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Patterns of resource allocation to somatic, defensive, and reproductive functions in the Mediterranean encrusting sponge Crambe crambe (Demospongiae, Poecilosclerida)
The sponge biomass per unit area increased with sponge size in both illuminated and dark environments. An increase with size was also found in the illuminated habitat for the investment in organic matter per unit area. The amount of silica per mm 2 was higher in the dark site where it also proved size-dependent. Investment in reproduction per unit area was higher in the illuminated wall and was positively correlated with size in both habitats. All variables related to sponge thickness showed significant differences between the two sites studied. Specimens were thicker in the illuminated habitat. There was a significant habitat effect on the amount of matrix, which was higher in the illuminated environment. This species seems able to shift its resource allocation as a function of size and environmental conditions. Higher competitive pressure in the shaded environment results in increased investment in defensive/supportive (mineral and organic) structures and a lower investment in somatic growth (organic matter) and reproductive output (larvae).