Studies On Karyotype And Digestive Physiology Of Platichthys Stellatus Pallas

This paper detects the Karyotype in traditional method.Histological changes of the digestive system and its associated glands are observed and analized by morphologic and slice technology from the first day (post-hatch) until 30 dph,and the activities of some digestive enzymes are assessed during the larval and juvenile development of Platichthys stellatusPallas,also including the influence from temperature and pH.The aims of this work are to instruct the genetics research,improve nutritional requirements and manual technology.The results of the work are summarized as follow:1,The karyotype of Platichthys stellatus Pallas is prepared from head kidney by PHA and colchicine injection and air drying method.,The karyotype is analyzed.The results show that the chromosome number of the species was 2n = 48,including 46 telocentric chromosomes and 2 submiddle chromosomes and there is no visible evidence of the sex chromosome and satellites.The karyotype formula is 2n = 48,2sm+46t,NF = 50.2,Histological changes of the digestive system and its associated glands are studied in Platichthys stellatus Pallas from the first day(first day post-hatch dph)until 30 dph.Specimens for this study are maintained at 11.0-13.5℃.The digestive duct is a straight tube lying dorsal to the yolk sac at the newly hatched larvae,while the mouth and anus are not opened.At mouth opening(4-5dph),lengthening of the digestive tract, mucosae differentiation and pancreas and liver appearance are the most apparent elements.The yolk is gradually resorbed and disappeared on 6 dph,while the digestive tract is differentiated into six portions: buccal-pharyngeal cavity,esoDha gus,stomach,anterior,posterior intestine and anus.The larval digestive system is morphologically ready to process external food at this time.The days from 6dph to 10dph are the mixed nutrition periods.During the following periods of independent life the most noticeable events occurring are an increase in mucosal folding,cellular differentiation in the luminal epithelia,gut segmentation and looping.Thus,these digestive tract and associated glands become mature gradually and complete the morphological digestive features characteristic with increasing age and feeding activity.Gastric glands are observed around 21dph,which indicates the passage through the juvenile period.3,In order to improve nutritional requirements and manual technology, the varitions in activities of main digestive enzymes(acid protease, alkaline protease) and alkaline phasphatasein different development stages of Platichthys stellatus Pallas are determined.It is shown from the determined results that the activities of acid protease can be detected when the mouth is open,and rise to the maximum gradually (12dph),then turn down rapidly until 27dph.Alkaline protease show a low level when the mouth is open,especially in 2dph and 6dph,but in 12dph it is the highest and then keep steady-going.The noticeable amylase activity is exhibited in the early larval stage and reaches the highest in 6dph and then keeps at a low specific activity level till 21～24.The alkaline phosphatase activity increases rapidly and steady except 6dph and 21dph,it reaches to the top in 24dph.which indicates the maturity of enterocytes and the improvement of digestive mechanism of intestines. 4,In this paper,the effects of temperature and pH on the protease and amylase digestive enzyme activities in Platichthys stellatus Pallas are studied.The results show that the temperature and pH affect protease and amylase digestive enzyme activities obviously.In definited range,the activities get up as the temperature and pH and then get down when exceed the best.The optimum temperature of protease and amylase activities in stomach,foregut,midgut and hindgut are 40℃and 45℃,40℃and 45℃, 40℃and 45℃,50℃and 45℃respectively.The optimum pH values of protease and amylase activities in stomach,foregut,midgut and hindgut are 2.0and8.0,8.5and8.0,8.5and8.0,8.0and8.5.