Post-ingestive digestion in small-scale deposit-feeding annelids: a new methodological approach

J PAN; GR LOPEZ

Puerto Madryn

Jornada; VI Jornadas Nacionales de Ciencias del Mar; 2006

The goal of this study is to develop sensitive methods for small annelids to measure the in vivo activities of different enzyme complexes involved in post-ingestive digestion. Our experimental approach consisted on simulating a matrix on which small annelids could feed while exerting their burrowing or tube-forming activities. 2% commercial gelatin matrices were supplemented with a casein-bound fluorescent dye (BODIPY FL dye; Molecular Probes) and then semi-transparent live organisms were incorporated into the matrix in multi-well plates. Digestion rates (extracellular protein digestion in the guts) were quantified in vivo by fluorescent counts (excitation 485nm-emission 535nm) with a microplate reader (assuming fluorescence is proportional to protease activity). For these experiments we collected specimens of Paranais litoralis (Oligochaeta: Naididae) and culture-reared specimens of Capitella sp. (Polychaeta: Capitellidae). Both Paranais and Capitella fluorescence counts increased linearly over time (R2= 0.97 and R2= 0.98 respectively) on experiments run over 3 hours. This trend suggests that for small annelids, the enzymatic degradation of proteins is constant over time. This methodological approach has the advantage of being sensitive for small species; it also enables to measure in vivo digestive activity in several specimens simultaneously, while performing continuous measurements over time. In our estimation, it constitutes a promising tool for characterizing the digestive environments of deposit feeders and quantify rates of organic matter degradation in intertidal mudflats.