Reproductive impairment and intersexuality inGomphina veneriformis(Bivalvia: Veneridae) by the tributyltin compound

Antifouling booster biocides in Latin America and the Caribbean: A 20-year review

This review summarized booster biocides studies from Latin America and the Caribbean during the last two decades. Studies were focused on six countries, with most of them in Brazil. In water and sediment, diuron and Irgarol were the most abundant and frequent biocides, probably due to their former intense use. Antifouling paint particles were also reported and had mainly DCOIT, which is currently the most used booster biocide. Toxicity of individual booster biocides was tested in laboratory, and most effects were related to chlorothalonil, DCOIT, dichlofluanid, and Irgarol, including, but not limited to DNA damage, fertility decrease, and mortality at different trophic levels. This review highlighted the need for further studies on environmental occurrence of booster biocides in Latin America and Caribbean associated to ecotoxicological studies. Such information is essential to determine the potential ecological risks and to create directives regarding safe limits of booster biocides in aquatic systems.

Gonadal Atresia, Estrogen-Responsive, and Apoptosis-Specific mRNA Expression in Marine Mussels from the East China Coast: A Preliminary Study

This preliminary survey analysed mussel atresia incidences, estrogen-responsive and apoptotic-specific molecular end points, and aqueous and gonadal levels of selected estrogens from the East China coast. Estrogen levels were low (e.g. < LOD-28.36 ng/L, < LOD-3.88 ng/g wet weight of tissue for BPA) relative to worldwide freshwater environments, but high oocyte follicle atresia incidences (up to 26.6%) occurred at selected sites. Expression of estrogen-responsive ER2 was significantly increased in males relative to females at sites with high atresia incidences in females. A second estrogen-responsive gene, V9, was significantly increased at two sites in April in females relative to males; the opposite was true for the remaining two sites. Apoptosis-specific genes (Bcl-2, fas) showed elevated expression in males relative to females at the site with the highest atresia incidence. These results provide coastal estrogen levels and the utility of several estrogen-specific molecular-level markers for marine mussels.

Potencies of organotin compounds in scallop RXRa responsive activity with a GAL4-based reconstituted yeast assay in vitro

Retinoid X receptor (RXR) has been found to be a major target in various processes of endocrine disruption from the exposure to organotin compounds (OTCs), including imposex in gastropod mollusks. It was also reported in bivalves that OTCs caused intersex and skewed sex ratio. In order to evaluate the effect of these ligand-like OTCs, we constructed a reconstituted yeast system (CfRE system) based on GAL4 yeast two-hybrid principle using scallop Chlamys farreri retinoid X receptor (CfRXRa) and retinoid X response element (RXRE) to investigate the ligand-induced transactivation of CfRXRa. Responses of CfRXRa to 9-cis retinoic acid (9cRA) and tested four OTCs showed concentration-dependent response which is comparable with reported RXRa in vitro assay of human and gastropods. The detective limits of the CfRE system were found to be 100 nM for 9cRA and 10-1000 nM for the tested OTCs. While the tested non-Sn endocrine disrupting chemicals, including Benzo[a]pyrene, 2,4-Dichlorophenol, Nonylphenol, and Tetrabromobisphenol A, showed no effect on CfRXRa response. The present assay system may provide a valuable tool for screening assessments of unidentified environmental ligand chemicals on bivalve mollusks. It is also useful for comparison of sensitivity differences among species exposed to EDCs.

Xenobiotics Result in Hormonal and Enzymatic Dysregulations in the Red Mussel Mytilus galloprovincialis (Lamarck, 1819) (Bivalvia, Mytilidae)

&lt;b&gt;Background and Objective:&lt;/b&gt; The contaminants in a marine ecosystem like mercury and synthetic hormones can disrupt the regulation of natural endocrine and reproductive systems of most organisms. This study aims to study the effect of organic and inorganic mercury on the viscera of &lt;i&gt;Mytilus galloprovincialis&lt;/i&gt; after intracoelomic injection of 17α-ethinylestradiol, 17β-estradiol and Dichlorodiphenyltrichloroethane (DDT) and check the histological changes in the gonads. &lt;b&gt;Materials and Methods:&lt;/b&gt; Mussels are collected during June-August, 2018 from Ras el tin beach of the Mediterranean Sea of Alexandria, Egypt. This study aims to: test the effect of 17α-ethinylestradiol, 17β-estradiol and DDT on vitellogenin (VTG) synthesis, enzymes dysfunction through intracoelomic injection of methyl mercury in a 0.75 μg/0.1 mL and mercury chloride to a 75 μg/0.1 mL. Gonads are studied histologically in control and treated mussels. Water-administered E2 and EE2 at 120 μL dose induced VTG expression in males 14 days exposure. &lt;b&gt;Results:&lt;/b&gt; The relative concentration of VTG in the induced groups increases significantly as compared to the control. Alterations in the gonadal tissues and the maturation stages of the mussels are observed. The imposex mussels are characterized by concomitant secondary male sexual characteristics and the female gonad shows testicular structure. Superoxide Dismutase (SOD) activity in mussel digestive glands differed significantly (p = 0.002) after 72 hrs of MeHg exposure. &lt;b&gt;Conclusion:&lt;/b&gt; Significant correlation can be observed between the activities of Glutathione S-Transferases (GST) and Glutathione Reductase (GR) in the digestive glands of mussels treated with MeHg, the enzyme activities of digestive glands treated with HgCl&lt;sub&gt;2&lt;/sub&gt; and between Superoxide Dismutase&lt;i&gt;-&lt;/i&gt;Catalase (SOD-CAT), SOD-GR and GST-GR.

Modified, optimized method of determination of Tributyltin (TBT) contamination in coastal water, sediment and biota in Sri Lanka

Tributyltin (TBT) is a toxic organotin compound that belongs to the group of Persistent Organic Pollutants (POPs) and it is documented to cause severe sexual disorders development in aquatic fauna. According to the present study, The TBT concentration in coastal water ranged from 303 ± 7.4 ngL^-1 to 25 ± 4.2 ngL^-1 wherein sediment was from 107 ± 4.1 ngKg^-1 to 17 ± 1.4 ngKg^-1. TBT in Perna viridis was found to range from 4 ± 1.2 ngKg^-1 to 42 ± 2.2 ngKg^-1 wet weight and in ascending order of the body weight. The highest TBT level in water and sediment was found in the Colombo port where the highest level of TBT in P. viridis (42 ± 2.2 ngKg^-1) was recorded from the Dikkowita fishery harbor. A positive correlation between the number of male P. viridis and TBT level (p < 0.05) suggests possible reproductive impairment in aquatic animals exposed continuously to a high concentration of TBT.

Counteracting effects of heavy metals and antioxidants on male fertility

Infertility is regarded as a global health problem affecting 8-12% of couples. Male factors are regarded as the main cause of infertility in 40% of infertile couples and contribute to this condition in combination with female factors in another 20% of cases. Abnormal sperm parameters such as oligospermia, asthenospermia, and teratozoospermia result in male factor infertility. Several studies have shown the deteriorative impact of heavy metals on sperm parameters and fertility in human subjects or animal models. Other studies have pointed to the role of antioxidants in counteracting the detrimental effects of heavy metals. In the currents study, we summarize the main outcomes of studies that assessed the counteracting impacts of heavy metal and antioxidants on male fertility. Based on the provided data from animal studies, it seems rational to administrate appropriate antioxidants in persons who suffer from abnormal sperm parameters and infertility due to exposure to toxic elements. Yet, further human studies are needed to approve the beneficial effects of these antioxidants.

Intersexuality in aquatic invertebrates: Prevalence and causes

This review is the first assembling information on intersexuality in aquatic invertebrates, from freshwater to estuarine and marine environments. Intersex is a condition whereby an individual of a gonochorist (separate sexes) species has oocytes or distinct stages of spermatogonia, at varying degrees of development, within the normal gonad of the opposite gender (i.e. spermatocytes in the ovary or oocytes in the testis), often involving alterations in the gonadal structure, reproductive tract or external genitalia. By the end of 2016 we found approximately 340 records of aquatic invertebrate species evidencing signs of intersexuality (or imposex), all comprised within the Phyla Mollusca and Arthropoda. Gastropod molluscs are by far the group with more examples documented (256 species), followed by crustaceans, i.e., decapods, copepods and amphipods. To our knowledge no further cases of intersexuality were known concerning other invertebrate taxa. Despite some reports suggesting that a baseline level of intersexuality may occur naturally in some populations, the causes are multifaceted and mostly linked with environmental contamination by estrogenic and organotin endocrine disrupting chemicals (EDCs), parasitism, and genetic/environmental sex determination abnormalities. A more comprehensive discussion about the origin of intersexuality, prevalence and causes, knowledge gaps and future research directions in the light of new omics scientific advances (genomics, proteomics and transcriptomics) is also provided. The lack of studies linking molecular responses of invertebrate intersex individuals to multiple stressors represents a true challenge to be further investigated in the future.

Dynamics of nuclear receptor gene expression during Pacific oyster development

BACKGROUND

Nuclear receptors are a highly conserved set of ligand binding transcription factors, with essential roles regulating aspects of vertebrate and invertebrate biology alike. Current understanding of nuclear receptor regulated gene expression in invertebrates remains sparse, limiting our ability to elucidate gene function and the conservation of developmental processes across phyla. Here, we studied nuclear receptor expression in the early life stages of the Pacific oyster, Crassostrea gigas, to identify at which specific key stages nuclear receptors are expressed RESULTS: We used quantitative RT-PCR to determine the expression profiles of 34 nuclear receptors, revealing three developmental key stages, during which nuclear receptor expression is dynamically regulated: embryogenesis, mid development from gastrulation to trochophore larva, and late larval development prior to metamorphosis. Clustering of nuclear receptor expression patterns demonstrated that transcriptional regulation was not directly related to gene phylogeny, suggesting closely related genes may have distinct functions. Expression of gene homologs of vertebrate retinoid receptors suggests participation in organogenesis and shell-formation, as they are highly expressed at the gastrulation and trochophore larval initial shell formation stages. The ecdysone receptor homolog showed high expression just before larval settlement, suggesting a potential role in metamorphosis.

CONCLUSION

Throughout early oyster development nuclear receptors exhibited highly dynamic expression profiles, which were not confined by gene phylogeny. These results provide fundamental information on the presence of nuclear receptors during key developmental stages, which aids elucidation of their function in the developmental process. This understanding is essential as ligand sensing nuclear receptors can be disrupted by xenobiotics, a mode of action through which anthropogenic environmental pollutants have been found to mediate effects.