GRAZING PREDATION ON A POPULATION OF AMPELISCA-TENUICORNIS (GAMMARIDAE, AMPHIPODA) OFF THE SOUTH COAST OF ENGLAND

Grazing impact was assessed for a population of the tubicolous amphipo d Ampelisca tenuicornis from a shallow sublittoral muddy-sand communit y off the east coast of the Isle of Wight, England. Damage resulting f rom grazing predation or failed predator attack was indicated by the p resence 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 a mong appendage groups and the intensity of grazing were both found to be dependent on body size and sex. At maturity, a proportion of time i s spent in the water column and this is associated with changes in the pattern of injury and intensity of grazing. Seasonal grazing intensit y correlated with temperature and was related to life-cycle characteri stics. The intensity, though not the pattern, of grazing was negativel y correlated to the abundance of A. tenuicornis. The impact of grazing on reproductive output was determined. Although grazing on the popula tion was high, rapid regeneration and compensatory feeding appeared to minimise the impact. The length of antennae and their relative propor tions are important taxonomic characters used to separate species; if antennal grazing is a common feature of ampeliscid populations, then d ue care should be taken in selecting undamaged holotype material and i n the use of antennal characters in identification keys.