INDUCTION OF ECTODERMAL CELLS FROM VEGETAL-ENDODERMAL BLASTOMERES OF AMPHIOXUS(BRANCHIOSTOMA BELCHERI TSINGTAUNESE) EMBRYOS BY THE CALCIUM IONOPHORE A23187

INTRODUCnONAInPhioxusl6-celleInbryosconsistoftwotiersofblastomeres,eighboInalblas-tomeres,A8,andeightvegetalblastomeres,V8(Fig.l).Tungetal.(l958)shOWedthaV8isolatedatthel6-cellstage,whenculndexplan,gaVeriseInainlytointestineandoccasionalltonotochoal,muscleandneUraltube,butneverformedepidends-bendng-ly,thedeveloPmentalfateofV8blastomeresap~tobedetendnedatthel6-cellStag.HOWeVer,thesamauthors(l961)shoWedIaterthatifvegetal-mostblastomersatthe32-cellstage,thedescendansofV8,wereisolateda…     

Artificial culture of amphioxus (Branchiostoma belcheri tsingtauense)

Mature amphioxus (Branchiostoma belcheri tsingtauense) collected by trawl in June, 1994 from Qingdao Shazikou sea area bottom sands, were cultured under controlled indoor conditions, where they spawned and their eggs were fertilized and hatched into larvae which gradually settled at the bottom and dug into the sands after 40-50 days culture in a water trough outdoors. The total survival rate of the larvae(LSR)was 5.5% before they went into the sands, 1.9% in 4 months, 0.7% in 10 months. The survival rate of the young fish which had dug into the sands (YSR) was 35.6% in 4 months, and 12.6% in 10 months. The amphioxus number tended to be constant from the 11th month on. In the first five months after incubation, the amphioxus body length increased by an average of about 1.5 mm a month, and about 0.4 mm a month from Dec. to May of next year. The maximum length after ten months was 24 mm; the average was about 11 mm. After two years culture in the water trough, the maximum length could reach 34-35 mm, when the amphioxus gonads began to develop.     

Morphological and functional studies on the epidermal cells of amphioxus (Branchiostoma belcheri tsingtauense) at different developmental stages

Epidermal cells of amphioxus at different developmental stages were investigated by electron microscopy and colloidal carbon tracing experiments. Amphioxus epidermal cells showed different ultrastructural characteristics at larval and adult stages. The epidermal cells at all larval stages studied (24–96 h) had numerous vesicles containing electron dense materials in their apical cytoplasm. In tracing experiments, carbon particles were found in apical vesicles and interoellular spaces. Under scanning electron microscope, many crater-like protrusions were observed on the surface of the cells. These results indicated that amphioxus larval epidermal cells may be capable of endocytosis. The epidermal cells of 3-month and adult amphioxus were obviously secretory ones characterized by well-developed peripheral filaments, a prominent Golgi apparatus and abundant apical secretory vesicles. This study also showed that adult amphioxus body surface mucus contained lectin that could agglutinate human red blood cells. The authors propose that the epidermal cells of amphioxus larva and adult may contribute to the immune defense of the amimal by different means. Project 3860811 supported by NSFC and study also supported by the Shandong Natural Science Foundation (Grant No. 92D1144).     

Laboratory observation on spawning,fecundity and larval development of amphioxus (Branchiostoma belcheri Tsingtaunese)

Although amphioxus is widespread in temperate and tropical seas, its population is diminishing because of environmental pollution. To keep the population of this evolutionarily important animal from diminishing, study on its reproduction and development is necessary. The main findings in this study on the spawning and fecundity of the amphioxus reared in laboratory and its larval development are as follows. 1. Water temperature markedly affected the spawning. It spawned only when water temperature reached 21°C. 2. Spawning of the amphioxus in laboratory was markedly extended. Initially, the amphioxus spawned at about 7:00 PM, but spawning time was postponed as spawning days went on. 3. The number of eggs produced by a female ranged from 1400 to 12800, average of 5800. This also represents the fecundity of the amphioxus because it shedded all eggs within the ovary at a time. 4. During the first few months of life of the amphioxus, its growth rate changed seasonally. The growth rate in summer and fall was greater than that in winter. 5. The pelagic larva became a benthic adult after 50 days. 6. The amphioxus reared in laboratory from fertilized eggs could produce fertile eggs and sperms. These findings can be a foundation for measures to address the problem of diminishing amphioxus population. Contribution No. 2274 from the Institute of Oceanology, Chinese Academy of Sciences This work was supported by CNNSF, and Chinese Academy of Sciences.