JUVENILE GROWTH OF THE POLYCHAETE NEREIS-VIRENS FEEDING ON A RANGE OFMARINE VASCULAR AND MACROALGAL PLANT SOURCES

A laboratory experiment was conducted to examine variation of juvenile growth (% d(-1)) of the polychaete Nereis virens (Sars) in relation t o tidal flat plant species as food sources. We used vegetable material s (algae and vascular plants) which are carried along by tidal current s and are found abundantly at the upper tidal level. Juveniles (less t han or equal to 2-yr-old) markedly increased in wet weight with the al gae Laminaria ia Eongicruris (weight-specific growth rate mu: 1.7% d(- 1)) and Enteromorpha intestinalis (mu: 1.6% d(-1)) as food sources. A higher value of assimilation efficiency was observed for algal species (L. longicruris 55.1 +/- 7.9%; E. intestinalis 54.8 +/- 0.5%; Fucus v esticulosus 40.6%) than for marine vascular plants (Spartina alternifl ora 26.8 +/- 10.9%; Zosteta marina 1.4%). The digestion of marine vasc ular species lasts longer (19 to 38 h) than that of algal species. All these characteristics (growth, assimilation efficiency and duration o f the digestive process) seem to correlate positively with lignin and cellulose concentrations in the plant structure.