First baseline for bioenergetic biomarkers in Cnesterodon decemmaculatus as test organism in ecotoxicological studies.

Cnesterodon decemmaculatus is a Neotropical teleost fish frequently used in ecotoxicological evaluations, whose biology has been thoroughly studied. Although there is considerable information on its response to different toxicants, no range of reference values has been so far established for the different biological parameters proposed as biomarkers of effect or exposure. Moreover, no study has yet examined the possible influence of the metabolic status of the exposed animals on their response to toxic stress. Therefore, the aim of this work was to provide a first baseline for a set of bioenergetic biomarkers in C. decemmaculatus adults exposed to a control medium under previously standardized conditions, and to assess their possible intrinsic seasonal variability. The responses of the biomarkers obtained from the controls were contrasted with those from the reference toxicant (Cadmio-Cd) and receiving waters (surface waters of the Reconquista River RR, Buenos Aires Province, Argentina). We conducted four 12-day assays (one in each season) of exposure to control media, (reconstituted moderate hard water, MHW) and two assays of exposure to Cd in MHW and surface river water (RR) in both summer and autumn. The variables recorded were: Food intake (In), fecal production (F), specific assimilation (A) and cumulative mortality, oxygen extraction efficiency (OEE), specific metabolic rate (SMR), ammonia excretion (N), ammonia quotient (AQ) and scope for growth (SFG). The seasonal variation shown by some physiological parameters, points to the need for establishing a baseline obtained from standardized media, preferably on a seasonal basis. Moreover, SFG and A appeared as the most sensitive biomarkers, emphasizing the importance to consider the metabolic status of the test organisms for the appropriate interpretation of results from ecotoxicological studies performed under controlled experimental conditions. The obtained results provide useful information on C. decemmaculatus as model species in ecotoxicological bioassays involving biomarkers of early effect.

Effects of the synthetic estrogen 17α-ethinylestradiol on Heterandria formosa populations: Does matrotrophy circumvent population collapse?

Feminization responses have been observed in some wild populations of fish living in rivers and streams, some of which have been shown to arise as a consequence of exposure to sewage treatment (STP) effluent discharges and the endocrine disrupting chemicals (EDCs) they contain which mimic or antagonize the actions of steroid hormones. The synthetic estrogen, 17α-ethinylestradiol (EE2), commonly used in oral contraceptives, is present in surface waters receiving STP effluents at concentrations ranging from non-detectable to 5 ng/L. Despite extensive evidence that EE2 negatively affects the reproductive health of fishes, relatively little is known about effects at the population level - and especially so for live-bearing fishes. To investigate the potential for such impacts, populations of the least killifish (Heterandria formosa) were exposed to 0 or 5 ng/L EE2. Exposures were started with newborn fish and continued for seven months. Chronic exposure to 5 ng/L EE2 caused significant reductions in population size, in abundances of newborns and males, and in population growth rates. The exposure also resulted in a female-biased sex ratio. However, individuals' survival rates were not affected. This study showed that chronic exposure to 5 ng/L EE2 negatively affected population dynamics in a live-bearing fish, demonstrating that the levels of EE2 detected near STPs have the potential to impact wild populations of these fish.

Effects of 17α-ethinylestradiol on sex ratio, gonadal histology and perianal hyperpigmentation of Cnesterodon decemmaculatus (Pisces, Poeciliidae) during a full-lifecycle exposure.

The effects of 17α-ethinylestradiol (EE2) on sex ratio, gonopodium morphology, and gonadal histology of C. decemmaculatus were assessed by a full-lifecycle exposure experiment. Newborn fish were waterborne exposed to 30, 100, and 300 ng EE2/L for 90 d, using 50 fish per treatment. Additionally, in December of 2016, a field survey was conducted on a C. decemmaculatus population inhabiting the Girado Creek downstream of the Chascomus city wastewater effluent discharge. After 90 d of exposure, EE2 was able to histologically skew the sex ratio toward females and inhibit the full gonopodium development since the lowest tested concentration (LOEC = 30 ng/L). At higher concentrations, EE2 was toxic, inducing mortality in a concentration-dependent fashion (90 d-LC50 = 109.9 ng/L) and altering the gonadal histoarchitecture, causing neither testes nor ovaries discernible histologically (LOEC = 100 ng/L). In addition, a novel response, perianal hyperpigmentation, was discovered been induced by the EE2 exposure in a concentration-dependent fashion (90 d-EC50 = 39.3 ng/L). A higher proportion of females and perianal hyperpigmentation were observed in wild fish collected from the Girado Creek. The major reached conclusions are: i) EE2 induce different effects on the sexual traits of C. decemmaculatus when exposed from early-life or adult stages. ii) The most sensitive effects observed in the laboratory occur in a creek receiving wastewater effluent. iii) The perianal hyperpigmentation comes-up as a promising biomarker of exposure to estrogenic compounds.

Photoperiodic effects on somatic growth and gonadal maturation in Mickey Mouse platy, Xiphophorus maculatus (Gunther, 1866).

Photoperiod is important in initiation or suppression of reproductive timing and gonadal maturation which varies with species. The aim of the present study was to investigate the effect of two photoperiodic manipulating regimes, i.e., long (18L:6D) and short (10L:14D) photoperiods for a period of 60 days on somatic growth and gonadal maturation of a live-bearer ornamental fish, Mickey Mouse platy (Xiphophorus maculatus). The control fish were further kept under the laboratory environmental condition. The results showed a significant increase in weight gain, specific growth rate, and gonadosomatic index in fish under long photoperiod than those exposed to short photoperiod and control condition (P < 0.05). A condition factor showed significant variations between long photoperiod and control groups. Furthermore, a long photoperiod also induced a significant increase in the number of fish with mature embryo and middle-eyed embryo in the ovary. Similarly, histological analysis of testes of males showed an increase in the number of mature spermatid and spermatozoa under long photoperiod when compared to those of control and short photoperiod ones. Thus, it can be concluded that long-day photoperiodic manipulation may be applied for healthy growth and early gonadal maturation of live-bearer ornamental fishes.

Environmental risk assessment (ERA) of pyriproxyfen in non-target aquatic organisms.

Pyriproxyfen (PPF) is a synthetic substance and an insect juvenile hormone agonist with growth regulating effect. It is used worldwide as a pesticide in agriculture and public health campaigns, including the control of Aedes aegypti proliferation. It has low volatility, high Kow value and high lability in aerobic aquatic systems but is considered persistent in anaerobic systems, with a half-life of 288.9 days. The objective of this study is to survey the environmental contamination by pyriproxyfen in aquatic environmental matrices, to review the acute and chronic toxicity in non-target aquatic organisms and to make a risk assessment for the organisms addressed in the bibliographic survey. Pyriproxyfen quantification studies in aquatic environmental matrices are quite scarce and punctual-not representative of regional and global contamination. The water of the River Júcar (Spain) presented the highest concentration of PPF (99.59 ng L-1) among the matrices analysed, which is equivalent to 1% of the maximum dose allowed by the World Health Organization for use in drinking water. Acute and chronic aquatic toxicity studies with LC50, EC50, LOEC and NOEC values of PPF were compiled and interpreted to evaluate possible risks to non-target aquatic organisms. Pyriproxyfen caused a high risk at concentrations detected in aquatic environments for Daphnia magna, with probable reproductive effects and occasional survival risk. This species was the most sensitive to the pesticide, with the lowest estimated concentration of 50 % of effect values, followed by a freshwater fish (Xiphophorus maculatus) and estuarine crustaceans (Eurytemora affinis and Leander tenuicornis). The most resistant organisms to PPF within the endpoints addressed in this review were Danio rerio (zebrafish) and Capitella sp. (polychaete). Through the species sensitivity distribution (SSD), it was possible to estimate HC5 at 0.214 µg L-1 and that 2.3 % of the species present high sensitivity to pyriproxyfen in the environmental concentration detected in river water and 25.82 % of the species are affected in the concentration allowed for lavicidal use. In order to obtain more accurate risk estimates, we suggest ecotoxicological assessments in other species, covering various taxa, with emphasis on microcrustaceans due to their fundamental role in the aquatic food web and taxonomic proximity to pesticide target organisms. Furthermore, additional studies of contamination in aquatic environmental matrices are required, with particular attention to freshwater and estuarine environments due to the proximity to the sources of pyriproxyfen and environmental characteristics suggesting high accumulation. Thus, it will be possible to estimate realistic exposure levels and risks in different environments, contributing to effective and safe decision making, integrating development, public health and environmental policy.

Mosaic Heterochrony in Neural Progenitors Sustains Accelerated Brain Growth and Neurogenesis in the Juvenile Killifish N. furzeri.

Although developmental mechanisms driving an increase in brain size during vertebrate evolution are actively studied, we know less about evolutionary strategies allowing accelerated brain growth. In zebrafish and other vertebrates studied to date, apical radial glia (RG) constitute the primary neurogenic progenitor population throughout life [1]; thus, RG activity is a determining factor of growth speed. Here, we ask whether enhanced RG activity is the mechanism selected to drive explosive growth, in adaptation to an ephemeral habitat. In post-hatching larvae of the turquoise killifish, which display drastic developmental acceleration, we show that the dorsal telencephalon (pallium) grows three times faster than in zebrafish. Rather than resulting from enhanced RG activity, we demonstrate that pallial growth is the product of a second type of progenitors (that we term NGPs for non-glial progenitors) that actively sustains neurogenesis and germinal zone self-renewal. Intriguingly, NGPs appear to retain, at larval stages, features of early embryonic progenitors. In parallel, RGs enter premature quiescence and express markers of astroglial function. Altogether, we propose that mosaic heterochrony within the neural progenitor population might permit rapid pallial growth by safeguarding both continued neurogenesis and astroglial function.

Dietary Intake of ß-Glucans Can Prolong Lifespan and Exert an Antioxidant Action on Aged Fish Nothobranchius guentheri.

One of the widely accepted conjectures regarding mechanisms of aging is probably the oxidative stress hypothesis. ß-1,3-Glucans, well-known immunostimulants, have been shown to increase nonspecific immunity and resistance against infections or pathogenic bacteria in several fish species, but its antiaging function remains poorly understood. By feeding of ß-1,3-glucans to the annual fish, Nothobranchius guentheri, we detected the survivorship of the fish and estimated the development of age-related biomarkers at different stages. We first showed that administration of ß-1,3-glucans was able to prolong the lifespan of the fish (p < 0.05). We then showed that ß-1,3-glucans clearly reduced the accumulation of lipofuscin in the gills and the senescence-associated ß-galactosidase in the caudal fins. Moreover, ß-1,3-glucans were able to lower the levels of protein oxidation, lipid peroxidation, and reactive oxygen species (ROS) in the muscles. Finally, ß-1,3-glucans could promote the activities of the antioxidant enzymes, including catalase, superoxide dismutase, and glutathione peroxidase in the fish, and slow down the increase of P66shc, a critical factor involved in the regulation of intracellular ROS contents. These data together suggest for the first time that ß-1,3-glucans can extend the lifespan, delay the onset of age-related biomarkers and exert an antioxidant action of the aged fish, N. guentheri. It also implies that ß-1,3-glucans may be potentially useful for health care in the elderly, including extension of the lifespan.

Single and joint effects of chronic exposure to chlorpyrifos and glyphosate based pesticides on structural biomarkers in Cnesterodon decemmaculatus.

Worldwide freshwater bodies that cross agricultural or urban areas are exposed to mixtures of xenobiotics. In particular, pesticides are usually part of these mixtures and could come into direct or indirect contact with biota and therefore, organisms have to cope with this altered scenario and the detrimental effects of these substances. Commercial formulations of chlorpyrifos and glyphosate, and their mixtures were evaluated using a set of biomarkers in the native fish C. decemmaculatus exposed to relevant environmentally pesticides concentrations. The biomarkers measured were: histopathological indices and tissue ultrastructure in liver and nuclear abnormalities and micronuclei in erythrocytes. During 42 days adult females were exposed to the following concentrations of Clorfox and Roundup Max (chlorpyrifos and glyphosate, respectively): 0.84 nl/l and 8.4 nl/l of Clorfox (CF), 0.2 and 2 mg/l of Roundup Max (RM) and all the combinations of these concentrations. Being the low concentrations of both pesticides environmentally relevant. Nuclear abnormalities of erythrocytes were registered under CF, RM and only one mixture. Histological inflammatory alterations increased in individuals exposed to CF and two mixtures. Finally, some pesticide combinations increased the circulatory alterations in liver. Ultrastructural changes in hepatocytes were registered at all the pesticide treatments. The different biomarker responses showed in the mixtures treatments reflected complex interactions, showing the mixture of the low concentrations of both pesticides (the environmentally relevant), potentiated effects. According to our results the presence of these substances in freshwaters could impose important risks for natural populations by causing deleterious effects on the native fish species C. decemmaculatus.

Spatio-temporal expression profile of sirtuins during aging of the annual fish Nothobranchius furzeri.

The founding member of the sirtuin family, yeast Sir2, was the first evolutionarily conserved gene to be identified as a regulator of longevity. Sirtuins constitute a protein family of metabolic sensors, translating changes in NAD + levels into adaptive responses, thereby acting as crucial regulators of the network that controls energy homeostasis and as such determines healthspan. In mammals the sirtuin family comprises seven proteins, SIRT1-SIRT7, which vary in tissue specificity, subcellular localization, enzymatic activity and targets. Here, we report the identification and a detailed spatio-temporal expression profile of sirtuin genes in the short-lived fish Nothobranchius furzeri, from embryogenesis to late adulthood, mapping its entire life cycle. Database exploration of the recently published N. furzeri genome revealed eight orthologues corresponding to the seven known mammalian sirtuins, including two copies of the sirt5 gene. Phylogenetic analysis showed high cross species similarity of individual sirtuins in both their overall amino acid sequence and catalytic domain, suggesting a high degree of functional conservation. Moreover, we show that N. furzeri sirtuins exhibit ubiquitous and wide tissue distribution with a unique spatial expression pattern for each individual member of this enzyme family. Specifically, we observed a transcriptional down-regulation of several sirtuin genes with age, most significantly sirt1, sirt5a, sirt6 and sirt7 in a wide range of functionally distinct tissues. Overall, this spatio-temporal expression analysis provides the foundation for future research, both into genetic and pharmacological manipulation of this important group of enzymes in Nothobranchius furzeri, an emerging model organism for aging research.

Rapid growth and large body size in annual fish populations are compromised by density-dependent regulation.

We tested the effect of population density on maximum body size in three sympatric species of annual killifishes Nothobranchius spp. from African ephemeral pools. We found a clear negative effect of population density on body size, limiting their capacity for extremely fast development and rapid growth. This suggests that density-dependent population regulation and the ephemeral character of their habitat impose contrasting selective pressures on the life history of annual killifishes.

Acute and sub-chronic toxicity bioassays of Olive Mill Wastewater on the Eastern mosquitofish Gambusia holbrooki.

Olive oil production generates large volumes of wastewaters mostly in peri-Mediterranean countries with adverse impacts on the biota of the receiving aquatic systems. Few studies have however documented its toxicity on aquatic species, with an almost total lack of relative studies on fish. We assessed the acute and sub-chronic OMW toxicity, as well as the acute and sub-chronic behavioural, morphological and biochemical effects of OMW exposure on the mosquitofish Gambusia holbrooki. LC50 values of the acute bioassays ranged from 7.31% (24 h) to 6.38% (96 h). Behavioural symptoms of toxicity included hypoactivity and a shift away from the water surface, coupled with a range of morphological alterations, such as skin damage, excessive mucus secretion, hemorrhages, fin rot and exophhalmia, with indications also of gill swelling and anemia. Biochemical assays showed that OMW toxicity resulted in induction of catalase (CAT) and inhibition of acetylcholinesterase (AChE) activities. The implications of our results at the level of environmental policy for the sustainable management of the olive mill industry, i.e. the effective restriction of untreated OMW disposal of in adjacent waterways, as well as the implementation of new technologies that reduce their impact (detoxification and/or revalorization of its residues) are discussed.

Impact of Long-Term Exposure to 17α-Ethinylestradiol in the Live-Bearing Fish Heterandria formosa.

17α-ethinylestradiol (EE2) is a potent synthetic estrogen that is routinely detected in aquatic ecosystems and exhibits estrogenic activity. Acute and chronic toxicity have been described for oviparous and ovoviviparous fish species; however, no information is available on the impacts of EE2 on viviparous, matrotrophic fish despite their ecological importance. The present study investigated the consequences of long-term EE2 exposure in the least killifish (Heterandria formosa). Effects on growth, time-to-sexual maturity, fecundity, and offspring survival were examined in an 8-month, life-cycle experiment. Starting as 0-6-day-old fish, least killifish were continuously exposed to EE2 at nominal concentrations of 0, 5, or 25 ng/L (measured concentrations averaged 0, 4.3, and 21.5 ng/L respectively). In the F0 generation, EE2-exposure did not affect survival but resulted in increased time-to-sexual maturity and a sex-dependent effect on size; female standard length was reduced while male standard length was increased. This caused the ordinarily larger females and smaller males to become more similar in size. Condition factor was reduced for both sexes. Fecundity was reduced by 50% and 75% at 5 and 25 ng/L EE2-exposure respectively. Continued EE2-exposure in the F1 generation resulted in significantly reduced survival. These results suggest that despite their matrotrophic development, these fish experience delayed development and reduced reproductive success from EE2-exposure and that effects appear to intensify in the second generation.

Identification and expression of mangrove rivulus (Kryptolebias marmoratus) histone deacetylase (HDAC) and lysine acetyltransferase (KAT) genes.

During gametogenesis and embryonic development, precise regulation of gene expression, across cell/tissue types and over time, is crucial. In vertebrates, transcription is partly regulated by histone lysine acetylation/deacetylation, an epigenetic mechanism mediated by lysine acetyltransferases (KAT) and histone deacetylases (HDAC). Well characterized in mammals, these enzymes are unknown in fish embryology outside of zebrafish development. Here, we characterized putative KAT and HDAC enzymes in the self-fertilizing mangrove rivulus fish, Kryptolebias marmoratus, a species that naturally self-fertilizes and can produce isogenic lineages. This unique feature provides an opportunity to elucidate the role of epigenetic mechanisms as a source of phenotypic plasticity. In this study, twenty-seven KAT and seventeen HDAC genes have been identified. Their conserved domains and their phylogenetic analysis suggest conservation of the enzymes' activity in our species, relative to other vertebrates in which the enzymes have been characterized. Furthermore, the dynamics of KAT and HDAC mRNA expression during embryogenesis, in adult gonads and brains, argues for a putative biological function in early and late development as well as in male/hermaphrodite gametogenesis and adult neurogenesis. Our study aimed to provide a basis about the epigenetic actors putatively regulating histone acetylation in a self-fertilizing fish, the mangrove rivulus. Unique among vertebrates, the great number of isogenic lineages occurring naturally in this species allows exploring the contribution of the enzymes regulating histone acetylation only to reproduction and development in teleost fishes, which are very powerful models in fundamental and applied researches that include aquaculture, ecotoxicology, behaviour, evolution, sexual determinism and human diseases.

Nothobranchius furzeri, an 'instant' fish from an ephemeral habitat.

The turquoise killifish, Nothobranchius furzeri, is a promising vertebrate model in ageing research and an emerging model organism in genomics, regenerative medicine, developmental biology and ecotoxicology. Its lifestyle is adapted to the ephemeral nature of shallow pools on the African savannah. Its rapid and short active life commences when rains fill the pool: fish hatch, grow rapidly and mature in as few as two weeks, and then reproduce daily until the pool dries out. Its embryos then become inactive, encased in the dry sediment and protected from the harsh environment until the rains return. This invertebrate-like life cycle (short active phase and long developmental arrest) combined with a vertebrate body plan provide the ideal attributes for a laboratory animal.

Ecologically relevant biomarkers reveal that chronic effects of nitrate depend on sex and life stage in the invasive fish Gambusia holbrooki.

Agricultural intensification and shifts in precipitation regimes due to global climate change are expected to increase nutrient concentrations in aquatic ecosystems. However, the direct effects of nutrients widely present in wastewaters, such as nitrate, are poorly studied. Here, we use multiple indicators of fish health to experimentally test the effects of three ecologically relevant nitrate concentrations (<10, 50 and 250 mg NO3-/l) on wild-collected mosquitofish (Gambusia holbrooki), a species widely introduced for mosquito biocontrol in often eutrophic waters. Overall, biomarkers (histopathology, feeding assays, growth and caloric content and stable isotopes as indicators of energy content) did not detect overt signs of serious disease in juveniles, males or females of mosquitofish. However, males reduced food intake at the highest nitrate concentration compared to the controls and females. Similarly, juveniles reduced energy reserves without significant changes in growth or food intake. Calorimetry was positively associated with the number of perivisceral fat cells in juveniles, and the growth rate of females was negatively associated with δ15N signature in muscle. This study shows that females are more tolerant to nitrate than males and juveniles and illustrates the advantages of combing short- and long-term biomarkers in environmental risk assessment, including when testing for the adequacy of legal thresholds for pollutants.

The Kdm/Kmt gene families in the self-fertilizing mangrove rivulus fish, Kryptolebias marmoratus, suggest involvement of histone methylation machinery in development and reproduction.

Histone modifications such as methylation of key lysine residues play an important role in embryonic development in a variety of organisms such as of Pacific oysters, zebrafish and mice. The action of demethylase ("erasers") and methyltransferase ("writers") enzymes regulates precisely the methylation status of each lysine residue. However, despite fishes being very useful model organisms in medicine, evolution and ecotoxicology, most studies have focused on mammalian and plant model organisms, and mechanisms underlying regulation of histones are unknown in fish development outside of zebrafish. Here, putative histone lysine demethylases (Kdm) and methyltransferases (Kmt) were identified in an isogenic lineage of the self-fertilizing hermaphroditic vertebrate, the mangrove rivulus fish, Kryptolebias marmoratus. Evolutionary relationships with other animal demethylases and methyltransferases were examined, and expression patterns during embryonic development and in adult tissues were characterized. Twenty-five Kdm orthologues (Jarid2, Jmjd1c, Jmjd4, Jmjd6, Jmjd7, Jmjd8, Kdm1a, Kdm1b, Kdm2a, Kdm2b, Kdm3b, Kdm4a, Kdm4b, Kdm4c, Kdm5a, Kdm5b, Kdm5c, Kdm6a, Kdm6b, Kdm7a, Kdm8, Kdm9, UTY, Phf2 and Phf8) and forty-eight Kmt orthologues (Ezh1, Ezh2, Setd2, Nsd1, Nsd2, Nsd3, Ash1l, Kmt2e, Setd5, Prdm1, Prdm2, Prdm4, Prdm5, Prdm6, Prdm8, Prdm9, Prdm10, Prdm11, Prdm12, Prdm13, Prdm14, Prdm15, Prdm16, Setd3, Setd4, Setd6, Setd1a, Setd1b, Kmt2a, Kmt2b, Kmt2c, Kmt2d, Kmt5a, Kmt5b, Ehmt1, Ehmt2, Suv39h1, Setmar, Setdb1, Setdb2, Smyd1, Smyd2, Smyd3, Smyd4, Smyd5, Setd7, Setd9, Dot1l) were discovered. Expression patterns of both Kdm and Kmt were variable during embryonic development with a peak in gastrula stage and a reduction in later embryogenesis. Expression of both Kdm and Kmt was higher in male brains compared to hermaphrodite brains whereas specific expression patterns of Kdm and Kmt were observed in the hermaphrodite ovotestes and male testes, respectively. Putative histone demethylases (Kdm) and methyltransferases (Kmt) were for the first time characterized in a teleost besides zebrafish, the mangrove rivulus. Their domain conservation and expression profiles suggest that they might play important roles during development, gametogenesis and neurogenesis, which raises questions about epigenetic regulation of these processes by histone lysine methylation in K. marmoratus. Due to its peculiar mode of reproduction and the natural occurrence of isogenic lineages, this new model species is of great interest for understanding epigenetic contributions to the regulation of development and reproduction.

Development of G: a test in an amphibious fish.

Heritable variation in, and genetic correlations among, traits determine the response of multivariate phenotypes to natural selection. However, as traits develop over ontogeny, patterns of genetic (co)variation and integration captured by the G matrix may also change. Despite this, few studies have investigated how genetic parameters underpinning multivariate phenotypes change as animals pass through major life history stages. Here, using a self-fertilizing hermaphroditic fish species, mangrove rivulus (Kryptolebias marmoratus), we test the hypothesis that G changes from hatching through reproductive maturation. We also test Cheverud's conjecture by asking whether phenotypic patterns provide an acceptable surrogate for patterns of genetic (co)variation within and across ontogenetic stages. For a set of morphological traits linked to locomotor (jumping) performance, we find that the overall level of genetic integration (as measured by the mean-squared correlation across all traits) does not change significantly over ontogeny. However, we also find evidence that some trait-specific genetic variances and pairwise genetic correlations do change. Ontogenetic changes in G indicate the presence of genetic variance for developmental processes themselves, while also suggesting that any genetic constraints on morphological evolution may be age-dependent. Phenotypic correlations closely resembled genetic correlations at each stage in ontogeny. Thus, our results are consistent with the premise that-at least under common environment conditions-phenotypic correlations can be a good substitute for genetic correlations in studies of multivariate developmental evolution.

Feminization, altered gonadal development, and liver damage in least killifish (Heterandria formosa) exposed to sublethal concentrations of 17α-ethinylestradiol.

The widespread use of the synthetic estrogen 17 α-ethinylestradiol (EE2) has resulted in elevated levels in aquatic environments, where it is known to act as an endocrine disrupting chemical affecting fish and other aquatic organisms. Examining changes in the structure of the fish' gonads and liver has proven to be an effective approach for assessing these impacts. While changes have been reported for various fish species, it is not clear whether impacts are equally severe in live-bearing fishes. The present study looked at gonadal and liver development in EE2-exposed least killifish (Heterandria formosa), a live-bearing Poeciliid. Exposures to 0, 5, or 25 ng/L EE2 began within six days of birth and continued until fish became sexually mature 12-23 weeks later. Exposure to 5 ng/L EE2 resulted in severe intersex in fish with external male characteristics, a slowdown of spermatogenesis in these intersex fish and a slowdown of oogenesis in the female fish. Moreover, these fish had a variety of liver injuries. Fish exposed to 25 ng/L EE2 exhibited intersex but at a lower frequency than occurred at 5 ng/L. In contrast, liver damage and slowdown of both oogenesis and spermatogenesis exhibited the typical dose-dependence. These findings illustrate the importance of including histological analyses when assessing endocrine disruption in fish, demonstrate that the live-bearing mode of reproduction appears to provide limited protection from the effects of waterborne EE2, and provide further evidence that EE2 has multiple impacts on fish health and reproduction that are severe enough to potentially affect fish populations.

Ecological conditions drive pace-of-life syndromes by shaping relationships between life history, physiology and behaviour in two populations of Eastern mosquitofish.

The pace-of-life syndrome (POLS) hypothesis predicts variation in behaviour and physiology among individuals to be associated with variation in life history. Thus, individuals on the "fast" end of POLS continuum grow faster, exhibit higher metabolism, are more risk prone, but die earlier than ones on the "slow" end. Empirical support is nevertheless mixed and modelling studies suggested POLS to vary along selection gradients. Therefore, including ecological variation when testing POLS is vastly needed to determine whether POLS is a fixed construct or the result of specific selection processes. Here, we tested POLS predictions between and within two fish populations originating from different ecological conditions. We observed opposing life histories between populations, characterized by differential investments into growth, fecundity, and functional morphology under identical laboratory conditions. A slower life history was, on average, associated with boldness (latency to emergence from a refuge), high activity (short freezing time and long distance travelled), and increased standard metabolism. Correlation structures among POLS traits were not consistent between populations, with the expression of POLS observed in the slow-growing but not in the fast-growing population. Our results suggest that POLS traits can evolve independently from one another and that their coevolution depends upon specific ecological processes.

Phylogenetic analysis and expression profiling of the Klotho gene family in the short-lived African killifish Nothobranchius furzeri.

Members of the Klotho gene family have been identified as modulators of the aging process. Deletion of αklotho in the mouse results in a syndrome resembling rapid human aging. Conversely, overexpression of αklotho extends mammalian lifespan. Here, we identify klotho orthologs in the vertebrate aging model Nothobranchius furzeri and provide a detailed spatio-temporal expression profile of both paralogs, α and ßklotho, from embryogenesis until old age spanning the entire life cycle of the organism. Specifically, we observe low levels of expression of both paralogs during embryogenesis followed by a significant transcriptional induction as development proceeds. In adult killifish, αklotho is predominantly expressed in the liver, the kidney, and the developing pharyngeal teeth. Particularly high levels of αKlotho protein were identified in the kidney tubules, closely resembling mammalian expression patterns. Prominent ßklotho expression was detected in the killifish intestine and liver. Overall, qRT-PCR analysis of Klotho members as a function of age revealed steady transcript levels, except for ßklotho expression in the liver which was significantly downregulated with age. This spatio-temporal expression profiling may serve as a useful starting point to further investigate the distinct physiological roles of Klotho members during the aging process.