Radioisotope Turnover and Energy Flow in Terrestial Isopod Populations
1967
Reichle, David E.
Radiocesium turnover rates in terrestrial isopod populations were used to measure food consumption and metabolism under natural and laboratory—simulated field conditions. Four old—field and forest species were studied: Armadillidium vulgare (Latreille), Armadillidium nasatum Budde—Lund, Cylisticus convexus (DeGeer), and Metoponorthus pruinosus (Brandt). Uptake, body burden equilibria, and elimination rates for ¹ ³ ⁴Cs were related to environmental temperatures (Q₁ ₀°2). dietary supplements of stable Na, K, and Cs salts produced no effect upon ¹ ³ ⁴Cs elimination rates. Assimilation fractions from food were 60 to 64% for digestible dry matter, 70 to 73% for caloric intake, and 70 to 87% for radiocesium. Body equilibrium concentrations and biological half—lives of radiocesium in each species permitted estimates of food consumption comparable to gravimetric determinations. Food intake varied between different species and ranged from 1.5 to 3.5% of dry body weight per day. Bomb calorimetry and respirometry measurements were used to partition the total energy budgets, caloric inputs required for maintenance, production, and growth were determined. Radiocesium elimination rates were correlated with the metabolic rates of individual species, and radionuclide turnover rates in tagged individuals were demonstrated to be a practicable means of determining the activity and metabolism of species in the natural habitats.
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