2.4.2 COMPARISON WITH RELATED SPECIES
Metal toxicity for E. chloroticus were toward the low end of the range of toxicities reported for sea urchin embryos for all 3 metals. Toxicity range is 1.4 – 100 μg/L for copper, 34 - > 2000 μg/L for lead and 7.2 – 327 μg/L for zinc (Table 2.6). E. chloroticus is the only species of its genus and belongs to the Echinometridae family with Australian species of the genus Heliocidaris thought to be its closest related species based on morphological evidence (McRae 1959). However, a recent study showed E. chloroticus as being phylogenetically distinct from other members of its family (Gillard et al. 2014). Toxicity values reported for Heliocidaris were very similar to the present study and mostly toward the low end of the toxicity range although the different toxicity endpoints (EC50, NOEC, LOEC) make direct comparison between studies difficult.