This study examined the feeding selectivity and ecological role of the most dominant holothurian species — Holothuria atra, Holothuria hawaiiensis and Bohadschia vitiensis — on the tidal flats and in the shallow waters in the Red Sea at...
moreThis study examined the feeding selectivity and ecological role of the most dominant holothurian species
— Holothuria atra, Holothuria hawaiiensis and Bohadschia vitiensis — on the tidal flats and in the shallow waters
in the Red Sea at Hurghada, Egypt. The three species exhibited a wide range of variations in their gut
sediment contents, depending on their total weight. Medium-weight individuals, which require considerable
food for growth and gonad development, were found to consume more gravel than light- and heavyweight
individuals. The selective behaviour of the holothurians illustrates that gravel and coarse sands are
the main sediment components in the animals’ guts during the different seasons. During the spawning period
(early summer to autumn), the animals tended to assimilate fine sediments more than coarse sediments,
perhaps due to their increasing need for organic matter.
Sediment reworking processes by the different species varied during the year and depended on individual
numbers, food availability, individual sizes and local conditions. H. atra showed the highest sediment reworking
in July (summer) and November (autumn), H. hawaiiensis in autumn/winter (September and December,
and B. vitiensis mainly from summer (May to August. It was observed that the reworking lasted
from late spring to the end of autumn. This period covers the two essential phases of holothurian reproduction:
maturation and spawning.
