Information on the nutritional requirements and preferred diets of sea cucumber (Holothuriidae) larvae is
extremely limited and this has hindered development of hatchery cultur emethods. This study assessed ingestion
and digestion of two live (TISO and Chaetoceros muelleri) and six concentratedmicroalgae (Instant Algae®, Reed
Mariculture Inc.) by sandfish (Holothuria scabra) auricularia larvae of different ages using epifluorescence
microscopy. This is the first study to report the use of epifluorescence microscopy with larval echinoderms and
experiments were conducted using 2, 6 and 10 day old auricularia larvae. Seven of the eight microalgae tested
were ingested and digested by the larvae with digestion occurring more rapidly in older larvae. C. muelleri was
rapidly digested by 6-day and 10-day old larvae but our results indicate that C. muelleri is unsuitable as a food
for 2-day old sandfish larvae. TISO was well ingested by sandfish larvae in both live and concentrated forms
and live TISO was themost suitable of the microalgae tested in terms of ingestion and digestibility. All commercially
available microalgae concentrates tested were readily ingested and digested by H. scabra larvae with the
exception of Thalassiosira pseudonana (3H 1800®)whichwas not ingested by larvae of any of the three ages tested.
Our results show potential for using microalgae concentrates as alternatives to live microalgae in hatchery
culture of sandfish. However, further research should be conducted to assess the relative nutritional values of
digestible microalgae as a basis for optimising a diet for hatchery culture of sandfish, and to provide further
information on the nutritional requirements of sandfish larvae