| Pomacea canaliculata is the only freshwater snail listed among the 100 worst invaders worldwide, as well as one of the 16 most dangerous invaders in China. This snail has invaded in China for more than 30 years, researchers have been done many studies on the invasion mechanisms and control methods of P. Canaliculata in this period. This article conducted the environmental adaptability, abilities of establishment of population and survive of P. canaliculata by study the fecundity and shell regeneration, as well as the feasibility of P. canaliculata eggs as aquaculture feed to enhance the body color of ornamental fish. The results are as follows:1 Fecundity of golden apple snail, Pomacea canaliculata, in Sichuan area. Egg masses of P. canaliculata were collected monthly from three habitats including reservoir, rice field and irrigation canals and ditches in Ya'an, Sichuan Province from March to October 2012 and the fecundity and breeding seasons of P. canaliculata was studied by using the methods of collecting snail eggs in the fields and breeding in the laboratory. The field investigation results indicated that P. canaliculata breeding seasons are from March to October in Ya'an. Egg numbers per egg mass ranged from 33 to 621 (average 233.30) individual eggs per mass with a coefficient of variation of 55.0%. The egg diameter ranged from 2.17 to 3.20 mm (average 2.60), coefficient of variation was 8.95%. The number of eggs was significantly positively correlated with the weight of egg masses (y=80.906x+31.469, R2=0.854). The absolute fecundity of P. Canaliculata in May was the highest (403.1 eggs/mass), there was a difference (P<0.05) between that and the value in other month from March to October. The absolute fecundity from reservoir was higher (P<0.05) than that from rice field and irrigation canals and ditches by comparison fecundity from three kinds of habitats (reservoir, rice field and irrigation canals and ditches). Meanwhile, a comparative study on fecundity of P. canaliculata collected from Chengdu, Ya'an and Ziyang was also conducted by using the single-pair mating method in laboratory. The results showed that the female individual weight relative fecundity were 12.33,9.58,10.54 eggs per gram of snail body weight, and shell height relative fecundity were 4.55,3.92,3.54 eggs per millimetre of the snial shell height, respectively. The individual weight and shell height relative fecundity of P.Canaliculata from there aforementioned areas had no difference (P>0.05).2 The variation of haemocyte and calcium content of Pomacea canaliculata during the shell regeneration.After excision of shell from P. canaliculata, survival rates, repair process, haemocyte response and calcium content were observed and measured. The following experimental treatments were used:large shell heights with black-coloured (BL-group) or yellow-coloured (YL-group) snail, small shell heights with black-coloured (BS-group) or yellow-coloured (YS-group) snail. The survival rates in BL-, YL-, BS- and YS-group after making partial excisions of snail shell were, respectively,93.59%,94.87%,92.31% and 96.15%, and each group were no significant difference (P>0.05). Freshly regenerated shell could be seen at 1 day among the four groups after induction of shell regeneration (AISR). Regeneration shell filled the wound had occurred at 5-10 d AISR. The area of regenerated shell of yellow-coloured was significant higher (P<0.05) than that of black-coloured at 15d, but the thickness of regenerative shell was no significant difference (P>0.05). Multiple (three times) induction of shell regeneration significant (P<0.05) enhanced the thickness of newly formed shell. Two types of circulating haemocyte (hyalinocytes and granulocytes) were identified under light microscopy based on Wright's staining. Artificial induction of shell regeneration, rendered a significant (P<0.05) increase in the number of total circulating haemocytes, which was followed by decrease to pre-wounding levels levels. This peak value was 2.86.2.43,1.69 and 1.71-fold higher (P<0.05) than pre-wounding levels in group BL, YL, BS and YS, respectively. The number of total circulating haemocytes in yellow-coloured individuals was significant (P<0.05) higher than black-coloured. It is alleged that calcium content in mantle presented decrease and then increase trend, at the end of experiment, it returned pre-wounding levels, which similar to the trend of number of total circulating haemocytes. This study has revealed that apple snails have good shell regeneration abilities, and that haemocytes and calcium transportation probably play a crucial role in shell growth and regeneration.3 Effects of dietary supplementation of golden apple snail (Pomacea canaliculata) egg dry powder on survival, pigmentation and antioxidant activity of blood parrot.This study aims to evaluate the effects of supplementing golden apple snail (P. canaliculata) eggs powder 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%(5% group) and 15%(15% group) 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 (100%) 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 experiment, the carotenoid content in caudal fin and the number of scale chromatophores of the fish fed dietary with eggs powder were significant higher (P<0.05) than those of the control group, the carotenoid content in skin of 15% group was significant higher (P<0.05) than the control group.The eggs powder 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, high content of eggs powder could increased the antioxidant enzymes activities.In conclusion, P. canaliculata has the characteristics of long reproduction period and strong fecundity, these characteristics may help the populations establishment of this snail and promoted invasion and spreading. The ability of fast shell regeneration and low mortality after induction of shell regeneration in P. canaliculata show survival advantage of this species, as well as guaranteed the continuation of populations. This paper preliminary proved that the eggs of P. canaliculata have utilization value and set a foundation for further study about limitation the number of P. canaliculata by utilization of the eggs of P. canaliculata. |
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