ABSTRACT: Grazing impact was assessed for a population of the tubicolous amphipod Ampelisca tenuicornis from a shallow sublittoral muddy-sand community off the east coast of the Isle of Wight, England. Damage resulting from grazing predation or failed predator attack was indicated by the presence of tanned wounds. Almost all damage recorded was to appendages, with the principal feeding structures, the antennae, accounting for 84% of total injuries and the urosomal appendages accounting for 12%. Pereion and pleon limbs showed little damage. The pattern of injury among appendage groups and the intensity of grazing were both found to be dependent on body size and sex. At maturity, a proportion of time is spent in the water column and this is associated with changes in the pattern of injury and intensity of grazing. Seasonal grazing intensity correlated with temperature and was related to life-cycle characteristics. The intensity, though not the pattern, of grazing was negatively correlated to the abundance of A. tenuicornis. The impact of grazing on reproductive output was determined. Although grazing on the population was high, rapid regeneration and compensatory feeding appeared to minimise the impact. The length of antennae and their relative proportions are important taxonomic characters used to separate species; if antennal grazing is a common feature of ampeliscid populations, then due care should be taken in selecting undamaged holotype material and in the use of antennal characters in identification keys.

KEY WORDS: Ampelisca · Predation · Grazing · Tube beds

Published in MEPS Vol. 164 (1998) on April 9
ISSN: 0171-8630. Copyright © Inter-Research, Oldendorf/Luhe, 1998