Sand Dollar Larval Response to Environmental Stress
Authors:Christina Frieder, Mai Tran
Mentor:Lisa Levin, Professor/Researcher, University of California San Diego
Echinoidea, a class of marine invertebrate which includes heart urchins, sand dollars, and sea urchins, all have significant economical and environmental importance. Sustaining existing population numbers depends on the survival success of the larval stage. An important factor that directly affects larval growth and development is food availability. Food in the ocean is highly dynamic and larvae often face limited food in their lifetime. To determine the important parameters for larval health, morphometric and physiological analysis were conducted to assess the impact of varying food conditions on early life stages of the Pacific sand dollar, Dendraster excentricus. Larvae were fed no food, low food (600 algal cells ml-1), or high food (6000 algal cells ml-1) for 18 days. Of note, larvae grown in a high food environment had significantly longer arms (p < 0.05). In addition, development to the eight-arm stage varied with food environment; 16% with no food, 32% with low food and 83% of those in high food developed to the eight-arm stage. Based on clearance rate experiments which tested how much algal cells a single larva fed per hour, larvae in a high food environment fed 1.6 times more (p < 0.05) than those in low food or no food environments suggesting that food history does affect future larval feeding potential. Future studies will test the hypothesis that larvae may exhibit significant differences in the rate of energy acquisition, concentration of sodium/potassium pump, and protein content when grown in different food environments. High food availability may also modulate response to other environmental stressor such as low pH and high temperature, which are direct consequences of global warming and ocean acidification. These studies shed light on which physiological assays specific to the echinoids can be used to effectively predict and assess future environmental impact on species population.