Effects of diet, body size, age and temperature on growth rates in the amphipod Gammarus pulex

摘要: SUMMARY. Increase in body wet weight of Gammarus pulex fed on decaying elm leaves was followed to senescence and death. Growth juveniles approximately exponential; from birth death it conformed a logistic growth curve, with maximum absolute increments about half-way through life span 350–450 days at 15°C. Some individuals lived longer, for up 640–700 days. The instantaneous or specific rate maximal near birth, c. 5–6% wt day−1, declined exponentially increasing size age. Over the range 4.7–14.8°C there log-log relationship between temperature rate. 20°C newborn animals 15°C 6–9-mg animals. The young fastest well developed flora fungi other microorganisms. Leached without this supported lower latter diet sufficient survival individuals; detritus, faeces food items were not needed. Isolated specimens grew as fast those kept groups. generally slower leached oak sycamore. In fine roots aquatic plants (Veronica, Rorippa Glyceria), leaves; green living slower, detritus two streams pure culture an fungus. Consumption related leaf thickness. full gut (1.34–1.37 mg) volume (3.8–4.1 mm3) (for 20-mg animals) independent thickness but dependent animal size, 4-fold over 2–50 mg wt. Daily consumption (dry wt) equivalent 50% dry 5 20% 50 Individuals thick ingested more per day absorbed than when thin leaves, relative efficiency absorption same 36–59% 10–20-mg animals. Weight-specific highest decreased weight; larger individuals. Assuming energy value cal mg−1 daily mean intake by thegutof G. pu/ex was2.2 animaldry (9.2 J mg−1) 0.4 mgdry (2 wt), decreasing 0.3 (1.3 10 (50 wt). Growth is briefly reviewed hght work emphasized that all aspects feeding, metabol-ism should be specifically age individuals, using defined diets.