The aim of this study was to evaluate the toxicity of two rare earth elements (REE), cerium and lanthanum
on sea urchin embryos and sperm. Sea urchin (Paracentrotus lividus) embryos were reared for 72 h in
Ce(IV)- or La(III)-contaminated seawater at concentrations ranging from 108 to 105 M. Cleaving
embryos (5 h post-fertilization) were submitted to cytogenetic analysis, scoring mitotic activity and a
set of mitotic aberrations. Embryological analysis was carried out to determine percent developmental
anomalies and/or embryonic mortality. P. lividus sperm were suspended in Ce(IV) or La(III) (108–
105 M) for 1 h, and percent fertilized eggs were scored in cleaving embryos that were cultured up to pluteus
stage to score any developmental defects. Embryos reared in 105 M Ce(IV) resulted in 100% embryonic
mortality, whereas 105 M La(III) induced 100% developmental defects, without causing any
embryonic mortality. A significant concentration-related mitotoxic effect and induction of mitotic aberrations
were observed in Ce(IV)-exposed, but not in La(III)-exposed embryos, at concentrations ranging
from 107M to 3 106 M. Following sperm exposure, both Ce(IV) and La(III) induced a decrease in
sperm fertilization success at the highest tested concentration (105 M). The offspring of Ce(IV)-exposed,
but not of La(III)-exposed sperm displayed a significant concentration-related increase in developmental
defects. The results may suggest adverse impacts in REE-exposed biota and warrant further studies of a
more extended REE series.