Results of clearance tests on C. nucula showed low clearance rates, compared with values reported elsewhere [13], [14]; retention rates, however, were high, that is, the sponge expressed a strong impact on suspended bacteria.

Heritability estimates were close to one for shell size and relative shell aperture, suggesting a low impact of environmental factors in embryos. Estimates of Qst between ecotypes were significant and typically much higher than published Fst estimates from neutral markers, indicating a role for selection on shaping additive genetic variation. Estimates of Pst between ecotypes for adults were substantially larger than embryos´ Qst, suggesting also a role of phenotypic plasticity in ecotype differentiation. Our results suggest that Pst vs Fst comparisons should be taken with caution because they might not reflect real additive genetic effects, but Pst vs Qst comparisons could shed light into the role of phenotypic plasticity.