ENVIRONMENTAL-FACTORS AFFECTING DORMANCY IN THE FRESH-WATER SPONGE EUNAPIUS-FRAGILIS (LEIDY)

The gemmules of the freshwater sponge Eunapius fragilis from Gallup Pond in Connecticut are released from diapause by exposure to low temperature and/or drying. Air-drying gemmules that have been chilled at 4-degrees-C for several weeks may hasten the termination of diapause by as much as 2 months compared to low temperature treatment alone. Furthermore, chilling gemmules at 4-degrees-C for only one week may substantially enhance the capacity of the gemmules to emerge from diapause following desiccation. Chilled gemmules of E.fragilis from Stony Brook in Massachusetts appear to be less readily released from diapause by air-drying than those from Gallup Pond. In addition, partial osmotic dehydration in 5% NaCl solution resulted in little or no increase in the rate of activation of chilled gemmules. Although most gemmules are kept in a quiescent state by low temperature once diapause has been broken, a few gemmules germinate and develop into small sponges at 4-5-degrees-C.