Transcriptomic Responses and Larval-Stage Growth of Protandrous Yellowfin Seabream (Acanthopagrus Latus) to Different Polyethylene Microplastics Exposure

Polyethylene microplastics (PE-MPs) were widespread in the marine environment; thus, their influences on marine hermaphroditic fish cannot be ignored. This study intends to evaluate the adverse biological effects of two different sources of PE, identified by Raman spectroscopy, on protandrous yellowfin seabream (Acanthopagrus latus) larvae. Growth retardation, brain lesions, head/body length ratio increase, and neuroendocrine system disorders were found, and growth and neuroendocrine regulation-related genes such as sstr2, ghrb, irs1, UGT2B15, UGT2C1, drd4a, esr2b, hsd3b7, and hsd17b2 were identified. PE microbeads (100 μm) showed more severe tissue damage on fish, while environmental PE fibers (500-2500 μm) showed more imperceptible adverse effects. There were 218 DEGs up-regulated and 147 DEGs down-regulated in the environmental PE group, while 1284 (up) and 1267 (down) DEGs were identified in the virgin PE group. PE-MP stress influenced physiological processes like growth and neuroendocrine regulation and cholesterol-steroid metabolism, and caused tissue damage in the fish larvae. The study highlights the effects of environmental PE exposure on hermaphroditic protandrous fish.

The effect of bisphenol A on antioxidant defense and the structure and function of the liver of Siberian sturgeon (Acipenser baerii)

The present study was conducted to investigate the biochemical and histological changes of liver tissue in Siberian sturgeon (Acipenser baerii) exposed to different doses of bisphenol A (BPA). One hundred and eighty pieces of 1-year-old A. baerii with an average weight of 200-250 g bought and randomly distributed in 18 tanks (n = 10). After 2 weeks of adaptation, the fish received intraperitoneal injections of 1, 10, and 100 μg/g/week BPA and μg/g/week of 17β-estradiol intraperitoneally. The solvent control group received only peanut oil, while the control group did not receive any injections. In order to investigate histological changes of the liver, after 2 weeks the liver samples were taken, fixed in 10% formalin solution and slides prepared by routine histological methods. For assaying antioxidant defense status, the liver tissue from three fish of each replicates was captured and after homogenization, activity of catalase, superoxide dismutase, and glutathione peroxidase and malondialdehyde measured. The most important histological changes observed in the liver tissue were: vacuolation of hepatocytes, nuclear hypertrophy, necrosis of liver cells, expansion of sinusoids, and accumulation of fat cells. In the highest dose, the intensity of tissue changes increased. Activity of antioxidant enzymes and malondialdehyde content increased in fish exposed to 100 μg/g/week BPA in compare with other groups (p < .05). According to our findings, it could be concluded that liver histology was affected by BPA and tissue damage had occurred, which had led to changes in blood parameters. Also, the obtained results showed that the high concentrations of BPA used in this study stimulate the antioxidant defense. RESEARCH HIGHLIGHTS: BPA evoke oxidative stress in Siberian sturgeons in high dose of exposure. Severity of liver histologic lesions was dose dependent.

Endocrine disruption in the sub Antarctic fish Patagonotothen tessellata (Perciformes, Notothenidae) from Beagle Channel associated to anthropogenic impact

Situated in the sub-Antarctic region, Beagle Channel represents a unique marine ecosystem due to the connection between the Pacific and the Atlantic Oceans, and its proximity to the Antarctic Peninsula. Ushuaia city, the biggest settlement on the channel, exerts an increasing anthropogenic pressure by discharges of urban and industrial effluents. In the present work, we use Patagonotothen tessellata, one of the most abundant and widespread species in the channel, as a bioindicator species in order to evidence anthropic impact from Ushuaia Bay and surrounding areas. We first analyzed and characterized real time gene expression of androgen receptor, estrogen receptor and different forms of vitellogenin (VTG), under laboratory conditions. This was achieved by induction with estradiol of P. tessellata males. Then, the selected genes were used as biomarkers for an environmental biomonitoring study. Morphometric indices and circulating sex steroids (estradiol and testosterone) were also quantified in male fish collected from different sites. The qPCR analysis showed that vtgAb form is more inducible than vtgAa or vtgC forms after estrogen induction. The field survey revealed the up-regulation of vtgAb and the androgen receptor in fish from sites with higher anthropogenic influence. Sex steroids followed seasonal variations according to their reproductive cycle, with higher levels of estradiol and testosterone in winter and summer seasons. The use of biomarkers such as gene expression of VTG demonstrates that fish from Ushuaia Bay are likely to be exposed to endocrine disrupting compounds. To our knowledge, this research is the first attempt to assess the endocrine disruption associated to anthropic impact in a widespread fish of the Beagle Channel and contributes to a better understanding of the reproductive physiology of sub Antarctic ichthyofauna.

The effects of bisphenol A on liver proteome and mucus vitellogenin in comparison to plasma as a non-invasive biomarker in immature Siberian sturgeons (Acipenser baerii)

This study was done to evaluate the effects of Bisphenol A (BPA) on Siberian sturgeon (Acipenser baerii). As liver is the main organ in the homeostatic adjustments to stress, we used a proteomics method to address molecular response in this tissue. Also, we compared the levels of vitellogenin in plasma and mucus to propose that the last one be a non-invasive method to analyze this biomarker. The fish received 1, 10, and 100 μg g^-1 week^-1 BPA intraperitoneally for two weeks. The samples were taken on days 0, 7, and 14. Plasma vitellogenin level increased as the highest value was recorded in the group with 100 μg g^-1 week^-1 of BPA. Changes in the mucus and blood vitellogenin showed a similar pattern, suggesting that mucus could be used for evaluating the changes in blood vitellogenin. Comparative proteomics was used to determine the proteome of the liver of A. baerii in the highest dose of BPA in comparison with the control. Sixteen proteins were identified that their expression changed at least twice between the studied groups. The proteomic results showed that BPA increased the expression of proteins involved in the detoxification and metabolism, activated glycolysis, and produced necrosis in the liver.

Bioaccumulation and reproductive toxicity of bisphenol A in male-pregnant seahorse (Hippocampus erectus) at environmentally relevant concentrations

Seahorses, with brood pouch in adult males, are a bioindicator species that exhibit specialized reproductive strategy of "male pregnancy". Bisphenol A (BPA), one of the most pervasive endocrine-disrupting chemicals (EDCs), is hazardous for reproductive, immune, and neurological systems. However, no evidence of BPA toxicity to the male-pregnant animals is available. Herein, the reproductive toxicity of BPA was evaluated in lined seahorses (Hippocampus erectus) following exposure to environmentally relevant concentrations (10, 100, and 1000 μg/L) through physiological, histological, and transcriptional analyses. Our results indicated BPA bioaccumulation to be positively correlated with exposure doses in both sexes. Ovarian failure was only observed in the high-dose BPA treatment group, accompanied by the apoptosis of follicular cells and up-regulation of pro-apoptotic genes. However, brood pouches maintenance were surprisingly inhibited at low concentration, and transcriptomic analysis revealed disturbed profiles of genes involved in the extracellular matrix and cell-cell adhesion pathways. Interestingly, seahorse testes were less sensitive to BPA exposure than that in other teleosts. Thus, our study suggests that BPA at environmentally relevant concentrations might cause reproductive dysfunction in seahorses, potentially exerting adverse effects on the seahorse population since most of them inhabit shallow coastal areas with prevalent estrogenic contaminants.

Endocrine disrupting effects of binary mixtures of 17β-estradiol and testosterone in adult female western mosquitofish (Gambusia affinis)

Androgens and estrogens often co-exist in aquatic environments and pose potential risks to fish populations. However, little is known about the endocrine disrupting effects of the mixture of androgens and estrogens in fish. In this study, transcriptional level of target genes related to the hypothalamic-pituitary-gonadal-liver (HPGL) axis, sex hormone level, VTG protein concentration, histology and secondary sex characteristic were assessed in the ovaries and livers of adult female western mosquitofish (Gambusia affinis) exposed to 17β-estradiol (E2), testosterone (T), and mixtures of E2 and T for 91 days. The results showed that the transcriptional expression of cytochrome P450, family 19, subfamily A, polypeptide 1a (Cyp19a1a) was suppressed in the 200 ng/L T treatment and the 50 ng/L E2 + 200 ng/L T treatment in the ovaries. Steroidogenic acute regulatory protein (Star) and Cyp11a1 showed a similar expression pattern in the T treatment to its corresponding T + E2 mixtures. In the ovaries, the concentrations of 17β-estradiol and testosterone were decreased in most treatments compared with the solvent control. VTG protein was induced in all steroid treatment. However, exposure to T or E2 + T mixture did not cause the abnormal cells of the ovaries and livers and an extension of the anal fins in female G. affinis. This study demonstrates that chronic exposure to E2, T and their mixtures affects the transcripts of genes in the HPGL axis, steroid hormone level and VTG protein concentration in the ovaries and livers, but fails to cause the histopathological effect of the ovaries and livers and alter the morphology of the anal fins in G. affinis.

Gonadal Transcriptome Analysis of Sex-Related Genes in the Protandrous Yellowfin Seabream (Acanthopagrus latus)

Yellowfin seabream (Acanthopagrus latus), a protandrous hermaphroditic fish, is a good model for studying the mechanism of sex reversal. However, limited knowledge is known about the genetic information related to reproduction and sex differentiation in this species. Here, we performed de novo transcriptome sequencing analysis of the testis, ovotestis, and ovary to identify sex-related genes in yellowfin seabream. The results assembled 71,765 unigenes in which 16,126 and 17,560 unigenes were differentially expressed in the ovotestis and ovary compared to the testis, respectively. The most differentially expressed gene (DEG)-enriched Kyoto Encyclopedia of Genes and Genomes and GO pathways were closely associated with the synthesis of sex steroid hormones. Functional analyses identified 55 important sex-related DEGs, including 32 testis-biased DEGs (dmrt1, amh, and sox9, etc.), 20 ovary-biased DEGs (cyp19a, foxl2, and wnt4, etc.), and 3 ovotestis-biased DEGs (lhb, dmrt2, and foxh1). Furthermore, the testis-specific expression of dmrt1 and the brain-pituitary-ovary axis expression of foxl2 were characterized, suggesting that they might play important roles in sex differentiation in yellowfin seabream. Our present work provided an important molecular basis for elucidating the mechanisms underlying sexual transition and reproductional regulation in yellowfin seabream.

Modelling BPA effects on three-spined stickleback population dynamics in mesocosms to improve the understanding of population effects

Bisphenol A (BPA), a well-known endocrine-disrupting chemical, is ubiquitously present in the aquatic environment. Its impacts at the population level on three-spined sticklebacks (Gasterosteus aculeatus) have been studied in artificial streams with low-dose BPA concentrations. The causes explaining the observed effects remained unclear. Here, we used an individual-based model coupled to a Dynamic Energy Budget model to (i) assess the potential of modelling to predict impacts at the population level using individual level laboratory ecotoxicological endpoints and (ii) provide insight on the mechanisms of BPA toxicity in these mesocosms. To do that, both direct and indirect effects of BPA on three-spined sticklebacks were incorporated in the model. Indeed, direct BPA effects on fish have been identified based on literature data whereas indirect effects on sticklebacks have been taken into account using sampling data of their prey from the exposed artificial streams. Results of the modelling showed that direct BPA effects on fish (impacts on gonad formation, growth, male reproductive behavior, eggs and larvae survival) mainly explained the three-spined stickleback population structure in the mesocosms, but indirect effects were not negligible. Hence, this study showed the potential of modelling in risk assessment to predict the impacts on fish population viability from behavioral and physiological effects measured on organisms.

Fire increases the productivity of sugarcane, but it also generates ashes that negatively affect native fish species in aquatic systems

Sugarcane is one of the main crops used around the world as a feedstock for the production of sucrose and biofuel. Prior to harvesting, sugarcane dry leaves are burned to facilitate manual cutting and enhance productivity. This practice generates ashes from sugarcane straw (hereafter referred as SCA), which may be carried to aquatic ecosystems, where its impacts on organisms and ecosystem integrity remain unknown. Here, we experimentally tested the toxicity of five different concentrations of SCA (0, 1000, 1500, 2000 and 2500 mg/L) on three native (Astyanax lacustris, Moenkhausia bonita and M. forestii) and two non-native (Oreochromis niloticus and Poecilia reticulata) fish from the Paraná River Basin, Brazil. The toxicity was estimated by calculating the median lethal concentration (LC_50-24h) and the hepatosomatic index (HSI). We hypothesised that native fish are more sensitive to an increase in SCA than non-native fish. We verified that the mortality of native fish sharply increased with the increase in higher SCA concentration (LC_50-24h values: A. lacustris = 2525.71 mg/L, M. bonita = 2124.95 mg/L and M. forestii = 1981.74 mg/L). However, no deaths were recorded for non-native fish species in any SCA concentrations. Accordingly, the HSI index values statistically differed with the increase in SCA concentrations for native fish, while for non-native fish we did not observe any difference. Therefore, only native species died or suffered liver damage with an increase in SCA concentrations. Extrapolating our findings to natural environments, we suggest that sugarcane burning, a widely used agricultural technique, has the potential to reduce the population size of native organisms and facilitate the dominance of non-native fish species in aquatic ecosystems.