Changes In Reproductive Status Research Articles

Hemoparasites identified in birds of prey in the mesoregion of Triangulo Mineiro, Minas Gerais, Brazil

Hemoparasitosis are common in birds of prey and cause changes in reproductive status and therefore susceptibility to predator attacks. This work evaluated the prevalence of hemoparasites in those birds in the region of Triangulo Mineiro, Brazil. Were analyzed 55 birds of the orders Accipitriformes (n=12), Falconiformes (n=11), Strigiformes (n=21) and Cathartiformes (n=11) allocated in Federal University of Uberlandia and Hospital Veterinário de Uberaba. Parasitological analyses were performed on the blood smear, confirming parasitism in 78,18% (43/55) of the animals. Accipitriformes showed statistically lower parasitism (33,3% - 4/12) than Falconiformes (90,9 – 10/11). Plasmodium spp. Infection was observed in 43 birds (78,18%), and one (2,32%) mixed infection with Babesia spp. and Plasmodium spp. No hemoparasites were observed in the species Elanus leucurus and Falco peregrinus. We conclude that the birds evaluated showed a high rate of parasitism by Plasmodium spp. and Caracara plancus had an unprecedented infection by Babesia spp. It suggested studies for identification, taxonomic and epidemiological.

Re-evaluating the relationship between female social bonds and infant survival in wild baboons.

Over the past few decades studies have provided strong evidence that the robust links between the social environment, health, and survival found in humans also extend to non-human social animals. A number of these studies emphasize the early life origins of these effects. For example, in several social mammals, more socially engaged mothers have infants with higher rates of survival compared to less socially engaged mothers, suggesting that positive maternal social relationships causally improve offspring survival. Here we show that the relationship between infant survival and maternal sociality is confounded by previously underappreciated variation in female social behavior linked to changes in reproductive state and the presence of a live infant. Using data from a population of wild baboons living in the Amboseli basin of Kenya - a population where high levels of maternal sociality have previously been linked to improved infant survival - we find that infant- and reproductive state-dependent changes in female social behavior drive a statistically significant relationship between maternal sociality and infant survival. After accounting for these state-dependent changes in social behavior, maternal sociality is no longer positively associated with infant survival in this population. Our results emphasize the importance of considering multiple explanatory pathways-including third-variable effects-when studying the social determinants of health in natural populations.

Sheep Nocturnal Activity Dataset

Monitoring sheep’s behavior is of paramount importance, because deviations from normal patterns may indicate nutritional, thermal or social stress, changes in reproductive status, health issues, or predator attacks. The night period, despite being a more restful period in which animals are theoretically sleeping and resting, represents approximately half of the life cycle of animals; therefore, its study is of immense interest. Wearable sensors have become a widely recognized technique for monitoring activity, both for their precision and the ease with which the sensorized data can be analyzed. The present dataset consists of data from the sensorization of 18 Serra da Estrela sheep, during the nocturnal period between 18 November 2021 and 16 February 2022. The data contain measurements taken by ultrasound and accelerometry of the height from neck to ground, as well as measurements taken by an accelerometer in the monitoring collar. Data were collected every 10 s when the animals were in the shelter. With the collection of data from various sensors, active and inactive periods can be identified throughout the night, quantifying the number and average time of those periods.

Characterizing seasonal transitions: Breeding-like morphology and behavior during the late non-breeding season in green anole lizards

Seasonally breeding animals, such as green anole lizards (Anolis carolinensis), allow for the examination of the control of reproduction during different reproductive states. During the breeding season, the gonads are large and reproductively active. Following the breeding season, gonads regress and become less active, and the lizards enter a refractory period where breeding is inhibited. After this stage, a post-refractory period occurs during which the lizards are still in a non-breeding state, but environmental changes can trigger the onset of breeding. However, it is unclear what causes these changes in reproductive state and we hypothesized that this may be due to alterations in gonadotropin-releasing hormone (GnRH) signaling. The present study aimed to identify morphological and behavioral differences in GnRH- and saline-injected refractory and post-refractory male anoles when housed under the same non-breeding environmental conditions. We found that post-refractory anoles had increased testicular weight, recrudescence, sperm presence, and reproductive behavior, with no impact of GnRH injection. Renal sex segment size and steroidogenic acute regulatory protein (StAR) mRNA levels did not differ among groups, indicating that testosterone levels likely had not increased in post-refractory lizards. Post-refractory anoles in this study were beginning to transition towards a breeding state without exposure to changing environmental conditions, and GnRH was not necessary for these changes. These data reveal a complex interaction between the activation of breeding, changing environmental conditions, and the underlying physiology regulating reproduction in seasonally breeding lizards. Future studies are needed to further elucidate the mechanisms that regulate this relationship.

Enhancing Gonadotrope Gene Expression Through Regulatory lncRNAs.

The world of long non-coding RNAs (lncRNAs) has opened up massive new prospects in understanding the regulation of gene expression. Not only are there seemingly almost infinite numbers of lncRNAs in the mammalian cell, but they have highly diverse mechanisms of action. In the nucleus, some are chromatin-associated, transcribed from transcriptional enhancers (eRNAs) and/or direct changes in the epigenetic landscape with profound effects on gene expression. The pituitary gonadotrope is responsible for activation of reproduction through production and secretion of appropriate levels of the gonadotropic hormones. As such, it exemplifies a cell whose function is defined through changes in developmental and temporal patterns of gene expression, including those that are hormonally induced. Roles for diverse distal regulatory elements and eRNAs in gonadotrope biology have only just begun to emerge. Here, we will present an overview of the different kinds of lncRNAs that alter gene expression, and what is known about their roles in regulating some of the key gonadotrope genes. We will also review various screens that have detected differentially expressed pituitary lncRNAs associated with changes in reproductive state and those whose expression is found to play a role in gonadotrope-derived nonfunctioning pituitary adenomas. We hope to shed light on this exciting new field, emphasize the open questions, and encourage research to illuminate the roles of lncRNAs in various endocrine systems.

Roost Composition and Sexual Segregation in a Lowland Population of Daubenton's Bats (Myotis daubentonii)

Using data from 1100 day roosts containing a minimum of 9424 Myotis daubentonii bats, we compare the distribution of adult males, adult females, and juveniles, within SchweglerTM box roosts distributed across 394 ha of woodland adjacent to a river corridor in lowland England. Five social groups, containing both males and females (each comprising 55–230 adult bats per annum, using 37–127 known roosts per colony), occupy discrete roosting areas to which individuals show high inter-annual fidelity. Natal philopatry is also high, compared to between colony movements, for both sexes in our study population. Despite considerable spatial overlap and variability in roost composition over the summer (April to October), related to temporal changes in reproductive status, there is sexual segregation within day roosts. Bachelor (adult male dominated) roosts are situated significantly further from water than maternity (adult female or juvenile dominated) roosts on average. This spatial partitioning between maternity and bachelor roosts operates within rather than between colony home roost ranges, however, with adult males from some social groups found roosting closer to water than are adult females from adjacent colonies. The co-occurrence of maternity and bachelor groups roosting in close proximity, including extensive spatial overlap in roosts occupied, and temporal overlap during roost sharing between the sexes, provides novel insights into social organisation and potential drivers of sexual segregation and mating strategies for this widespread and common species within lowland habitats.

Physiological predictors of leptin vary during menses and ovulation in healthy women

Although research has shown interactions between the reproductive system and energy homeostasis, it is not clear how environmental or behavioral factors may factor into these associations. Here we aimed to determine how changes in reproductive state (i.e., phase of the menstrual cycle) and other behavioral and physiological factors may influence leptin levels in healthy women, as well as how sexual activity may play a role in leptin modulation. We collected serum and saliva from 32 healthy women and measured leptin, estradiol, and progesterone. Participants also completed surveys of demographics, health and sexual behaviors, and physical activity. Leptin was predicted by meals per day and missed meals at both menses and ovulation. However, estradiol and physical activity were stronger predictors of leptin at menses, while sexual activity was a stronger predictor of leptin at ovulation. These findings suggest that predictors of serum leptin, and possibly energy storage and expenditure, vary across the menstrual cycle.

Metabolic characterization of menopause: cross-sectional and longitudinal evidence

BackgroundWomen who experience menopause are at higher cardiometabolic risk and often display adverse changes in metabolic biomarkers compared with pre-menopausal women. It remains elusive whether the changes in cardiometabolic biomarkers during the menopausal transition are due to ovarian aging or chronological aging. Well-conducted longitudinal studies are required to determine this. The aim of this study was to explore the cross-sectional and longitudinal associations of reproductive status, defined according to the 2012 Stages of Reproductive Aging Workshop criteria, with 74 metabolic biomarkers, and establish whether any associations are independent of age-related changes.MethodsWe determined cross-sectional associations of reproductive status with metabolic profiling in 3,312 UK midlife women. In a subgroup of 1,492 women who had repeat assessments after 2.5 years, we assessed how the change in reproductive status was associated with the changes in metabolic biomarkers. Metabolic profiles were measured by high-throughput quantitative nuclear magnetic resonance metabolomics. In longitudinal analyses, we compared the change in metabolic biomarkers for each reproductive-status category change to that of the reference of being pre-menopausal at both time points. As all women aged by a similar amount during follow-up, these analyses contribute to distinguishing age-related changes from those related to change in reproductive status.ResultsConsistent cross-sectional and longitudinal associations of menopause with a wide range of metabolic biomarkers were observed, suggesting the transition to menopause induces multiple metabolic changes independent of chronological aging. The metabolic changes included increased concentrations of very small very low-density lipoproteins, intermediate-density lipoproteins, low-density lipoproteins (LDLs), remnant, and LDL cholesterol, and reduced LDL particle size, all toward an atherogenic lipoprotein profile. Increased inflammation was suggested via an inflammatory biomarker, glycoprotein acetyls, but not via C-reactive protein. Also, levels of glutamine and albumin increased during the transition. Most of these metabolic changes seen at the time of becoming post-menopausal remained or became slightly stronger during the post-menopausal years.ConclusionsThe transition to post-menopause has effects on multiple circulating metabolic biomarkers, over and above the underlying age trajectory. The adverse changes in multiple apolipoprotein-B-containing lipoprotein subclasses and increased inflammation may underlie women’s increased cardiometabolic risk in their post-menopausal years.

Is there reproductive diapause in the winterform of pear psylla Cacopsyla bidens?

Abstract Seasonal changes in reproductive state were investigated in the pear psylla Cacopsylla bidens (Šulc), with a particular emphasis on the evaluation of reproductive diapause during autumn and winter. Changes in reproductive status were observed in both seasons in populations living at four altitudes: 70, 300, 700 and 730 m. Winterform psylla females exhibited a period of slow ovarian development and a low mating rate. The onset, duration and extent of this period varied among the four sites but terminated synchronously, around December 20th. These changes were consistent within the same population over 3 years. Laboratory and field data suggested that winterform female C. bidens maintain some characteristics of reproductive diapause. By manipulating photoperiod and temperature during psylla development, we showed a major role for photoperiod in the induction of a reproductive diapause‐like state. However, as observed under natural conditions, the timing of the decrease in ovarian development and mating was highly dependent on the decrease in temperature. The fact that the initiation of reproductive activity was synchronous and highly predictable is very significant for the design of phenologically based management for this pest.

DAF-16 and TCER-1 Facilitate Adaptation to Germline Loss by Restoring Lipid Homeostasis and Repressing Reproductive Physiology in C. elegans.

Elimination of the proliferating germline extends lifespan in C. elegans. This phenomenon provides a unique platform to understand how complex metazoans retain metabolic homeostasis when challenged with major physiological perturbations. Here, we demonstrate that two conserved transcription regulators essential for the longevity of germline-less adults, DAF-16/FOXO3A and TCER-1/TCERG1, concurrently enhance the expression of multiple genes involved in lipid synthesis and breakdown, and that both gene classes promote longevity. Lipidomic analyses revealed that key lipogenic processes, including de novo fatty acid synthesis, triglyceride production, desaturation and elongation, are augmented upon germline removal. Our data suggest that lipid anabolic and catabolic pathways are coordinately augmented in response to germline loss, and this metabolic shift helps preserve lipid homeostasis. DAF-16 and TCER-1 also perform essential inhibitory functions in germline-ablated animals. TCER-1 inhibits the somatic gene-expression program that facilitates reproduction and represses anti-longevity genes, whereas DAF-16 impedes ribosome biogenesis. Additionally, we discovered that TCER-1 is critical for optimal fertility in normal adults, suggesting that the protein acts as a switch supporting reproductive fitness or longevity depending on the presence or absence of the germline. Collectively, our data offer insights into how organisms adapt to changes in reproductive status, by utilizing the activating and repressive functions of transcription factors and coordinating fat production and degradation.

Effects of Parental Status on Male Body Mass in the Monogamous, Biparental California Mouse.

Studies of biparental mammals demonstrate that males may undergo systematic changes in body mass as a consequence of changes in reproductive status; however, these studies typically have not teased apart effects of specific social and reproductive factors, such as cohabitation with a female per se, cohabitation with a breeding female specifically, and engagement in paternal care. We aimed to determine whether California mouse (Peromyscus californicus) fathers undergo systematic changes in body mass and if so, which specific social/reproductive factor(s) might contribute to these changes. We compared mean weekly body masses over a 5-week period in 1) males housed with another male vs. males housed with a non-reproductive (tubally ligated) female; 2) males housed with a tubally ligated female vs. males housed with a female that was undergoing her first pregnancy; and 3) experienced fathers housed with vs. without pups during their mate's subsequent pregnancy. Body mass did not differ between males housed with another male and those housed with a non-reproductive female; however, males housed with a non-reproductive female were significantly heavier than those housed with a primiparous female. Among experienced fathers, those housed with pups from their previous litter underwent significant increases in body mass across their mates' pregnancy, whereas fathers housed without pups did not. These results suggest that male body mass is reduced by cohabitation with a breeding (pregnant) female, but not by cohabitation with a non-reproductive female, and that increases in body mass across the mate's pregnancy are associated with concurrent care of offspring rather than cohabitation with a pregnant female. Additional work is needed to determine the mechanisms and functional significance, if any, of these changes in male body mass with reproductive condition.

Seasonal control of gonadotropin-inhibitory hormone (GnIH) in birds and mammals.

Animals inhabiting temperate and boreal latitudes experience marked seasonal changes in the quality of their environments and maximize reproductive success by phasing breeding activities with the most favorable time of year. Whereas the specific mechanisms driving seasonal changes in reproductive function vary across species, converging lines of evidence suggest gonadotropin-inhibitory hormone (GnIH) serves as a key component of the neuroendocrine circuitry driving seasonal changes in reproduction and sexual motivation in some species. In addition to anticipating environmental change through transduction of photoperiodic information and modifying reproductive state accordingly, GnIH is also positioned to regulate acute changes in reproductive status should unpredictable conditions manifest throughout the year. The present overview summarizes the role of GnIH in avian and mammalian seasonal breeding while considering the similarities and disparities that have emerged from broad investigations across reproductively photoperiodic species.

Changing motivations during migration: linking movement speed to reproductive status in a migratory large mammal

A challenge in animal ecology is to link animal movement to demography. In general, reproducing and non-reproducing animals may show different movement patterns. Dramatic changes in reproductive status, such as the loss of an offspring during the course of migration, might also affect movement. Studies linking movement speed to reproductive status require individual monitoring of life-history events and hence are rare. Here, we link movement data from 98 GPS-collared female moose (Alces alces) to field observations of reproductive status and calf survival. We show that reproductive females move more quickly during migration than non-reproductive females. Further, the loss of a calf over the course of migration triggered a decrease in speed of the female. This is in contrast to what might be expected for females no longer constrained by an accompanying offspring. The observed patterns demonstrate that females of different reproductive status may have distinct movement patterns, and that the underlying motivation to move may be altered by a change in reproductive status during migration.

Growth and reproductive consequences of photosynthetic tissue loss in the surface canopies of Macrocystis pyrifera (L.) C. Agardh

Macrocystis pyrifera (L.) C. Agardh provides biogenic habitat for species of significant commercial, cultural and recreational value; however, the floating surface canopies of M. pyrifera are particularly vulnerable to physical and biological disturbance (e.g., herbivory, storm events and harvesting). Given the key ecological roles of M. pyrifera, it is important to identify the impacts of photosynthetic tissue loss on growth and reproduction. I hypothesized that canopy removal would result in compensatory regeneration of the surface canopy. As life history theory posits a tradeoff between growth and reproduction, I also hypothesized that canopy removal would involve a reduction in reproductive investment, as either: (i) reduced production of reproductive structures; or (ii) changes in reproductive condition from fertile to sterile. To evaluate these hypothesizes I conducted two field experiments. In the first experiment, there was no significant difference in the generation of vegetative fronds or reproductive blades between controls (no loss of photosynthetic tissue from surface canopies) and treatments where photosynthetic tissue in surface canopies was thinned by either 30% or 70%. Relative to controls, the removal of entire surface canopies to a depth of 1.2m (i.e., simulated commercial harvesting) did not affect the generation of new vegetative fronds; however, the generation of reproductive blades was reduced by an average of 86%, suggesting that without the organic production supplied by the canopy, reproduction, but not growth, suffers. Further, the lack of evidence for compensatory growth despite reductions in reproduction suggests that M. pyrifera has little tolerance to canopy loss. The second experiment, which examined the effect of removing surface canopies on rate and longevity of changes in reproductive condition, found that although no control algae became sterile, 89% of algae with their surface canopies removed became sterile 50d after canopy removal, with effects persisting for up to 83d. As the supply of M. pyrifera propagules in the center of kelp forests can be tightly coupled to local reproductive output, induced sterility via the loss of photosynthetic tissue could affect the long-term stability of M. pyrifera beds. Further investigation into the scalability of these results and implications for long-term stability of M. pyrifera beds is warranted.

Aspects of breeding biology of chital (Axis axis) and sambar (Rusa unicolor) in the Western Ghats

Antler cycles are convenient external signs indicating internal changes in reproductive status of male deer. Antler phenology of chital (Axis axis) and sambar (Rusa unicolor) were studied in a deciduous habitat of Mudumalai Tiger Reserve, Western Ghats, using vehicle transects for 2 successive years. Apparent breeding seasonality occurred with the majority of adult stags in hard antlers from May to mid October in chital (>87 %), and October to May in sambar (>68 %). Adult hard antler in chital correlated with mean group size, while sambar showed a weak correlation between adult hard antler and group size. Chitals prefer forming large groups at forest edges and open habitats while sambars prefer dense vegetation cover. Adult hard antlers in chital and sambar showed a weak relation to fawning since most adult females were in oestrus during the peak rutting season. Adult hard antlers in chital associated positively with rainfall and day length while sambar responded weakly to rainfall. We conclude that environmental variables determined species-specific mating strategies in the two deer species.

Application of magnetic resonance imaging (MRI) to study the anatomy and reproductive condition of live Sydney rock oyster, Saccostrea glomerata (Gould)

Magnetic resonance imaging (MRI), a non-invasive technique, was used to study the soft tissue of live Sydney rock oysters (Saccostrea glomerata). The oysters were farmed in Port Stephens, Australia and the research was carried out during 2008–2011. MRI was performed on a Varian UNITY plus 300MHz spectrometer with a wide bore Oxford magnet system (7.05Tesla) equipped with a Varian Millipede microimaging probe. Relaxation parameters (T1 and T2) were found to be dependent on the type of tissue and also reflected seasonal changes in reproductive status of the gonad. The variation in T1 values of different types of soft tissue was used judiciously to optimise contrast in MR images. The MR images of live oysters revealed anatomical details of the gills and the labial palps that are consistent with the feeding mechanism of bivalves. An empirical equation (y=4.2x+14.9) was derived by traditional methods which describes the relationship between the condition index (y) of oysters and the percentage volume of soft tissue (x). A significant correlation (R2=0.871, P<0.01, n=5) was obtained between measurements of percentage volume of soft tissue by MRI and the traditional method. Hence, it was concluded that MRI is useful in determining the condition index of live oysters. An interesting observation from MR images was the development of gas bubbles within emersed oysters. Analysis of this gas revealed an elevated concentration of carbon dioxide (2760ppm after 3days of emersion and 6300 ppm after 8days). It was concluded that oysters produce gas bubbles by a physiological process for removing CO2 from soft tissue. The research findings presented here suggest that MRI, due to its non-invasive nature, could prove to be a unique tool for oyster research.

Response to exogenous kisspeptin varies according to sex and reproductive condition in Siberian hamsters ( Phodopus sungorus)

Most animals experience marked changes in reproductive status across development that are regulated by changes in the hypothalamo–pituitary–gonadal (HPG) axis. The upstream mechanisms regulating this axis remain less well understood. The neuropeptide kisspeptin serves as a positive regulator of reproduction; the precise actions of kisspeptin on the HPG axis in animals of differing developmental and seasonal reproductive states, however, remain unresolved. Further, sex differences in response to kisspeptin have not been fully explored. In Experiment 1, we investigated whether sensitivity to a broad range of kisspeptin doses differed in adult male and female Siberian hamsters held on reproductively inhibitory or stimulatory photoperiods. In Experiment 2, we asked whether the response to kisspeptin differed across stages of reproductive development. Males and females displayed elevated luteinizing hormone (LH) in response to kisspeptin; however, the sexes differed in this response, with males showing greater LH responses to kisspeptin than females. Hamsters responded to kisspeptin across all stages of reproductive development, although the magnitude of this response differed between animals of differental ages and between the sexes. Males showed significant increases in LH at an earlier developmental age than females; females also showed blunted LH responses during early adulthood whereas males remained relatively constant in their response to kisspeptin. These findings suggest that reproductively active and inactive hamsters are responsive to kisspeptin, but that the sexes differ in their responsiveness. Collectively, these data provide further insight into the basic actions of kisspeptin in the regulation of reproduction and provide a potential mechanism for the regulation of differential reproductive responses between the sexes.

Problems of the gonad index and what can be done: analysis of the purple sea urchin Strongylocentrotus purpuratus

The gonad index, GI, is widely used as a measure of changes in reproductive state. There are, however, problems with its use because it is based on the implicit assumption of an isometric relationship between gonad size and some measure of total size. If, for example, gonad weight and total weight are used, the exponent for an allometric relationship usually is ignored and hence assumed to be 1.0. It is further assumed that this exponent is fixed for all states of the reproductive cycle and that gonads begin to develop at size = 0. Data for the purple sea urchin Strongylocentrotus purpuratus at Gregory Point, Oregon, USA, gathered over a period of 31 months showed that these assumptions cannot be supported. The relation- ship is better modeled with a function that (1) takes into account size of initial gonad production and (2) allows allometric exponents that vary with site or season. Thus, a better approach is to use a wide range of sizes to estimate size when gonads begin to develop and then, with this correction, ANCOVA to test for differences of gonad size among samples. Gonad changes at Gregory Point were estimated using fixed sizes of 5 cm diameter and 60 g total weight. Publishing means for X and Y, the standard error of the estimate, R 2 , and slope for each regression are shown to

Long‐Term Patterns of Immune Investment by Wild Deer Mice Infected with Sin Nombre Virus

Immunocompetence of animals fluctuates seasonally, However, there is little consensus on the cause of these fluctuations. Some studies have suggested that these patterns are influenced by changes in reproductive condition, whereas others have suggested that differences result from seasonal variations in energy expenditures. The objective of our study was to examine these contrasting views of immunity by evaluating seasonal patterns of immune response and reproduction in wild populations of deer mice Peromyscus maniculatus exposed to Sin Nombre virus (SNV). Over three consecutive fall (September, October, November) and three consecutive spring (March, April, May) sampling periods, we used titration enzyme-linked immunosorbent assay (ELISA) to quantify virus-specific antibody production in 48 deer mice infected with SNV. Levels of reproductive hormones were quantified using ELISA. SNV antibody titers reached their lowest level during November (geometric mean titer [GMT] = 420) and their highest levels during September (GMT = 5,545) and May (GMT = 3,582), suggesting that the immune response of deer mice to SNV has seasonal patterns. The seeming decrease in antibody titer over winter coupled with the consistency in body masses suggests that during winter, immunocompetence may be compromised to offset the energetic costs of maintenance functions, including those associated with maintaining body mass. Deer mice showed distinct sex-based differences in SNV antibody production, with males producing higher antibody titers (GMT = 3,333) than females (GMT = 1,477). Levels of reproductive hormones do not appear to influence antibody production in either males or females, as there was no correlation between estradiol concentrations and SNV antibody titer in female deer mice (r² = 0.26), nor was there a significant relationship between levels of testosterone and SNV antibody titers in males (r² = 0.28). Collectively, this study demonstrates that immunocompetence of wild deer mice is seasonally variable; however, reproduction is not the primary stressor responsible for this variation. Rather, the data suggest that deer mice may compromise immunocompetence during winter to offset other maintenance costs during this period.

Effects of a Chemically Polluted Discharge on the Relationship Between Fecundity and Parasitic Infections in the Chub (Leuciscus cephalus) from a River in Southern England

In fish there is a close association between endocrine and immune function that during seasonal changes in reproductive status can affect the fishes susceptibility to parasitic infection. The effects of endocrine-disrupting pollution on this association are not known. The present study investigates the effects of a chemically polluted (ammoniacal nitrogen, zinc, bromide) discharge in Cranleigh Waters, a river in southern England, on the fecundity and parasitism of chub, Leuciscus cephalus, over an 18-month period. In the polluted site, the gonado-somatic index (GSI) of fish was lower in females and higher in males compared to an unpolluted upstream site, indicating an androgenic effect on reproduction. Parasite species richness, especially the intestinal helminths Proteocephalus torulosus and Pomphorynchus laevis, was increased in fish in the polluted site. However, the occurrence of the two most common parasite species in the river-Myxobulus sp. 1, a gill myxozoan, and Diplostomum sp., a trematode found in the eye-was unchanged between polluted and unpolluted river sites. Nevertheless, there was a significant relationship between GSI and the prevalence of these two parasite species in the unpolluted site but not the polluted site suggesting that endocrine disruption of reproduction did not lead to an increase in host susceptibility. The reasons for this are discussed.