Induction and termination of diapause in a freshwater zooplankton community

• I examined production of, and emergence from, diapausing eggs, together with planktonic dynamics of three cladoceran genera (Bosmina, Ceriodaphnia, and Daphnia) for 16 months in a shallow lake. In a complementary field experiment I manipulated environmental variables potentially important as cues for induction and termination of diapause. Ceriodaphnia and Daphnia, but not Bosmina, were dependent on emergence to initiate planktonic populations in spring. During the rest of the season, emergence was unimportant for population and community dynamics. The timing of diapausing-egg production differed between genera, but tended to coincide with peaks in abundance. No hatching was found in any of the experimental treatments, but diapausing-egg production was found in high nutrient treatments with no fish. Field study and experiment together imply that the types of environmental cues involved in diapause induction are different from the ones stimulating its termination. Seasonal cues such as photoperiod appear to govern the hatching of diapausing eggs. In comparison, the induction of diapausing-egg production seems less dependent on season and more on biotic factors.

Ämnesord

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Miljövetenskap (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Environmental Sciences (hsv//eng)

NATURVETENSKAP  -- Biologi -- Ekologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Ecology (hsv//eng)

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