Growth dynamics and bioactivity variation of the Mediterranean demosponges Agelas oroides (Agelasida, Agelasidae) and Petrosia ficiformis (Haplosclerida, Petrosiidae)

Growth dynamics and bioactivity variation of the Mediterranean demosponges
Agelas oroides and Petrosia ficiformis were investigated over 15 months at Paraggi
and Colombara within the Marine Reserve of Portofino Promontory (Mediterranean
Sea, Ligurian Sea, Italy). For both species, growth rates varied
between individuals and were unaffected by initial sponge size. The two species
showed a different trend in growth pattern: A. oroides did not vary significantly
between seasons, sites and depths; in contrast, some individuals of P. ficiformis
showed a seasonal pattern, shrinking during winter as water temperature
decreased and growing during summer when water temperature increased. Differences
in growth between the two species may result from different reproductive
cycles, food availability, species-specific thermophily and patterns of spatial
competition. Moreover, spatial competition probably induced sponges to produce
bioactive secondary molecules. Spatial and temporal variation of bioactivity
of both species was examined for the first time by studying its effect on
human neuroblastoma cells. The bioactivity of A. oroides extracts differed
significantly between seasons, sites and depths, whereas the cytotoxicity of
P. ficiformis differed significantly between seasons and depths (differences for
sites were not determined). These results suggest the possible influence of
environmental factors on bioactive metabolite biosynthesis.