The environmental control of hatching in <i>Fundulus heteroclitus</i>

Abstract

Abstract Salinity, pH, dissolved oxygen, hydration, and temperature were examined as possible environmental cues that might intiate hatching in Fundulus heterolitus . Incubation in or transfer to water adjusted to ranges of salinity, pH, and temperature within the physiological range of the species had no direct effect on hatching. Eggs incubated in water with dissolved oxygen concentrations greater than 6 ml O 2 /L or solutions of Carbowax PEG 4000 producing an osomotic flux of water out of the eggs delayed hatching indefinitely. Incubation of eggs in air delayed hatching, regardless of the pO 2 . Eggs delayed for periods of up to 1 mo by incubation in air or in highly oxygenated water hatched normally when placed in water of 4 ml O 2 /L or less. Additionally, eggs that were partially dehydrated by incubation in air did not hatch when placed in a pressurized container of mineral oil. These results indicate that both water and low dissolved oxygen concentration are necessary for hatching to occur. Both of these conditions are likely to exist in the field when stranded eggs are immersed in water.