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     

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.     

Metabolic adaptation of the intertidal worm Sipunculus nudus to functional and environmental hypoxia

The scope of anaerobic metabolism of Sipunculus nudus L. was assessed from the maximal activities of some enzymes of the intermediary metabolism and from the concentration of some metabolites accumulated during enhanced muscular activity and during prolonged experimental hypoxia.

1. Maximal enzyme activities demonstrate that the scope of anaerobic glycolysis, as indicated by maximal activities of glycogen phosphorylase (0.84 U g^-1 fresh wt), far exceeds the aerobic capacity, which is assumed not to surpass the activity of succinate dehydrogenase (0.09 U g^-1 fresh wt). Three pyruvate reductase activities (alanopine-, strombine- and octopine dehydrogenase) can possibly terminate anaerobic glycolysis.
2. During muscular activity, energy is provided by the degradation of phospho-L-arginine and by anaerobic glycolysis. Octopine is the major endproduct during functional anaerobiosis while the formation of strombine is less pronounced.
3. During exposure to a nitrogen atmosphere, several anaerobic endproducts are found to accumulate. Anaerobic glycolysis is terminated by strombine synthesis. This opine accumulates in concentrations much higher than octopine. In addition the concentrations of succinate, propionate and acetate are found to increase in tissues, and/or in the coelomic fluid and the incubation water.
4. The relative contribution of energy by the different anaerobic metabolic pathways are estimated during functional and environmental hypoxia.