Heavy Rare Earth Elements Affect Sphaerechinus granularis Sea Urchin Early Life Stages by Multiple Toxicity Endpoints

Abstract

Heavy rare earth elements (HREEs) were tested for adverse effects to early life stages of the sea urchin Sphaerechinus granularis. Embryos were exposed to analytically measured HREE concentrations ranging from 10 to 10 M. No significant developmental defect (DD) increases were observed in embryos exposed to 10 M HREEs, whereas 10 M HREEs resulted in significant DD increase up to 96% for HoCl versus 14% in controls. Embryos exposed to 10 M HREEs showed the highest DD frequency in embryos exposed to 10 M DyCl and HoCl. Cytogenetic analysis of HREE-exposed embryos revealed a significant decrease in mitotic activity, with increased mitotic aberrations. When S. granularis sperm were exposed to HREEs, the offspring of sperm exposed to 10 M GdCl and LuCl showed significant DD increases. The results warrant investigations on HREEs in other test systems, and on REE-containing complex mixtures.

What do we know about the ecotoxicological implications of the rare earth element gadolinium in aquatic ecosystems?

“…Gadolinium-exposed H. tuberculata embryos instead, showed respectively 80 and 90% reduction in the amount of Ca at both concentrations, at 24 hpf and at 48 hpf, The lowest Gd concentration tested (203 μg/L (500 nmol/L)) was sufficient to block calcium uptake. These results are in accordance with those obtained by Gravina et al (2018) and Oral et al (2017), where GdCl 3 exposure, in concentration ranging between 26.4 μg/L (10 −7 mol/L) and 2640 μg/L (10 −5 mol/L), resulted in significant damage to embryogenesis and inhibition of fertilization success in P. lividus, Arbacia lixula and Sphaerechinus granularis (Gravina et al, 2018;Oral et al, 2017). Changes on gene expression associated with skeletogenesis were already reported (Martino et al, 2018).…”

“…In the Earth's crust, Gd presents a concentration of approximately 6.2 mg/kg (Gravina et al, 2018). However, it does not occur as a free element form but, in nature, it is included in different mineral components (i.e.…”

Toxicological Impact of Rare Earth Elements (REEs) on the Reproduction and Development of Aquatic Organisms Using Sea Urchins as Biological Models

“…Regarding toxicological studies, it is well documented that echinoderm early life stages exhibit a high sensitivity to several toxicants, including heavy metals, persistent organic pollutants and microplastics [ 39 , 40 , 41 , 42 , 43 , 44 , 45 ]. The effects of lanthanides on sea urchins have also been evaluated; in particular, the potential damage of seawater contamination on gamete viability, fertilization, and larval development [ 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 ]. In these studies, many sea urchin species are utilized, in consideration of their availability in the different areas interested in ecotoxicological studies.…”

“…In the Sphaerechinus granularis (family Toxopneustidae), a sea urchin family inhabiting the Mediterranean Sea and eastern Atlantic Ocean, sperm exposure to REEs induces an overall inhibition of fertilization success and developmental defects. Of REEs, 10 −5 M Gd 3+ ions show the greatest sperm toxicity [ 55 ]. Cytogenetic analysis of REE-exposed S. granularis embryos reveals the induction of mitotic aberrations to different extents by all tested REEs, with the highest aberration frequencies being induced by 10 −6 M Gd 3+ .…”

“…Cytogenetic analysis of REE-exposed S. granularis embryos reveals the induction of mitotic aberrations to different extents by all tested REEs, with the highest aberration frequencies being induced by 10 −6 M Gd 3+ . The inhibition of mitotic activity and the frequency of mitotic aberrations were observed in embryos exposed to REEs at concentrations ranging from 10 −6 to 10 −4 [ 54 , 55 ].…”