Cellulase in Nereis virens

Abstract

IN their communication about direct uptake of organic solutes, Chapman and Taylor¹ commented on the contradictory published accounts of the food and feeding of the polychaete Nereis virens Sars. Verrill² stated that it is carnivorous, while Gross³ suggested that it is almost entirely herbivorous. Turnbull⁴ regarded the animal as omnivorous. The principal recognizable remains that we found in the guts of N. virens collected at Southend, Essex, were shells of the small gastropod Hydrobia, small fragments of small cockle (Cardium edule) shells, and the alga Enteromorpha intestinalis. When kept in aquaria, N. virens readily ate the flesh of cockles, mussels (Mytilus edulis), and shore crabs (Carcinus maenas), when these were placed near the entrances to the burrows. The shell-valves of cockles, approximately 5 mm in diameter, were broken by the jaws of the worms and ingested. Large cockles and mussels were eaten only when they died and gaped open. Moribund cockles and mussels occur in large numbers at Southend, resulting both from natural mortality and the activities of the “bait-diggers”, who accidentally bury these molluscs in their search for Nereis. Enteromorpha was also readily ingested, but it was observed during these experiments that the faecal pellets of the worms frequently contained strands of apparently undigested algae. This posed the question whether Nereis can digest the cell walls of algae which it has eaten or whether it can only utilize contents of cells broken mechanically.