Meeting Abstract

P1-52   -   Interactive effects of food availability and salinity on phenotypic plasticity of Echinarachnius parma larvae Uong, I/Q*; McAlister, J/S; College of the Holy Cross; College of the Holy Cross iquong22@g.holycross.edu

The larvae of many marine invertebrates exhibit phenotypic plasticity of traits associated with feeding, development, and growth. Pluteus larvae of the sand dollar Echinarachnius parma extend the lengths of feeding structures (arms) when food levels are low, thereby increasing their likelihood of food capture. By contrast, larvae reared with high food levels reach metamorphic competence sooner as more energy is allocated to food processing structures (stomachs) and juvenile structures (rudiments) required for metamorphosis. However, separate recent findings suggest that sand dollar larvae delay their hatching, and subsequent rates of development, when exposed to low salinity levels. While we have a good understanding of how these larvae respond to single environmental variables, such as food level or salinity, what remains unknown is how these (and many) organisms integrate multiple environmental variables during the expression of plastic phenotypes. This study examined the morphological and developmental plasticity of E. parma larvae in response to varied salinity and food level combinations. Larvae were reared under both constant and intermittent conditions of low salinity and either constant low or high algal food levels for 10 days. These treatments were designed to simulate the effects of longer-term environmental changes and shorter duration events such as heavy rainstorms. Images of larvae were taken daily, and morphological measurements were made from these images using ImageJ; developmental stage was noted for all larvae. Results and statistical analyses will be presented and discussed in the context of larval development and growth in response to environmental change. The results from this study will shed light on our understanding of the ways in which larvae integrate confounding environmental signals.