Hormetic Effects of Cerium, Lanthanum and Their Combination at Sub-micromolar Concentrations in Sea Urchin Sperm

Rare earth elements (REEs) cerium (Ce) and lanthanum (La) and their combination were tested across a concentration range, from toxic (10 −4 to 10 −5 M) to lower concentrations (10 −6 to 10 −8 M) for their effects on sea urchin (Sphaerechinus granularis) sperm. A significantly decreased fertilization rate (FR) was found for sperm exposed to 10 −5 M Ce, La and their combination, opposed to a significant increase of FR following 10 −7 and 10 −8 M REE sperm exposure. The offspring of REE-exposed sperm showed significantly increased developmental defects following sperm exposure to 10 −5 M REEs vs. untreated controls, while exposure to 10 −7 and 10 −8 M REEs resulted in significantly decreased rates of developmental defects. Both of observed effects–on sperm fertilization success and on offspring quality–were closely exerted by Ce or La or their combination.