The Yearly Life Cycle of the Amphipod, Corophium volutator

Abstract

THE Amphipod Corophium volutator (Pallas) occurs abundantly in the intertidal soil of nmd flats, salt marsh pools and brackish ditches at many localities around the coasts of Europe and North'America. Crawford (1937), in his review of the genus, lists the literature on this species up to 1935. Several authors have dealt with its distribution and the factors which govern its distribution. Amongst the more recent are Fraser (1932), Nicoll (1935), Thamdrup (1935), Wohlenberg (1937), Bassindale (1938) and Spooner & Moore (1940). Hart (1930) gives an account of the feeding mechanism and burrowing habits and also preliminary observations on the annual life cycle. The present paper is an attempt, based on over 50 samples collected on successive dates throughout 1938 and early 1939, to describe in some detail its annual life cycle. The species occurs abundantly, together with the closely related form C. arenarium Crawford (1937), in the estuary of the river Dovey, North Wales. The estuary runs, roughly, from east to west, with the river meandering mainly along its northern border. Some protection is afforded from the prevailing westerly winds by sand dunes which enclose the seaward side of the estuary, leaving only a comparatively small 'bottle neck' opening. At low tide an area of sand about 5 miles long and 2 miles broad is exposed. The soil of the greater part of this area is composed of a fine sand in which the typical animals Cardium edule, Macoma balthica, Tellina tenuis, Scrobicularia plana, Arenicola marina, Nereis diversicolor, Bathyporeia pilosa and B. pelagica occur. Corophium volutator is patchy in its distribution and occurs in areas which receive land drainage by brackish water streams from the bog-land which forms an extensive area on the south side of the estuary. These streams carry