DIVERSITY AND DISTRIBUTIONS, Issue 1 2008
Different routes towards long-term persistence
ABSTRACT A central tenet of conservation biology is that population size affects the persistence of populations. However, many narrow endemic species combine small population ranges and sizes with long persistence, thereby challenging this tenet. I examined the performance of three different-sized populations of Petrocoptis pseudoviscosa (Caryophyllaceae), a palaeoendemic rupicolous herb distributed along a small valley in the Spanish Pyrenees. Reproductive and demographic parameters were recorded over 6 years, and deterministic and stochastic matrix models were constructed to explore population dynamics and extinction risk. Populations differed greatly in structure, fecundity, recruitment, survival rate, and life span. Strong differentiation in life-history parameters and their temporal variability resulted in differential population vulnerability under current conditions and simulated global changes such as habitat fragmentation or higher climatic fluctuations. This study provides insights into the capacity of narrow endemics to survive both at extreme environmental conditions and at small population sizes. When dealing with species conservation, the population size,extinction risk relationship may be too simplistic for ancient, ecologically restricted organisms, and some knowledge of life history may be most important to assess their future. [source]

Reproductive and transgenerational effects of methylmercury or Aroclor 1268 on Fundulus heteroclitus

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2001
Mary Baker Matta
Abstract This research determined the potential for methylmercury or Aroclor 1268 to disrupt reproduction and sexual differentiation in Fundulus heteroclitus. The research determined whether fish that are exposed to mercury or Aroclor 1268 survive and successfully reproduce; whether offspring of exposed fish hatch, survive, produce eggs, and fertilize them; and whether the secondgeneration offspring of exposed fish hatch and survive. Fundulus heteroclitus were exposed to mercury or Aroclor 1268 via contaminated food. Endpoints evaluated included survival, growth, fecundity, fertilization success, hatch success, larval survival, sex ratios, and the prevalence of gonadal abnormalities. In general, polychlorinated biphenyls were highly bioavailable and accumulated well through feeding. The only statistically significant effect observed as a result of treatment with Aroclor 1268 was an increase in growth in the offspring of exposed fish. Mercury was accumulated in a dose-dependent fashion via food exposures. Exposure to mercury in food increased mortality in male F. heteroclitus, which possibly occurred as a result of behavioral alterations. Increased mortality was observed at body burdens of 0.2 to 0.47 ,g/g. Offspring of F. heteroclitus fed mercury-contaminated food were less able to successfully reproduce, with reduced fertilization success observed at egg concentrations of 0.01 to 0.63 ,g/g, which corresponds with parent whole-body concentrations of 1.1 to 1.2 ,g/g. Offspring of exposed fish also had altered sex ratios, with treatment at moderate concentrations producing fewer females and treatment at the highest concentration producing more females than expected. Alterations in sex ratios were observed at concentrations of less than 0.01 ,g/g in eggs or between 0.44 and 1.1 ,g/g in parents. Offspring of mercury-exposed fish also had increased growth in moderate treatments, when egg concentrations were less than 0.02 ,g/g, or when parent whole bodies contained 0.2 to 0.47 ,g/g. In summary, exposure to mercury reduced male survival, reduced the ability of offspring to successfully reproduce, and altered sex ratios in offspring. Both direct effects on exposed fish and transgenerational effects were observed. [source]

Proximate Determinants of Reproductive Skew in Polygyne Colonies of the Ant Formica fusca

ETHOLOGY, Issue 11 2002
Minttumaaria Hannonen
Understanding the determinants of reproductive skew (the partitioning of reproduction among co-breeding individuals) is one of the major questions in social evolution. In ants, multiple-queen nests are common and reproductive skew among queens has been shown to vary tremendously both within and between species. Proximate determinants of skew may be related to both queen and worker behaviour. Queens may attempt to change their reproductive share through dominance interactions, egg eating and by changing individual fecundity. Conversely, workers are in a position to regulate the reproductive output of queens when rearing the brood. This paper investigates queen behaviour at the onset of egg laying and the effect of queen fecundity and worker behaviour on brood development and reproductive shares of multiple queens in the ant Formica fusca. The study was conducted in two-queen laboratory colonies where the queens produced only worker offspring. The results show that in this species reproductive apportionment among queens is not based on dominance behaviour and aggression, but rather on differences in queen fecundity. We also show that, although the queen fecundity at the onset of brood rearing is a good indicator of her final reproductive output, changes in brood composition occur during brood development. Our results highlight the importance of queen fecundity as a major determinant of her reproductive success. They furthermore suggest that in highly derived polygyne species, such as the Formica ants, direct interactions as a means for gaining reproductive dominance have lost their importance. [source]

Reproductive skew in birds: models, problems and prospects

JOURNAL OF AVIAN BIOLOGY, Issue 2 2000
Robert D. Magrath
In recent years there has been a resurgence of interest in models to explain the partitioning of direct reproduction (,reproductive skew') among members of one sex within social groups. We review models of skew, identify problems of testing models, and consider how to make progress. One series of models assumes that dominants have complete control of subordinate reproduction, but may allow subordinates some reproduction as a way of enticing them to help or getting them to share the cost of reproduction. Another series of models assume that dominants have limited control of subordinate reproduction. Reproductive skew may also be affected by incest avoidance or control by the opposite sex. Models are largely untested because no study of birds has quantified all relevant parameters, and we see no prospect of this happening soon. A common simplifying approach is to test qualitative predictions about the effect on skew of relatedness among group members. However, these data alone cannot distinguish among models because models do not make unique predictions, partly because skew is also affected by other factors. A major problem in cooperatively-breeding birds is that any effect of relatedness will often be confounded by covariation with relatedness asymmetry and subordinate competitiveness. Progress can be made with the development of theory, controlling confounding variables through the choice of study species or types of social group, and, most importantly, testing assumptions underlying hypotheses. [source]

Estrogen and Bone,a Reproductive and Locomotive Perspective,

JOURNAL OF BONE AND MINERAL RESEARCH, Issue 11 2003
Teppo Ln Järvinen MD
Abstract The primary function of the skeleton is locomotion, and the primary function of estrogen is reproduction. When the skeleton is considered within this locomotive context, the onset of estrogen secretion at puberty leads to packing of mechanically excess mineral into female bones for reproductive needs. Accordingly, the unpacking of this reproductive safety deposit at menopause denotes the origin of type I osteoporosis. Introduction: According to the prevailing unitary model of involutional osteoporosis, female postmenopausal bone loss can be described as having an initial accelerated, transient phase (type I), followed by a gradual continuous phase (type II). Estrogen withdrawal is generally accepted as the primary cause of the type I osteoporosis. Thus, the quest to uncover the origin of type I osteoporosis has focused on the estrogen withdrawal-related skeletal changes at and around the menopause. However, considering that the cyclical secretion of estrogen normally begins in early adolescence and continues over the entire fertile period, one could argue that focusing on perimenopause alone may be too narrow. Materials and Methods: This is not a systematic review of the literature on the skeletal function of estrogen(s), but rather, an introduction of a novel structure- and locomotion-oriented perspective to this particular issue through pertinent experimental and clinical studies. Results and Conclusions: When considering locomotion as the primary function of the skeleton and integrating the classic findings of the pubertal effects of estrogen on female bones and the more recent hypothesis-driven experimental and clinical studies on estrogen and mechanical loading on bone within this context, a novel evolution-based explanation for the role of estrogen in controlling female bone mass can be outlined: the onset of estrogen secretion at puberty induces packing of mechanically excess bone into female skeleton for needs of reproduction (pregnancy and lactation). Accordingly, the unpacking of this reproductive safety deposit of calcium at menopause denotes the accelerated phase of bone loss and thus the origin of type I osteoporosis. [source]

Parity is associated with lower cervical E-cadherin expression in postmenopausal women

JOURNAL OF OBSTETRICS AND GYNAECOLOGY RESEARCH (ELECTRONIC), Issue 6 2008
Vasileios Sioulas
Abstract Aim:, Epithelial cadherin (E-cadherin), a transmembrane glycoprotein involved in calcium-dependent homophilic cell-cell adhesion, is expressed aberrantly during cervical carcinogenesis. E-cadherin expression and putatively implicated predictors in healthy women remain a rather under-investigated area. The objective of this study is to evaluate the possible associations between E-cadherin expression and reproductive/lifestyle factors in cervical epithelial cells from postmenopausal women. Methods:, A total of 105 healthy postmenopausal women (aged 45,68 years old) attending a university menopause clinic were enrolled in this cross-sectional study. Pap smears were derived and E-cadherin immunostaining was evaluated in squamous, glandular and squamous metaplastic cells, using a semi-quantitative method (rating scale: 0,3). Reproductive and lifestyle factors were obtained from patients' chart review. Results:, In squamous cells, women with a history of 0,1 deliveries presented with a higher score vs women with 2,4 deliveries (P = 0.003). Social drinkers and women drinking alcohol daily exhibited a higher E-cadherin immunostaining score in squamous cells vs non-drinkers (0.96 ± 0.72 vs 0.56 ± 0.65, P = 0.004). A higher dietary calcium intake was marginally correlated with a lower staining score in squamous cells (0.94 ± 0.78 for low, 0.71 ± 0.70 for average, 0.45 ± 0.52 for high consumption, P = 0.073). Conclusions:, E-cadherin expression seems to be associated with reproductive history and lifestyle habits in squamous cervical cells from healthy postmenopausal women. E-cadherin might participate in the molecular mechanisms underlying the role of parity as a risk factor for cervical cancer. [source]

Pelvic floor disorders and quality of life in women with self-reported irritable bowel syndrome

ALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 3 2010
J. WANG
Aliment Pharmacol Ther,31, 424,431 Summary Background, Quality of life among women with irritable bowel syndrome may be affected by pelvic floor disorders. Aim, To assess the association of self-reported irritable bowel syndrome with urinary incontinence, pelvic organ prolapse, sexual function and quality of life. Methods, We analysed data from the Reproductive Risks for Incontinence Study at Kaiser Permanente, a random population-based study of 2109 racially diverse women (mean age = 56). Multivariate analyses assessed the association of irritable bowel syndrome with pelvic floor disorders and quality of life. Results, The prevalence of irritable bowel syndrome was 9.7% (n = 204). Women with irritable bowel had higher adjusted odds of reporting symptomatic pelvic organ prolapse (OR 2.4; 95% CI, 1.4,4.1) and urinary urgency (OR 1.4; 95% CI, 1.0,1.9); greater bother from pelvic organ prolapse (OR 4.3; 95% CI, 1.5,11.9) and faecal incontinence (OR 2.0; 95% CI, 1.3,3.2); greater lifestyle impact from urinary incontinence (OR 2.2; 95% CI, 1.3,3.8); and worse quality of life (P < 0.01). Women with irritable bowel reported more inability to relax and enjoy sexual activity (OR 1.8; 95% CI, 1.3,2.6) and lower ratings for sexual satisfaction (OR 1.8; 95% CI, 1.3,2.5), but no difference in sexual frequency, interest or ability to have an orgasm. Conclusions, Women with irritable bowel are more likely to report symptomatic pelvic organ prolapse and sexual dysfunction, and report lower quality of life. [source]

Fertility and assisted reproduction: The costs to the NHS of multiple births after IVF treatment in the UK

BJOG : AN INTERNATIONAL JOURNAL OF OBSTETRICS & GYNAECOLOGY, Issue 1 2006
William L Ledger
Objectives, To determine the cost to the NHS resulting from multiple pregnancies arising from IVF treatment in the UK, and to compare those costs with the cost to the NHS due to singleton pregnancies resulting from IVF treatment. Design, A modelling study using data from published literature and cost data from national sources in the public domain, calculating direct costs from the diagnosis of a clinical pregnancy until the end of the first year after birth. Setting, Academic Unit of Reproductive and Developmental Medicine. Population, Theoretic core modelling study using data from published literature. Methods, The analysis was based on the total annual number of births resulting from an IVF treatment in the UK. Main outcome measures total direct costs to the NHS per IVF singleton, twin or triplet family. Main outcome measures, Cost of singleton, twin and triplet IVF pregnancies in the UK. Results, Total direct costs to the NHS per IVF twin or triplet family (maternal + infant costs) are substantially higher than per IVF singleton family (singleton: £3313; twin: £9122; and triplet: £32,354). Multiple pregnancies after IVF are associated with 56% of the direct cost of IVF pregnancies, although they represent less than 1/3 of the total annual number of maternities in the UK. Conclusions, Multiple pregnancies after IVF are associated with high direct costs to the NHS. Redirection of money saved by implementation of a mandatory ,two embryo transfer' policy into increased provision of IVF treatment could double the number of NHS-funded IVF treatment cycles at no extra cost. Further savings could be made if a selective ,single embryo transfer' policy were to be adopted. [source]

Phylogenetic analysis of bovine pestiviruses: testing the evolution of clinical symptoms

CLADISTICS, Issue 5 2004
L. R. Jones
This study presents a phylogenetic analysis of 115 bovine pestiviruses. A sequence data set from the 5, untranslated genomic region was analyzed with maximum parsimony, bootstrapping and parsimony jackknifing. We tested for the proposed classifications of the group and analyzed the evolution of the symptoms associated with Pestivirus infections in bovines. Based on the historical framework provided by our phylogenetic trees, we also characterized the extent and importance of contamination caused in biologicals by the virus. Our phylogenetic analyses showed that the previously defined genotypes are monophyletic, except for genotype 1a. Based on our cladograms, we propose the existence of more than 12 monophyletic groups within the species BVDV 1. The mapping of clinical symptoms suggests that the emergence of some genotypes could have been driven by a change in the pathogenic process. Enteric Problems appear to be ancestral, while Reproductive and Respiratory Problems arise with the emergence of genotypes 1b, 1d and the herein-proposed genotype Arg 1. The distribution of contaminant strains on the cladograms shows that pestiviral contamination is a common process, and also suggests that a contaminated product might be a vehicle for virus dispersion. Implications for virus evolution, virus taxonomy, veterinary medicine and biotechnology are discussed. [source]

Developmental toxicity of estrogenic chemicals on rodents and other species

CONGENITAL ANOMALIES, Issue 2 2002
Taisen Iguchi
ABSTRACT, Antenatal sex-hormone exposure induces lesions in mouse reproductive organs, which are similar to those in humans exposed in utero to a synthetic estrogen, diethylstilbestrol. The developing organisms including rodents, fish and amphibians are particularly sensitive to exposure to estrogenic chemicals during a critical window. Exposure to estrogens during the critical period induces long-term changes in reproductive as well as non-reproductive organs, including persistent molecular alterations. The antenatal mouse model can be utilized as an indicator of possible long-term consequences of exposure to exogenous estrogenic compounds including possible environmental endocrine disrupters. Many chemicals released into the environment potentially disrupt the endocrine system in wildlife and humans, some of which exhibit estrogenic activity by binding to the estrogen receptors. Estrogen responsive genes, therefore, need to be identified to understand the molecular basis of estrogenic actions. In order to understand molecular mechanisms of estrogenic chemicals on developing organisms, we are identifying estrogen responsive genes using cDNA microarray, quantitative RT-PCR, and differential display methods, and genes related to the estrogen-independent vaginal changes in mice induced by estrogens during the critical window. In this review, discussion of our own findings related to endocrine distuptor issue will be provided. [source]

Orexins and the regulation of the hypothalamic-pituitary-testicular axis

ACTA PHYSIOLOGICA, Issue 3 2010
M. Nurmio
Abstract Orexins (OX), OX-A and OX-B, were initially identified as hypothalamic neuropeptides primarily involved in the control of food intake and states of arousal. Thereafter, orexins have been substantiated as putative pleiotropic regulators of a wide diversity of biological systems, including different neuroendocrine axes. Among the latter, compelling experimental evidence has recently been documented that orexins, mainly OX-A, may act at different levels of the hypothalamic-pituitary-gonadal (HPG) axis to modulate reproductive function. These actions are likely to include regulatory effects on the hypothalamic centres governing the HPG axis, as well as direct actions at the gonadal level. We review herein the experimental evidence, gathered in recent years, supporting a reproductive ,facet' of orexins, with special emphasis on our current knowledge of their patterns of expression and potential functional roles in the testis. Overall, the available data strongly suggest that, by acting at different levels of the HPG axis, orexins may operate as putative neuroendocrine and autocrine/paracrine regulators of gonadal function. [source]

,EVEN IF YOU'RE POSITIVE, YOU STILL HAVE RIGHTS BECAUSE YOU ARE A PERSON': HUMAN RIGHTS AND THE REPRODUCTIVE CHOICE OF HIV-POSITIVE PERSONS

DEVELOPING WORLD BIOETHICS, Issue 1 2008
LESLIE LONDON
ABSTRACT Global debates in approaches to HIV/AIDS control have recently moved away from a uniformly strong human rights-based focus. Public health utilitarianism has become increasingly important in shaping national and international policies. However, potentially contradictory imperatives may require reconciliation of individual reproductive and other human rights with public health objectives. Current reproductive health guidelines remain largely nonprescriptive on the advisability of pregnancy amongst HIV-positive couples, mainly relying on effective counselling to enable autonomous decision-making by clients. Yet, health care provider values and attitudes may substantially impact on the effectiveness of nonprescriptive guidelines, particularly where social norms and stereotypes regarding childbearing are powerful, and where providers are subjected to dual loyalty pressures, with potentially adverse impacts on rights of service users. Data from a study of user experiences and perceptions of reproductive and HIV/AIDS services are used to illustrate a rights analysis of how reproductive health policy should integrate a rights perspective into the way services engage with HIV-positive persons and their reproductive choices. The analysis draws on recognised tools developed to evaluate health policies for their human rights impacts and on a model developed for health equity research in South Africa to argue for greater recognition of agency on the part of persons affected by HIV/AIDS in the development and content of policies on reproductive choices. We conclude by proposing strategies that are based upon a synergy between human rights and public health approaches to policy on reproductive health choices for persons with HIV/AIDS. [source]

Sex-role reversal is reflected in the brain of African black coucals (Centropus grillii)

DEVELOPMENTAL NEUROBIOLOGY, Issue 12 2007
Cornelia Voigt
Abstract In most bird species males compete over access to females and have elevated circulating androgen levels when they establish and defend a breeding territory or guard a mate. Testosterone is involved in the regulation of territorial aggression and sexual display in males. In few bird species the traditional sex-roles are reversed and females are highly aggressive and compete over access to males. Such species represent excellent models to study the hormonal modulation of aggressive behavior in females. Plasma sex steroid concentrations in sex-role reversed species follow the patterns of birds with "traditional" sex-roles. The neural mechanisms modulating endocrine secretion and hormone,behavior interactions in sex-role reversed birds are currently unknown. We investigated the sex differences in the mRNA expression of androgen receptors, estrogen receptor ,, and aromatase in two brain nuclei involved in reproductive and aggressive behavior in the black coucal, the nucleus taeniae and the bed nucleus of the stria terminalis. In the bed nucleus there were no sex differences in the receptor or aromatase expression. In the nucleus taeniae, however, we show for the first time, that females have a higher mRNA expression of androgen receptors than males. These results suggest that the expression of agonistic and courtship behavior in females does not depend on elevated blood hormone levels, but may be regulated via increased steroid hormone sensitivity in particular target areas in the brain. Hence, aggression in females and males may indeed be modulated by the same hormones, but regulated at different levels of the neuroendocrine cascade. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2007 [source]

Gross anatomy of the musculature and a new description of the reproductive system of Tanaisia bragai and Tanaisia inopina (Trematoda: Eucotylidae) analysed by confocal laser scanning microscopy

ACTA ZOOLOGICA, Issue 2 2010
Sthefane D'ávila
Abstract D'ávila, S., Manso, P. P. A., Bessa, E. C. A., Rodrigues, M. L. A. and Dias, R. J. P. 2010. Gross anatomy of the musculature and a new description of the reproductive system of Tanaisia bragai and Tanaisia inopina (Trematoda: Eucotylidae) analysed by confocal laser scanning microscopy. ,Acta Zoologica (Stockholm) 91: 139,149 Confocal scanning laser microscopy has become an important tool to clarify the organization of the musculature and innervation, as well as the morphology of the reproductive and alimentary tract of various helminth species. The goal of this work was to describe the morphology of the reproductive system and the gross anatomy of the musculature of adults of the species Tanaisia bragai and Tanaisia inopina by means of confocal scanning laser microscopy. The helminths were found parasitizing the kidney collection ducts of Columba livia, in the municipality of Juiz de Fora, Brazil. These helminths were stained with Mayer's carmalum, mounted on permanent slides and observed through a confocal scanning laser microscope. The tomographic images showed the morphology of the organs and glands of the reproductive system, along with the general morphology of the musculature of the body wall, oral sucker, acetabulum, pharynx, intestinal caeca, oesophagus and reproductive system ducts. The present work is the first re-characterization of the reproductive tract of T. bragai and T. inopina. We also present the first description of the general morphology of the gametes and cells of the glands associated with the reproductive apparatus of these species. [source]

Abundance , occupancy relationships in macrofauna on exposed sandy beaches: patterns and mechanisms

ECOGRAPHY, Issue 5 2004
Matthew T. Frost
We studied the relationship between abundance and extent of occupancy of 158 species of macrofauna inhabiting 66 sandy beaches around the coast of Great Britain. We also used these data to test the predictions of two hypotheses proposed to explain positive abundance-occupancy relationships. We found a strong positive relationship between abundance and extent of occupancy; this pattern was apparent in taxonomic subsets of organisms which have contrasting reproductive and dispersal traits such as planktotrophic/lecithotrophic development in the plankton vs brood development under parental care. Moreover, the abundance-occupancy relationships in these taxonomic subsets had statistically indistinguishable slopes, and elevation. We propose that this lends support to the notion that differences in population structure such as the tendency to form metapopulations may not be primary determinants of the abundance-occupancy pattern in these taxa as proposed by the rescue/metapopulation hypothesis. To test the predictions of the niche-breadth hypothesis we derived values describing the range of sediment grain-sizes exploited by members of two taxonomic subgroups: amphipods and bivalves. We found a weak, statistically non-significant relationship between this niche-breadth measure and occupancy in bivalves which have been shown to respond to grain-size in previous studies, however this was negated after correction for possible artefacts of sampling effort. All other relationships between abundance or occupancy and grain-size range were non-significant. The consistency of the demonstrated abundance-occupancy relationship with those demonstrated in other studies of primarily terrestrial fauna indicates some shared mechanistic explanation, but our data fail to provide support for the two mechanistic hypotheses investigated. [source]

Does the diapause experience of bumblebee queens Bombus terrestris affect colony characteristics?

ECOLOGICAL ENTOMOLOGY, Issue 1 2000
M. Beekman
Summary 1. Bumblebee colonies show much variation in the number of workers, drones, and queens produced. Because this variation prevails even when colonies are kept under identical conditions, it does not seem to be caused by extrinsic factors but rather by differences between founding queens. 2. The most likely factor that could cause differences between queens is diapause. Although colonies are raised under standardised conditions, the queens often experience diapause of different length. If there are costs associated with diapause that influence post-diapause reproduction, the diapause history of the queens could affect colony characteristics. 3. Here, several colony characteristics are compared: number of first and second brood workers; total number of workers, drones, and queens; energy spent on sexuals; sex ratio; rate of worker production; time to emergence of first reproductive; and colony lifetime. Colonies were used where the queens experienced a diapause treatment of 0 (nondiapause queens), 2, and 4 months. 4. Although no proof was found for the existence of costs associated with diapause, the colony characteristics of nondiapause queens were significantly different from those of diapause queens. Colonies of nondiapause queens produced the lowest number of workers but the highest number of young queens. 5. It is argued that these nondiapause colonies are more time-constrained than diapause colonies because nondiapause colonies produce two generations within the same season and should therefore be more efficient in producing sexual offspring. 6. Moreover, nondiapause colonies should rear a more female-biased sex ratio because they can be certain of the presence of males produced by other (diapause) colonies. [source]

Sexual conflicts, loss of flight, and fitness gains in locomotion of polymorphic water striders

ENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 3 2007
Pablo Perez Goodwyn
Abstract In insect wing polymorphism, morphs with fully developed, intermediate, and without wings are recognized. The morphs are interpreted as a trade-off between flight and flightlessness; the benefits of flight are counterbalanced by the costs of development and the maintenance of wings and flight muscles. Such a trade-off has been widely shown for reproductive and developmental parameters, and wing reduction is associated with species of stable habitats. However, in this context, the role of water locomotion performance has not been well explored. We chose seven water striders (Heteroptera: Gerridae) as a model to study this trade-off and its relation to sexual conflicts, namely, Aquarius elongatus (Uhler), Aquarius paludum (Fabr.), Gerris insularis (Motschulsky), Gerris nepalensis Distant, Gerris latiabdominis Miyamoto, Metrocoris histrio (White), and Rhagadotarsus kraepelini Breddin. We estimated the locomotion performance as the legs' stroke force, measured on tethered specimens placed on water with a force transducer attached to their backs. By dividing force by body weight, we made performance comparisons. We found a positive relationship between weight and force, and a negative one between weight and the force-to-weight ratio among species. The trade-off between water and flight locomotion was manifested as differences in performance in terms of the force/weight ratio. However, the bias toward winged or wing-reduced morphs was species dependent, and presumably related to habitat preference. Water strider species favouring a permanent habitat (G. nepalensis) showed higher performance in the apterous morph, but in those favouring temporary habitats (A. paludum and R. kraepelini) morphs' performance did not differ significantly. Males had higher performance than females in all but three species studied (namely, A. elongatus, G. nepalensis, and R. kraepelini); these three have a type II mating strategy with minimized mating struggle. We hypothesized that in type I mating system, in which males must struggle strongly to subdue the female, males should outperform females to copulate successfully. This was not necessarily true among males of species with type II mating. [source]

Effect of temperature on development, overwintering and establishment potential of Franklinothrips vespiformis in the UK

ENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 2 2007
Eleni Larentzaki
Abstract This study investigated the effect of temperature on the development and overwintering potential of the predatory thrips Franklinothrips vespiformis (Crawford) (Thysanoptera: Aeolothripidae), a biological control agent used against glasshouse pests in continental Europe and Israel. Developmental rates increased linearly with rearing temperatures. It was estimated that 304.9 degree days, above a lower threshold temperature of 11.9 °C, were required for F. vespiformis to complete development from egg to adult eclosion. The effect of low temperatures (,5, 0, and 5 °C) was examined on adult female and larval survival. Subsequent reproductive and developmental attributes of survivors were also investigated. Lethal time experiments indicated that larval stages are more cold tolerant than adult F. vespiformis females. Surviving larvae increased their developmental times to adults with decreasing temperature and increasing exposure periods and second instars were significantly more successful than first instars in reaching adulthood. Surviving adult females decreased their oviposition rate with decreasing temperature and increasing exposure periods, and exposures to low temperatures affected the number of viable eggs produced. The results are discussed in the context of overwintering and establishment potential of F. vespiformis in the UK in the event of introducing the predatory thrips as a biological control agent against glasshouse pests. [source]

Novel strategies targeting pathogen transmission reduction in insect vectors: Tsetse-transmitted trypanosomiasis control

ENTOMOLOGICAL RESEARCH, Issue 4 2007
Brian L. WEISS
Abstract Insect vectors are essential for the transmission of important human diseases such as malaria, leishmaniasis, Chagas and sleeping sickness. Insects are also responsible for the transmission of agricultural diseases that affect livestock and crops. Traditionally, control of the vector populations has been an effective disease management strategy. Recently, vector control strategies have been fortified by research in insect biology and in insect,pathogen interactions as well as by the development of transgenic technologies. In addition to insect population reduction methods, disease control via selective elimination of pathogens in insects can now be explored. Here we explore the tsetse vectors of African trypanosomes and describe the application of recent knowledge gained in their symbiotic, reproductive and vectorial biology to develop novel disease control strategies. [source]

Investigating the link between pulp mill effluent and endocrine disruption: Attempts to explain the presence of intersex fish in the Wabigoon River, Ontario, Canada

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2010
Michael S. Pollock
Abstract The ability of some pulp mill effluents (PME) to act as reproductive and endocrine disrupters in fish is well documented in the literature. However, changes are not always consistent with regard to species, gender, hormones, or reproductive effects. In the present study, the presence of the first intersexed fish that, to our knowledge, has been found in a Canadian river exposed to PME, is reported. A field survey of the Wabigoon River near Dryden, Ontario, in the fall of 2000 found intersexed walleye (Sander vitreus vitreus) with significantly altered hormone levels and reduced gonad size. The Wabigoon River receives discharge from a bleached kraft pulp and paper mill and a municipal wastewater (MWW) plant. It also has historical sediment contamination (wood fiber mats) contributing to extended periods of low dissolved oxygen under low flow, drought conditions. A mesocosm-based partial life cycle test exposing fathead minnows (Pimephales promelas) to reference water, 20% effluent volume to river volume (v/v), 40% (v/v), or 60% (v/v) PME as well as a field survey of the walleye in the Wabigoon River were conducted. The only change in our mesocosm exposure was a decrease in testosterone in males with increasing effluent concentration and vitellogenin induction in males exposed to 60% (v/v) effluent. These results did not reflect the magnitude of endocrine disruption seen in the wild fish survey. Several hypotheses that may explain these discrepancies are proposed. Specifically, evidence is offered from published studies indicating that either hypoxia or MWW, alone or in combination with PME, may explain the discrepancy between our field experiment and the wild fish survey. The present study illustrates the complexities of multistressor receiving environments and the need for the development of cumulative effects assessment approaches. Environ. Toxicol. Chem. 2010;29:952,965. © 2010 SETAC [source]

Integrated condition indices as a measure of whole effluent toxicity in zebrafish (Danio rerio)

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2002
Roel Smolders
Abstract Toxic exposure of organisms interferes with organismal integrity at the biochemical level and ultimately gives rise to effects at the individual level. These effects may result in reductions in ecologically relevant characteristics such as growth, reproduction, and survival. A chronic toxicity test with zebrafish (Danio rerio) was conducted where fish were exposed to 50, 75, and 100% effluent for 28 d under flow-through conditions. Effects of effluent exposure were determined using endpoints of physiological (respiration during swimming), growth (condition, length, and weight), and reproductive (spawning and hatching) processes within the same population. Results clearly indicate that the condition and growth of zebrafish is depressed by exposure to the effluent. Also, increased oxygen consumption was found after 14, 21, and 28 d of exposure. Reproduction proved to correlate well with the condition of the motherfish in the control, and spawning and hatching were significantly depressed by effluent exposure. These results indicate that the evaluation of endpoints describing different ecologically relevant processes provides a rational assessment of the cause,effect relationships of effluent toxicity. This approach can quantify effects on different biological processes and can determine the interactions that occur between these different processes. [source]

Use of freshwater rotifer Brachionus calyciflorus in screening assay for potential endocrine disruptors

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2000
Benjamin L. Preston
Abstract eports of the effectsofendocrinedisruptorsonaquatic invertebrates arebecoming increasingly common. However, little is known about the endocrine systems of most aquatic invertebrates, limiting the development of assays based on endocrine mechanisms. As a result, endocrine disruption is often inferred through the effects caused by the chemical of interest, making it difficult to rule out other mechanisms of toxicity. To be a good candidate for an endocrine disruptor, effects should be observed in processes known to be under endocrine control, at life stages where endocrine signals are known to be active, and at concentrations below acute and chronic toxic effects. We developed a 96-h reproductive assay using the freshwater rotifer Brachionus calyciflorus to screen for potential endocrine disruptors and examined cadmium, chlorpyrifos, naphthol, pentachlorophenol, estradiol, methoprene, precocene, nonylphenol, flutamide, and testosterone for effects on asexual and sexual reproduction. Flutamide, testosterone, and nonylphenol inhibited fertilization of sexual females at concentrations of 1, 10, and 50 ,g/L, respectively. The fertilization no-observable-effect concentrations (NOECs) for these compounds were 5 to 200 times lower than previously described reproduction NOECs for B. calyciflorus. Sexual reproduction was inhibited with no effects on asexual reproduction, increasing the likelihood that these specific reproductive effects occurred through an endocrine mechanism. Rotifer reproduction assays may be a useful, rapid, and inexpensive method for screening compounds suspected to have endocrine disrupting activity in aquatic invertebrates. [source]

Proximate Determinants of Reproductive Skew in Polygyne Colonies of the Ant Formica fusca

Models of reproductive skew: A review and synthesis (Invited Article)

ETHOLOGY, Issue 1 2000
Rufus A. Johnstone
Animal societies vary markedly in reproductive skew, the extent to which breeding is monopolised by dominant individuals. In the last few years, a large number of different models have been developed to explain this variation. Here, I review existing models of reproductive skew, distinguishing between two basic types. Transactional models focus on group stability and the constraints this places on the division of reproduction. Compromise models, by contrast, ignore issues of group stability and view the division of reproduction as the outcome of a conflict in which each group member has a limited or partial ability to enforce its own optimum. I go on to show, however, that the division between transactional and compromise models is somewhat artificial, and that both approaches may be combined in a single, synthetic treatment. Different models of reproductive skew are thus better seen as special cases of a general underlying theory, rather than alternative paradigms. I conclude with a brief discussion of the possibilities and problems of empirically testing this unified theory of skew, and the prospects for future theoretical advances. [source]

CHARACTER DISPLACEMENT AS THE "BEST OF A BAD SITUATION": FITNESS TRADE-OFFS RESULTING FROM SELECTION TO MINIMIZE RESOURCE AND MATE COMPETITION

EVOLUTION, Issue 10 2005
Karin S. Pfennig
Abstract Character displacement has long been considered a major cause of adaptive diversification. When species compete for resources or mates, character displacement minimizes competition by promoting divergence in phenotypes associated with resource use (ecological character displacement) or mate attraction (reproductive character displacement). In this study, we investigated whether character displacement can also have pleiotropic effects that lead to fitness trade-offs between the benefits of avoiding competition and costs accrued in other fitness components. We show that both reproductive and ecological character displacement have caused spadefoot toads to evolve smaller body size in the presence of a heterospecific competitor. Although this shift in size likely arose as a by-product of character displacement acting to promote divergence between species in mating behavior and larval development, it concomitantly reduces offspring survival, female fecundity, and sexual selection on males. Thus, character displacement may represent the "best of a bad situation" in that it lessens competition, but at a cost. Individuals in sympatry with the displaced phenotype will have higher fitness than those without the displaced trait because they experience reduced competition, but they may have reduced fitness relative to individuals in allopatry. Such a fitness trade-off can limit the conditions under which character displacement evolves and may even increase the risk of "Darwinian extinction" in sympatric populations. Consequently, character displacement may not always promote diversification in the manner that is often expected. [source]

EVOLUTION OF MOUTHBROODING AND LIFE-HISTORY CORRELATES IN THE FIGHTING FISH GENUS BETTA

EVOLUTION, Issue 4 2004
Lukas Rüber
Abstract The origin of and evolutionary transitions among the extraordinary diverse forms of parental care in teleost fish remain largely unknown. The "safe harbor" hypothesis predicts that the evolution from a "guarding" to a "brooding" form of care in teleost fish is associated with shifts in reproductive and life-history features such as reduced fecundity, and increased egg volume with higher parental investment. Robust phylogenetic hypotheses may help to identify evolutionary changes in key traits associated with differences in the form of parental care. Here, we used reconstruction of ancestral character states to study the evolution of the two forms of parental care, bubble nesting and mouthbrooding in the fighting fish genus Betta. We also applied a comparative analysis using the phylogenetic generalized least-squares method to test the "safe harbor" hypothesis by evaluating differences between the two forms of parental care in standard length, life-history traits, and three habitat variables. Evolutionary hypotheses were derived from the first molecular phylogeny (nuclear and mitochondrial DNA sequence data; 4448 bp) of this speciose group. Ancestral character state reconstructions of the evolution of the form of parental care in the genus Betta, using the methods of unweighted parsimony and maximum likelihood, are uncertain and further indicate a high rate of evolutionary transitions. Applying different weights for the suspected directionality of changes, based on the consistent phenotypic and behavioral differences found between bubble nesters and mouthbrooders, recurrent origin of mouthbrooding in the genus Betta is favored using parsimony. Our comparative analyses further demonstrate that bubble nesters and mouthbrooders do not have a consistent set of life-history correlates. The form of parental care in Betta is correlated only with offspring size, with mouthbrooders having significantly bigger offspring than bubble nesters, but is not correlated with egg volume, clutch size, and broodcare duration, nor with any of the three habitat variables tested. Our results thus challenge the general predictions of the "safe harbor" hypothesis for the evolution of alternative brood care forms in the fighting fish genus Betta. [source]

The utility of reproductive skew models in the study of male primates, a critical evaluation

EVOLUTIONARY ANTHROPOLOGY, Issue 2 2010
Markus Port
First page of article [source]

Modelling past and present geographical distribution of the marine gastropod Patella rustica as a tool for exploring responses to environmental change

GLOBAL CHANGE BIOLOGY, Issue 10 2007
FERNANDO P. LIMA
Abstract A climate envelope approach was used to model the distributions of the intertidal gastropod Patella rustica, to test the robustness of forecast responses to climate change. The model incorporated variables that were likely to determine the abundance and the northern range limit of this species in the NE Atlantic. The model was built using classification and regression tree analysis (CART) trained with historical distribution data from the mid 1950s and a set of corresponding climatic and oceanographic variables. Results indicated air and sea temperature, in particular during the reproductive and settlement periods, as the main determinants of the Atlantic distribution of P. rustica. The model was subsequently fed with contemporary climatic data and its output was compared with the current distribution and abundance of P. rustica, assessed during a 2002,2003 survey. The model correctly hindcasted the recent collapse of a distributional gap in northern Portugal, as well as an increase in abundance at locations within its range. The predicted northward expansion of the northern range limit did not occur because the absence of the species was confirmed in a survey encompassing the whole Atlantic French coast up to Brest. Stretches of unsuitable habitat too long to be overcome by dispersal are the likely mechanism controlling the northern limit of the distribution of this intertidal species. [source]

Fish community comparisons along environmental gradients in lakes of France and north-east USA

GLOBAL ECOLOGY, Issue 3 2007
Pascal Irz
ABSTRACT Aim, To assess whether eight traits of fish communities (species richness, three reproductive traits and four trophic traits) respond similarly to environmental gradients, and consequently display convergence between the lakes of France and north-east USA (NEUSA). Location, 75 French and 168 north-east USA lakes. Methods, The data encompass fish surveys, the assignment of species into reproductive and trophic guilds, and environmental variables characterizing the lakes and their catchments. The analytical procedure was adapted from the recommendations of Schluter (1986) [Ecology, 67, 1073,1085]. Results, The comparison of the regional pools of lacustrine fishes indicated that NEUSA was about twice as speciose as France, mostly due to higher species turnover across lakes, although NEUSA lakes were consistently about 20% more speciose than French lakes for a given surface area. Warmer environments were consistently inhabited by a higher proportion of phytophilous and guarder species than were colder lakes. Hence there was convergence in community reproductive traits. Conversely, there was no evidence of convergence in the trophic structure of lacustrine fish communities between regions. Main conclusions, The influence of temperature on the availability and quality of spawning substrates appears to be a major constraint on present-day lacustrine fish communities. In parallel, phylogenetic constraints, past events such as the diversification of the North American fish fauna, and selective extinctions during Pleistocene glaciations and subsequent recolonizations contribute to explaining the dissimilarities between the communities of the two regions and differences in their relationship to the environment. [source]

Fungal alkaloids in populations of endophyte-infected Festuca rubra subsp. pruinosa

GRASS & FORAGE SCIENCE, Issue 3 2007
B. R. Vázquez-de-Aldana
Abstract Festuca rubra subsp. pruinosa is a grass that grows on coastal cliffs along the Atlantic coast of Europe. Asymptomatic plants of this species are systemically infected by the fungal endophyte Epichloë festucae. It is not known whether the alkaloids, ergovaline and peramine, are produced by the endophyte in F. rubra subsp. pruinosa. Plants from four populations were collected from the northern coast of Galicia (Spain) and examined for the presence of fungal endophytes. Ergovaline and peramine concentrations were analysed over two consecutive years, at two plant growth stages, and in different types of plant tissues. Infected plants of F. rubra subsp. pruinosa contained ergovaline but not peramine. Ergovaline was detected in 0·80 of the plants, with concentrations ranging from 0·05 to 1·9 ,g g,1 dry matter. The differences in ergovaline concentration between different types of plant tissues (vegetative and reproductive), plant populations and sampling dates were not statistically significant. [source]