Resource allocation in Tomocerus flavescens (Insecta, Collembola): a study with C-14-labelled food.

Abstract

Individuals of the collembolan species Tomocerus flavescens from a beech wood on limestone near Göttingen (West Germany) were fed with C-14-labelled algae in the laboratory. On an average, T. flavescens exchanged almost all of its endogenous carbon after 3.4 moults. In periods of starvation the interval between two ecdyses increased from 5.2 to 6.1 days (17°C). The assimilation efficiency was determined in three independent ways (carbon use of different algal components; A=C-FU; C=P+R+FU, A=P+R): it ranged from 0.34 to 0.40 (converted to energy values 0.30 to 0.45). It could be raised in phases of high mobility and in periods of food shortage by lowering the gut passage rate. The decrease in feeding activity (demonstrated by gut contents analyses) in case of a detoriation of the food quality and the food availability can be partly compensated in this way. For individuals which did not reproduce, the ratio of production to assimilation was 0.24 (converted to energy values 0.31). T. flavescens showed an increased body growth in connection with reaching sexual maturity. Specific demands of nutritive substances in periods of physiological changes could possibly be compensated by a more efficient resource use as well as by differences in resource allocation. The studied population of T. flavescens was compared both with that of a Danish beech forest and general data from the literature. The production of few eggs rich in energy, the high weight of newly hatched individuals, the high growth as well as the storage of carbon connected with egg production, the comparatively low respiration metabolism and the high amount of energy invested in search for food have to be regarded as an adaptation to the habitat. According to conservative estimates climbing individuals of this species consume 0.83 g of the algal dry mass growing on one beech tree during one summer. T. flavescens mainly uses the ethanol-soluble components of the algae.