STUDY ON GAMETOPHYTE VEGETATIVE GROWTH OF UNDARIA PINNATIFIDA AND ITS APPLICATIONS

When cultured under certain environmental coriditions (25℃, light intensity 80 μmol/m~2 ·s, LD12/12, in enriched seawater medium with 7 × 10~(-4)mol/L NO_3,-N, 1.56× 10~(-4)mol/L, PO_4-P and supplementsof other elements like Mn, Fe, I, etc.), mate and female gametophytes of U pinnatifida keptgrowing vegetatively and propagated fast at average daily fresh weight increase rate of about 20%. Theempirical formula G_m=G_o. 3~m was established to estimate the output of vegeative gametophytes. Vigorousvegetative gametophyte cells began to form reproductive structures (oogonium and spermatangium, whenthe tmperature was lower than 25℃ and other environmental factors wrre kept optimal. The sufficientsupply of gametophyte cells provided enough seeds for raising Undaria sporelings on prodiction scale.Controlled cross-breeding experiments using selcted male and female gametophyte clones which increasetheir cell number by mitosis instead of meiosis were also carried out in vitro. Juvenile sporophytes fromthe cro     

Reproductive periodicity in Evechinus chloroticus in the Hauraki Gulf

Test diameter and gonad volume were recorded over 1 year for bimonthly samples of Evechinus chloroticus (Valenciennes) from each of 3 subtidal populations 10 km apart in the Hauraki Gulf. Histological analysis was used to relate cellular events during gametogenesis to the annual cycle of change in gonad size. Mean gonad sizes of the different sea urchin populations were compared by analysis of covariance. Gametogenesis began in the spring, and major spawning occurred in mid to late summer. The proportion of the gonads taken up by nutritive phagocyte cells increased from autumn to spring. During proliferation and growth of gametes the nutritive phagocytes declined in abundance and globulation, suggesting that reserves stored in these cells were transferred to developing gametes. Gonad size doubled during gametogenesis, declined after spawning, and remained low in autumn and winter. Differences in gonad size between populations were significant during most of the year, and were most pronounced in mid summer. Although synchronous gametogenesis occurred in the 3 populations studied, spawning occurred at different times. This suggested that spawning in this species was induced by factors acting either within sea urchin populations or over distances of a few km or less.     

Circadian rhythms in the growth and reproduction of the brown alga Undaria pinnatifida and gametogenesis under different photoperiods

Circadian growth rhythm of the juvenile sporophyte of the brown alga Undaria pinnatifida was measured with the computer-aided image analysis system in constant florescent white light under constant temperature (10 ℃). The growth rhythm persisted for 4 d in constant light with a free-running period of 25.6 h. Egg release from filamentous gametophytes pre-cultured in the light-dark regime was evaluated for six consecutive days at fixed time intervals in constant white light and 12 h light per day. Egg release rhythm persisted for 3 d in both regimes, indicating the endogenous nature. Temporal scale of egg release and gametogenesis in 18, 16, 12 and 8 h light per day were evaluated respectively using vegetatively propagated filamentous gametophytes. Egg release occurred 2 h after the onset of dark phase and peaked at midnight. Evaluation of the rates of oogonium formation, egg release or fertilization revealed no significant differences in four light-dark regimes, indicating the great plasticity of sexual reproduction. No photoperiodic effect in gametogenesis in terms of oogonium formation and egg release was found, but fertilization in short days was significantly higher than in long days. Results of this investigation further confirmed the general occurrence of circadian rhythms in intertidal seaweed species.     

CYTOLOGICAL COMPARISON OF GAMETOGENESIS OF SCALLOPS,ARGOPECTEN IRRADIANS AND CHLAMYS FARRERI

ＩＮＴＲＯＤＵＣＴＩＯＮＫｎｏｗｌｅｄｇｅｏｆｇａｍｅｔｏｇｅｎｅｓｉｓｉｎｖａｌｕａｂｌｅｍａｒｉｎｅａｎｉｍａｌｓｉｓｖｅｒｙｉｍｐｏｒｔａｎｔｔｏｃｏｍｍｅｒｃｉａｌｆｉｓｈ ｅｒｙ.Ｇａｍｅｔｏｇｅｎｅｓｉｓｉｎｂｉｖａｌｖｅｓｗａｓｅｘｔｅｎｓｉｖｅｌｙｓｔｕｄｉｅｄａｔｄｉｆｆｅｒｅｎｔｌｅｖｅｌｓ (Ｄｏｈｍｅｎ ,1 983 ;ＤｏｒａｎｇｅａｎｄＬｅＰｅｎｎｅｃ ,1 989ａ,ｂ) .Ｓｃａｌｌｏｐｓａｎｄｏｔｈｅｒｍａｒｉｎｅｂｉｖａｌｖｅｓｈａｖｅｓｉｍｉｌａｒｒｅｐｒｏｄｕｃｔｉｖｅｃｙｃｌｅ…     

CYTOLOGICAL COMPARISON OF GAMETOGENESIS OF SCALLOPS, ARGOPECTEN IRRADIANS AND CHLAMYS FARRERI

Histological characteristics of gametogenesis of two kinds of scallops, gonochoric Chinese scallop, Chlamys farreri and hermaphroditic bay scallop, Argopecten irradians were investigated in this study. Spermatogenesis in C. farreri has different developmental stages: spermatogonia, primary spermatocyte, second spermatocyte, spermatid and spermatozoon. A large number of same developmental stage spermatic cells converge at a definite area of the testis. Premeiotic, previtellogenic and vitellogenic oocytes can be found during oogenesis in C. farreri, where oocyte distribution is obviously irregular. The A. irradians gonad consists of two different parts in one individual: one part functions as testis, the other as ovary. Between these two parts is a special appearance area, where a large number of spermatic cells are bound with two layers of acellular substance with many oocytes in it.     

Characterization,Expression and Function Analysis of DAX1 Gene of Scallop （Chlamys farreri Jones and Preston 1904） During Its Gametogenesis

DAX 1,a member of nuclear receptor superfamily,has a function in the sex determination and gonadal differentiation of several vertebrate species.However,little information about DAX1 of invertebrates is available.Here we cloned a homolog of scallop （Chlamys farreri Jones and Preston 1904） dax1,Cf-dax1,and determined its expression characteristics at mRNA and protein levels.The cDNA sequence of Cf-dax1 was 2093 bp in length,including 1404 bp open reading frame （ORF） encoding 467 amino acids.Unlike those of vertebrates,no conserved LXXLL-related motif was found in the putative DNA binding region of Cf-DAX1.Fluorescence in situ hybridization showed that Cf-dax1 located on the short arm of a pair of subtelocentric chromosomes.Tissue distribution analysis using semi-quantitative RT-PCR revealed that Cf-dax1 expressed widely in adult scallop tissues,with the highest expression level found in adductor muscle,moderate level in mantle,gill and testis,and low level in kidney,ovary and hepatopancreas.The result of quantitative real-time PCR indicated that the expression of Cf-dax1 was significantly higher （P＜0.05） in testis than in ovary at the same stage,showing a sex-dimorphic expression pattern.Furthermore,immunohistochemical detection found that Cf-DAX1 mainly located in spermatogonia and spermatocytes of testis and in oogonia and oocytes of ovary,implying that DAX1 may involve in gametogenesis of bivalves.     

夜光藻高效培养方法建立及其有性繁殖发生机制的初步研究

夜光藻(Noctilucascintillans)是典型的赤潮生物,在世界多个海域形成过大面积赤潮,对海洋生态系统构成一定的威胁。夜光藻赤潮的发生不仅受外界环境因子的影响,其有性繁殖的方式在赤潮发生过程中也起着重要作用。本研究从连云港海域分离获得一株夜光藻,利用自行设计的饵料藻投喂装置,以天然海水为培养基,在温度20～25℃范围内实现了夜光藻的室内长期培养,并观察记录了夜光藻配子发生全过程。研究结果表明,夜光藻不同生长阶段培养体系中配子母细胞与营养细胞密度变化趋势基本一致,显示夜光藻的有性繁殖发生与种群丰度存在一定的相关性,但它们之间的因果关系还有待进一步探讨。本研究结果加深了对夜光藻有性繁殖的认识,有助于阐明其种群增长模式,并深入理解其赤潮暴发机制。