Promotion of a model fish rosy barb（Puntius conchonius）：Embryogenesis，effect of salinity on early development and histopathological toxicity to CCl<,4>
Development of a single celled fertilized egg to a multi-celled，fully differentiated organism has always been a subject of endless information and mystery since centuries.The morphological and physiological changes,which occur in the process of development.are very complex，especially in higher living beings.Inspite of this，the fundamental organization of most vertebrates is generally homologous,making it possible to understand the morphological，physiological and genetic mechanisms in a slower breeding higher organism，including humans via studying some small and rapidly breeding organism.In this work we have focused on various aspects of embryogenesis，effect of salinity on early development and toxicity to a tropical fish rosy barb(Puntius conchonius).which，we hope,may provide information relevant to other vertebrates.
Recently,rosy barb is rapidly becoming a popular model animal for ecOtoxicological and biotechnological studies.However，a study on the complete development of rosy barb embryos from fertilization to hatching was surprisingly lacking.We therefore presented for the first time,a detailed table of normal development of the rosy barb embryos from fertilization until post hatching，which is likely to lay a foundation for research in the fields of development biology and biotechnology.Based on embryological staging by morphological criteria,six broad periods of embryogeneis i.e.the zygote，cleavage，blastula，gastrula and larval periods has been defined.These divisions highlight the changing spectrum of major developmental processes taking place during this period.Furthermore，we have examined the process of neurulation and notocord development occurring during the early stages of this fish.
Fertilization and embryogenesis in most teleosts occur externally，and their embryonic and larval developments therefore are readily influenced by environmental factors including salinity. In order to study the osmoregulatory mechanisms and the effect of salinity on the development of embryos，we exposed 2-4 cell，blastula and gastrula stage rosy barb embryos to 4,6,8 and 10‰ salinity.The results demonstrated that 2-4 cell stage embryos were incapable of tolerating salinities higher than 8‰.and，blastula stage embryos were unable to survive a salinity of 10‰，while，gastrula stage embryos were able to develop to the hatching stage at salinities of 10‰ though the hatching success was markedly reduced(17±2.64 ％).This showed that salinity tolerance of the embryos increased with ongoing development stages.Histological studies of blastula stage embryos revealed that the nuclei and volumes of the cells of cleaving embryos were affected by higher salinity.In addition，we found that higher salinity affected the normal development of the hatching glands resulting in the hatching failure of the larvae exposed to higher salinity.
The liver is one of the main target organs for carbon tetrachloride toxicity.With this in mind，we wished to determine the homology of vertebrate liver with the digestive caecum of the amphioxus via toxicological approach.The 96 h LC50values for rosy barbs and amphioxus was calculated.Based on these values，rosy barbs and amphioxus were exposed to sub-lethal concentrations(5，7.5 and 10 mg/L)of CCl4.It was found that the prominent targeted organ was the digestive caecum in amphioxus and the liver in rosy barbs，suggesting that the digestive caecum of amphioxus is homologous to the liver of rosy barb at least in respect to toxic damages of CCl4.In addition to liver in rosy barbs，other organs affected by CCl4 were the kidneys and gills.In amphioxus,the gills were slightly affected at higher concentration of CCl4.
The ontogenic growth and development on rosy barb is relatively rapid.We undertook a histological approach to study the morphological development of the digestive tract.At hatching，the mouth was closed and the digestive tract was simply a short tube.Liver appeared for the first time on day 4 and mouth opened on day 6 of hatching.By day 22,the digestive tract was almost a complete compact structure representing that of a juvenile consisting of a buccopharyngeal cavity,oesophagus,post-oesophageal swelling and intestine.
rosy barb;embryogenesis;salinity;histopathology;digestive tract
中国海洋大学
博士
Marine Biology
Zhang Shicui
2006
Q178.53
93
2007-08-07（万方平台首次上网日期，不代表论文的发表时间）