Hatching timing of Daphnia mendotae diapausing eggs of different ages
Fox, Jennifer Ann
published: Jan 1, 2007
ArtNo. ESP141016801003, Price: 29.00 €
Many annual-plant and invertebrate species produce seeds or eggs that can survive in dormancy for many years before germinating or hatching. The ability of the resulting seed or egg banks to influence population dynamics is a function of the success and duration of germination or hatching and subsequent development. To explore this for Daphnia mendotae, I collected diapausing eggs from the sediments of Onondaga Lake, NY, incubated them in spring photoperiod and temperature conditions, and measured the duration of different life stages for eggs from recent (< 5 year-old) and older (15-20 year-old) sediments. a total of 432 D. mendotae hatched. Many of these hatchlings were inviable (39-44%), with a higher proportion of late hatchers from both egg ages showing inviability. The days to hatch for two eggs from a single ephippium (egg case) is highly positively correlated, indicating either a genetic or maternal component to survival. Older eggs take, on average, 8.6 days longer to hatch than recent eggs. When the total time to maturity is considered for the subset of animals surviving to reproduce, there is no significant difference between older and younger diapausing eggs in the time from when an egg first receives the hatching stimulus to the release of the hatchling's first brood. These results suggest that for those eggs receiving a hatching cue, neither egg age nor hatching timing alone is a good predictor of the potential impact of the egg bank on population dynamics, but both must be considered.