A Preliminary Study On The Developement Of Pigmentcells In Neocaridin Denticulata Sinensis

Neocaridina denticulate sinensis was commonly known as sakura shrimp.It belongs to the Neocaridina,Atyidae,Decapoda,Crustaceans,Arthropoda.Because of its rapid growth,tenacious vitality,short development cycle,easy to breed,and strong breeding ability,so it's a favourable experimental materials.Furthermore,because of its ornamental feature and a variety of different body color obtained through artificial cultivation,it became a popular ornamental shrimp at present.Body color is an important economic character for ornamental animals,and the formation mechanism of body color is the theoretical basis of ornamental shrimp breeding.At present,there are few studies on it's developmental biology.In this paper,the embryonic development and the formation process of pigment cells were described in detail,the pigment composition of the halfbred shrimp was observed and analysized.The results are as follows.1.The embryonic development of N.denticulata sinensis.The embryo process of N.denticulata sinensis is roughly divided into six stages,including: the zygote period,the cleavage stage,the blastocyst stage,the original gastrula stage,the nauplius stage,and the zoea stage.At a temperature of 23 ?,it took about 15 days to finish embryonic development.The zygote of N.denticulata sinensis was oval.After 6~7hours,the zygotes started cleavage.The cleavage stage proceeded about 20 hours.The embryo was cleaved by mintosis into two cells,four cells,eight cells,sixteen cells,thirty-two cells,sixty-four cells,and so on.The embryo volume was invariant,but the number of cleavage balls continues to increase until the entire embryo was full covered.Then he embryo turned into the blastocyst stage,with the surface of the embryo slightly raised,color deepening.About 2~3 days later.The embryo turned into the original gastrula stage.In this period,the cleavage balls on the embryo surface was integrated to form a complete oval,and a transparent film covered on the surface of the embryo.The embryo remained in this state for about 4 to 5 days and turned into the the nauplius stage.The transparent zone begined to appear in the embryonic animal pole.With the differentiation of cells,the early pigment cells appeared in the embryo.At this stage,the cephalothorax was temporarily indistinguishable,heartbeat occured at the later stage of the nauplius stage,about 120 to 140 times /min.Embryo turned into the zoea stage about 2 to 3 days later,and further differentiation continued the yolk continued to shrink,somite produced,and the compound eyes,cephalothorax ostracum,the abdominal and caudal carapace could be observed and the number of abdominal limbs could be calculated,and the types of pigment increased.At this stage,the heartbeat was about 160 to 180 times /min.After 3 or 4 days,they hatched into larvae,the embryonic developmental process came to the end.2.The development of N.denticlata sinensis' s pigment cell.A pair of red pigment cells appeared which located in front of the compound eyes in the nauplius stage(23?,about 6 days after fertilization).Then 7 to 8 red pigment cells appeared and strung on each side of the body.When embryon turned into the zoea stage(25 ?,around 10 days after fertilization),more red pigment cells appeared around the previous red pigment cells.The red pigment cells on cephalothorax were arranged in a mess,meanwhile,the red pigment cells in abdomen were distributed along the central of body segment about 6~7 red pigment cells.At early developmental stages,the red pigment cells normally were in point-like contraction state.At the zoea stage,the yellow pigment cells,blue pigment cells,melanocytes and white pigment cells began to appear,which sporadically spread on cephalothorax.They then gradually spread in other parts of the body,the distribution pattern of them were similar to red pigment cells.3.The characteristics of pigment cells in the hybridized offspring(F1)of the N.denticlata sinensis' s with different strains.The strains of red,blue,yellow,chocolate and transparent were crossbred.The offsprings of hybridization from different strains of N.denticulata sinensis were calculated and the pigment cells in offspring were observed.The offspring usually contains parental types and hybrid types.The number of hybrid types is 3~4 times as that of parental types.The types of pigment cells from hybrid F1 contained all of the parental types.The morphology of pigment cells was variety.The pigment cells were overlapped and existed as pigmental cell clusters.If there were more blue pigment cells,the color was darker,however,if there were more red and yellow pigmental cells,the color was more grey.The color of the parental types was close to the parent and the species of pigment cells were unitary...