Mature Female Fish Research Articles

Ecological risk of methylmercury to piscivorous fish of the Great Lakes region

Contamination of fish populations with methylmercury is common in the region of the Laurentian Great Lakes as a result of atmospheric deposition and methylation of inorganic mercury. Using fish mercury monitoring data from natural resource agencies and information on tissue concentrations injurious to fish, we conducted a screening-level risk assessment of mercury to sexually mature female walleye (Sander vitreus), northern pike (Esox lucius), smallmouth bass (Micropterus dolomieu), and largemouth bass (Micropterus salmoides) in the Great Lakes and in interior lakes, impoundments, and rivers of the Great Lakes region. The assessment included more than 43,000 measurements of mercury in fish from more than 2000 locations. Sexually mature female fish that exceeded threshold-effect tissue concentrations of 0.20 μg g(-1) wet weight in the whole body occurred at 8% (largemouth bass) to 43% (walleye) of sites. Fish at 3% to 18% of sites were at risk of injury and exceeded 0.30 μg g(-1) where an alteration in reproduction or survival is predicted to occur. Most fish at increased risk were from interior lakes and impoundments. In the Great Lakes, no sites had sexually mature fish that exceeded threshold-effect concentrations. Results of this screening-level assessment indicate that fish at a substantive number of locations within the Great Lakes region are potentially at risk from methylmercury contamination and would benefit from reduction in mercury concentrations.

Population dynamics and conservation management of Himalayan mahseer (Tor species) in riverine aquatic ecosystem in Garhwal region of Uttarakhand (India)

The mahseer, an Indian carp (Tor species) known as ‘Sport fish’ continues to be decimated by the large scale natural and anthropogenic factors and categorized as threatened fishes in India. The present research data revealed that total species richness of 33 and 24 number of fish species were identified in river Ganga and Yamuna respectively. The size group of mahseer (400-460mm) recorded as a dominant size of catch composition and contributed about 36.8% and 42.6% based on different sampling sites in river Yamuna and Ganga respectively. The populations of Tor tor, T. putitora have shown a decreasing trend at very alarming rate and influenced the sex ratio, maturity size and natural breeding condition. Only 12.5 to 14.8% mahseer female brooders have shown maturity phase or emenable to release ova during particular breeding seasons. The fecundity of mature female fish brooders ranged from 2500-4500 no. of eggs during July-August. The current status of mahseer fishery may be attributed to the over exploitative nature in riverine system. ‘In situ and Ex-situ” breeding techniques should be practiced for enhancement of viable population size of mahseer species to restore the genetic loss under mahseer conservation programme in aquatic ecosystem of Himalayan region.

Fecundidad de Otocinclus spectabilis.

Titulo en ingles: Otocinclus spectabilis fecundity.RESUMEN: La fecundidad en peces, es la estimación de la cantidad de ovocitos que una hembra podría expulsar en un desove, siendo uno de los indicadores más utilizados para evaluar el potencial reproductivo de una especie y sus posibilidades para la piscicultura. Para aportar al conocimiento de este criterio, se estudiaron los ovarios de hembras silvestres maduras, las cuales fueron pesadas individualmente al igual que sus ovarios y calculado el Índice gonadosómatico (IGS). Luego cada ovario fue digerido en solución Gilson durante 20 días y luego tamizado en malla de 500 µm y los ovocitos retenidos fueron contados y obtenida la fecundidad. La fecundidad relativa a peso (FRP) también fue calculada así como los diámetros ovocitarios medidos bajo estereoscopio. Una decima parte de cinco ovarios fueron procesados para histología convencional H & E y una vez analizados, deducido el desarrollo de los ovocitos y el tipo de desove comparando la información obtenida.Se obtuvo una fecundidad de 62 ± 8 ovocitos / hembra y una FRP = 91 ± 10 ovocitos g-¹ peso total, el IGS fue de 13,2 ± 1,1 %, y el diámetro ovocitario de los ovocitos maduros fue de 1.366,5 ± 203,8 µm, siendo que las frecuencias de los diámetros de los ovocitos mayores de 500 µm encontradas en conjunto con las placas histológicas estudiadas, mostraron dos grupos de ovocitos en crecimiento, lo que permite concluir que el desarrollo del ovario es asincrónico y el desove parcial.Palabras clave: desarrollo ovocitario, desove, diámetros ovocitarios, fecundidad relativa, índice gonadosómatico, otocinclo.ABSTRACT: Fecundity is the estimated number of oocytes which a female could be expected to expel during one spawning; this is thus one of the most used indicators for evaluating fish species'reproductive potential and their farming potential. The ovaries of mature wild female fish were studied to contribute towards knowledge regarding this criterion. Fish and ovaries were weighted individually and the gonadosomatic index (GSI) was calculated. Each ovary was digested in Gilson's solution for 20 days and then screened through a 500 µm mesh; the retained oocytes were counted (by stereomicroscope) and fecundity was thus estimated. The relative fecundity to weight (RFW) ratio was also calculated and oocyte diameters were measured. Atenth part of five ovaries was processed by conventional histology (haematoxylin and eosion- H&E - stain) to study oocyte development andtypes of spawning.This led to 62 ± 8 oocytes / female fecundity and 91 ± 10 oocytes g-¹ total weight RFW being obtained; the GSI was 13.2 ± 1.1 % and mature ovaries'oocyte diameter was 1,366.5 ± 203.8 µm. Oocyte diameter frequency and the histological slides revealed two oocyte growth groups having greater than 500 µm, thereby leading to the observation that ovarian development was asynchronous and spawning was partial in this sample.Key words: gonadosomatic index, oocyte development, oocyte diameter, otocynclos, relative fecundity, spawning

Cryopreservation of sperm from natural and sex-reversed orange-spotted grouper (Epinephelus coioides)

The shortage of males and/or sperm has been an impediment to the aquaculture of orange-spotted grouper (Epinephelus coioides). This study reversed orange-spotted grouper females into males using hormone implants. A cryopreservation protocol for sperm was developed using normal males, and then using similar procedures the cryopreservation of sperm from sex-reversed males was compared. Immature, young and mature female fish were injected with 4 mg kg−1 BW 17α methyltestosterone as implants and the gonad development stage was monitored over a 120-day period. All treated females converted into functional males within 120 days of the experimental period. Younger females (2Y) were all males within 30 days, although not all were capable of fertilizing fresh ova until day 60. The time after injection to sex reversal in immature fish was 50% shorter than in older females. Postthaw fertilization (81%, 82%) and hatching (45%, 47%) of cryopreserved sperm from natural males were the highest in trehalose (15–20%) with 150 mmol NaCl treatment; however, it was less than the control (89% fertilization and 69% hatch). There was no difference in the postthaw fertilization and the hatch percentages between sex-reversed male sperm (64% and 46% respectively) compared with natural male sperm (59% and 49%). The findings of this study suggest the potential use of sex-reversed males and cryopreserved sperm for commercial production of orange-spotted grouper seed for aquaculture.

DNA methylation levels in the 5′ flanking region of the vitellogenin I gene in liver and brain of adult zebrafish (Danio rerio)—Sex and tissue differences and effects of 17α-ethinylestradiol exposure

Vitellogenin is produced in the liver of sexually mature female fish in response to endogenous estrogens. Exogenous estrogens also induce synthesis of vitellogenin in the liver of male and juvenile fish and vitellogenin is a frequently used biomarker for estrogen exposure. The epigenetic state, e.g. histone acetylation and DNA methylation, in the region of a gene or in its 5′ flanking region influences the gene expression. DNA methylation positions in multicellular eukaryotes are mostly found on cytosine bases located 5′ to guanine, i.e. in CpG sites. Here, we have for the first time analyzed the DNA methylation levels of three CpG sites located in the 5′ flanking region of the vitellogenin I gene in liver and brain from adult zebrafish (Danio rerio) utilizing Pyrosequencing technology. This sequencing technique allows determination of methylation levels of multiple individual CpG sites. Our purpose was to assess any differences in methylation levels related to sex, tissue and exposure to estrogen. Out of the seven vitellogenin genes identified in the zebrafish, vitellogenin I is the most highly expressed during vitellogenesis. We found that the methylation levels of all three CpG sites were higher in male liver than in female liver. In brain, which does not express vitellogenin, females and males showed similar, high methylation levels in the analyzed CpG positions. Exposure of adult zebrafish to 17α-ethinylestradiol (100ng/L) for 14 days decreased the methylation levels in the 5′ flanking region of vitellogenin I in the liver in both females and males. These results suggest that induced expression of vitellogenin in fish following exposure to estrogens might involve alterations in DNA methylation.

Change in Tetrodotoxin Content of the Puffer Fish Takifugu rubripes during Seed Production from Fertilized Eggs to Juveniles

Changes in tetrodotoxin (TTX) content of the puffer fish Takifugu rubripes during seed production were examined. Two mature female puffer fish T. rubripes (samples 1 and 2) that contained TTX were used. The toxic eggs were artificially fertilized, and hatchlings were reared in an indoor tank for 50 days and then in a netcage at sea for an additional 48 or 38 days. The TTX content of the fertilized eggs of sample 1 was initially 13.0 microg TTX/g, transiently increased to 67.6 microg TTX/g at 4 days after hatching, and then gradually decreased to 0.28 microg TTX/g at 98 days. In contrast, the total TTX content in an individual was 0.016 microg TTX at the fertilization stage and 0.01-0.03 microg TTX at the larval stage until 30 days after hatching. Thereafter, the total TTX content increased remarkably during culture in the netcage at sea, reaching 4.80 microg TTX at 98 days. Change in the TTX content of sample 2 showed a similar tendency to that of sample 1. The present study showed that the TTX content per gram of puffer fish body weight decreased during progression from fertilized eggs to juveniles, whereas the total TTX content increased.

Generation of a fluorescent transgenic zebrafish for detection of environmental estrogens

To establish a novel in vivo test system for rapid detection of environmental estrogens, an ere-zvtg1: gfp transgenic zebrafish line has been generated. In this transgenic line, under control conditions, GFP was exclusively expressed in the liver of mature adult female fish. Male and larval transgenic fish did not express GFP but could be induced to express GFP in the liver after exposure to 17-α-ethynylestradiol (EE 2). Concurrent accumulation of zvtg1 and gfp mRNAs in embryos and larvae after EE 2 exposure was observed, which indicated that the expression of gfp transgene was driven by the zvtg1 promoter. Green fluorescence was first observed in the liver at 53, 74, 100 or 131 h post-fertilization (hpf) after exposure to 100, 10, 1 or 0.1 ng/L EE 2 from 1 to 2 cell stage, respectively. As for mature male transgenic zebrafish, green fluorescence was observed after exposure to 100, 10, 1 or 0.1 ng/L EE 2 for 2, 3, 4 or 7 days, respectively; as for mature female, fluorescence was increased after exposure to relatively high concentrations of EE 2 (10 and 100 ng/L). Green fluorescence in the liver was increased with prolonging of exposure time and was repeatedly induced after removal and re-addition of EE 2. We also demonstrated that GFP expression could be induced by other estrogenic compounds, including β-estradiol (E 2, 0.1 μg/L), cadmium chloride (CdCl 2, 10 μg/L), zearalenone (50 μg/L), estriol (E 3, 1 μg/L), diethylstilbestrol (DES, 50 ng/L) bisphenol A (BPA, 1 mg/L) but not by weakly estrogenic compounds such as nonylphenol (NP, up to 10 mg/L), or non-estrogenic steroid hormones such as progesterone (up to 100 mg/L) and 17-hydroxysteroid (up to 50 mg/L). These data suggest the transgenic zebrafish is sensitive and specific for detection of estrogenic compounds. Because the observed-effect concentrations are as low as those of environment and the observed-effect exposure times are very short, this transgenic fish is a promising candidate system for monitoring environmental estrogens directly, rapidly and easily.

Collagen Type-I α1 Chain mRNA is Expressed in the Follicle Cells of the Medaka Ovary

Follicle rupture during ovulation is a well-regulated biological process of extracellular matrix degradation in the vertebrate ovary. Although proteolytic enzymes responsible for the rupture have recently been identified in the medaka, Oryzias latipes , the lack of knowledge about the ovarian expression and distribution of extracellular matrix components in lower vertebrates prevents the understanding of this process's molecular mechanism. To approach the problem, we cloned a cDNA coding for the medaka collagen type-I alpha1 chain and examined its mRNA expression in the fish ovary. The deduced amino acid sequence of the collagen type-I alpha1 chain was homologous to those of the proteins from other vertebrate species. The alpha1 chain mRNA was expressed in various tissues of the adult fish. In the ovary sections of mature female fish, this mRNA was detected in a line surrounding ovarian follicles of all sizes. A comparison with the distribution of gelatinase B mRNA in follicles that had just ovulated indicated that the collagen type-I alpha1 gene is expressed in the theca cells. The current results strongly suggest that collagen type I is synthesized by theca cells and is localized in the same cell layer of the follicles.

Fecundity and Maturity of Orange Roughy (Hoplostethus atlanticus Collett 1889) on the Porcupine Bank, Northeast Atlantic

The first, comprehensive analysis of the fecundity and reproductive maturity of orange roughy, Hoplostethus atlanticus, from a specific area in the Northeast Atlantic is reported. Specimens were collected from aboard vessels, targeting this species on the Porcupine Bank (ICES subarea VII), in waters of between 1400 m and 1,650 m depth. Between September and December 2002, a non-random, stratified, sampling protocol was implemented by on board fisheries biologists to collect mature female fish between 300 mm and 540 mm SL. Ovaries from 65 individuals, representing the majority of 10 mm SL size classes, formed the analytical sample. A novel, digital method of oocyte counting was developed, allowing digital images of oocytes to be annotated, counted and stored. Total fecundity ranged between 20,352 and 244,578 oocytes per female and mean total fecundity was estimated to be 97,368 oocytes per female (SD = 48,322). Relative fecundity was estimated to be 33,376 oocytes per kg (SD = 11,407). Fecundity was shown not to decrease with age. Macroscopic analyses showed that 50% of females were not mature until they reached 27.5 years and 37 cm SL. Comparison with stocks from the southern hemisphere indicate that orange roughy from the Northeast Atlantic mature at a larger size and generally have a higher mean fecundity than those found in the southern hemisphere. This may reflect differences in growth rates influenced by environmental variables and fishing pressure.

Reproductive Biology of Three Commercially Important Hemiramphid Species in South-eastern Australia

The reproductive biology of eastern sea garfish Hyporhamphus australis, eastern river garfish H. regularis ardelio, and snub-nosed garfish Arrhamphus sclerolepis were described throughout their respective ranges in the coastal waters of New South Wales (NSW), Australia. Peaks in gonadosomatic indices indicated that spawning of eastern sea garfish occurred in late spring and early summer (November–December) on the south coast of NSW, and in winter and early spring (June–September) on the north coast. Eastern river garfish spawned between July and December in NSW estuaries and snub-nosed garfish spawned between October and January in the Clarence River. The sex ratios in commercial catches of eastern sea garfish from the north coast of NSW were biased toward male fish, but approached equality for fish caught from the south coast. Sex ratios were significantly biased toward female snub-nosed garfish, and female eastern river garfish from all estuaries sampled. Mean (±SE) batch fecundity was 1498 ± 110 (range: 98 – 3449) ripe oocytes per female for eastern sea garfish, 917 ± 36 (range: 102 – 2268) ripe oocytes per female for eastern river garfish, and 716 ± 104 (range: 20 – 2956) ripe oocytes per female for snub-nosed garfish across the range of mature sizes examined. There was a linear relationship between batch fecundity and fish size for all three species of garfish. Eastern sea garfish approached 50% maturity at a larger size than snub-nosed, or eastern river garfish. Size at 50% maturity was similar for male and female eastern river and snub-nosed garfish, but male eastern sea garfish matured at a significantly smaller size than females. All three species appear capable of spawning in the spawning season immediately following the one in which they were born. Mature female fish of all three species had distributions of oocyte diameters consisting of three or four modes, which strongly suggests asynchronous oocyte development and a multiple spawning strategy during the spawning season. Implications for the management of garfish fisheries in NSW are also discussed.

Sex and low-level sampling stress modify the impacts of sewage effluent on the rainbow trout ( Oncorhynchus mykiss) immune system

The objective of the present study was to investigate the influence of chronic exposure to municipal sewage treatment effluent at environmentally relevant concentrations on immune parameters in rainbow trout ( Oncorhynchus mykiss), including the assessment of potential differences in reactivity between sexually mature male and female fish. Trout were exposed to 1.5 and 15% (v/v) secondary treated municipal sewage effluent for 32 weeks. Fish were injected intra-peritoneally either with inactivated Aeromonas salmonicida to simulate an infection or with PBS as control for this immune challenge 6 weeks prior to sampling. Exposure to effluent resulted in a decrease in A. salmonicida-specific serum antibody level and blood lymphocyte numbers in mature females, but not in male fish. Injection of A. salmonicida resulted in enhanced serum lysozyme activity in mature male trout, which were not exposed to effluent. This stimulating effect of A. salmonicida could not be found in effluent-exposed trout, again potentially revealing a suppressive effect of the effluent. An influence of sampling fish on two consecutive days was observed in many immune parameters, most likely reflecting handling stress. Leucocyte and lymphocyte numbers in peripheral blood were consistently lower in male and female fish on the second sampling day. Phagocytosis in head kidney macrophages from male trout was also influenced by sampling day, whereby a stimulation of this reaction occurred on the second day of sampling. Liver mixed function oxygenase activity was found to be enhanced in mature male trout exposed to 15% effluent. In conclusion, the study showed, that exposure to sewage treatment plant effluent, in surface water relevant concentrations, can lead to potentially adverse effects on selected immune reactions in rainbow trout. However, this study also demonstrated that both handling stress and the sex of mature fish have distinct influences on the immune response detected in male and female fish and are likely to influence measured immune parameters to the extent that subtle effluent induced changes may be difficult to detect.

Reproduction, growth, mortality and yield of Tilapia mariae Boulenger 1899 (Cichlidae) in a Nigerian rainforest wetland stream

The biology and fisheries of Tilapia mariae, the only tilapiine cichlid fish in the Iba Oku (Uyo, Nigeria) wetland stream was studied. There were more females than males in the population. The smallest sexually mature female fish was 11.0 cm total length (TL) while the size at 50% maturity was 17.1 cm TL. Absolute fecundity (Fe) ranged from 953 to 3200 eggs and was positively correlated with TL. The fish bred year-round with peaks in November, March–April and July–September. The seasonalized von Bertalanffy growth function (VBGF) was fitted to the 12 consecutive months length–frequency data (n = 2439) to obtain a VBGF with the following parameters: L∞ (asymptotic length) = 30.4 cm TL, K (growth coefficient) = 0.4 year−1, C (amplitude of growth oscillation) =0.4, and WP (winter point) = 0.9. The seasonalized length-converted catch curve method gave Z (instantaneous total mortality coefficient) as 1.75 year−1, M (instantaneous natural mortality coefficient) was 0.99 year−1 while F (instantaneous fishing mortality coefficient) was 0.76 year−1 and E (=F/Z the current exploitation rate) was 0.43. Length at first capture (Lc) was 17.7 cm TL. The fish was recruited to the fishery year-round with two pulses. From the Beverton and Holt relative yield per recruit analysis via the selection ogive procedure, Emax (predicted maximum exploitation rate) was 0.54. The stock was not overexploited, since E < Emax. This study also showed that the fish is an r-selected species with a few K-selected traits.

Modeling vitellogenesis in female fish exposed to environmental stressors: predicting the effects of endocrine disturbance due to exposure to a PCB mixture and cadmium

A wide variety of chemical and physical environmental stressors have been shown to alter the reproductive processes in fish by interfering with endocrine function. Most endocrine indicators or biomarkers are static measures from dynamic hormonally-mediated processes, and often do not directly relate to reproductive endpoints of ecological significance. Adequate production of the yolk precursor protein, vitellogenin, is critical for the survival and normal development of the sensitive egg and yolk-sac larval fish life stages. We developed a model that simulates vitellogenesis in a mature female sciaenid fish. The model simulates the major biochemical reactions over a 6-month period from the secretion of gonadotropin (GtH) into the blood to the production of vitellogenin. We simulated the effects of two endocrine disrupting chemicals (EDCs) that have different actions on vitellogenin production: a PCB mixture and cadmium. Predicted changes in steroid concentrations and cumulative vitellogenin production compared favorably with changes reported in laboratory experiments. Simulations illustrate the potential utility of our model for interpreting reproductive endocrine biomarkers measured in fish collected from degraded environments.

Gill net selectivity for European hake Merluccius merluccius from southern Portugal: implications for fishery management

: A study of European hake Merluccius merluccius gill net selectivity was undertaken off the Algarve (Southern Portugal), between 1999 and 2001. Four nominal mesh sizes (70, 80, 90 and 100 mm) were used in fishing trials and the ‘share each length class catch total’ (SELECT) method was used to fit gill net selectivity curves. Hake were caught in the same size range by all mesh sizes, between 17 and 65 cm total length. While most fishes were wedged, significant and similar proportions were entangled in all mesh sizes, contributing to the wide size range, and in some cases, bimodal shape of catch size frequency distributions. Insignificant numbers of undersized hake were caught, with most catches consisting of mature female fish. Catch rates decreased sharply with increasing mesh size. The bimodal model gave the best fit for hake that were wedged, with estimated modal lengths of 40.1, 46.7 and 51.0 cm for the 70, 80 and 90 mm nominal mesh sizes, respectively. The high catch per unit effort of the smallest mesh size, with most fish caught being female, together with the fact that the modal length of the fitted selectivity curve is well below the size at maturity for hake in Portuguese waters, suggests that the 80 mm nominal mesh size is more appropriate for ensuring resource sustainability.

Estradiol reduces pituitary responsiveness to somatostatin (SRIF-14) and down-regulates the expression of somatostatin sst 2 receptors in female goldfish pituitary

Sex steroid hormones have been shown to regulate somatostatin (SRIF) gene expression in goldfish brain, which in turn influences the regulation of GH secretion. In this study, the influences of sex steroids on pituitary responsiveness to SRIF-14 and the pituitary expression of a type two SRIF receptor (sst 2) were examined. Results from in vitro perifusion of pituitary fragments show that pituitaries from estradiol-primed sexually regressed female fish have significantly lower GH release responsiveness to pulse exposure to SRIF-14 than pituitaries from control or testosterone-treated sexually regressed females. Results from in vitro static culture show that pituitaries from sexually mature female fish have lower GH release responsiveness to SRIF-14 than those from sexually regressed females. In addition, the sst 2 receptor mRNA levels in pituitaries from mature and recrudescent female fish are significantly lower than in sexually regressed female fish. Our results indicate that estradiol acts at the level of the pituitary to regulate GH secretion by influencing the responsiveness to SRIF-14. The underlying mechanism includes, in part, reduction of the expression of sst 2 receptors, presumably leading to the lower number of the receptors available for SRIF binding.

Dynamics and cytochemistry of oogenesis in Astyanax fasciatus (Cuvier) (Teleostei, Characiformes, Characidae) from Rio Sapucaí, Minas Gerais State, Brazil

Oogenesis involves a set of transformations which are undergone by female germ cells These cells change into oogonias and then into mature oocytes. Sexually mature female fish were collected monthly, during one year, from the Sapucai River, a tributary of the Rio Grande, which is part of the Furnas Reservoir in the state of Minas Gerais. During the several stages of maturation, we observed small round oogonias with a large nucleus, a single nucleolus, and weakly stained cytoplasm with eosinophilic granules. The primary oocytes showed a large basophilic nucleus, with a developed peripheral nucleolus and a reduced cytoplasm. The previtellogenic oocytes presented voluminous cytoplasm and nucleus with several small peripheral nucleoli. The oocytes underwent vitellogenesis with the development of the zona radiata and the follicle cells. Their cytochemical reactions indicated that the two layers of the zona radiata of A. fasciatus contained proteins and polysaccharides. The initially squamous follicle cells, became cuboidal. In mature oocytes, the nucleus moved toward the periphery, next to the micropyle, and the yolk granules formed by proteins, fulfilled the cytoplasm. The clear unstained vesicles are likely to be the cortical alveoli in the perivitelline region.

Whole-cell response characteristics of ciliated and microvillous olfactory receptor neurons to amino acids, pheromone candidates and urine in rainbow trout.

Olfactory lamellae of teleosts contain two morphologically different types of olfactory receptor neurons (ORNs): ciliated ORNs (cORNs) and microvillous ORNs (mORNs). However, little is known about the functional difference between these two types of ORNs in fish olfaction. We isolated cORNs and mORNs using a Ca(2+)-free solution method from olfactory organs of the rainbow trout and examined their response characteristics to various odorants including fish pheromone candidates by whole-cell voltage-clamp techniques. Quadruple mixture of amino acids, single amino acids, steroids (analogues of DHP; 17 alpha, 20 beta-dihydroxy-4-pregnen-3-one and ECG; etiocholan-3 alpha-ol-17-one glucuronide), prostaglandins (PGFs) and urine samples collected from immature and mature female fish were applied focally to olfactory cilia or microvilli using a multi-barreled stimulation pipette with a pressure ejection system. Inward current responses to odorants were recorded from both cORNs and mORNs at a holding potential of -60 mV. cORNs responded to the amino acid mixture, single amino acids, urine samples and ECG, whereas mORNs responded specifically either to the amino acid mixture or single amino acids. The response profiles of both cORNs and mORNs to various odorants varied widely. None of cORNs and mORNs responded to fish pheromone candidates, PGFs and DHPs. Androgen treatment of immature fish did not influence olfactory sensitivity of both cORNs and mORNs to the amino acid mixture and both urine samples. Amino acid and bile acid analyses by HPLC showed that both urine samples contained 35 amino acids (1-40 mM) and trace amounts of taurocholic acid and glycoursodeoxycholic acid. Our results suggest that cORNs are 'generalists' that respond to a wide variety of odorants, including pheromones, whereas mORNs are 'specialists', specific to amino acids, and also suggest that PGFs and DHPs are not pheromones for the rainbow trout.

Mosquitofish ( Gambusiaaffinis) vitellogenin: identification, purification, and immunoassay

Vitellogenin is a phospholipoglycoprotein precursor of egg yolk. In mature female fish, vitellogenin is synthesized and secreted by the liver in response to circulating estrogens. Vitellogenin is normally undetectable in the blood of male fish, but can be induced by exposure to compounds possessing estrogenic activity. Thus, the presence of vitellogenin in blood of male fish can serve as a useful biomarker for assessing previous exposure to estrogenic compounds. In the present study, we report identification and purification of vitellogenin in the mosquitofish ( Gambusia affinis). Anti-vitellogenin immune serum was generated and used to develop an immunoblot assay for detection of vitellogenin. A combination of immunoblotting and densitometric scanning was used to assess the time- and dose-dependent effects of 17α-ethynylestradiol on vitellogenesis in male G. affinis. The results indicate that changes in the level of vitellogenin in mosquitofish blood can be reliably detected by the immunoblot assay, and that the mosquitofish may be a useful bioindicator organism for detecting estrogenic contamination of the aquatic environment.

Aspects of the reproductive biology of the red Pandora &lt;i&gt;Pagellus bellottie&lt;/i&gt; (Pisces: Sparidae) in Ghana

The reproductive biology of Pagellus bellottii (Stenidachner, 1882) occurring in Ghana is reported in this paper. Data was collected on monthly samples taken from November 1993 to October 1995. Specimens longer than 18.9 cm TL were predominantly males, but the ratio of males to females was not significantly different in small fishes. Overall, the males were numerically dominant. The smallest mature male and female fish measured 13.6 cm TL, and 13.5cm TL, respectively. These sizes correspond to maturity age of 0.65 yr. The length at which 50% of the fish are matured was estimated at 21.0 and 20.0cm TL which corresponded to 1.5 and 1.3 yr, respectively, for males and females. Changes in the gonadosomatic index (GSI) suggested a minor spawning activity in January and February, and a major spawning from June to September. Spawning in the species, therefore, occurred during the upwelling seasons in Ghanaian waters. The occurrence of two distinct groups of ova representing mature and immature stocks indicated possible discontinuous breeding in the species. JOURNAL OF THE GHANA SCIENCE ASSOCIATION Volume 2 No. 1 (2000) pp. 23-30

Identification and spatial distribution of the mRNA encoding an egg envelope component of the Cyprinid zebrafish, Danio rerio, homologous to the mammalian ZP3 (ZPC)

Using degenerate reverse transcription polymerase chain reaction (RT-PCR) techniques we have isolated a cDNA encoding a putative component of the zebrafish Danio rerio egg chorion, homologous to the mammalian ZP3 (ZPC). The predicted protein (zfZPC) has a calculated molecular mass of 58.4 kDa and contains a signal peptide (located in the N-terminal region) composed of 11 hydrophobic amino acid residues followed by a signal peptide cleavage site. The zfZPC contains the ZP domain, a characteristic amino acid sequence shared by all ZP proteins of the mammalian zona pellucida and of both amphibian and bird egg envelope components. The zfZPC also exhibits certain unique features including five N-terminal Q-rich tandem repeats presumably involved in the hardening of the chorion after the fertilization of the egg and a long C-terminal tail containing two potential sites of N-linked type glycosylation. RT-PCR and in situ hybridization revealed a restricted pattern of tissue distribution: the gene encoding zfZPC is transcribed only in the growing oocyte of sexually mature female fish.