The expression of estrogen receptors during the Mytilus galloprovincialis ovarian cycle

Sex and gametogenesis stage are strong drivers of gene expression in Mytilus edulis exposed to environmentally relevant plasticiser levels and pH 7.7

Plastic pollution and changes in oceanic pH are both pressing environmental issues. Little emphasis, however, has been placed on the influence of sex and gametogenesis stage when investigating the effects of such stressors. Here, we examined histology and molecular biomarkers of blue mussels Mytilus edulis exposed for 7 days to a pH 7.7 scenario (- 0.4 units) in combination with environmentally relevant concentrations (0, 0.5 and 50 µg/L) of the endocrine disrupting plasticiser di-2-ethylhexyl phthalate (DEHP). Through a factorial design, we investigated the gametogenesis cycle and sex-related expression of genes involved in pH homeostasis, stress response and oestrogen receptor-like pathways after the exposure to the two environmental stressors. As expected, we found sex-related differences in the proportion of developing, mature and spawning gonads in histological sections. Male gonads also showed higher levels of the acid-base regulator CA2, but females had a higher expression of stress response-related genes (i.e. sod, cat, hsp70). We found a significant effect of DEHP on stress response-related gene expression that was dependent on the gametogenesis stage, but there was only a trend towards downregulation of CA2 in response to pH 7.7. In addition, differences in gene expression between males and females were most pronounced in experimental conditions containing DEHP and/or acidified pH but never the control, indicating that it is important to consider sex and gametogenesis stage when studying the response of mussels to diverse stressors.

Behavioral, physiological and biochemical responses and differential gene expression in Mytilus galloprovincialis exposed to 17 alpha-ethinylestradiol and sodium lauryl sulfate

Mixture of contaminants often determine biological responses of marine species, making difficult the interpretation of toxicological data. The pharmaceutical 17 alpha-ethinylestradiol (EE2) and the surfactant Sodium Lauryl Sulfate (SLS) commonly co-occur in the marine environment. This study evaluated the effects of EE2 (125.0 ng/L) and SLS (4 mg/L), acting individually and combined, in the mussel Mytilus galloprovincialis. Contaminated mussels closed their valves for longer periods than control ones, especially in the presence of both contaminants, with longer closure periods immediately after spiking compared to values obtained one day after spiking. Nevertheless, males and females increased their metabolism when in the presence of both contaminants (males) and SLS (females), and independently on the treatment males and females were able to activate their antioxidant and biotransformation defences. Although enhancing defences mussels still presented cellular damage and loss of redox balance, especially noticed in the presence of EE2 for males and SLS for females. Histopathological damage was found at mussel's gills in single and mixture exposure, and qPCR analysis revealed a clear estrogen receptor expression with no additive effect due to combined stressors. The results obtained highlight the harmful capacity of both contaminants but further research on this matter is needed, namely considering different climate change scenarios.

Consequences of combined exposure to thermal stress and the plasticiser DEHP in Mytilus spp. differ by sex

Little is known about the combined effect of environmental factors and contaminants on commercially important marine species, and whether this effect differs by sex. In this study, blue mussels were exposed for seven days to both single and combined stressors (i.e., +3 °C elevated temperature and two environmentally relevant concentrations of the plastic softener DEHP, 0.5 and 50 μg/l) in a factorial design. Males were observed to be more sensitive to high temperature, demonstrated by the significant increase in out-of-season spawning gonads and higher gene expression of the antioxidant catalase and the estrogen receptor genes. On the other hand, while the gametogenesis cycle in females was more resilient than in males, DEHP exposure altered the estrogen-related receptor gene expression. We show that the combined stressors DEHP and increased temperature, in environmentally relevant magnitudes, have different consequences in male and female mussels, with the potential to impact the timing and breeding season success in Mytilus spp.

Reproductive performance is associated with seasonal plasma reproductive hormone levels, steroidogenic enzymes and sex hormone receptor expression levels in cultured Asian yellow pond turtles (Mauremys mutica)

In order to understand the endocrine mechanism associated with fecundity of seasonally breeding animals, we investigated the plasma reproductive hormones levels and detected the differences in steroidogenic enzymes and sex hormone receptor mRNA levels in female Mauremys mutica. These turtles were divided into higher fecundity (HF) group than those in lower fecundity (LF) group based on paternity identification in our previous research. The plasma estrogen (E2), testosterone (T) and progesterone (P4) levels were significantly higher in pre-breeding season (PBS) than those in non-breeding season (NBS) and were markedly higher in the HF group than those in LF group. In the hypothalamus, there was significantly higher mRNA abundance of P450-cholesterol side-chain cleavage enzyme (P450Scc) encoded by Cyp11α1, aromatase (Cyp19α1) and 5-reductase (5α-R), but significantly lower mRNA levels of follicular stimulating hormone receptor (FSHR) and progesterone receptor (PR) detected in PBS than those in NBS. The pituitary steroidogenic acute regulatory protein (StAR), cytochrome P450-17alpha-hydroxylase (Cyp17α1), 3-hydroxy-steroid dehydrogenase (3βHSD), 17-hydroxy-steroid dehydrogenase 3 (17βHSD3), Cyp19α1, 5α-R, FSHR, estrogen receptor 1 (ESR1), androgen receptor (AR) and PR transcriptional levels in HF group were up-regulated significantly compared with the LF group. In the ovary, Cyp17α1 and 17βHSD3 transcriptional levels were markedly higher in PBS than those in NBS. We detected significantly increased expression levels of all steroidogenic enzymes, but notably lower mRNA levels of FSHR and PR in uterus during the PBS, and the HF group has significantly higher expression levels of StAR, Cyp17α1, 5α-R and AR than LF group. Our work reveals seasonal variations in hormone regulation as well as gene regulation in turtles, providing reliable information to understand the mechanisms underlying the different reproductive capacity of reptiles.

Spermatogenesis and regulatory factors in the wall lizard Podarcis sicula

Spermatogenesis is an extraordinarily complex process, regulated by several factors, which leads to the differentiation of spermatogonia into spermatozoa. Among vertebrates, several reports have been focused on the lizard Podarcis sicula, a seasonal breeder and a good model for the study of reproductive processes. The goal of this review is to resume all the available data about systemic and above all local control factors involved in the control of P. sicula testicular activity. During the seasonal reproductive cycle, the variation of the expression levels of these factors determines significant variations that induce the activation or blocking of spermatogenesis. The data supplied in this review, in addition to analyze the current literature regarding the main actors of Podarcis sicula spermatogenesis, will hopefully provide a basic model that can be used for further studies on the intratesticular interaction between molecular factors that control spermatogenesis.