International Journal of Marine Science 2016, Vol.6, No.35, 1-8
2
are generally performed better in terms of growth and feed efficiency than diets containing alternative plant based
sources (Moyan et al., 1992; Webster et al., 1992; Kikuchi, 1999). In spite of efforts to replace microalgae by inert
feed, aquaculturists are even now dependent on the production and use of microalgae as live food for
commercially important molluscs, fish and crustaceans (Pauw and Pruder, 1986). Algal concentrates made by
centrifugation are fed to bivalves and prawn larvae with successful results (Souza et al., 2000; Heasman et al.,
2000; Robert et al., 2001).
The marine cyanobacteria have been tested for their nutritional values for hybrid
Tilapia
fish fry and found that
most of the strains of
Phormidium valderianum
are acceptable as single-ingredient feed based on nutritional
quality and non-toxic nature (Mitsui et al., 1981). The prawns are mainly predators feeding on organisms that are
utilizing the benthic filamentous cyanobacteria like
Spirulina
sp
.
, as a primary carbon source (Stoner and
Zimmerman, 1988). The
Spirulina
species have gained commercial importance as a source of proteinaceous food
and aquatic food (Vonshak et al., 1988). Nutritive value of marine cyanobacteria in prawn diet has been studied
by Subramanian (Subramanian, 1998). Marine cyanobacterium,
Phormidium tenue
was tested as supplementary
feed for two species of shrimp
Penaeus monodon
and
P. semisulcatus
(Palaniselvam and Kathiresan, 1998). The
marine cyanobacterium
Phormidium valderianum
BDU 30501 was proved to be an aquaculture feed (Thajuddin
and Subramanian, 2005) along with
Synechococcus
sp
.
and
Phormidium
sp
.
, as feed for shrimp
Penaeus monodon
(Sivakumar et al., 2011, 2014). Although filamentous forms of cyanobacteria are well studied for dietary potential,
unicellular marine forms are only little studied. Hence, the present work focused on
Synechocystis salina
as a
supplementary feed for the shrimp
Penaeus monodon
.
Materials and methods
Composition of shrimp feed
The cyanobacterial species,
Synechocystis salina
was isolated from mangrove sediment and cultured under
laboratory conditions using Marine Nutrient (MN) medium (Rippka et al., 1979). The MN medium was prepared
by mixing seawater (750 ml), distilled water (250 ml), magnesium sulphate (0.04 g), sodium nitrate (0.75 g),
sodium carbonate (0.02 g), dipotassium hydrogen orthophosphate (0.02 g), calcium chloride (0.02), citric acid
(0.003 g), ferric ammonium citrate (0.003 g), ethylene diamine tetra acetic acid (0.000 5 g) and A5 micronutrients
(1 ml). A5 micronutrients were prepared by adding distilled water (500 ml), boric acid (1.43 g), manganous
chloride (0.95 g), zinc sulphate (0.111 g), sodium molybdate (0.008 6 g) and copper sulphate (0.039 5 g). The
subculture of actively growing cells was maintained from stock cultures. Ten days old sub culture (500 ml/day)
was added as additional feed directly to 20 L of experimental shrimp tank. The commercial feed without addition
of cyanobacteria was used as control diet.
Feeding experiment of shrimp
The tiger shrimp
Penaeus monodon
popularly cultured in the aqua farms was used as the test organism. The active
and healthy shrimps were visually sorted out and stocked for three days for acclimatization to laboratory
conditions. The acclimatized animals were kept starved for 3 days prior to the feeding experiment. Ten animals of
the same length (5.13 ±0.44 cm) and weight (1.14 ±0.28 g) were used for each treatment. Before stocking, the
shrimps were measured for total length and wet weight. The experiment was conducted for 15 days in a 40 L
plastic tank containing 20 L of filtered seawater. The water salinity 30 ±2 g l
-1
, temperature 29 ±1
℃
, pH 8.0 ±1
and dissolved oxygen 5 ±0.5 mg l
-1
are maintained till the end of the experiment. The dissolved oxygen was
maintained by using air-stone aerator, by adding freshwater and lime to maintain water salinity and pH. The feed
was given at 10% of animal body weight. The fecal matter and excess of feeds were collected daily before water
exchange, dried and weighed. For each treatment, triplicates were maintained. The parameters such as mean
weight, production, relative growth rate, assimilation efficiency and food conversion efficiency were calculated
(Crip, 1971). Then, the shrimps were scarified for the determination of carbohydrate (Dubois et al., 1956), protein
(Lowry et al., 1951) and lipids (Folch et al., 1957).
