transplanted directly into N. hombergi-sediment survived in inverse proportion to their numbers and only the lowest densities (equivalent to 480 m⁻²) survived as well as those in their own sediment. Given the choice to invade the other species' sediment, more N. hombergi than N. diversicolor finally made the change, and there was some evidence that the smallest N. diversicolor suffered predation in consequence. Otherwise there was little evidence for inter-species interaction. There appeared to be some disruption of oocyte maturation of the N. diversicolor which may have been due to changes in tidal rhythm and salinity at the experimental site.     

Paleogene igneous intrusion and its effect on thermal maturity of organic-rich mudstones in the Beibuwan Basin,South China Sea

The seismic, drilling and logging data reveal that a large-scale igneous intrusion with a width of 14 Km and a maximum thickness of 170 m intruded within the Paleogene Liushagang Formation in the Fushan Depression, Beibuwan Basin, South China Sea (SCS). In this study, we report the geochemistry and Sr-Nd-Pb-Hf isotopic compositions of the igneous rocks, and evaluate the thermal effect induced by this large-scale igneous intrusion on the host rocks. The analyzed igneous samples exhibit strong enrichment in light rare earth elements (LREE) and large-ion lithophile elements (LILE), having characteristics similar to intra-plate oceanic island basalts (OIB). The Sr-Nd-Pb-Hf isotopic data display narrow ranges (e.g. ⁸⁷Sr/⁸⁶Sr_i = 0.7042–0.7044, ¹⁴³Nd/¹⁴⁴Nd_i = 0.5128–0.5129, ²⁰⁶Pb/²⁰⁴Pb_i = 18.90–18.94, εHf(t) = +7.56∼+9.60). Geochemical and isotopic compositions suggest a mixed mantle source between depleted mid-ocean-ridge-basalt (MORB) mantle (DMM)-like mantle and enriched mantle type II (EMII, possibly the Hainan mantle plume). Vitrinite reflectance values, major mineralogical changes together with a maturity-related biomarker [Ts/(Ts + Tm)] all reveal significant thermal effect induced by the igneous intrusion. Vitrinite reflectance values of the host rock are up to 2.5% in the intrusion region, whereas lower reflectance values (0.62–0.73%) occur in the unaffected area of the same strata. Moreover, our results suggest that the host rocks above the igneous intrusion are characterised by higher maturity than below, which should be attributed to the different behavior of hydrothermal fluids. These observations suggest that the thermal effect of large-scale thick igneous intrusions is much more intense than that of thin igneous intrusions, and the behavior of hydrothermal fluids induced by magmatic intrusive events should be a critical impact factor during heat transfer process.     

Effects of benzo[a]pyrene on DNA damage and histological alterations in gonad of scallop Chlamys farreri

To investigate the biological impact of polycyclic aromatic hydrocarbons (PAHs) on reproductive system, scallops Chlamys farreri were continuously exposed to benzo[a]pyrene (BaP) (0.5, 3, 10 μg L^?1) during 15 days. DNA damage and histological alterations were examined in female gonad. DNA strand break levels significantly increased after 12 h exposure, and remained high and significantly different from control values until the end of the exposure. In the ovaries of the scallops exposed to 10 μg L^?1 BaP for ten days, histological analysis showed that the cytoplasts of the oocytes in the outer layer of the ovaries became sparse, and the nuclear membranes were obscure. Damaging effects on ovaries and oocytes were more severe after 15 days exposure. Degenerating oocytes increased and the connective tissue of the ovary envelops became loose. Electron microscopic examination revealed ultrastructural aspects of degenerating oocyte and degenerated oocyte after 15 days exposure.     

Cellular responses in the mussel Mytilus edulis following exposure to diesel oil emulsions: Reproductive and nutrient storage cells

The objectives of this study were to examine, and quantify with the aid of stereological techniques,^1,2 the effects of exposure to hydrocarbons on the reproductive and nutrient storage cell systems in the marine mussel, Mytilus edulis. In addition, the capacity for recovery of these cell systems was quantified following a period of hydrocarbon depuration. The second phase of these investigations examined the significance of nutritional reserves at the time of exposure to hydrocarbons and how this may influence the animal's ability to survive the insult. The results (Table 1) indicated that, first, hydrocarbons had a deleterious effect on the nutritional storage cells leading to reduced fecundity and oocyte atresia (degeneration). Given a period of depuration, however, there were indications of a recovery in both the reproductive and storage cell systems. Second, the ability of mussels to survive hydrocarbon exposure was dependent upon the nutrient reserves at the onset of exposure.