Defensive synergy : the antipredatory role of glass spicules in Caribbean demosponges

UNCW Author/Contributor (non-UNCW co-authors, if there are any, appear on document)
Adam C. Jones (Creator)
Institution
The University of North Carolina Wilmington (UNCW )
Web Site: http://library.uncw.edu/
Advisor
Stephen Kinsey

Abstract: Many sponge species produce secondary metabolites that deter predation. Sponges also contain siliceous spicules, but previous studies have provided little evidence that spicules offer any defense against generalist fish predators. However, feeding assays in past investigations tested sponge skeletal elements in isolation, and did not consider whether they may enhance chemical defenses. To determine whether the two components have an additive, antagonistic, or synergistic interaction, crude organic extracts and spicules from 8 Caribbean sponge species were isolated and tested in laboratory assays. The sponges used included one chemically defended reef sponge (Agelas clathrodes) and seven sponges known to be intermediately deterrent. These included six reef species (Calyx podotypa, Cinachyra alloclada, Cribrochalina vasculum, Niphates digitalis, Rhaphidophlus juniperinus, and Xestospongia muta) and one mangrove species (Tedania ignis). Extracts and spicules were used in various concentrations, both individually and in combination, in laboratory feeding assays with the bluehead wrasse, Thalassoma bifasciatum. A SAS based GENMOD procedure based on an isobolographic analysis model was used for statistical comparisons. Four sponges (A. clathrodes, C. alloclada, R. juniperinus, and X. muta) showed evidence of synergisms. Of these species, synergy in C. alloclada, R. juniperinus, and X. muta was caused by approximate natural concentrations of extracts and spicules. Extracts of A. clathrodes were deterrent, but combination assays required unnatural reductions in extract concentrations and increases in spicule concentrations to show the synergistic effect. Contrary to previous findings, spicules from Cribrochalina vasculum and X. muta were deterrent at natural concentrations. These results indicate that, for some sponges, structural elements may serve to enhance chemical defenses against consumers.

Additional Information

Publication
Thesis
A Thesis Submitted to the University of North Carolina at Wilmington in Partial Fulfillment Of the Requirements for the Degree of Master of Science
Language: English
Date: 2009
Keywords
Demospongiae--Animal defenses, Sponges--Caribbean Area, Sponges--Defenses
Subjects
Demospongiae -- Animal defenses
Sponges -- Defenses
Sponges -- Caribbean Area