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EN
The aim of the investigations was to determine the effect of hypoxia and anoxia on the osmoregulation of Corophium volutator. The experiments were performed at salinities of 3.0, 6.6,15.0, and 25.0 PSU in conditions of hypoxia (saturation = 30% O2) and anoxia at a constant temperature of 10°C. Control experiments in aerated water were conducted simultaneously. Hypoxia (saturation = 30% O2) had no statistically significant effect on the osmoregulation of C. volutator after either 6 h or 48 h. However, after 6 h it did lower the osmotic concentration slightly. After 6 h anoxia had no effect on osmoregulation, but no subsequent effects of this factor (after 24 and 48 h) were detectable due to high animal mortality. Anoxia also had no effect on osmoregulation after 24 h at salinities of 15.0 and 25.0 PSU or 48 h at 15.0 PSU.
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EN
The purpose of this paper is to determine the differences in energetic value of American crayfish existing in the Vistula Lagoon with reference to their sex and size within the period of three months: August, September and October. The average total energetic value for all the Orconectes limosus aggregates at 10.64± SD 3.19 J* mg-1 DW, and for organic matter 13.99 ± SD 3.97 J* mg-1 ash free dry weight – AFDW. Total energetic value of American crayfish females estimated on average at 13.44 ± SD 2.53 J* mg-1 DW, and in case of males at 8.95 ± SD 2.21 J* mg-1 DW. Total female energetic value is approximately higher by 33.4 per cent than that of males.
EN
In 2002-2003, seasonal variations in the occurrence of the prawns Crangon crangon, Palaemon adspersus, and Palaemon elegans were investigated in the littoral zone of the Gulf of Gdańsk (at depths of 0.5 – 1.0 m and 5.0 – 10.0 m). C. crangon was quantitatively dominant (82%), while the proportions of P. elegans (16%) and P. adspersus (2%) were insignificant. The density, biomass, dimensions, reproductive period, and distribution of these prawn species were found to vary depending on the time of year. Individuals of C. crangon, P. adspersus, and P. elegans coexist in the littoral zone of the Gulf of Gdańsk.
EN
The main aim of the present study was to determine the effect of low salinity conditions (3 PSU and 7 PSU) on the hatching success, growth and mortality of Orconectes limosus. The results revealed that berried females survived exposure to salinities of 3 PSU and 7 PSU whilst incubating their eggs. The reproductive success reached 100% at both salinities. The length increment of young crayfish per molt was larger at 7 PSU than at 3 PSU – but their condition was affected by higher salinity. The mortality among juveniles reached approximately 50% within 5 weeks of hatching at both salinities.
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