Utilization of the aquatic research facility and fertilization syringe unit to study sea urchin development in space

Methods were developed for the investigation of the effects of microgravity on early development in sea urchins within the Canadian Space Agency's Aquatic Research Facility (ARF). The ARF payload provided light, temperature control, automated fixation capability, and a 1 G on-orbit centrifuge control. Eggs and embryos of either the sea urchin species Lytechinus pictus or Strongylocentrotus purpuratus were loaded into Standard Container Assemblies (SCAs) which comprised the experimental aquaria (33 mL volume) contained within the ARF. A newly developed Fertilization Syringe Unit (FSU) was used to achieve "in-flight" fertilization capability. Fixative solutions were preloaded into fixation blocks maintained adjacent to the SCAs and injected at pre-selected time points, resulting in final (diluted) concentrations of either 0.5% or 2% glutaraldehyde (depending upon embryonic stage). Light, scanning, and transmission electron microscopy determined that all desired embryonic and cell division stages (16-cell stage, blastula, gastrula, and pluteus) were preserved using the experimental protocols and fixation capability provided by the ARF/FSU system.