2.4.3 EFFECT OF METALS ON LARVAL DEVELOPMENT
All three metals adversely affect calcification in addition to various enzymatic processes, as illustrated by the predominance of shell deformity in H. iris and abnormal arm development in E. chloroticus. These abnormalities are typical of metal effects on abalone (Conroy et al. 1996, Gorski & Nugegoda 2006, Stofberg et al. 2011) and sea urchins (Bielmyer et al. 2005, Ghorani et al. 2013). Such abnormal development in the very early stages of larval development is a severe consequence of metal exposure, that usually results in failure to metamorphose and thus is a strong indicator of eventual mortality. A study on abalone showed that abnormal veligers did not recover even when maintained in clean seawater for an extended period following toxicant exposure (Conroy et al. 1996).
Copper and lead induced shorter arms compared to total body length in normal E. chloroticus larvae. With lead this effect was visible before developmental abnormality. This suggests that pluteus size is a better indicator of lead toxicity than development in E. chloroticus but not in H. iris. Previous studies showed a similar effect of lead on pluteus size from 250 μg/L (Parocentrotus lividus and Echinometra mathaei), although total body length was measured instead of arm/body ratio(Fernández & Beiras 2001, Ghorani et al. 2013). Lead competes with calcium for absorption in many organisms (Eisler 2007) and has recently been shown to lower whole body calcium accumulation in sea urchin larvae (Tellis et al. 2014). Leadinduced calcium deficiency may impair skeletal rod and thus arm formation in pluteus larvae (Warnau & Pagano 1994, Ghorani et al. 2013).