Page 66 - World Aquaculture Magazine - March 2011
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64
M
arch
2011
Contamination problems using
Sargassum
sp. extract with the sea cucumber,
Holothuria leucospilota,
in captive breeding
A
bdul
-R
eza
D
abbagh
,
*1
M
ohammad
-R
eza
S
edaghat
2
and
M
usa
K
eshavarz
1
There are many parasitic protozoans and metazoans
that infest echinoderms, especially holothuroids. These
are harmful to their hosts and can sometimes result in
death (Eeckhaut
et al
. 2004). Some live on the skin, oth-
ers internally. Parasitic ciliates living in the digestive tract
and in the respiratory trees of holothuroids have been re-
viewed by Eeckhaut
et al
. (2004). It is possible that some
of these problem organisms may be also introduced into
culture vessels with
Sargassum
sp. extracts, which are
used to induce larvae to settle. The aim of this work was
to investigate this possibility.
Study Methods
To induce doliolaria larvae of
H
.
leucospilota
to meta-
morphose to pentacularia and settle,
Sargassum
sp. ex-
tract was used.
Sargassum
sp was collected at low tide in
Bandar-e Lengeh, Hormozgan province, Iran in summer
2009. It was washed with freshwater. Next, the algae was
submerged in sodium hypochlorite and then rinsed again
with freshwater.
After putting in the settlement plates that had become
coated with
Sargassum
sp. extracts, a few samples were
taken from the larval tanks. The samples containing lar-
vae and a fine layer of algal extracts were observed un-
der a microscope. A few days later, all the doliolaria had
settled onto the plates.
Results
In our samples, two ciliates,
Vorticella
sp. and
oxytrichid, were observed. Also many nematodes were
seen. No ciliates or nematodes were observed on the lar-
val and juvenile sea cucumbers.
Discussion
When the first doliolaria larvae appeared, suitable
settlement surfaces were provided. These included plas-
tic sheets (PVC, polythene or polypropylene), fiberglass
plates, mesh screens and rough surface tiles submerged
in the larval tanks. There were many ways to prepare the
settlement surfaces. One of these involved using extracts
of filtered seaweed
Sargassum
sp. over a period of 4-5
days to deposit a fine coating on the settlement surfaces
(Agudo 2006). Laxminarayana (2005) reported using a
fine coat of algal extract to induce settlement of larvae.
No contaminating organisms were observed on the
larvae and juveniles. This suggested that these organisms
only had a competitive relationship with the sea cucum-
bers. As soon as the organisms were found, the growth
rate of juvenile sea cucumbers fell, so that by day 56,
the juveniles were 2.5 mm long. Agudo (2006) reported
growth of juveniles to be 4-5 mm/week. Pentactula larvae
were obtained on day 20. We concluded that unwanted
organisms could lower the growth rate, so it was better if
the algal extract for inducing larval settlement is washed
with a detergent.
Notes
1
Department of Marine and Fisheries Biology, Hormozgan Uni-
versity, P.O. Box 3995, Bandar Abbas, Iran.
*
Corresponding
author:
2
Persian Gulf Mollusc Research Station, Bandar-e Lengeh,
Iran.
References
Agudo, N. 2006. SandFish Hatchery Techniques. New Caledo-
nia : ACIAR, SPC and the World Fish Center,
.
worldfishcenter.org/resource_centre/WF_2393.pdf.
Eeckhaut I., E. Parmentier, P. Becker, S. Gomez da Silva and
M. Jangoux. 2004. Parasites and biotic diseases in field and
cultivated sea cucumbers. Advances in sea cucumber aqua-
culture and management. FAO Fisheries Technical Report
No. 463, FAO, Rome.
Laxminarayana A. 2005. Induced spawning and larval rearing
of the sea cucumbers,
Bohadschia marmorata
and
Holothu-
ria atra
in Mauritius.SPC Bêche-de-mer Information Bul-
letin 22:48-52.
