Larval growth and metabolic energy storage of Micropterna lateralis (Trichoptera: Limnephilidae) in an intermittent stream: glycogen dominates in final instars.

The caddisfly species Micropterna lateralis is an abundant representative of limnephilids in intermittent streams. Yet, its basic life history characteristics and adaptations related to environmental factors, such as stream drying, are comparatively understudied. Here, we investigated larval growth and metabolic energy reserves (glycogen, triglycerides) through development in their natural habitat. We concentrated on the larval development because this period represents the important phase of energy accumulation necessary for growth, metamorphosis and embryogenesis. Besides larval physiology, female adults were studied in terms of ovarian maturation. Our results indicate that adult females lack an imaginal diapause, which is otherwise often observed in intermittent stream-inhabiting Limnephilidae. Further, M. lateralis is univoltine and exhibits a relatively fast larval development with five distinct instars, of which four are characterised here (instars II-V). Accrual of biomass occurs in final instars, where a high amount of glycogen is accumulated. Lipid concentrations, on the other hand, are kept constant in final stages and slightly lower than in preceding instars. This dominance of glycogen in final instars found in M. lateralis is highly unusual in insects and of potential adaptive significance for the species' ability to exploit intermittent habitats. [ABSTRACT FROM AUTHOR]