ARTIFICIAL FILAMENT BREAKAGE OF THE DIATOM SKELETONEMA-EOSTATUM INTENDED FOR MOLLUSK AQUACULTURE

Optimization of intensive rearing systems, especially those involved i n yields of marketable sizes of bivalve-molluscs, must pass through se veral technical improvements. One such improvement is described here: it concerns the experimental use of a simple centrifugal pump that cau ses artificial breakage of the chains of the diatom Skeletonema costat um (Grev.) Cleve used to feed adults of the Manila clam Ruditapes phil ippinarum (Adams and Reeve). The breakage process progressively reduce d the size distribution of the algal particles but eliminated all alga l chains longer than 60 mum. Scanning electron microscope (SEM) observ ations indicated that the breakage process impacts on both algal cells themselves (60% of broken structures)- and siliceous structures conne cting sibling cells (40% of broken structures). Some expected implicat ions of the breakage process are presented in connection with the inte nsive rearing system and nutritional requirements of Manila clam.