Ref ID : 1444
John J. Gilbert and Dorothee K. Schreiber; Induction of diapausing amictic eggs in Synchaeta pectinata. Hydrobiologia 313/314:345-350, 1995
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Amictic females of a clone of S. pectinata from Star Lake (Norwich, Vermont) may produce diapausing as well as non-diapausing (subitaneous) eggs. The proportion of diapausing eggs produced in cultures was unaffected by temperature (12 vs. 19 degrees C) of rotifer population density (minima of 0.33 vs. 3 ind.ml-1) at 19 degrees C. However, at 19 degrees C this proportion was higher in cultures maintained at a low food level suppressing reproduction (5x10E3 cells ml-1 Cryptomonas erosa) than in those maintained at a high food level (2x10E4 cells ml-1); the treatment effect was marginally significant (p=0.067). Consistent with the effect of low food availability, a period of starvation was very effective in inducing the development of diapausing eggs. None of 19 females cultured individually from hatching at 19 degrees C on C. erosa (2x10E4 cells ml-1) in 1-ml volumes produced by any diapausing eggs in 4 days (0 out of 349 eggs), while 13 out of 16 females subjected to a 15-hour starvation period 6 hours after birth produced one or more diapausing eggs during that time (34% of the 158 eggs produced by the 16 females were diapausing). Diapausing eggs produced and left at 19 degrees C hatched after 4 to 13 days. Those produced in cultures with a low food level took significantly longer to hatch (9.7 days) than those produced in cultures with a high food level (8.1 days) (p=0.022). In natural communities, S. pectinata should be able to respond directly and rapidly to poor food conditions by producing eggs that undergo an obligatory dormant period before resuming development.