Dataset: Phillips_2011 - Experiment 1 Settlement Challenge 18

In this experiment, larvae were placed into feeding treatments with different types of phytoplankton to determine larval nutritional strategies.

Larvae hatched on Sept 24, 2009 and were distributed into tubs on 500mL filtered sea water (FSW). Three larval feeding treatments with different species of phytoplankton, all at 10 x 104 cells mL-1: Isochrysis galbana (‘‘Iso’’ treatment), Dunaliella tertiolecta (‘‘Dun’’ treatment), a 1:1 ratio of I. galbana and D. tertiolecta (‘‘Mixed’’ treatment), plus an Unfed treatment in which larvae were raised in FSW. A hemocytometer was used to count algal cells and calculate densities of phytoplankton stocks and amount of stock to add to containers for each treatment. On day 18 (Oct 12, 2009).

The 18-day settlement challenge was similar to the 10-day challenge, except that all larvae remaining alive in feeding treatments were mixed from each replicate container and redistributed equally into three replicate settlement containers. Therefore, there were different initial numbers of larvae per replicate settlement challenge container from each larval feeding treatment: 13 from Dun, 13 from Iso, 14 from Mixed and 7 from Unfed treatments (total N larvae per food treatment = 21–42

Complete metamorphosis was evident by several obvious morphological changes: the previously long and active foot was lost, the margin of the protoconch aperture became light pink, and early growth of the juvenile tube. In most cases at metamorphosis, the protoconch became cemented to the substratum (either the coral rubble or the bottom of the container), but in others the shell remained unattached. Investigators left swimming larvae in the containers and removed dead larvae. The water in the settlement challenge containers was changed each day.