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Indian J. Fish., 59(4) : 163-168, 2012
Diet and eyestalk ablation induced changes in lipid and fatty acid composition of female spiny lobster Panulirus homarus (Linnaeus, 1758) M. ANBARASU*, R. KIRUBAGARAN AND N. V. VINITHKUMAR National Institute of Ocean Technology, Ministry of Earth Sciences, Tambaram, Pallikaranai Chennai - 600 100, Tamil Nadu, India *Mandapam Regional Centre of Central Marine Fisheries Research Institute, Ramanathapuram - 623 520 Tamil Nadu,- India e-mail:
[email protected]
ABSTRACT One of the obstacles to successful spiny lobster farming is the lack of a suitable formulated feed to rear early juveniles to marketable size. An experiment was carried out to examine the effect of diet and eyestalk ablation on the fatty acid profiles of the female spiny lobster (Panulirus homarus). The normal and ablated juvenile lobsters were stocked separately in three FRP tanks, each holding 1000 l filtered seawater. Experimental (pelleted feed) and control (green mussel) diets were fed ad libitum daily at 1830 hrs for 30 days. At the end of the 30 days trial, the total lipid content was high in the hepatopancreas and muscle tissue (162.2±8.1 and 110.2±5.8 mg g-1 respectively) of unablated lobsters fed with pellet diet compared to that of green mussel fed lobsters (104.6±6.1 and 76.4±4.7 mg g-1, respectively). The fatty acid composition of the hepatopancreas and muscle of ablated and unablated lobsters reflected the respective dietary treatments. Polyunsaturated fatty acids (PUFA) content was high in the muscle of unablated lobsters fed pellet diet (21.94±0.36%) compared to that of other groups. The formulated diet played a major role in maintaining the essential fatty acids levels, especially PUFA in the muscle tissue of juvenile lobsters. Keywords: Eyestalk ablation, Fatty acid, Feed, Panulirus homarus, Spiny lobster
Introduction Spiny lobsters are important candidate species for mariculture and sea farming in India. The prospects for the culture of these species have been long thought of and have been studied and reviewed by many workers (Radhakrishnan, 1994, 2000; Rahman and Srikrishnandas, 1994; Radhakrishnan and Vijayakumaran, 1996; Raghavan, 2000). Fattening of spiny lobsters has also been regarded as a lucrative venture (Sakthivel, 2002). Lobsters are carnivorous and accept a wide range of feeds. However, they are most often reported as selective feeders and prefer shellfish/finfish as their food. Green mussel is the most preferred diet as also clam meat and trash fishes (Griffiths and Seiderer, 1980; Joll and Phillips, 1986; Barkai et al., 1996; James and Tong, 1997; 1998; Radhakrishnan, 2000; Mayfield et al., 2001). The recent practice is feeding spiny lobsters in fattening ponds with green mussel, clam meat as well as smaller crustaceans (Radhakrishnan, 2000; Rajeev Raghavan, 2000). The disadvantages of such fresh feed are high cost, fluctuations in availability, inconsistent nutritional value, need for frozen storage, water quality deterioration and increased risk of transmission of pathogens. Successful
culture of any crustacean under controlled conditions requires the availability of a nutritionally balanced diet and effective feed management strategies. In the near future, commercialisation of spiny lobster aquaculture will require the development of either indoor or outdoor intensive culture systems where all nutrient requirements have to be met by providing formulated feeds. Several reports are available on biochemical as well as nutritional studies on various species of spiny lobsters distributed in the Pacific and Atlantic Oceans and also the Far East Asian waters. (Lemmens, 1994; James and Tong, 1997; Crear et al., 2000; Phleger et al., 2001; Thomas et al., 2003). In India, experimental studies on the biochemistry and nutrition of common species of spiny lobsters have been conducted by Vinith Kumar et al. (2002) and Dharani et al. (2002). However, very few studies have reported on the lipids and fatty acid composition of spiny lobsters as well as their optimum requirements for survival and growth. The present study was undertaken to elucidate the variations in lipid and fatty acid profiles of eyestalk ablated or unablated female Panulirus homarus (Linnaeus, 1758) after feeding with green mussel and a formulated diet.
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Materials and methods Experimental animals Wild caught female juvenile lobsters (P. homarus) were purchased from local fisherman at Royapuram, Chennai, south-east coast of India. They were brought to the laboratory and acclimated for 10 days during which period they were fed with green mussel. Subsequently, the healthy animals were selected for the experimentsal rearing. Selected animals were randomly separated into two groups. Group 1 fed with green mussel Perna viridis (D1) served as control and group 2 fed on formulated pelleted feed (D2) (Table 1) served as the experimental treatment group Table 1. Composition of the formulated diet (D2)
collected were dried and weighed for calculating the feeding rate. The same procedure was followed for the control animals fed with fresh green mussel. The experiment was terminated after 30 days, and animals were weighed and the carapace length, total body length and moulting stages were noted. Further, the animals were sacrificed and the hepatopancreas and tail muscle were dissected out and frozen at –20 ºC until further analysis. Water stability of diet Water stability of the diet was done as per Jayram and Shetty (1981) with minor modification as reported by Sridhar et al. (1999). Fifteen gram of each diet was weighed in three replicates and transferred to 4"x 4" pouches made of bolting silk. These were then immersed in 4 l of water in plastic tubs with mild aeration. The pouches were removed from water at 1, 2, 3 and 4 h respectively and rinsed well in distilled water. The contents were then transferred to pre-weighed petridishes and dried in a hot air oven at 80 °C and the resultant loss in dry matter calculated.
Ingredient
g 100 g dry diet-1
Squid meal
30.00
Spirulina
10.00
Fish meal
25.00
Wheat flour
25.35
Cod liver oil
6.50
Chemical analyses
Vitamin and mineral mix
2.15
Binder (Guargum)
1.00
Control and formulated diets were analysed for proximate composition according to standard methods (AOAC, 1990). Fatty acid composition of the diets and lobster tissues were determined by gas chromatography with flame ionisation detector (GC-FID). Total lipids were extracted by gravimetric procedure as per Folch et al. (1957). Methyl esters for constituent fatty acids were prepared by the method of Kashiwagi et al. (1997). Fatty acid composition of samples was analysed by Gas Chromatograph provided with flame ionisation detector (Thermaquest) using a capillary column (Alltech 30 m x 0.32 mm; film thickness, 0.25 µm). Operating parameters were column temperature –210 °C, detector temperature – 250 °C, carrier gas He 30 ml min-1. The fatty acid methyl esters were identified by comparing their relative retention times and equivalent chain lengths with that of authentic standards procured from Sigma.
Experimental set-up Female P. homarus juveniles were subjected to two dietary treatments (D1 and D2) with or without bilateral eyestalk ablation. Prior to the experiment, the molt stage of each animal was determined based on the condition of the setae on the uropods (Aiken, 1973). Only intermolt animals were used in the experiment. Ablation was performed by securing the base of the eyestalk with a pair of hot fine forceps and using a sterilised pair of fine scissors to excise the eyestalk just above the position of the forceps. The hot forceps effectively closed and cauterised the excision. To minimise stress in bilateral ablation, only one eyestalk was ablated at first and the other eyestalk on the following day. Each treatment had three replicates comprising 6 lobsters each, with average carapace length (CL) of 40.6±0.4 mm and body weight (W) of 102.9±5.3 g. The juvenile lobsters were stocked in three units of 1000 l FRP tanks filled with filtered seawater. Six animals were stocked in each tank. The tanks were provided with continuous aeration throughout the feeding trial. The water quality parameters were maintained within the range recommended for lobster culture (Pillips et al., 1980). Thirty five percent water exchange was carried out daily and complete water exchange was done every third day. Diets were fed ad libitum in a single daily dose at 18 30 hr. Tanks were cleaned and the uneaten feed were collected the following morning after the feeding. Uneaten feed
Statistical analyses One way ANOVA was performed along with Newman- Keul’s test (p
