Morphological differences between subitaneous and diapause eggs of Boeckella triarticulata (Copepoda: Calanoida)

1. Many calanoid copepods produce subitaneous eggs that hatch immediately and diapause eggs that remain dormant for long periods of time. Boeckella triarticulata (Copepoda: Calanoida) produces diapause eggs that hatch asynchronously over an extended period of time and appear identical under light microscopy to those that hatch immediately.
2. We compared the internal morphology of subitaneous and diapause eggs of B. triarticulata that had been prepared for transmission electron microscopy by four methods.
3. Subitaneous eggs had a thin, single-layered shell whereas diapause eggs had a thick, three-layered shell that appeared consistent over 3 months of diapause. Boeckella triarticulata appears to enter diapause at the multicellular stage.
4. Consistent morphological differences between subitaneous and diapause eggs of B. triarticulata suggest that these two egg types also have distinct differences in physiology, and are not merely extremes of a continuum from subitaneous to diapause eggs.