The Study Of Early Growth And Gonadal Development In Nibea Albiflora (Richard)

The gonadal samples were randomly colleeted in process of Nibea albifloracultivation. Using histological method, the research was about sex differentiation anddevelopment within Nibea albiflora，which was allround and systematic investigation inmicro-level. To gain foundament date, the data was provided for Nibea albiflora biologyand artifical propagation investigate and so on. The results showed as follows:1. The development of embryo was observed by Nikon Eclipse50i microscope, andthe morphological characteristics of Nibea albiflora was also investigated in the larva,juvenile and young stages. The embryo of Nibea albiflora is buoyancy, round andtransparent and the diameter of the egg is0.89±0.028mm. The oil is at the center of the eggand the diameter of the oil globule is about0.025mm. The egg is belong to telolecithal eggand discoidal cleavage. The embryo began to break the membrane after22h30minpost-fertilization at the temperature of24℃and the salinity of27. The embryonicdevelopment was divided into24stages. In the postembryonic development stage, yolk-sacstage was1-3DAH (day after hatching); Larvae of4DAH began feeding, and the yolk-sacdisappeared, entering pre-flexion stage; Larvae of6DAH entered the stage of exogenousnutrients, and the oil globule disappeared; Larvae of16DAH formed the caudal fin boneTam, entering into flexion stage; Larvae of21DAH entered post-flexion stage, meanwhilethe primordial of Dorsal fin, Anal fin, Pelvic fin formed; The fry of26DAH enteredjuvenile stage, and their bodies were covered with chrysanthemum-like melanin; After31DAH, the fry entered young stage, and scales were all around their bodies. The young fishwas same as adult in morphology. At the temperature of25~27℃and the salinity of26~28,the total length correlated significantly with the age of fry, and the linear relation modelbetween total length and age is TL=0.0008d~3-0.0159d~2+0.0738d+2.4212(R~2=0.9942,P<0.05), where TL is total length(mm), d for the day. This study indicates that the growthof total length of juvenile has obviously increased, in order to decrease the cannibal rate, weshould consider the size heterogeneity and prey availability.2. Gonadal development and differentiation of Nibea albiflora (Richardson) wereobserved by using histological techniques．The differentiation stage could be divided intothree phrases，i．e．，the primary，the early differentiation stage and the completedifferentiation stage． Gonad remained undifferentiated36days after hatching． Thepresumptive ovary proliferated more rapidly after36d，and contained clusters of primarygerm cells，some of which came into mitosis．The presumptive testis was small and narrow,which contained less primary germ cells without any mitotic phase． At46days afterhatching，the presumptive ovary began to form an ovarian cavitv and possessed the primaryoocyte．In presumptive testis，the formation of efferent duct and seminiferou tubu1es fist occurred in fish of approximately55days and61days after hatching respectively，Thecytological differentiation of the testis was about19days later than that of theovary．Gonadal development of Nibea albiflora was studied by light microscopy. Thedevelopmental chronology of gonad is composed of5stages. The development of ovariesand testes was asynchronous.3. The metaphase chromosomes of Nibea albiflora (Richardson)and Nibea japonicawere obtained from kidney tissue by the method of PHA and colchicines injection and thekaryotype of these two fish were analyzed. The results showed that both fish had48telocentric chromosomes in the diploid and the karyotype formula was2n=48t, NF=48. Therelative length of chromosomes ranges from3.06±0.20to5.94±0.33in N. albiflora, andfrom2.66±0.14to5.68±0.22in N. japonica. Karyotype data of Sciaenidae species inprevious reports were also collected including N. diacanthus, N. miichthioide andPseudosciaena crocea. The clustering analysis was made for karyotype evolutionarydistance among N. albiflora, N. japonica, N. diacanthus, N. miichthioide, P. crocea. Theresults showed that the relationships between N. albiflora and N. diacanthus, and betweenN. japonica and N. miichthioide, were relatively close based on karyotype evolutionarydistance; and the largest karyotype evolutionary distance (0.0648) were between N.miichthioide and P. crocea, indicating the distant relationship between them. Results fromthe clustering analysis were consistent with the phylogeny based on the morphology ofthese species.