Growth, regeneration and predation in three species of large coral reef sponges

To understand differences in survival strategies in 3 large Caribbean sponges, Neofibularia nolitangere, Ircinia strobilina and Agelas clathrodes, growth rates, regeneration efficiencies and aspects of predation were studied. All 3 species showed irregular and unpredictable growth in situ with wide variations in growth rate (including temporal shrinkages) within and among species. I. strobilina, but not the other species, grew more rapidly in the vertical than the horizontal direction. I. strobilina was the slowest growing, while N. nolitangere showed the highest growth rate and volume increase. Larger individuals of I. strobilina and A. clathrodes increased more slowly in volume than smaller ones; such a relation was not found for N. nolitangere. Linear growth rates of 0.7 to 2.4 cm yr⁻¹ for these sponges are similar to rates reported for other sessile reef organisms such as gorgonians and scleractinian corals. All 3 species regenerated all lesions efficiently. There was spatial differentiation in regeneration rates: top lesions in N. nolitangere and lateral lesions in I. strobilina regenerated faster than other lesions. Initial closure of the lesion by scar tissue was completed within 1 wk in I. strobilina, but N. nolitangere was the first to show total regeneration (minimum of 5 wk). A. clathrodes showed the slowest and most uniform regeneration rate. Predation by Pomacanthinae (angelfishes) occurred only on N. nolitangere. Force-feeding pieces of I. strobilina appeared to cause paralysis and narcosis; force-fed A. clathrodes appeared to irritate the feeding tracts of the fishes. By their remarkable regeneration capacity and effective anti-predatory mechanisms these sponges appear to be well adapted to the dynamic reef environment.