Predicting the Effects of Endocrine Disrupting Chemicals on Fish Populations

This study evaluates the applicability and sensitivity of fish population dynamics modeling in assessing the potential effects of individual chemicals on population sustainability and recovery. Fish reproductive health is an increasingly important issue for ecological risk assessment following international concern over endocrine disruption. Life-history data from natural brook trout and fathead minnow populations were combined with effects data from laboratory-based studies, mainly concerning species other than brook trout and fathead minnows, to assess the likely impact of nonylphenol (NP) and methoxychlor (MXC) on brook trout (Salvelinus fontinalis) and fathead minnow (Pimephales promelas) population size. A delay differential equation (DDE) model with a 1-day timestep was used to predict the population dynamics of the brook trout and fathead minnows. The model predicts that NP, could enhance populations by up to 17% at a concentration of 30?µg l^?1 based on the results of reduction in survival and increased fecundity from life-cycle toxicity tests, however attempting to allow for growth reduction and its effect on fecundity results in a prediction of a 28% reduction in population numbers. For fathead minnows the DDE model predicts that the same concentration of NP could cause a population reduction of 21%. The differences in these predictions are related to these two species having different life history strategies, which are considered in the parameterization of the model. Post-application concentrations of MXC may peak around 300?µg l^?1 and then decline rapidly with time. Predictions show that such applications could cause a reduction of up to 30% in brook trout populations if the application occurs at the peak of the spawning season on successive years but that the effect would be less than 1% if the spawning season is avoided. Effects on the fathead minnow population size are predicted to be smaller (<4%) even if application occurs during the spawning period. Risk based statistics generated by the population dynamics models, such as interval decline risk or quasiextinction risk and predicted time to recovery complement traditional effects parameters such as LC50 and LOEC and may ultimately prove to be more useful in risk assessment.     

Analyses of Sexual Reproductive Success in Transgenic and/or Mutant Plants

The pistil, the female reproductive organ of plants, is a key player in the success of sexual plant reproduction. Ultimately, the production of fruits and seeds depends on the proper pistil development and function. Therefore, the identification and characterization of pistil expressed genes is essential for a better understanding and manipulation of the plant reproduction process. For studying the function of pistil expressed genes, transgenic and/or mutant plants for the genes of interest are used. The present article provides a review of methods already exploited to analyze sexual reproductive success. We intend to supply useful information and to guide future experiments in the study of genes affecting pistil development and function.     

Determining Indicators of Exposure and Effects for Endocrine Disrupting Chemicals (EDCs): An Introduction

Endocrine disruptors are characterized by their influence on animal endocrine systems resulting in reproductive, developmental, neurological, and immune dysfunction. The purpose of this overview is to provide the reader with a sense of the activities within the U.S. Environmental Protection Agency (USEPA), in particular NHEERL, that address the many facets of research on endocrine disrupting chemicals (EDCs) and to highlight the approach being taken at the different organizational levels within the USEPA, including screening, testing and evaluating endocrine disrupting chemicals. As a part of this endeavor, the USEPA continues to evaluate the current research activities in order to better understand and refine the process of risk characterization of EDCs. Thus, the participants in this session were asked to review their research within the framework of a better identification of EDC effects, better characterization of those compounds that have endocrine disrupting activity and how to incorporate this information into the risk assessment paradigm. Specifically, the goals of the ensuing papers were to compare individual vs. population indicators of endocrine disrupting effects, examine comparable and multiple mechanisms of toxicity, and describe the use of effects as indicators to identify toxicants and their sources. Mammalian and fish reproductive endpoints served as models to emphasize commonalities between human and wildlife risks.     

Environmentally Contingent Reproductive Strategies in Mayan and Ache Males

This research explores male reproductive parameters, particularly the timing of first reproduction, in two traditional populations. Predictions are drawn from theoretical arguments that have their roots in evolutionary psychology and behavioral ecology, and that interpret variation in reproductive outcomes as environmentally contingent adaptations. In both Ache and Mayan samples, father absence, predicted to act as a stressor that causes precocious sexuality and reproduction as well as unstable pair bonds, did not affect the timing of first reproduction in male offspring in the expected way. Father absence in Mayan men, however, was found to be associated with responses to questionnaire items indicating lack of willingness to pay time and energy costs to maintain existing sexual unions. The results suggest that father absence affects male mating strategy, but that strategic differences did not translate into reproductive outcomes in the sample. In the Mayan population, education was associated with early reproduction, more lifetime sex partners, and higher fertility, which was also contrary to the predicted pattern based on a life-history tradeoff approach. Parental resources were associated with earlier reproduction in the Mayan sample, confirming the prediction that restricted resources should delay reproduction.     

Endocrine and behavioral correlates of drought in wild olive baboons (Papio anubis)

As part of a long-term study in behavioral endocrinology, wild olive baboons (Papio anubis) living in the Serengeti ecosystem of East Africa have been under study since 1978. The present report documents behavioral and endocrine changes associated with the severe drought of 1984. During this time, the annual rainy season failed and grassland biomass was severely reduced in the Serengeti. Baboons were able to maintain body weight but spent significantly more time foraging for food. In four prior years of study, basal testosterone concentrations were remarkably stable in adult and subadult males. In contrast, during the drought, there was a highly significant 60% decline in basal concentrations of the steroid. This testicular suppression was apparent in males of all ranks (by approach-avoidance criteria). Prior studies with this population, which examined the role of acute and chronic stressors in similarly suppressing testosterone concentrations, suggested that the present instance was in response to the stress of the drought. The drought was also associated with significant reductions in the rates of escalated aggression among males. However, the distribution of fights between high-ranking males, between low-ranking males, and between high- and low-ranking males did not change from prior years, nor was the dominance hierarchy inordinately unstable during this time. These findings agree with previous evidence that indicates that suppressed testosterone concentrations in males can be associated with lower rates of aggressive behaviors but that the steroid plays a predominantly facilitative rather than activational role. Finally, rates of approach-avoidance interactions and of male sexual behaviors were unchanged during the drought. These findings agree with an endocrine literature that indicates that reproductive behavior or physiology in primates is rarely disrupted by suppression of testosterone concentrations of the magnitude of the present case.     

Reproductive costs of sons and daughters in Rocky Mountain bighorn sheep

Differential maternal investment theory predicts that in sexuallydimorphic and polygynous species mothers should invest morein sons than in daughters. We tested the hypothesis that bighornewes that raise sons incur greater reproductive costs than ewesthat raise daughters. Although ewe mass gain during lactationand subsequent winter body mass loss were independent of lambsex, lambs born the year following the weaning of a son hadlower survival than lambs born after a daughter. The effectsof lamb sex on subsequent reproductive success of ewes becamemore evident at high population density. Lamb sex did not affectmaternal survival. Population density, weather, and ewe agedid not alter the relationship between lamb sex and subsequentreproductive success of the ewe. The year after weaning a son,ewes were more likely to have a daughter than a son, while ewesthat had previously weaned a daughter had similar numbers ofsons and daughters. Our results show that for bighorn sheepewes, sons have a greater life-history cost than daughters,suggesting a differential maternal investment in the sexes.     

Assessment of Consequences of Notifiable Fish Disease Incursions in England and Wales

A consequence assessment framework was developed to evaluate the economic and environmental consequences of an exotic disease in the context of supporting policy level decisions on mitigation strategies. The framework adopted a semi-qualitative analysis of impacts supported by expert judgement. The efficacy of the framework was illustrated via assessment of the notifiable fish disease, Gyrodactylus salaris. In this example, the economic cost of an illustrative outbreak of G. salaris ranged from £0.22 million to £90 million. The cost of the most likely scenario (regional spread) was estimated to be £7.5 million (minimum to maximum range of £2–22 million), reflecting the uncertainty in the extent of spread of the parasite before detection. The environmental impacts vary by a factor of 35 between incursion scenarios reflecting the number of affected catchments in the scenarios.     

Reproductive promiscuity in the splendid fairy-wren: effects of group size and auxiliary reproduction

Extrapair fertilizations complicate our understanding of cooperativebreeding in a number of ways. For example, auxiliaries may reducethe costs of seeking extrapair fertilizations for breeding malesor females, and auxiliary males may themselves seek copulationswith the breeding female in their own group. We employed microsatellitemarkers to examine patterns of parentage in the cooperativelybreeding splendid fairy-wren (Malurus splendens melanotus).Our study population exhibited a relatively high level of extrapairpaternity (42% of 386 offspring) with considerable annual variation(range = 24–52%). Across years the proportion of offspringsired by extrapair males was significantly correlated with theaverage number of auxiliaries per group. Furthermore, the proportionof extrapair young within a brood was related to group composition;groups with multiple auxiliaries were twice as likely as groupswith zero or one auxiliary to contain extrapair young. Mostoffspring were sired by dominant breeding males, but auxiliarymales sired approximately 25% of all extrapair young (10% ofall offspring), and about half of these were cases in whichthe auxiliary male sired offspring in his own group. Within-groupsirings by auxiliary males were most common after replacementof the breeding female, and they also appeared to be more likelywhen the auxiliary was not related to the breeding male. Thus,the presence of auxiliary males increased the likelihood thatfemales would produce extrapair young, and although incest avoidancemechanisms usually prevent within-group copulations by auxiliarymales, a conflict of interest among group males arises whena new female joins the group.     

Endocrine regulation of the reproduction in crustaceans: Identification of potential targets for toxicants and environmental contaminants

Progress in ecotoxicological research documents that crustaceans are highly vulnerable to diverse chemicals and toxicants in the environment. In particular, pollutants affecting endocrine homeostasis in crustaceans (i.e., endocrine disruptors) are intensively studied, and serious reproductive disorders have been documented. In this review, current knowledge about the endocrine regulation of the crustacean reproduction is put together with the published ecotoxicological data with an attempt to summarize the potential of xenobiotics to affect crustacean reproduction. Following gaps and trends were identified: (1) Studies are required in the field of neurohormone (serotonin and dopamine) regulation of the reproduction and possible modulations by environmental toxicants such as antidepressant drugs. (2) Molting-related parameters (regulated by ecdysteroid hormones) are closely coordinated with the development and reproduction cycles in crustaceans (cross-links with methyl farnesoate signalling), and their susceptibility to toxicants should be studied. (3) Other biochemical targets for xenobiotics were recently discovered in crustaceans and these should be explored by further ecotoxicological studies (e.g., new information about ecdysteroid receptor molecular biology). (4) Some sex steroid hormones known from vertebrates (testosterone, progesterone) have been reported in crustaceans but knowledge about their targets (crustacean steroid receptors) and signalling is still limited. (5) Determination of the sex in developing juveniles (affecting the sex ratio in population) is a sensitive parameter to various xenobiotics (including endocrine disruptors) but its modulation by general environmental stress and non-specific toxicity should be further studied.     

Widespread endocrine disruption and reproductive impairment in an estuarine fish population exposed to seasonal hypoxia

The long-term effects on marine fish populations of the recent increase worldwide in the incidence of coastal hypoxia are unknown. Here we show that chronic environmental exposure of Atlantic croaker (Micropogonias undulatus) to hypoxia in a Florida estuary caused marked suppression of ovarian and testicular growth which was accompanied by endocrine disruption. Laboratory hypoxia studies showed that the endocrine disruption was associated with impairment of reproductive neuroendocrine function and decreases in hypothalamic serotonin (5-HT) content and the activity of the 5-HT biosynthetic enzyme, tryptophan hydroxylase. Pharmacological restoration of hypothalamic 5-HT levels also restored neuroendocrine function, indicating that the stimulatory serotonergic neuroendocrine pathway is a major site of hypoxia-induced inhibition. Inhibition of tryptophan hydroxylase activity to downregulate reproductive activity could have evolved as an adaptive mechanism to survive periodic hypoxia, but in view of the recent increased incidence of coastal hypoxia could become maladaptive and potentially affect fish population abundance and threaten valuable fishery resources.     

Endocrine Correlates of Reproductive Status in Breeding and Nonbreeding Wild Female Moustached Tamarins

In callitrichid primates, reproduction is usually restricted to a single female per group. Reproductive rate is high and the occurrence of a postpartum estrus can lead to simultaneous lactation and pregnancy. In contrast, nonreproductive females often show ovarian inactivity. However, most studies on callitrichid reproductive physiology have been conducted in captivity, where conditions differ considerably from those in the wild, so that reproductive conditions may be strongly modified. Using fecal estrogen and progestogen measurements to monitor female reproductive status in 2 groups of wild moustached tamarins (Saguinus mystax), we examined 1) whether reproductive females in free-ranging groups also show postpartum estrus and 2) whether nonreproductive females demonstrate signs of ovarian activity. In both reproductive females, clear changes in the excretion pattern of progestogen and estrogen metabolites over time in combination with information on parturition dates allowed us to differentiate between pregnancy, a period of postpartum ovarian inactivity lasting for 54 and 64–82 days, and a period of ovarian activity before conception. Nonreproductive females demonstrated temporal fluctuations in hormone concentrations and absolute hormone levels that were similar to ones in the breeding females during the phase of ovarian activity. The results suggest that, in contrast to most captive female tamarins, reproductive females in wild groups of moustached tamarins do not have a postpartum estrus and that nonreproductive females show ovarian activity despite the presence of a breeding female. We therefore conclude that findings from captivity should be only carefully compared to the situation in the wild.     

Probabilistic Estimation of Regional Dietary Exposure to Dioxins in Fish in Japan on the Basis of Market and Fish Distribution Network Data

Dietary consumption of fish is the greatest contributor to dioxin exposure of the general population in Japan. Unlike with other routes of exposure to dioxins, exposure via foodstuffs does not necessarily occur from local sources. Clarifying the distribution of fish from the catch area to local markets helps to control dioxin exposure from the head of the distribution chain down. We analyzed the data from 30 major central wholesale fish markets to determine both the market share of fish by catch area and the market share of major fish types in fish consumption markets. Probabilistic estimation of dietary exposure of the general population to dioxins in fish was conducted in seven regions in Japan. Probabilistic density functions (PDFs) were assigned to express the variability of data from monitoring of dioxin levels in fish by catch area or by fish type. From histograms of dioxin levels in fish by catch area, the mean and 5th to 95th percentile range of dietary exposure to dioxins in the region with the largest 95th percentile value were estimated, respectively, as 55.5 and 12.9–172.9 pg-TEQ/day. No statistically significant differences in dietary exposure to dioxins in fish were observed among the seven regions. Some specific coastal catch areas and some types of fish that had a greater impact than others on exposure were pinpointed for each region.     

Reproductive sharing in relation to group and colony-level attributes in a cooperative breeding fish

The degree to which group members share reproduction is dictated by both within-group (e.g. group size and composition) and between-group (e.g. density and position of neighbours) characteristics. While many studies have investigated reproductive patterns within social groups, few have simultaneously explored how within-group and between-group social structure influence these patterns. Here, we investigated how group size and composition, along with territory density and location within the colony, influenced parentage in 36 wild groups of a colonial, cooperatively breeding fish Neolamprologus pulcher. Dominant males sired 76% of offspring in their group, whereas dominant females mothered 82% of offspring in their group. Subordinate reproduction was frequent, occurring in 47% of sampled groups. Subordinate males gained more paternity in groups located in high-density areas and in groups with many subordinate males. Dominant males and females in large groups and in groups with many reproductively mature subordinates had higher rates of parentage loss, but only at the colony edge. Our study provides, to our knowledge, the first comprehensive quantification of reproductive sharing among groups of wild N. pulcher, a model species for the study of cooperation and social behaviour. Further, we demonstrate that the frequency of extra-pair parentage differs across small social and spatial scales.     

Endocrine cells in atresic chick embryo intestine: histochemical and immunohistochemical study

Intestinal motility disorders are an important problem in the postoperative management of patients with intestinal atresia. Intestinal motility could be initiated by luminal factors that activate intrinsic and extrinsic primary afferent nerves involved in the peristaltic reflex. Endocrine cells act as a key point, because they transfer information regarding the intestinal contents and intraluminal pressure to nerve fibers lying in close proximity to the basolateral surface of the epithelium. In chick embryo, experimental intestinal atresia is associated with disorders in the development of the enteric nervous system, related to the severity of intestinal dilation. Our aim was to investigate the distribution pattern of endocrine cells in the developing endocrine system of chick embryo small intestine with experimentally-induced atresia on day 12 and on day 16. Changes in enteroendocrine population were examined in gut specimens (excised proximal and distal to the atresia) from experimental embryos 19 days old and in control sham-operated chick embryos at the same age. Sections from proximal and distal bowel and control bowel were stained with Grimelius silver stain, a valuable histochemical method for detecting the argyrophil and argentophilic cells, and with an immunohistochemical procedure for detecting serotonin and neurotensin immunoreactive cells. In chick embryo proximal bowel, intestinal dilation differed in the various embryos. We found significantly higher enteroendocrine cell counts in proximal bowel than in distal and control bowel. The differences depended on the precociousness of surgery and the severity of dilation. Considering the major contribution of enteroendocrine cells to the peristaltic reflex, our data may help to explain the pathogenesis of motility disorders related to intestinal atresia.     

Temporal and Spatial Requirement of EMF1 Activity for Arabidopsis Vegetative and Reproductive Development

EMBRYONIC FLOWER （EMF） genes are required to maintain vegetative development via repression of flower homeotic genes in Arabidopsis. Removal of EMF gene function caused plants to flower upon germination, producing abnormal and sterile flowers. The pleiotropic effect of ernfl mutation suggests its requirement for gene programs involved in diverse developmental processes. Transgenic plants harboring EMF1 promoter：：glucuronidase （GUS） reporter gene were generated to investigate the temporal and spatial expression pattern of EMF1. These plants displayed differential GUS activity in vegetative and flower tissues, consistent with the role of EMF1 in regulating multiple gene programs. EMFI：：GUS expression pattern in emf mutants suggests organ-specific auto-regulation. Sense- and antisense （as） EMF1 cDNA were expressed under the control of stage- and tissue-specific promoters in transgenic plants. Characterization of these transgenic plants showed that EMF1 activity is required in meristematic as well as differentiating tissues to rescue emf mutant phenotype. Temporal removal or reduction of EMF1 activity in the embryo or shoot apex of wild-type seedlings was sufficient to cause early flowering and terminal flower formation in adult plants. Such reproductive cell memory is reflected in the flower MADS-box gene activity expressed prior to flowering in these early flowering plants. However, temporal removal of EMF1 activity in flower meristem did not affect flower development. Our results are consistent with EMF1＇s primary role in repressing flowering in order to allow for vegetative growth.     

Male Dominance Rank,Female Mate Choice and Male Mating and Reproductive Success in Captive Chimpanzees

Mating and consequently reproductive success in male vertebrates are predominantly determined by intermale competition and female mate choice. Their relative importance however, is still poorly understood. We investigated the interrelationship between male dominance rank — a formal indicator of male competitive ability — female mate choice, and male mating success in a multimale-multifemale group of captive chimpanzees. In addition, we examined the relationship between male dominance rank and reproductive success determined by genetic paternity analysis over a 13-yr period in the same captive population. We related the frequencies of sociosexual behaviors to the female anogenital swelling stage and female fertile phase as determined by urinary and fecal progestogen analysis. Rates of behaviors in both sexes increased with increasing intensity of female swelling, but they were not influenced by the timing of the fertile phase. Male mating success was clearly related to male dominance rank, with high-ranking males performing the overwhelming majority of copulations. This was mainly due to both rank-related rates of male soliciting behavior and intermale aggressiveness during the period of well-developed female anogenital swelling. Although females solicited copulations mainly from the high-ranking males and thus expressed a mate choice based on rank, their overall contribution in initiating copulations and thus influencing male mating success was low. The data on paternity from the population, which always contained 4 adult males, revealed that -males sired the majority (65%) of offspring. We conclude, that male dominance rank is an important determinant of male mating and reproductive success in captive (and presumably wild) chimpanzees and that female mate choice is of minor importance in modulating male reproductive outcome.