ISSN 1063-0740, Russian Journal of Marine Biology, 2007, Vol. 33, No. 4, pp. 222–226. © Pleiades Publishing, Ltd., 2007.
Original Russian Text © Yu.Ya. Latypov, 2007, published in Biologiya Morya.
Hermatypic (reef-building) corals with colonial
growth forms represent a large proportion of modern
scleractinians. The acquired colonial form gives them
large advantages over solitary forms. Hermatypic cor-
als acquired the ability to rise above the bottom and
avoid the adverse effect of silting, which is a major fac-
tor inhibiting the development of sessile benthic organ-
isms. The colonial form allows the scleractinians to
achieve the optimal arrangement of polyps in space and
thereby to better use light energy and capture plankton.
The extremely large variety of scleractinian colony
forms is related to their strategy for survival in the reef
biotopes . Most of the reef-building scleractinians
that lead the attached mode of life have branching, mas-
sive, funnel-shaped, and encrusting colonies. Solitary
sessile scleractinians are less diverse taxonomically
and are markedly smaller. Generally, they live on soft
bottoms and can form settlements of many hundreds of
specimens [7, 11, 13]. The so-called mushroom corals
or fungiids are peculiar in that at the very early stages
of growth they are attached to the substrate but after
having attained a size of 1–3 cm across, fungiids
become unattached or free-living and, moreover, are
able to move on their own with the aid of the tentacles
of the polyp. However, solitary and unattached corals
are secondary components in the formation of the
biodiversity and calcareous structure of the reef and
loose biogenic sediments. Alhough they live under spe-
ciﬁc epibiotic conditions, unattached corals occur in
almost all zones of the reef and occasionally inhabit the
soft bottoms of the fore-reef.
There is little data available on ahermatypic free-liv-
ing scleractinians in the reefs of the world [4, 5, 12, 17].
A few works describe the ecological conditions of the
sandy sediments [6, 14, 15]. More complete informa-
tion exists on habitat conditions and the distribution of
free-living scleractinians (21 species) on the reefs of
Madagascar . During the study of the coral reefs of
the Seychelles Islands in February 1989 (R/V “Aka-
demik Aleksandr Nesmeyanov”), numerous unattached
forms of solitary and colonial corals that are usually
attached to the substrate were found in different zones of
the reef, particularly in the deep zone. This paper is con-
cerned with their morphology, ecology, and chorology.
Observations were performed on reefs of Aldabra
and Derosh in the Seychelles Islands. Forty-seven sam-
ples of corals were collected in a lagoon on medium-
grained and coarse sand (depth 6–9 m), on the reef
slope and at the reef base on pebbles (depth 11–35 m).
Each colony was measured with a slide gauge, its posi-
tion on the bottom was marked, the upper and lower
parts of colony were designated.
RESULTS AND DISCUSSION
Species Diversity and Colony Forms
The free-living corals of the investigated reefs are
fairly diverse taxonomically. Thirty-nine species that
belong to 22 genera of 9 families have been recorded
(see table). Most of the corals (24 species) occur
attached to hard substrates and occasionally (when
damaged as a result of wave action or mechanical
effects, or attacked by ﬁsh, etc.) can be dislodged.
The rest of the scleractinians (15 species) live free for
much of their life. It should be noted that the free-living
Diaseris fragilis, Cycloseris cyclolites, C. vaugh-
and all species of the genus
) belong to the
same family Fungiidae. Species of this family are soli-
tary, and only young individuals attach themselves to
Free-living Scleractinian Corals on Reefs of the Seychelles Islands
Yu. Ya. Latypov
Institute of Marine Biology, Far East Division, Russian Academy of Sciences, Vladivostok, 690041 Russia
Received February 1, 2007
—Thirty-nine species of unattached scleractinian corals that belong to 22 genera of 9 families were
found on the Seychelles reefs. Variations of the colony form of corals living on soft sediments under continuous
wave action are described. Irrespective of their initial growth form and taxonomic position, corals assume a
form close to spherical. Because of the worldwide deterioration of coral reefs, the adaptation to changing eco-
logical conditions by reef-building corals needs to be studied.
Seychelles Islands, free-living scleractinians, adaptation.