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Effect of Varying Food Concentrations on Purple Urchin (Strongylocentrotus purpuratus) Larvae Development

CSEF · 2017 Zoology Fourth Award

Insun Won · Palos Verdes Peninsula High School, Rolling Hills Estates, Los Angeles County

Overview

Objectives/Goals This project was designed to determine the effects of varying concentrations of phytoplankton on the larval arm to body ratio of Strongylocentrotus purpuratus, which is essential for the urchin to stay upright in the water column. It was hypothesized that a smaller concentration of food for the larvae would lead to a larger arm to body ratio, as noted in similar experiments in this organism. Methods/Materials Sea urchins were chemically induced to spawn for this experiment. On the third day post-fertilization, the blastula were thinned out into approximately equal quantities and were placed in treatment groups (food concentration of 0, 1000, 3000, 10000, 30000 cells/mL). The food given was Isochrysis galbana paste. On the 13th day, photos of five randomly selected individuals per treatment were taken. Then, using image analysis, the larval arm and body lengths were measured. Results Generally, there is a negative correlation between the concentration of food and the arm to body ratio of S. purpuratus larvae. Surprisingly, the arm to body ratio of the starved condition was smaller than the ratio for the condition with 1000 cells/mL. The analyzed data showed that there were significant differences between treatments, signifying that an increased quantity of food leads to a smaller ratio. Conclusions/Discussion The results supported my hypothesis that a larger concentration of food would lead to a smaller arm to body length ratio. Knowing the effects of the changing food quantities on the urchin larvae is important when the future of phytoplankton densities and distributions is uncertain.

Summary statement

As found by the varying arm to body ratios in urchins, I found that urchin larvae have significantly shorter arms when fed greater quantities of food.

Help received

I received help with spawning urchins with syringes at Cabrillo Marine Aquarium. Dr.Darrow and other aquarium staff helped supervise my project, but I designed and experimented on my own.

Awards (1)

Competition history

  • CSEF 2017 Zoology · Entry S2318

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