Physiologische anpassungen eines marinen insekts. I. Die zeitliche steuerung der entwicklung

The Baltic populations of Clunio marinus (Chironomidae, Diptera) differ from their Atlantic counterparts in three ways: they neither pupate nor hatch in synchrony with a lunar rhythm; they live in a permanently submersed habitat; the structures of their gelatinous egg-masses are different. C. marinus produces two generations each year. The spring generation, which hibernates in the 4th larval stage, hatches in May; the summer generation hatches at the end of July or beginning of August; hatching periods last only a few days. In the laboratory, a permanent short-day period (8 h light, 16 h dark; LD 8:16) induces larval quiescence (oligopause), which can be terminated by long-day conditions (ca. LD 16:8). If larval populations are exposed to continuous light (LL) for 4 days every 30 days, particularly large numbers of imagos hatch about the time of the next LL-period. Increased illumination may influence the time of hatching. Raising the temperature for a few days does not affect hatching. The roles of photoperiod, illumination and temperature are discussed with regard to the temporal programming of development and the start of mass hatching in the natural habitat.

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Herrn Professor Dr. D. Neumann danke ich für die Anregung und Betreuung dieser Arbeit, die Teil einer Dissertation ist.

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Communicated by O. Kinne, Hamburg