Environmentally induced twinning in echinoderm embryos and its effects on larval development
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.
Armstrong, A. Francis and Allen, Jonathan D., "Environmentally induced twinning in echinoderm embryos and its effects on larval development" (2011). Marine Lab Faculty Bibliography. 59.