In recent decades, water temperatures have been increasing and salinities have been decreasing in the Gulf of Maine. How these environmental changes affect the development of marine organisms has yet to be systematically investigated. We fertilized eggs of three different echinoderm species (Asterias forbesi, Strongylocentrotus droebachiensis, and Echinarachinus parma) under several combinations of temperature and salinity to observe what effect these stressors have. In all three species, a novel response of embryonic twinning was seen under at least one combination of environmental conditions. Twinning rates were variable among the three species with E. parma having the highest observed rates. Significant variation in twinning rates was also observed within species. In the most extreme cases up to 28% of embryos in a single treatment were observed to twin. To see how twinning affected development, we followed replicate pairs of E. parma larvae that were derived from twinning events. Twins were measured and compared to untwinned siblings. Overall, twins grew at a slower rate than untwinned siblings. In addition to reduced growth rates, twins were also delayed in reaching subsequent developmental stages. While twins were the focus of our study, other types of multiples also formed: triplets, quadruplets, quintuplets and sextuplets. We did not track whether these more extreme multiples were viable beyond hatching. In addition to the production of multiples, a delay of hatching was seen in twins and singles from three different females. Some embryos had gastrulated and others were four-arm larvae before hatching. The production of multiples and delays in hatching were unexpected responses to environmental stress and their consequences for coastal populations should be explored further.
So I’m back at William and Mary and back to conducting research in the ordinary lab. It’s sad not being in the coastal studies center and being able to go out and see the ocean everyday. There’s no more loud sea water pumps and no more daily collecting of animals. Back to mixing Insta-Ocean and getting animals shipped to us.
My summer of research is officially over. It was a good summer full of lots of new experiences. I spent a lot of time in the lab and feel happy with the amount of work I got done. The crazy hours and long days were worth it in the end. I made some good progress with my project. We were successful in producing and rearing twins. I didn’t get as much growth data as I would have liked but I still have lots of data to analyze and I ended up working on projects I hadn’t planned on. So I guess it all evened out.
Sand Dollars put out their gametes once a year when an environmental cue triggers them to start spawning. Once a few of them put out gametes, the others in the area will usually all start too. After several trials where we were unable to induce animals to release any usable eggs, it seems this behavior worked out poorly for us and that all of the animals we collected originally spawned out when we were not in the lab. So, more sand dollars were ordered from down east Maine (which is apparently Northern Maine).
Things are set up pretty well for my research. We’ve collected over 50 sand dollars and have successfully started spawning them. We’ve pretty much worked out the preliminary details and gotten the kinks worked out of the experimental design. Unfortunately, lately, right when I think I can start getting more data, something breaks. For instance the water heaters stopped working, the stirring rack broke, the thermometers went missing, and the algae died all over the past weekend. Every impediment has just been a minor one thankfully. It usually complicates the data I collect that day, but nothing major has happened.