Study On The Reproductive Biology, Variations In Biochemical Composition During Embryonic Development Of The Procambarus Clarkii Giard

The red swamp crayfish Procambarus clarkii (Cirard) belongs to Decapoda, Reptantia, Cambaridae, Procambarus. It originally distributed in the north of Mexico and the south of America, and was introduced into China by Japanese in the 1930s. Now it distributes in more than 10 provinces of China. This freshwater crawfish has been popular and become one of the main aquatic animals in China recently due to its delicious taste and abundant nutrition. Now it has become one of the most important freshwater aquatic products in the cultivation. However, the natural resource of this crawfish has been decreased dramatically in recent several years because of its economic value and fishing without limit. So the artificial reproduction technique is imminently required to be developed for protecting the resource and for meet the need of the markets. In this study, we have investigated on the reproductive biology and the changes of biochemical components during embryonic development of the Procambarus clarkii Giard. The data may provide a base for developing the artificial reproductive technique.1. Investigation on the reproductive habits of Procambarus clarkii. The reproductive habits of the red swamp crayfish were investigated by outdoor survey and indoor observation. The results are as following: (1) the most feasible method to distinguish the males from the females of this crawfish is based on their pleopods. The ends of the last two pairs of pleopods in males are white and extend ventrad to thorax. While, the pleopods of females do not look white. (2) the mating and spawning of Procambarus clarkii do not need ecdysis, which is different from some other prawns, such as Macrobrachium rosenbergii. Therefore, some literatures saying that the red swamp crayfish need ecdysis before mating are not true. (3) in areas around Wuhan, the red crawfish has two main reproductive period, one is around May, and the other one is around mid-October. (4) the amount of spawning of the female is mostly about 200-300 at one time. We never observed the amount was up to 1,000 as some reports. (5) embryogenesis of this crawfish normally lasts 25-33 days at the water temperature of around 25℃.2. Variations of biochemical components during embryonic development of the Procambarus clarkii Giard. The biochemical components in 5 different embryonic developing stages were analyzed. The results showed that the water in the embryos was increased with the processing of embryogenesis. The zoea before hatching contains most water comparing with the other developing stages before. The content of both total carbohydrate and total protein were decreased with embryonic development. The carbohydrate content reduced from 5.65% of dry weight in the fertilized egg to 1.9% in the zoea. The protein declined from 63.3% of dry weight in the fertilized egg to 41.8% in the zoea. The total amino acid content displayed the parabola shape. The fertilized egg contained 52.72% of amino acids. When the embryos developed to cleavage stage, the ratio of amino acids reached to 60.22% of dry weight. Then the percentage reduced to 47.94% at the zoea stage. In the essential amino acids (EAA), the ratio of Leucine was relatively higher, while the content of glutamine acid was relatively more in the nonessential amino acids (NEAA). With the development of embryos, the fatty acid of C18:3(n-3) and C20:5(n-3) were gradually decreased. Yet in general, the contents of the fatty acid did not change a lot. These results suggest that protein and amino acid are the main nutrition in the process of embryonic development, which were not only used to build the embryonic tissues and organs, but also to provide the energy for developing embryos. On the other hand, the embryos of the red crawfish contain high amount of polyunmatured fatty acids, which is required for human body. So it is a good resource for exploiture.