This study aims to evaluate the effects of supplementing golden apple snail (Pomacea canaliculata) eggs powder (EP) in the diet as a source of natural carotenoids on survival, pigmentation and antioxidant activity of Blood parrot. A total of 90 fish were divided into three treatment groups with three replicates per treatment. Blood parrot were fed with diets containing 0 (control), 5 % (EP 5 %), and 15 % (EP 15 %) dry powder of golden apple snail egg for 60 days, and nine fish per group were sampled at 20, 40, and 60 days. No differences in survival of the fish among treatments were found throughout the experiment. The body coloration of Blood parrot was enhanced in the skin and caudal fin with increasing content of golden apple snail egg powder in the diet. At the end of the experiment, the carotenoid content in the caudal fin and the number of scale chromatophores of the fish fed dietary with EP were higher (P < 0.05) than those of the control group. The EP 15 % treated fishes showed a significant higher (P < 0.05) in the activities of SOD after 60 days, but we could not observe significant changes (P > 0.05) in CAT activities. Results demonstrated that golden apple snail eggs can be used as a colorant to promote the pigmentation efficacy of Blood parrot.
Keywords: Golden apple snail egg, Carotenoid, Blood parrot, Pigmentation, Antioxidant activity
Blood parrot is a hybrid of female Cichlasoma synspilum and male Cichlasoma citrinellum artificially cross-bred in Taiwan as early as 1980s (Yang et al. 2012). Currently, Blood parrot is one of the most popular and high-value ornamental fish because of its bright body color, their size is often 10–12 cm. At present, they can be breed and produced with commercial feed in fish farm. Nonetheless, the fish cannot synthesize their own carotenoid color. As the body color is the major factor that affects the market value of ornamental fish, enhancing it by supplementing pigments in diets is therefore necessary (Gouveia et al. 2003; Mills and Patterson 2009; Olson and Owens 1998). Astaxanthin is a pigment widely used in the foodstuff and forage industries as a dietary supplement for developing prospects (Spiller and Dewell 2003). In aquaculture, the carotenoids can be produced synthetically and are commonly used for pigmentation of fishes; furthermore, alternative natural carotenoid sources (yeast, algae, higher plants, and crustacean meal) have also been studied (Büyükçapar et al. 2007; Chatzifotis et al. 2011; Teimouri et al. 2013; Kalinowski et al. 2007; Lee et al. 2010; Pham et al. 2014; Wang et al. 2006; Whyte and Sherry 2001). In addition, carotenoids were reported to be able to change antioxidant activity of fish (Pham et al. 2014; Wang et al. 2006).
Golden apple snail (Pomacea canaliculata) is a freshwater gastropod that has become a serious pest of agriculture and included in the world’s 100 worst invasive alien species (Lowe et al. 2000). This species has invaded several European, North American, and Asian countries and damages rice and aquatic organisms (Accorsi et al. 2014; Horgan et al. 2014; Karraker and Dudgeon 2014). Given the adverse effect of this species, physical, chemical, and biological control techniques have been established; such methods include crop rotation (Wada et al. 2004), use of molluscicides (Cruz et al. 2000; Quijano et al. 2014), and use of predators (Su Sin 2006; Ip et al. 2014; Yusa et al. 2006). As an abundant aquatic living resource, utilization of egg of golden apple snails has been rarely reported.
Apple snail eggs were collected from the trunks or stems of the plants or on the walls above the water in rural paddy fields, lotus ponds, and streams in Ya’an city, Sichuan Province, southwest China, in May 2014. The eggs were dried in an oven at lower than 50 °C and then powdered with a grinder to avoid destructing the components in the eggs. The egg powder was sifted and added to the diet at different proportions. The powder content protein, total lipid, total carbohydrate, ash and moisture are 15.05, 1.96, 0.41, 57.26, 5.55 % respectively.