Effects of different microalgal feeds and their influence on larval development in the white-spined sea urchin Tripneustes gratilla

Abstract

Nutrition is a major factor governing early development of sea urchins. The morphological development and survival of Tripneustes gratilla larvae, from field-collected urchins, was investigated from two separate feeding trials under different feeding regimes. Microalgae Isochrysis sp., Pavlova lutheri and Chaetoceros muelleri were tested as feed in May 2010 and Tetraselmis suecica, Skeletonema pseudocostatum and C. muelleri were tested in September 2010. Morphometric measurements of post-oral arm (PO), total width, total length, stomach length and mid-body line (MBL) were recorded every second day. In May, larvae fed Pavlova died after 23 days and did not reach competence. Larvae grew significantly better on Chaetoceros and Isochrysis, reaching competence on day 16 and 18 respectively, and had survival rates of 5.12% and 13.8% respectively. In the September trial, larvae fed Tetraselmis died by day 9, whereas larvae fed Skeletonema and Chaetoceros reached competence by day 22. Survival rates for Skeletonema and Chaetoceros were 2.14% and 2.3% respectively. There was a significant difference in the body profile (PO:MBL) between feed treatments at day 8 in both trials. The study suggests that C. muelleri, S. pseudocostatum and Isochrysis sp. are all suitable feeds for rearing T. gratilla larvae.