Endocrine disruption effects on the sexual differentiation of the brown shrimp Crangon crangon: a field test and characterization of a biomarker
Dr Chiara Benvenuto (firstname.lastname@example.org)
A striking phenomenon in the evolution of animal mating systems is sequential hermaphroditism1. As the name suggest, sequential hermaphrodites change their sex during their life: individuals reproduce initially as males and then change to females or vice versa. Sequential hermaphroditism is a successful life history strategy: sex changers increase their lifetime reproductive success and thus tend to maximise their fitness2,3.
Recently, the number of studies reporting examples of sexual instability in gonochoristic organisms (with two separate fixed sexes) is increasing. “Intersexes” present simultaneously (completely or partially) male and female characters, similar to what happen to sequential hermaphrodites in their transition form from the first to the second sex. But if transitional forms are the norm in sequential hermaphrodites, this type of intersexuality is an aberration of the otherwise gonochoristic development of organisms4. Such changes in the normal sexual differentiation can be due to exogenous chemicals released by humans in the environment, collectively called endocrine disruptors (ED). ED are natural or synthetic hormones or substances that mimic specific hormones or act as their antagonists. They are accumulating mainly in rivers and along the coastal lines (close to human urbanized areas)5,6 and might interfere with the normal hormonal processes of organisms, affecting growth, development, behaviour and reproduction7.
There is a long and consolidated tradition in the use of macroinvertebrates as bioindicators and biomonitors of water quality, but the use of invertebrates in general, and crustaceans in particular, to detect ED is still limited8. This project focuses on the brown shrimp, Crangon crangon L. (Decapoda, Caridea), a crustacean commonly found along the European coasts, which uses estuarine areas (potentially highly impacted by human pollution) as nursery ground. Its sexual mode of reproduction is still debated, being described as gonochoristic, but also as obligate protandric (male to female sex changer) or facultative protandric (some but not all individuals change sex). This suggests a degree of sexual plasticity which makes this shrimp an interesting candidate to study the effects of ED on sexual differentiation: due to its natural plasticity, the brown shrimp might be particularly sensitive to the effect of substances that influence the pathway of sexual differentiation.
The goals of this project are: (1) to determine the effects of ED chemicals on the sexual differentiation of the brown shrimp C. crangon and (2) to characterize an effective ED biomarker in this species. The successful candidate will:
- Perform field sampling of C. crangon in contaminated and non-contaminated sites;
- Determine its sex (morphologically9 and through gonadal histological analyses);
- Analyse sex ratios and sexual differentiation in the populations under study;
- Test the use of vitellogenin (Vtg) as an effective ED biomarker (using recently developed protocols which, for example, employ LC-MS-MS, liquid chromatography tandem mass spectrometry10-11).
The brown shrimp is a species with high ecological and economic importance, characterized by a plastic mode of sexual differentiation. This is an innovative research project, with three strong components: 1) a practical component – the monitoring of the effects of ED in the brown shrimp at the individual level (sex determination and sex differentiation) and at the population level (sex ratio); 2) an applied component – the characterization of Vtg as an effective ED biomarker in this species; 3) a more theoretical component – the study of the reproductive ecology (still debated) of this species under normal and contaminated conditions.
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- Ghiselin M.T., 1969. The evolution of hermaphroditism among animals. Quarterly Review of Biology 189–208.
- Warner R.R., 1975. The adaptive significance of sequential hermaphroditism in animals. American Naturalist 109, 61–82.
- Ford A.T., 2012. Intersexuality in Crustacea: An environmental issue? Aquatic Toxicology 108, 125–129.
- Davies I.M., Vethaak D., 2012. Integrated marine environmental monitoring of chemicals and their effects. ICES Cooperative Research Report No. 315. 277 pp
- Oberd¿rster E., Cheek A.O., 2001. Gender benders at the beach: endocrine disruption in marine and estuarine organisms. Environmental Toxicology and Chemistry 20, 23–36.
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- Yang G., Kille P., Ford A.T., 2008 Infertility in a marine crustacean: Have we been ignoring pollution impacts on male invertebrates? Aquatic Toxicology 88, 81–87.
- Schatte J., Saborowski R. 2006. Change of external sexual characteristics during consecutive moults in Crangon crangon L. Helgoland marine research 60, 70–73.
- Jubeaux G. Simon R., Salvador A., Quéau H., Chaumot A., Geffard O., 2012.Vitellogenin-like proteins in the freshwater amphipod Gammarus fossarum (Koch, 1835): Functional characterization throughout reproductive process, potential for use as an indicator of oocyte quality and endocrine disruption biomarker in males. Aquatic Toxicology 112, 72–82.
- Simon R., Jubeaux G., Chaumot A., Lemoine J., Geffard O., Salvador A., 2010. Mass spectrometry assay as an alternative to the enzyme-linked immunosorbent assay test for biomarker quantitation in ecotoxicology: Application to vitellogenin in Crustacea (Gammarus fossarum). Journal of Chromatography A 1217, 5109–5115.