Studies on the Development of the Sea Urchinstrongylocentrotus DROEBACHIENSIS.I. Ecology and Normal Development

Methods for obtaining viable gametes and embryos of the arctic-boreal sea urchin Strongylocentrotus droebachiensis are presented and practical suggestions are made regarding the suitability of this material for embryological use. 2. The useful breeding season extends from early January to mid-April for animals obtained from shallow subtidal regions of Cape Cod Bay or beginning roughly a month later for animals collected from the Gulf of Maine. The "season" can be extended by at least two months by holding the ripe animals at 4° C. 3. The time course for the first division and for development to the four-armed echinopluteus are given for various temperatures. Development time follows an inverse log relationship with temperature over the range of -1° C to 9° C. 4. The susceptibility of the eggs and embryos to temperatures in excess of 10° C and of the hatched blastulae to bacterial action are discussed in regard to laboratory experimentation and the natural distribution of the organism.