Are Chemical Defenses Allocated within Sponges to Defend Regions Most at Risk to Predator Attack?

The allocation of chemical defenses to regions most at risk to predator attack may provide adequate protection at minimal metabolic cost. This study examined chemical defense allocation within three sponge species from a temperate reef by investigating the predictions that: concentrations of chemical defenses are 1) higher in the outer 2 mm of the sponge tissue, 2) positively correlated with tissue nutritional quality, 3) negatively correlated with sponge structural components, and 4) varied enough to have differential effects on predator deterrence. The concentrations of chemical defenses varied within Ircinia felix and Aplysina fulva, but were equal throughout I. campana. There were, however, no consistent positive or negative correlations between chemical defenses and nutritional quality or structural components and no clear correlation between chemical defense concentration and predator deterrence. Together, these results suggest the need for a reevaluation of currently accepted ideas regarding chemical defense allocation within sessile prey