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.

---

---

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

---

Communicated by O. Kinne, Hamburg     

Characteristics of suspensions of Kuwait oil and Corexit 7664 and their short-and long-term effects on Tisbe bulbisetosa (Copepoda: Harpacticoida)

A technique for preparing seawater suspensions of Kuwait oil and Corexit was developed. The resulting hydrocarbon concentrations were analysed by gas-chromatography and spectrofluorometric methods and the stability of the suspensions with time was determined. It was established that the suspensions have an effective stability from Days 3 to 15 after preparation, since in this period the concentration varies within a relatively narrow range. Adult female Tisbe bulbisetosa appeared to be quite tolerant of this type of hydrocarbon suspension, in short-term experiments, especially considering that the concentrations used in the bioassays were about 200 times higher than those measured in a relatively polluted area of the lagoon of Venice. Long-term effects on number of eggs produced, number of nauplii and hatching success for females of the third and fourth generations, subject to continuous exposure, were negligible compared with controls.