WHAT ARE THE MAIN FOOD ITEMS FOR CORAL REEF HOLOTHURIAN, Holothuria atra (JÄGER, 1833) AT THE SEAGRASS BED IN CHUUK, FSM?

Abstract

The coral reef holothurian, Holothuria atra have been used in traditional medicine and human food in many countries. Abundance of the sea cucumber population is declined in recent. The sea cucumber has an important role in nutrient recycling as a sediment-feeder in coral reef ecosystems. They often occur in high densities, and consume significant amounts of sediment. This cycling contributes to the high productivity in coral reefs. Limited information is available on the main food sources of H. atra, despite their importance on the reefs. This study investigates the food items (i.e. microalgae and meiofauna) consumed by the sediment feeding holothurian, H. atra for aquaculture. Sediment samples in front of the mouth, faeces at the posterior and the intestines of the sea cucumbers were taken from each individual. The different samples were fixed in 10% formalin for later qualitative and quantitative analysis of microalgae and meiofauna. Taxonomical determination of microalgae was performed with an inverted microscope. Extraction of the meiofauna was performed using Ludox HS 40 and the species were identified to the class level. Total number of microalgae and meiofauna was identified to 25 species and 10 classes in three different samples, respectively. Microalgae and meiofauna in before feeding sediment was recorded 349 cells ml–1 and 12.2 ind. ml–1 with the major groups of Bacillariophyceae and Polychaeta, respectively. After feeding, the microalgae and meiofauna were ingested up to 85.6% and 79.1% by the holothurians. In the intestine, the abundance of Bacillariophyceae without chlorophyll was higher than other groups while the abundance of Polychaeta was lower than other groups. This data demonstrated that Bacillariophyceae and Polychaeta were main ingested food items of H. atra. This information will be used to determine the selection of feeds for hatchery-based aquaculture of this species.