Study On The Biological Characteristics And Healthy Breeding Technology Of Platichthys Stellatus

Platichthys stellatus is one of the rare fish in northern China and an ideal object for cultivation. In this study, combining the large-scale production of Platichthys stellatus, morphological attributes and early stages of development characteristics were observed and studied systematically by using experimental ecology approaches, physiological methods and many kinds of molecular techniques in the cultured stocks of Platichthys stellatus. Characteristics and status of germplasm resources of cultured stocks of Platichthys stellatus were analyzed and explained from the cytology (karyotype), biochemistry (biochemical compositions of tissues) and molecular genetics (RAPD and AFLP) levels; the germplasm resource status of Platichthys stellatus was stated, and healthy seed production and breeding technology system were also established. This study has laid a theoretical foundation for the protection and breeding of this precious resource which summarized in following 4 aspects:1,The external morphological characters and internal tissue and organ system of cultured Starry flounder were described and measured by traditional morphology and anatomy methods. Regression analysis of Starry flounder's measurable morphological parameters was done by bio-statistics, which shows a significant linear correlationship. TL=1.3864SL-0.3035; the relation of standard length (SL)and body weight(W) presents power function correlation and their general correlation equation was W=0.0339SL3.0606. These results indicated that distinct morphological differences existed between different geographic populations. The skull of Platichthys stellatus has the common characteristic of Pleuronectiformes, especially in that ethmoidal region and orbital region shifts to the side of eyes and urohyal bone is in bow shape. The front half part of hypopharyngeal is grown together and pharyngeal tooth is small. There is a pair of thin otolith with 5-6 Processus mammillaris. Platichthys stellatus has a stomach with "I" shape, and 2-4 pyloric caecums. The liver lies on the side of eyes in the left-eyed Platichthys stellatus. On the contrary, the liver lies on the blind side in the right-eyed ones.Muscle protein, lipids, ash and other biochemical components of cultured Platichthys stellatus were determined, and the concentrations of 16 kinds of common amino acids and major fatty acids were also analyzed. The results showed that Platichthys stellatus is a high-proteined and low-fat fish; Essential amino acids and flavor amino acids showed higher levels. The BCAA/AAA value in muscle protein was 2.33. In the various types of fatty acids, oleic acid (18:1 n) had the highest content, followed by linoleic acid (18:2 n6) and palmitic acid (16:0).2,The genetic diversity of a cultured stock of Platichthys stellatus was studied by using RAPD technology.18 primers selected from 20 random primers were used for stock genetic analysis, and a total of 133 clear RAPD bands ranging from 100 to 2000 bps were recognized. The number of polymorphic bands was 83.1 to 14 bands were amplified by each primer, and the averaged bands amplified by a primer were 7 bands. The mean percentage of polymorphic bands of the stock was 62.41%, and Shannon information index and Nei's diversity index were 0.21 and 0.316 respectively.The AFLP technology was used to analyze the genetic diversity of the cultured stocks of Verasper moseri, Platichthys stellatus and Paralichthys lethostigma.8 pairs of EcoRⅠ/MseⅠprimer combinations were used, and 196,207,187 AFLP bands were amplified for the three, respectively. Within these three stocks, the percentages of polymorphic locus were 26.02%,25.12% and 39.57%, and the Nei's genetic diversity values were 0.1101,0.1587 and 0.1008, while Shannon indexes were 0.1456,0.1566 and 0.2238. Moreover,19 species specific bands were found, and the numbers of exclusive bands found in barfin flounder, starry flounder and southern flounder were 44,34 and 45. The UMPGA dendrogram based on genetic distance values among these three flounders was constructed to reveal the relationship of the species.3,In order to study the early embryonic development pattern of starry flounder, (Platichthys stellatus), the fertilized eggs and larvae, juvenile stages' morphological development attributes were observed and recorded by microscope. The early developmental pattern and time of Starry flounder, (Platichthys stellatus) was established.Hybridization experiments were carried out between Platichthys stellatus♀×Verasper moseri(?),Platichthys stellatus♀×Verasper variegates(?) and Psetta maxima♀×Platichthys stellatus(?), in order to explore the distant hybridization possibility of Starry founder(Platichthys stellatus.). The results showed that incompatibility did not exist between Platichthys stellatus♀×Verasper moseri(?) and Platichthys stellatus♀×V. variegates(?), and the fertilized eggs can develop normally and the filial generation can survive and grow normally. Although the crossbred embryo of Psetta maxima♀×Platichthys stellatus(?) can develop too, the hatched larval was malformed and died 24h later.4,An integrated method for regulating the gonad ripening of parental Platichthys stellatus was established. Furthermore, the optimum temperature range of embryonic development and larvae culture was proposed. A series of breeding technologies were established, including nutrition enrichment and feeding technology in a seed period, suitable breeding density, size of pellet bait and feeding technique in different cultivation periods. Aquaculture products can reach exporting standards.