Egestion rates of the estuarine mysid Neomysis integer (Peracarida : Mysidacea) in relation to a variable environment

The hyperbenthic, estuarine mysid Neomysis integer (Crustacea: Mysidacea) i s exposed to wide fluctuations of temperature and salinity on tidal and sea sonal cycles. Using sieved sediment as an environmentally relevant food sou rce and egestion rates as a measure of ingestion, the feeding rates of N. i nteger have been quantified at temperatures (5, 10 and 15 degrees C) and sa linities (1, 10, 20 and 30 parts per thousand) experienced in the field. Eg estion rates (0.017-0.049 mg faeces mg(-1) dry wt. mysid h(-1)) increased w ith increasing temperature (Q(10) values ranged from approximate to 1.9-2.4 ) and with increasing salinity. There was a significant interaction between temperature and salinity such that egestion rates were suppressed at high temperature (greater than or equal to 10 degrees C) in combination with hig h salinity (30 parts per thousand). Male egestion rates were not significan tly different from those of females at any temperature/salinity combination . Absorption efficiency (approximate to 0.35) was unaffected by temperature or salinity, confirming that egestion rates are representative of energy a cquisition by N. integer. In the estuarine environment, mysid feeding rates are predicted to be low for much of the tidal cycle as the sites occupied by N. integer are dominated by low salinity, cold river water. (C) 2000 Els evier Science B.V. All rights reserved.