Study On Reproductive Biology Of Oratosquilla Oratoria From Pikou Bay, Dalian

Oratosquilla oratoria is a kind of important economic marine animal because of delicious taste and nutritions. In recent years, due to overfishing and environmental deterioration, Oratosquilla resource is in a serious recession. However, demand and market prices continue to rise. In order to protect the existing resources to meet the growing market demand, Oratosquilla breeding is necessary to study. A large number of artificial seed breeding is a key process for artificial breeding. However, the full understanding of Oratosquilla reproductive physiology is a prerequisite to promote this process.To investigate the reproductive biology of mantis shrimp, the population which distributed in the area of Pikou Bay, Dalian was monthly collected from May 2014 to April 2015, randomly. A preliminary study on reproductive biology of Oratosquilla in Dalian Pikou Bay was conducted by the histological technology. Seasonal variations in the reproductive cycle and seasonal changes in biochemical composition(water content, lipid, glycogen, protein) in different tissues(muscle, gonad, hepatopancreas) of the male and female mantis shrimp by using traditional methods. Estradiol and testosterone levels were determined by enzyme-linked immunosorbentassay(ELISA) in the gonad of mantis shrimp. The major results of the study are presented as follows:1. The results showed that there was no difference between the sex ratio with an anticipated value 1:1 except July(χ2=0.500,P>0.05). The sex ratio was changed from 0.79 to 1.34, consequently. The annual mean sex ratio was 1.04±0.05(mean±S.E.). The tendency of gonadal development between female and male were similar while male seemed to be faster than female. Both male and female had two peaks of sexual maturity throughout the year, female was in May and November while male was in April and November, respectively. Oogenesis of mantis shrimp could be divided into oogonium, primary oocyte, secondary oocyte, previtellogenic oocyte, vitellogenic oocyte, early mature oocyte and mature oocyte. And ovarian development could be divided into non-developmental stage, primary oocyte stage, early growth stage, middle growth stage, late growth stage, pre-maturation stage, maturation stage and finally atretic stage. Correspondingly, the spermatogenesis could be divided into spermatogonium, spermatocyte and sperm, while testis development should be divided into four stages: spermatogonium stage, spermatocyte phase, early sperm and sperm phase.2. Biochemical assay results showed that, little change in water containing anniversary of muscle and hepatopancreas of Oratosquilla. The water of muscles all year round is about 80% and of hepatopancreasr is 70% ~ 85%. There is obvious seasonal variation in the water content in the ovary, and the water content is high during the breeding season. The anniversary change of water content in testicle is no obvious. The protein content in the gonad(mg/g wet weight) range of 31.2 ~ 201.31 mg/g. There was a clear peak in May and November. In addition, with the maturation of the gonad, the lipids content increased gradually, providing the necessary nutrients for the development of reproductive. Glycogen concentration in muscle of female have shown two peaks in February and September, respectively, and subsequent decreased during the peaks of reproduction. In hepatopancreas and gonad, we observed the largest reserves of glycogen in the autumn and a subsequent decrease during the transition from autumn to winter in male and female, respectively. These findings suggested that in mantis shrimp, proteins and lipids seem to be an important constituents and energy reserve for the reproduction. Whereas, the glycogen in ovary and male hepatopancreas may be used during the period of intense activity and starvation.3. Estradiol and testosterone levels were determined by enzyme-linked immunosorbent assay(ELISA) in the gonad of mantis shrimp. The range of estradiol level( pg/g wet weight) is 14.80 ~ 43.08 pg/g. At the stage of oocyte maturation, the content of estradiol decreased gradually and increased gradually during theatretic stage, while the highest in the oocyte. The change range of testosterone levels is 6.16 ~ 14.92 pg/g. The content of testosterone reached the maximum at sperm cell stage, later decreased significantly, when the content reaches the minimum period of sperm.The results in this study provide not only for the formulation of Oratosquilla oratoria resource management strategies but also theoretical support and scientific basis.