Lower Gonadosomatic Index Research Articles

Assessment of Stress-Related Bioindicators in Winter Flounder (Pleuronectes americanus) Exposed to Discharges from a Pulp and Paper Mill in Newfoundland: A 5-Year Field Study

This study assessed the effects of discharges from a sulphite-bleaching paper mill on winter flounder (Pleuronectes americanus) sampled each spring over a 5-year period in St. George's Bay, Newfoundland, prior to foraging activity. The fish were captured by SCUBA divers near the mill and at a reference site 10 km up current. Several bioindicators were used to assess fish health. Larger and older flounder exhibiting gross and microscopic tissue lesions, lower condition factor, and elevated hepatosomatic index but lower gonadosomatic index that was associated with delayed development, were observed in samples caught near the mill compared to those at the reference site. Additionally, fish examined near the mill were infested with an ectoparasite, Cryptocotyle lingua, that causes black spot disease but harbored fewer numbers of a digene, Steringophorus furciger, in the digestive tract than samples taken at the reference site. These results suggest that abnormal size distribution, interruption of growth, high prevalence of lesions, lower condition factor, enlarged liver, delayed gonadal development, and differences in parasitic levels were indicative of stress in winter flounder caused by discharges from the mill compared to samples from a reference site. There was no evidence of a population decline in the inlet because of annual recruitment possibly from St. George's Bay into which it opens.

Basic physiological biomarkers in adult female perch ( Perca fluviatilis) in a chronically polluted gradient in the Stockholm recipient (Sweden)

By measuring a battery of basic physiological biomarkers and the concentration of ∑DDT in adult female perch ( Perca fluviatilis), an assumed aquatic pollution gradient was confirmed, with the city of Stockholm (Sweden) as a point source of anthropogenic substances. The investigation included an upstream gradient, westwards through Lake Mälaren (46 km), and a downstream gradient, eastwards through the Stockholm archipelago (84 km). The results indicated a severe pollution situation in central Stockholm, with poor health status of the perch: retarded growth, increased frequency of sexually immature females, low gonadosomatic index, and disturbed visceral fat metabolism. ∑DDT, measured as a pollution indicator, was 10–28 times higher than the background in perch from the Baltic Proper. Besides the main gradient other sources of pollution also influenced the response pattern of the measured biomarkers. In particular, there were strong indications of pollution coming from the Baltic Sea.

Toxicological effects and reproductive impairments in female perch ( Perca fluviatilis) exposed to leachate from Swedish refuse dumps

We have previously found that leachate from a Swedish refuse dump caused toxicological effects, including endocrine disruption and reproductive failures, in feral female perch ( Perca fluviatilis) from Molnbyggen and in brook trout ( Salvelinus fontinalis) from Vadbäcken. This raised concerns that leachate-induced toxicity might affect fish in other leachate-contaminated lakes. This study looks at female perch from three different regions in Sweden, focusing on toxicological biomarkers (skin lesions, liver-somatic index (LSI), ethoxyresorufin O-deethylase (EROD) activity and DNA adducts) and reproductive biomarkers (number of mature females, gonadosomatic index (GSI), aromatase (P450arom), progesterone, 17α-hydroxyprogesterone (17α-OHP), testosterone (T) and 17β-estradiol (E2)). Five out of seven contaminated locations had lower numbers of mature females and most of them exhibited higher frequencies of fin erosion relative to their comparable reference sites. Females from Lake Nedre Vättern exhibited these effects, as well as body sores, high EROD activity, high levels of DNA adducts in the liver and the intestinal mucosa, low GSI and low plasma levels of T and E2, similar to the anti-estrogenic effects earlier found in SM perch from Molnbyggen in 1997 and in brook trout from Vadbäcken. No effects on LSI, GSI, aromatase, or circulating steroids were found in mature females from Molnbyggen in this study. This indicated less leachate-contamination, but low numbers of mature females in Lake Siljan, at the sewage treatment plant which now processes the leachate that earlier contaminated Molnbyggen and Vadbäcken, suggested insufficient sewage treatment at this site. All females in Lake Simshyttsjön were mature, and their high GSI and LSI, low EROD activity, high level of 17α-OHP and low level of T, suggest an estrogenic rather than an anti-estrogenic effect. The results show that our earlier findings in Molnbyggen and Vadbäcken are not common, but neither are they unique. This study also shows that refuse dumps should be considered as potential point-sources for environmental pollutants, and that uncontrolled leachate-contamination of lakes and freshwater reservoirs could be a serious environmental hazard for both wildlife and humans.

Isolation and characterization of two cytochrome P450 aromatase forms in killifish ( Fundulus heteroclitus): Differential expression in fish from polluted and unpolluted environments

Populations of killifish ( Fundulus heteroclitus) persist in many different highly polluted environment indicative of adaptation or tolerance. In this study, we sought to determine whether long term, multigenerational exposures to environmental contaminants has affected reproductively relevant genes and biological processes. A homology cloning strategy was used to isolate the killifish cytochrome P450 aromatase (P450arom, estrogen synthetase) cDNAs. Consistent with previous fish studies, killifish were found to have two P450arom forms, which segregated into A- and B-gene clades and were differentially expressed in brain (B ≫ A) and ovary (A ≫ B). Comparison of killifish from highly polluted (New Bedford Harbor, NBH) and unpolluted (Scorton Creek, SC) environments revealed no site-related differences in P450arom coding sequences or in overall tissue distribution patterns. As measured by real-time quantitative PCR (QPCR) analysis, however, P450arormB (a known marker of estrogen effect) was approximately two-fold higher in the brain of NBH than of SC fish, a difference seen in reproductively active and inactive males and females. Providing further evidence of exposure to estrogen-like pollutants or metabolites in NBH, vitellogenin (vtg) mRNA and protein were elevated in seasonally active and inactive males, and in reproductively inactive females, when compared to SC fish. By contrast, during the period of reproductive activity, NBH females had a lower gonadosomatic index, lower plasma estrogen, a decreased hepatosomatic index, and reduced vtg expression as compared to SC females, indicating that the female hypothalamic-pituitary-gonadal (HPG)-liver axis is impaired in the polluted environment. As measured by a decrease in plasma androgen (but not GSI), the male HPG axis was impaired in reproductively active NBH versus SC fish. In agreement with reports that NBH killifish are resistant to dioxin-like chemicals (DLC) that activate arylhydrocarbon receptor (AhR) signaling, ovarian P450aromA (a marker of dioxin-like effect in zebrafish embryos) did not differ in SC and NBH fish. In conclusion, the killifish population at the NBH Superfund site maintains a level of reproductive competence in the face of evidence of exposure to estrogen-like pollutants and endocrine disruption.

Effect of epibiosis on the fitness of the sandy shore snail Batillaria zonalis in Hong Kong

Batillaria zonalis is a common snail on Hong Kong sandy shores, occupying the low-mid shore. Shells of B. zonalis (basibiont) are often fouled with the rock oyster Saccostrea cucullata and the barnacle Balanus reticulatus (epibiont). This epibiotic interaction has a negative impact on the fitness of B. zonalis in terms of impairing fecundity, mobility and metabolism of fouled individuals. During the reproductive season, fouled snails had lower Gonadosomatic Index and fewer egg-bearing individuals than non-fouled snails. Fouled snails crawled in a more tortuous pathway and with lower speed when compared with non-fouled snails. Reduction in oxygen consumption and metabolic rate in fouled snails further suggested the restriction in mobility of B. zonalis by the epibionts. Glycogen content in the foot muscle tissues and hepatopancreas of fouled and non-fouled snails was, however, similar, revealing epibiosis does not influence the energy storage of B. zonalis. Mortality of fouled and non-fouled snails was similar under laboratory conditions, suggesting epibiosis does not influence the survivorship of B. zonalis in Hong Kong. Impairment in the fitness of fouled B. zonalis indicates that epibiosis can influence the population dynamics of B. zonalis in Hong Kong.

Reproductive biology of the school shark, Galeorhinus galeus, off Argentina: support for a single south western Atlantic population with synchronized migratory movements

synopsis We sampled school sharks, Galeorhinus galeus, in Anegada Bay, Argentina, to investigate reproductive ecology. Males dominated the catches in October and April, while females were more abundant than males from November to March. Males were estimated to mature at a smaller size (108-119 cm total length) than females (mean 125 mm total length). Differences between fecundity and fertility were not dependent on mother size. The largest embryos were found in late October and November, coinciding with ovulation. This indicates that gestation lasts about 12 months. Embryonic growth was best described by a Gompertz model. Four groups of females were recognized: (1) juveniles up to 129 cm TL, with translucent-to-white ovarian follicles; (2) mature, non-pregnant, pre-ovulatory females with yellow ovarian follicles and low gonadosomatic index (GSI); (3) mature non-pregnant ovulating females with large yellow ovarian follicles, high GSI; and (4) pregnant females carrying near term embryos, with minute ovarian follicles. These observations support a 3-year female reproductive cycle. The patterns of occurrence, reproductive condition, and embryonic growth of school sharks in northern Argentina are complementary to those from southern Brazil, supporting the hypothesis that there is a single large population of school sharks in the south western Atlantic.

Successful detection of (anti-)androgenic and aromatase inhibitors in pre-spawning adult fathead minnows ( Pimephales promelas) using easily measured endpoints of sexual development

Screening assays have been successfully developed for the detection of (anti-)oestrogenic substances in several fish species, including the fathead minnow ( Pimephales promelas). Previous work suggested that pre-spawning adult fathead minnows might be an appropriate life-stage for developing a screen to detect endocrine active substances (EASs). Pre-spawning adult fathead minnows, in which their phenotypic sex could be determined, were exposed in flow-through systems to three reference substances for 21 days, at 25 °C. Male and female fish, held in separate tanks, were exposed to dihydrotestosterone (DHT, androgen), flutamide (anti-androgen) and fadrozole (aromatase inhibitor). Nominal (mean measured) concentrations for DHT were 10 (6.0), 32 (6.1) and 100 (8.6) μg l −1, for flutamide, 100 (95.3), 320 (320.4) and 1000 (938.6) μg l −1 and for fadrozole, 25 (24.8), 50 (51.7) and 100 (95.5) μg l −1. After 14 and 21 days exposure, fish were evaluated for growth, secondary sexual characteristics (SSCs, number and prominence of nuptial tubercles), gonadosomatic index (GSI) and plasma vitellogenin (VTG) concentrations. Development of nuptial tubercles was sensitive to both DHT and flutamide exposure. Exposure to DHT significantly increased the number of nuptial tubercles (male characteristic) in both males (more abundant) and females, after 14 days. Flutamide (938.6 μg l −1, day 21) significantly reduced nuptial tubercle number in male fish. Fadrozole significantly inhibited ovarian growth (lower GSI) and significantly induced testis growth (51.7 and 95.5 μg l −1), after 21 days. Plasma VTG concentrations were significantly elevated in male fish (6.1 and 8.6 μg l −1), but inhibited in female fish (6.0 μg l −1), exposed to DHT. Flutamide had no effect on plasma VTG in male fish, but significantly induced VTG in female fish, after 21 days. Fadrozole significantly inhibited VTG in females and induced VTG synthesis in males, at day 21. These results show that SSCs, GSI and plasma VTG concentrations can be used in pre-spawning adult fathead minnows to screen for a range of classes of EASs. This work complements other published studies in supporting the current OECD effort towards validating a 21 days non-spawning fish screening assay for assessing (anti-)oestrogens, aromatase inhibitors and (anti-)androgens.

General condition biomarkers in relation to contaminant burden in European flounder ( Platichthys flesus)

In respect to the differences found for vitellogenin (VTG) expression in male and immature flounder, general biological aspects and a set of chemical residues in the liver were compared between flounder from the Mersey and Dee estuaries (UK). Except for α-HCH, all pollutant chemicals analysed in flounder liver differed highly significantly between Mersey and Dee fish. Overall, the higher liver contaminant concentrations were found in VTG-induced Mersey flounder. The biomarkers studied were not found to indicate significant differences between Mersey and Dee fish. However, when all of the minor differences are taken into consideration, it appears that the slightly lower growth rates after age 2 in Mersey flounder, lower gonadosomatic index in both mature male and female animals, less precise seasonal patterns of condition factor (CF), hepatosomatic index and gonadosomatic index, and lower CF in immature Mersey fish may well be signs of a contaminant-affected Mersey population.

First evidence of endocrine disruption in feral carp from the Ebro River

Feral carps ( Cyprinus carpio) were collected in spring 2001 from five sites along the lower course of Ebro River (Spain) with the aim of investigating the existence of endocrine-disrupting effects. Several findings (low gonadosomatic index (GSI), plasmatic vitellogenin (VTG), depressed levels of testosterone, and histological alterations in gonads) detected in male carps downstream of Zaragoza's sewage treatment plant (STP) strongly suggest that the concentration of sewage effluent in the area is a major causal factor leading to the detected estrogenic effects. Important alterations (viz. delayed maturation in females, indications of arrested spermatogenesis in males) were detected in carps from Flix, a heavily industrialized area. Low ovarian P-450 aromatase and reduced glucuronidation of testosterone and estradiol in males were observed in Zaragoza and Canal Imperial de Aragón—an agricultural area—which suggest decreased estrogen synthesis, and possibly, reduced sex hormone excretion in those organisms. These results were related to some in vitro assays aimed to assess the interference of model compounds (atrazin, vinclozolin, diuron, pp'-DDE, dicofol, triphenyltin, nonylphenol, and fenarimol) with the glucuronidation of testosterone and estradiol by liver microsomal fractions. The fungicide fenarimol (10–20 μM) and nonylphenol (50 μM) were found to significantly inhibit (20%) both activities at relatively low doses. Overall, this work provides the first evidence of the existence of significant alterations of the endocrine system of carps from the medium-low course of the Ebro River and demonstrates the ability of several chemicals to modulate the inactivation of endogenous steroids.

Gonad development and plasma steroid profiles by HRGC/HRMS during one reproductive cycle in reference and leachate-exposed female perch ( Perca fluviatilis)

Endocrine processes were studied in reference female perch ( Perca fluviatilis) from Lake Djursjön and in leachate-exposed females from Lake Molnbyggen during one reproductive cycle. A high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS) technique enabled the analysis of circulating sex steroids [progesterone (P), 17α-hydroxyprogesterone (17α-OHP), androstenedione (A), testosterone (T), estrone (E1), and 17β-estradiol (E2)], the maturation-inducing hormone (MIH) 17α,20β-dihydroxy-4-pregnen-3-one (17α,20β-P), and glucocorticoids [11-deoxycortisol (11-DC) and cortisol]. Body and organ measurements, ratio of sexually mature (SM) females, and frequencies of body lesions, were also recorded. High frequencies of body lesions and a low ratio of SM females were generally found in Molnbyggen. These females also had lower gonadosomatic index (GSI) and liver-somatic index (LSI) in the early stages of vitellogenesis, indicating either a delayed onset of oogenesis or an impaired vitellogenesis. Non-reproducing females from both lakes showed a similar LSI cycle as SM females. Increasing T and A levels in SM females from Djursjön coincided with the GSI peak at the time of spawning. These two androgens were on several occasions lower in SM females from Molnbyggen, possibly the result of a disrupted 17,20-lyase activity of the P450 17α enzyme because only minor effects were observed on circulating P and 17α-OHP levels. E2 and E1 levels increased during vitellogenesis in females from both lakes, with E1 levels more closely resembling the peaks of A and GSI. Peak levels of 17α,20β-P at the time of spawning confirmed its function as the MIH in perch, while the simultaneous peak of 11-DC suggests that it also may be involved in final maturation of the oocytes.

Delayed gametogenesis and progesterone levels in soft-shell clams ( Mya arenaria) in relation to in situ contamination to organotins and heavy metals in the St. Lawrence River (Canada)

There is a growing awareness that contaminants in the aquatic environment may alter steroid hormone levels and affect the reproductive success of the invertebrates. To verify if heavy metals and organotins affect sexual maturation in Mya arenaria, individuals were collected from July to November 1998, at different sites along the South coast of the St. Lawrence maritime estuary. Near the Rimouski harbour, clams showed high levels of tributyltin (TBT), DBT in the gonad, along with a lower gonado-somatic index {GSI=gonad wet weight (g)/body wet weight without shell (g)×100}, low progesterone levels and a delay in sexual maturation when compared to the reference site. Sites that had intermediate levels of contaminants exhibited intermediate responses of hormones and sexual maturation stages. It is therefore suggested that TBT, DBT are endocrine disruptors in clams. Further studies will however be necessary to investigate in more details how contaminants as TBT can affect the steroid hormones production in the gonads of M. arenaria.

Morphometric and Histopathological Parameters of Gonadal Development in Adult Common Carp from Contaminated and Reference Sites in Lake Mead, Nevada

Abstract This study examined the hypothesis that exposure to sublethal concentrations of contaminants alters the gonadal condition of feral common carp Cyprinus carpio. Adult common carp in Lake Mead, Nevada, were collected from a contaminated site (Las Vegas Bay) that receives municipal and industrial effluent and from a reference site (Overton Arm) with a relatively low level of contamination. Fish were sampled seven times over a 1-year period extending over two separate spawning seasons. Morphometric and histopathological parameters of gonadal and germ cell development were determined. In males, the pattern of seasonal changes in the gonadosomatic index (GSI) was similar between the sites and showed no clear association with site-specific seasonal temperature profiles. However, Las Vegas Bay males had consistently lower GSI values and, on one of the sampling dates, a lower proportion of sperm relative to other germ cell stages (determined histologically). Further, Las Vegas Bay males had a higher incid...

Modulation of goldfish testicular testosterone production in vitro by tumor necrosis factor alpha, interleukin-1beta, and macrophage conditioned media.

The relevance of immune-endocrine interactions to the regulation of testicular steroidogenesis in teleosts is virtually unexplored. The objectives of the present study were: 1) to investigate the effects of murine cytokines, tumor necrosis factor-alpha (TNFalpha) and interleukin-1beta (IL-1beta), and trout (Oncorhynchus mykiss) macrophage conditioned media (MCM) on testosterone (T) production by goldfish (Carassius auratus) testis pieces in vitro; and 2) to identify the site(s) of the inhibitory action of TNFalpha on hCG-stimulated T formation. TNFalpha (0-100 ng/ml) affected basal T production differentially depending on the gonadosomatic index (GSI) value of the fish. TNFalpha stimulated basal T of fish with a relatively low GSI (average 1.99), but inhibited T production by testis of fish with a higher GSI (average 5.14). The remaining studies used fish with only high GSI values. IL-1beta (0-10 ng/ml) inhibited basal T production, while MCM (0-25% v/v) had no effect. The cytokines significantly inhibited hCG-stimulated T production at all doses tested, whereas MCM was inhibitory only at the lower doses of 2.5-5% v/v. TNFalpha did not affect basal or hCG-stimulated cAMP levels, but did inhibit forskolin (0.5 microM; adenylate cyclase activator) and 8-bromo-cAMP (0.15 mM; cAMP analog) stimulated T levels. The inhibitory actions of TNFalpha on T production were greatly reduced by treatment of testis with 25-hydroxycholesterol (1 and 10 microg/ml), pregnenolone (50 and 100 ng/ml), and 17 alpha-hydroxypregesterone (50 ng/ml). TNFalpha caused a moderate decrease in pregnenolone (100 ng/ml)-stimulated T production. Together, these data demonstrate that regulatory actions of TNFalpha may occur at multiple sites within the steroid biosynthetic pathway, but the major effect appears to be related to cholesterol availability in the mitochondria. In conclusion, the results of this study implicate macrophage-derived factors in the regulation of teleost testicular androgen biosynthesis.

An evaluation of biomarkers of reproductive function and potential contaminant effects in Florida largemouth bass ( Micropterussalmoidesfloridanus) sampled from the St. Johns River

The objective of this study was to describe and compare several reproductive parameters for Florida largemouth bass ( Micropterus salmoides floridanus) inhabiting the St. Johns River and exposed to different types and/or degrees of contamination. Welaka was selected as the reference site in this study because of its low urban and agricultural development, Palatka is in close proximity to a paper mill plant, the Green Cove site is influenced by marine shipping activities and Julington Creek site receives discharges of domestic wastewater and storm water runoff from recreational boating marinas. For this study, bass were sampled both prior to (September 1996) and during the spawning season (February 1997). In order to characterize chemical exposure, bass livers were analyzed for up to 90 trace organics and 11 trace metal contaminants. Reproductive parameters measured included gonadosomatic index (GSI), histological evaluation of gonads and plasma concentrations of vitellogenin (VTG), 17β-estradiol (E 2) and 11-ketotestosterone (11-KT). In general, the sum of organic chemicals was highest in livers from Palatka bass and bass from Green Cove and Julington Creek had higher hepatic concentrations of low molecular polycyclic aromatic hydrocarbons and polychlorinated biphenyls when compared to fish from Welaka. Metals were more variable across sites, with highest mean concentrations found in bass from either Julington Creek (Ag, As, Cr, Cu, Zn) or Welaka (Cd, Hg, Pb, Se, Tn). Female bass from Palatka and Green Cove had lower concentrations of E 2, VTG and lower GSI in relation to Welaka. Males from Palatka and Green Cove showed comparable declines in 11-KT in relation to males from Julington Creek and GSI were decreased only in Palatka males. These results indicate a geographical trend in reproductive effects, with changes being most pronounced at the site closest to the paper mill (Palatka) and decreasing as the St. Johns River flows downstream. Since reproductive alterations were most evident in bass sampled from the site closest to the paper mill discharge, it is possible that exposure to these effluents might explain at least some of the results reported here. However, the presence of reproductive alterations in fish sampled at a considerable distance from the mill discharge (Green Cove, 40 km) would suggest exposure to chemicals released from sources other than the paper mill plant. It is clear that additional studies are needed to evaluate the potential impact of these reproductive changes in populations of Florida largemouth bass inhabiting the St. Johns River.

Biparental mouthbrooding of the catfish Phyllonemus filinemus in Lake Tanganyika

This article reports biparental mouthbrooding of the bagrid catfish Phyllonemus filinemus in Lake Tanganyika, based on analysis of specimens collected during SCUBA diving. This catfish was nocturnally active, and in the daytime it was concealed singly or in pairs beneath rocks. Within a breeding pair, the male or female alone incubated all the brood in the mouth until the offspring attained 12 mm or so in total length, but thereafter joint mouthbrooding or guarding by both parents took place. Most females of nonbrooding pairs showed high values of gonadosomatic index (GSI), whereas all females of brooding pairs and most single females showed low GSI values. This fact indicated that a pair is formed at a time near the gonadal maturation of the female and separates after the brood is reared. No significant difference in body condition among parents of different reproductive states was observed, which suggested that their condition does not deteriorate markedly as the result of foraging by an off-duty parent.

Maternal effects as a recruitment mechanism in Lake Michigan yellow perch (Perca flavescens)

Changes that occurred in the distribution of adult Lake Michigan yellow perch (Perca flavescens) phenotypic traits suggest that maternal effects on larval traits may be substantially influencing the recruitment of this heavily exploited species. We investigated maternal effects on yellow perch larvae at hatching in 10 maternal lines to test the null hypothesis of no effect of maternal phenotype on offspring phenotype and condition. Analyses lead to a rejection of the null hypothesis and indicated that the observed maternal effects likely resulted from differences among females in size, age, gonadosomatic index, and egg production. The observed maternal effects were expressed in the offspring by differences in larval total length, yolk volume, dry weight, and DNA quantity. Older, larger females were found to have high fecundity, yet low gonadosomatic index. Furthermore, older, larger females produced offspring that were, on average, short with large yolk sacs and high quantities of body reserves, as measured by dry weight and total DNA content. We conclude that the distribution of Lake Michigan yellow perch larval traits at hatching is linked to maternal influences and that this linkage may provide a mechanism through which managers can help rebuild the population.

Effects of estrogenic ( o,p′ -DDT; octylphenol) and anti-androgenic ( p,p′-DDE) chemicals on indicators of endocrine status in juvenile male summer flounder ( Paralichthys dentatus)

Laboratory experiments were conducted with male summer flounder to assess the value of selected measures of endocrine status in fish as indicators of exposure to endocrine-disrupting contaminants. Effects of 1,1,1-trichloro-2-( p-chlorophenyl)-2-( o-chlorophenyl) ethane ( o,p′-DDT), octylphenol and 1,1-dichloro-2,2-bis ( p-chlorophenyl) ethylene ( p,p′-DDE) on hepatosomatic and gonadosomatic indices, plasma steroid hormone levels, vitellogenin production, and gonadal development were evaluated in laboratory-raised, juvenile male summer flounder. Flounder were injected twice with test chemical in a coconut oil carrier. Each chemical was tested at three different concentrations. Estrogenic ( o,p′-DDT; octylphenol) and anti-androgenic ( p,p′-DDE) chemicals were evaluated alone and in combination (octylphenol plus o,p′-DDT or p,p′-DDE). Additionally, some fish were treated with the natural ligand for the estrogen receptor, 17β-estradiol. Blood and tissues from different fish in each treatment were sampled 4, 6 and 8 weeks after the first injection. Fish exposed to a combination of o,p′-DDT plus octylphenol were also sampled after 15 weeks. In all cases, responses of fish exposed to a test chemical were compared to control fish sampled at the same time. The following significant differences, relative to controls, were observed in at least one sampling time or at least one concentration of chemical. 17β-Estradiol-treated flounder exhibited decreased gonadosomatic index (GSI), altered hepatosomatic index (HSI), elevated plasma estradiol, reduced plasma testosterone, and high levels of plasma vitellogenin. Fish treated with o,p′-DDT showed lower GSI, no change in HSI or plasma estradiol, depression of plasma testosterone, and induction of vitellogenesis. Octylphenol treatment resulted in lower GSI, no change in HSI, initially increased plasma estradiol and decreased testosterone, and no vitellogenin production. p,p′-DDE treatment did not significantly alter any indicator relative to controls. In experiments using combinations of chemicals, flounder receiving o,p′-DDT plus octylphenol had lower GSI after 8 weeks and elevated plasma estradiol after 15 weeks exposure. Fish treated with p,p′-DDE plus octylphenol for 8 weeks exhibited a significantly lower GSI. Overall, lower GSI and plasma testosterone levels, relative to controls, were consistent indicators of exposure to estrogenic chemicals in juvenile male flounder. No indicators were found that would identify exposure to the mammalian anti-androgen p,p′-DDE.

Annual changes in testicular activity and plasma steroid hormones in the golden rabbitfish Siganus guttatus (Bloch)

SUMMARY: Characteristics in annual reproductive activity of the male golden rabbitfish, Siganus guttatus, were examined by observing testicular histology and measuring plasma levels of steroid hormones, testosterone (T), 11-ketotestosterone (11-KT), and 17α,20β-dihydroxy-4-pregnen-3-one (DHP) by enzyme immunoassay (EIA). The testicular development was divided into four periods: immature (November–March); pre-spawning (April–May); spawning (June–July); and post-spawning (August–October). The immature period was associated with low gonadosomatic index (GSI) values, and the testicular lobules were exclusively occupied by spermatogonia. In the pre-spawning period the testes were characterized by a new generation of spermatogenic cells. Spermatozoa appeared in some testes at the beginning of that period, and became dominant in the testes and the sperm duct in the spawning period. In the post-spawning period, only spermatogonia were observed in the testis, but residual spermatozoa were still observed in the seminal lobules and the sperm duct. Plasma T, 11-KT and DHP levels simultaneously increased during the pre-spawning period, rose markedly at the spawning period, and remained low from the post-spawning to immature periods, suggesting that these changes apparently were related to the annual testicular activity in S. guttatus.

Prospects of selecting for late maturity in tilapia ( Oreochromis niloticus) : III. A selection experiment under laboratory conditions

An experiment was carried out to investigate the possibility of retarding the maturation process in Oreochromis niloticus under laboratory conditions by selection to evaluate an applied breeding programme relevant for the tilapia industry. The breeding base consisted of 35 full sib families of the Lake Manzala strain, Egypt. On the basis of a standard testing procedure maturation status was determined by slaughtering 80 individuals (half of each family) at an age of 136 days. Gonad weight, gonadosomatic index (GSI) and the visual classification of the gonadal development were used as indicators for the maturation process. Family selection was carried out separately for each sex, using GSI for males and a visual assessment of gonadal development for females as selection trait. Only families with a minimum weight equal to or above the average family means were considered for selection to avoid the selection of families with high proportion of underdeveloped offspring which have retarded or insignificant gonadal development. For establishing the next generation in the selected line, matings were restricted to combinations of female spawners derived from selected `female' families with males derived from the selected `male' families but avoiding full-sib matings. To keep the generation interval as short as possible and to ensure a condensed breeding period, the heaviest fish within each selected families were used as spawners for the next generation (ca. 25% heaviest fish for males and the 50% heaviest fish for females). A random sample of two males and four females per family and generation was chosen as spawners for the control line. The number of families evaluated varied from 25 to 31 for the selection and control line in the first and from 30 and 32 in the second generation, respectively. After two generations significant responses of -1.25 standard deviations were realized both for GSI in males and for the maturity stage of gonads in females. Additionally, males of the selected line had significantly lower gonad weights than control males indicating a lower stage of maturity. Females of the selected line had significantly lower GSI values and a tendency for lower gonad weights than control females. Body weights did not differ significantly between the selected and control lines.

Sex-specific life history strategies in capelin (Mallotus villosus)?

The life history of capelin (Mallotus villosus) is presently suggested to be sex specific: while males follow a semelparous batch-spawning strategy, females are iteroparous. This hypothesis is based on predictions from a life history simulation model of Barents Sea capelin that shows that iteroparity is more profitable than semelparity for females, but for males, semelparity with several matings with females may be as profitable as iteroparity. These predictions are supported by (i) reports of males mating with several females during a spawning season, (ii) males having a lower gonadosomatic index than females and instead spending their energy on mating and somatic growth, and (iii) an observed higher mortality for males after spawning. The Darwinian fitness of female capelin is limited by the amount of eggs they can carry, and offspring production may only be increased by undertaking several spawning seasons with yearly intervals. Added together, these indices suggest that male and female capelin follow different life history strategies.