Anatomical and ultrastructural studies of chemical defence in the sponge Dysidea fragilis |
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Authors: | A Marin M D López M A Esteban J Meseguer J Muñoz A Fontana |
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Institution: | (1) Departamento de Ecología e Hidrología, Facultad de Biología, Universidad de Murcia, E-30100 Murcia, Spain, ES;(2) Departamento de Citología e Histología, Facultad de Biología, Universidad de Murcia, E-30100 Murcia, Spain, ES;(3) Istituto per la Chimica di Molecole di Interesse Biologico, CNR, via Toiano 6, I-80072 Arco Felice, Naples, Italy, IT |
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Abstract: | The marine sponge Dysidea fragilis from El Mar Menor, a hypersaline coastal lagoon (Murcia, Spain), contains the furanosesquiterpenoid ent-furodysinin as the major secondary metabolite. D. fragilis emits a defensive white fluid when it is disturbed. Electron micrographs of this fluid revealed intact vesiculated cells
together with other amorphous material. Dissociated cells are more rounded in shape but maintain the same ultrastructural
features as cells observed in ultra-thin sections of the whole sponge. The defensive secretion is composed mainly of sponge
cells with abundant light vesicles. Sometimes these light vesicles appear to open into the intercellular space; this correlates
with surface blebs on these cells observed under scanning electron microscopy. The intracellular location of ent-furodysinin was confirmed by Erlich staining. In laboratory assays, we examined the role of ent-furodysinin as a feeding deterrent to generalist fish predators. It was isolated from D. fragilis and incorporated into a carrageenan-based artificial diet. The addition of ent-furodysinin to the artificial diet reduced feeding by the fish Thalassoma pavo. Similarly, fish did not feed on artificial diet above which defensive secretion of D. fragilis had been ejected with a small syringe.
Received: 4 June 1997 / Accepted: 28 January 1998 |
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