the use of mulberry (Morus alba) extract in the mass production of blue swimming crab (Portunus pelagicus) larvae

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the use of mulberry (Morus alba) extract in the mass production of blue swimming crab (Portunus pelagicus) larvae
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  Aquatic Science and Technology ISSN 2168-9148 2014, Vol. 2, No. 1 www.macrothink.org/ast 1 The Use of Mulberry (  Morus alba ) Extract in the Mass Production of Blue Swimming Crab ( Portunus pelagicus  L.) Larvae to Overcome the Mortality Rate Due to Molting Syndrome Yushinta Fujaya Department of Fisheries, Faculty of Marine and Fisheries Science, Hasanuddin University Makassar 90245, Indonesia E-mail: fyushinta@yahoo.com Dody Dharmawan Trijuno Department of Fisheries, Faculty of Marine and Fisheries Science, Hasanuddin University Makassar 90245, Indonesia Andi Nikhlani Department of Fisheries, Faculty of Marine and Fisheries Science, Mulawarman University Samarinda 1068, Indonesia Indra Cahyono BAKIKDIWA Institute of Marine Science and Technology Makassar 90245, Indonesia Hasnidar    Department of Fisheries, Faculty of Fisheries and Marine Science Indonesian of Moslem University Makassar 90245, Indonesia  Aquatic Science and Technology ISSN 2168-9148 2014, Vol. 2, No. 1 www.macrothink.org/ast 2 Received: May 7, 2013 Accepted: June 30, 2013 Published: January 1, 2014 doi:10.5296/ast.v2i1.4048 URL: http://dx.doi.org/10.5296/ast.v2i1.4048 Abstract  One of the problems in blue swimming crab seedling is the high rate of mortality. This study is aimed at analyzing the influence of mulberry extract (ME) on the survival rate of crab larvae which are managed to metamorphose to the next stage and on the rate of larval development, as well as identifying various factors causing mortality in the mass cultured larvae, mainly mortality caused by molting syndrome. There are 4 treatments of different doses of mulberry extract being tested which are: 0 mg/100 g (control), 1 mg/100 g, 2 mg/100 g, and 4 mg/100 g. Mulberry extract is given through feeding since day-8 of the stocking, which is the time when larvae enter zoea 3. The rearing process is done over 19 days in a concrete tank with a volume of 1 ton with the initial number of zoea at ± 350.000. The findings show that mulberry extract has a significant influence on the survival rate, stage growth, and the mortality rate of blue swimming crab larvae due to molting syndrome. The higher the dose of ME in the artificial food, the higher the survival rate and the lower the mortality rate due to molting syndrome. The treatment with 4 mg of mulberry extract/100 mg is the only treatment which successfully enters megaloph and crab stage. Control treatment and the dose of 1 mg/100 g can only reach zoea 3 while the dose of 2 mg/100 g can only reach zoea 4. This study shows that the total mortality rate is still high, but it is found that the main cause is not molting syndrome. Mortality rate due to molting syndrome in the treatment of the dose of 4 mg of mulberry extract is only ± 15.61% of the total larval mortality. The unidentified factors dominate the cause of mortality (± 57.47%). Other factors are fungal attack (±17.65%), morphological disorder (±9.28%), and cannibalism (±14.93%). Keywords:  Mulberry (M orus alba ), Metamorphoses, Mortality, Blue Swimming Crab ( Portunus pelagicus  L.), Larvae  Aquatic Science and Technology ISSN 2168-9148 2014, Vol. 2, No. 1 www.macrothink.org/ast 3 1. Introduction Portunus pelagicus  L. is one of the commercial crabs traded widely around the world. In Indonesia, the crab species is under intensive development to meet the increasing overseas market demand. The export volume reaches 23 to 25 million tons per year. The increasing amount of crab fishing caused decrease in natural populations, in both quantity and quality. FAO (2011) in World Bank (2012) mentioned that in 2008, Indonesia contributed 20 % of the world blue swimming crab production and ranked second of the biggest producer after China. Unfortunately, along with the increase of human needs and pressure on the marine biological resources environment, the live stock of crabs in Indonesia is continually decreasing by 20 - 30% each year (Mahesa, 2010).   Therefore, other methods to increase crab the supply of crab raw material is highly needed, for example through culture. The blue swimming crab can be cultured in ponds but the seeds still rely on the catch from natural habitat so this action is still potential to press the natural population. Attempts to culture them using seeds from hatchery is still being studied, and have not yet carried out in mass production. One of the causes is that blue swimming crab seedling in hatchery has not given any consistent result yet. The survival rate of seeds usually fluctuates and is generally low. Maheswarudu (2008) reported that the highest survival rate (10.3±5.76%) from zoea-1 to Crab-1 is achieved in low density stocking (50 larvae/liter). Moreover, Juwana et al.,  (2010) was successful in increasing the survival rate from 2.2% to 8.7% through probiotic administration. Zmora et al. , in 2005 then reported that cannibalism is one the factors causing high mortality, so it is suggested to use the shelter and size grading, and decrease stock density. The main problem in the blue swimming crab seedling is mortality (Soundarapandian et al.,  2008). Mortality is caused by various factors, such as disease attack (Govindasamy & Srinivasan, 2012; Talpur et al ., 2011a; Talpur et al ., 2011b), molting syndrome (Hamasaki et al ., 2002 and cannibalism (Soundarapandian et al ., 2008). Many ways have been done to overcome those problems, such as nutrition enrichment of natural food using HUFA to increase EPA and DHA in order to increase larval resistance (Hamasaki et al ., 2002; Samuel et al. , 2011) by using probiotic to control the pathogenic bacterial attack, Vibrio (Juwana et al ., 2010), adjusting the amount and feeding time of natural food (Ikhwanuddin et al ., 2012; Redzuari et al ., 2012), using shelter and size grading, and reducing stock to reduce cannibalism (Zmora et al ., 2005). Nevertheless, litte investigation has focused on the control on molting syndrome through hormonal regulation controlling molting syndrome in crab larvae. In arthropods and crustaceans, hormone regulating molting is ecdysteroid (Huberman, 2000). ecdysteroid controls ecdysis (molting) and metamorphosis. Molting is a process of skin change which enables larvae to develop and metamorphose from zoea 1-4 phase to megaloph and crab. The increase of ecdysteroid in the circulation will stimulate molting; conversely, the decrease of ecdysteroid will stimulate the release of hormone inhibiting molting (Lockwood, 1967). The use of exogen hormone to increase hormone titer in vivo has been widely used in the  Aquatic Science and Technology ISSN 2168-9148 2014, Vol. 2, No. 1 www.macrothink.org/ast 4 high class of animals and humans. However, little effort of this kind has been done in crabs. Azra et al ., (2012) used 20-Hydroxyecdysone exogen added into the rearing of P. pelagicus  larvae to stimulate molting. Phytoecdysteroid of spinach (Amaranthaceae) has also been used to stimulate molting in the production of soft-shell crabs (Aslamyah & Fujaya, 2010; Fujaya, 2011; Fujaya et al ., 2011). Phytoecdysteroid has an analogous structure with growth hormone of insects and some other invertebrates such as crustaceans (Feldman, 2009). Phytoecdysteroid is produced by some species of plants for self-defense against insectal attacks (Schmelz et al ., 2002) and nematodes (Soriano et al ., 2004). One of the plants producing phytoecdysteroid is mulberry (  Morus  sp). This plant produces phytoecdysteroid and has long been used as food in silkworm cultivation (Nguku et al ., 2007). Phytoecdysteroid contained in the Moraceae and Amaranthaceae plants is analogous with ecdysteroid contained in crabs ( Callinectes sapidus ), so Ecdybase names it Inokosterone ( Callinecdysone A ). This study is aimed to analyzing the influence of mulberry extract (ME) on the survival rate of the blue swimming crab larvae which are managed to metamorphose to the next stage and on the rate of larval development, as well as identifying various factors causing mortality of mass cultured larvae, mainly mortality caused by molting syndrome. The application of ME is expected to be able to successfully stimulate and cause molting simultaneously in the stage change so mortality rate can be decreased. 2. Material and Method of Study   2.1 Broodstock of Crabs Broodstock used in this study are caught from the sea around Pangkep- Barru waters, South Sulawesi. Next, broodstock of the crabs are brought to home scale hatchery (backyard) in Palie village, Takkalasi district, Barru regency. Every broodstock of the crabs that have contained black eggs is placed in a concrete tank with a capacity of 1 ton to hatch their eggs. 2.2 Mulberry Extract and Artificial Food Mulberry extract (ME) is in the form of powder obtained from Fisheries and Marine Biotechnology Laboratory Center for Research Hasanuddin University. 100 mg extract is dissolved in 10 mL ethanol (p.a) 80%. Extract solvent is then sprayed to the food made of commercial shrimp larvae. The food is air-dried to evaporate the ethanol before kept and used. The commercial artificial food (1) which is in the form of powder used for zoea contains at least 48% protein and 8% fat, while for megaloph, the commercial artificial food (2) is in the form of flake containing 48 – 53% protein and 3-5% fat. 2.3 Larval Rearing The rearing is done over 19 days in a concrete tank with a volume of 1 ton with initial density of zoea-1 at ± 350.000. Food containing mulberry extract is given on the eight day after the stocking, which is the time when larvae enter zoea-3. During the rearing, live food ( rotifers  and artemias nauplii ) is still given based on the schedule (Table 1). Moreover, water exchange and aeration are performed to keep the oxygen content and to keep larvae away  Aquatic Science and Technology ISSN 2168-9148 2014, Vol. 2, No. 1 www.macrothink.org/ast 5 from gathering in certain spot. The placement of artificial seagrass in the tank as shelter is  performed in the stage Zoea-4. Table 1. Feeding regime used for culturing the different growth stages of blue swimming crabs in this study Food Stage of the Blue Swimming Crab Larvae Z 1  Z 2  Z 3  Z 4  M C Rotifers Artemias nauplii  Commercial artificial food 1 Commercial artificial food 2  Notes: Particulars: Z = zoea; M = megaloph; C = crab 2.4 Experimental Design and Data Analysis This study is based on the complete random design with 4 treatments and 3 replicates (Gaspesz, 1991). The dose treatments of ME mixed in larval artificial food are: (A1) control (without ME in food), (A2) 1 mg ME /100 g food, (A3) 2 mg ME /100 g food, and (A4) 4 mg ME /100 g food. Data collected in this study are the survival rate of crab larvae which successfully metamorphose to the next stage, the rate of larval development, and factors causing mortality. The Survival rate (%) of each larval stage is calculated based on the number of larvae which are successful to metamorphose to the next stage divided by the number of larvae in each of the beginning of the re-treatments. Larval development is determined based on the modification of Larval stage Index (LSI) of Redzuari et al.  (2012) (Table 2). To calculate LSI and determine factors causing mortality, larvae are identified using dissecting microscope. Morphological characteristics of stadia refer to the instructions  by Arshad et al,  (2006) (Table 3), characteristics of molting syndrome follow the procedures introduced by Hamasaki et al ., (2002), and cannibalism is indicated by an incomplete larval morphological condition. An illustration of the identification of LSI is as follows: If there are 10 larvae in the sampling from each treatment, 7 of them are in the stage Zoea-2 and 3 others are in the stage Zoea-1, so the LSI is: LSI = [(2 x 7) + (1 x 3)]/10 = 1.7 ˜ 2.0, meaning that the larvae is in the stage 2
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