Chromosomal complements of two forms of Neanthes japonica (Polychaeta,Nereididae) with evidence of male-heterogametic sex chromosomes

Karyotypes of the brackish-water polychaeteNeanthes japonica (Izuka) collected from five rivers in Japan from 1984 to 1988 were examined with air-drying and flame-drying methods using materials consisting of regenerating tails, clumps of spermatogonia and youngN. japonica specimens (embryos, larvae or juveniles). A diploid number of 28 was determined in well-spread metaphase chromosomes of mitotic cells. The presence of an XX-XY (male heterogametic) sex chromosome system was established for the first time in polychaetes. The Y chromosome was larger than the X chromosome. Slight differences in karyotype were found between two forms (the small- and large-egg forms), which are very similar in adult morphology but can be distinguished by reproductive and developmental characteristics.     

Environmental controls on shell growth rates and δ<Superscript>18</Superscript>O of the shallow-marine bivalve mollusk <Emphasis Type="Italic">Phacosoma</Emphasis><Emphasis Type="Italic">japonicum</Emphasis> in Japan

Microgrowth patterns and the oxygen isotope composition of juvenile, shallow-marine bivalve mollusk shells of Phacosoma japonicum (Reeve) in Japan were analyzed and cross-calibrated with environmental parameters. Mark-and-recovery experiments indicate that a pair of two microgrowth lines and two microgrowth increments is produced every lunar day. This finding makes it possible to assign exact calendar dates to each portion of the shell. Average daily growth rates decrease by 61% from age two to three and 55% from age three to four. The length of the growing season and the growth rate are mainly controlled by temperature: shell growth ceases below 14.2°C (age two) and 16.8°C (age four) and is most rapid between 24.6°C and 27.2°C. Based on local temperature cycles, the growing season is longest in Seto Inland Sea, central Honshu (from May to November) and shortest at Hakodate Bay, North Japan (from June to October). The annual oxygen isotope profiles of the shells reflect the temperature cycle and the varying amounts of freshwater added to the seawater by precipitation. The most negative '¹⁸O values of -3.15‰ occur during the rainy season, i.e. during the monsoon and typhoon seasons. Growth rates are only slightly affected by salinity changes. Strongly reduced growth rates during the second half of the year at Seto Inland Sea and to a lesser extent at Tokyo Bay are explained by nutrient deprivation. Our study provides the basis for the use of P. japonicum in high-resolution ecological studies and environmental reconstructions.     

Effect of modified magnetic field on the ocean migration of maturing chum salmon, Oncorhynchus keta

To investigate the role of magnetic compass orientation in oceanic migrating chum salmon, Oncorhynchus keta, an ultrasonic telemetry study was carried out in the western North Pacific off the coast of Kushiro, Hokkaido. Four salmon were fitted with a tag which generated an artificial magnetic field and modified the geomagnetic field around the head of the fish. Initially, the free-ranging salmon with stomach-implanted ultrasonic transmitters were tracked for a period of several hours before the magnetic field was altered for a period of 16 h. The generator produced an alternating magnetic field intensity of about 6 gauss, with polarity which reversed every 11.25 min. There was no observable effect on the horizontal and vertical movements of the salmon when the magnetic field was modified. However, it was noted that salmon slowed their swimming speed significantly before changing direction, regardless of whether the fish were swimming under the normal geomagnetic field or whether they were swimming under the modified field. Received: 6 April 1997 / Accepted: 29 April 1997     

黄土性土壤对铬砷的吸附量及其吸附形态

采用室内实验方法研究了黄土性土壤对Cr和As的吸附特性及Cr和As在土壤中的吸附和迁移形态。结果表明:(1)随着加入Cr、As质量浓度的增大,黄土性土壤对Cr和As的吸附量逐渐增大,吸附率下降;在同一质量浓度下,黄土性土壤对As的吸附量明显大于对Cr的吸附量。黄土性土壤对Cr和As的吸附都符合Langmuir模型,利用Langmuir模型计算出黄土性土壤对Cr的最大吸附量为146.2μg?g-1,对As为510.8μg?g-1。(2)在平衡溶液pH值为3.0～7.0范围内,随pH增加,黄土性土壤对Cr和As的吸附量逐渐增加,吸附量在pH值为7.0时达最大,随后pH增大,吸附量明显下降。黄土性土壤中Cr被吸附的主要形态是HCrO4-,迁移形态是CrO42-;土壤中As的吸附形态主要为H2AsO4-,而迁移形态则为HAsO42-。     

乡土植物在广梧高速公路生态绿化中的应用

绿化关系到高速公路的长期效益,是生态高速公路建设的重要内容。广梧高速公路的生态绿化,以利用乡土植物为原则,模拟自然生态系统的组成和结构,实现公路景观与周边自然景观的和谐统一。对广梧高速公路双凤至平台段的自然条件、植被类型及植物种类进行了全面调查,结果显示该地域共有维管束植物342种,隶属于95科244属,然后结合植物本身的生物学、生态学及生理学特征,从中筛选出适于本段高速公路两侧绿化带、边坡绿化的乡土植物53种;并根据沿线具体的生境条件,按照群落学的原则对其组合应用进行了设计。     

土壤中元素碳的测定与研究

采用化学方法测定土壤中元素碳的含量。取黄土样品做本方法的平行性实验,平行性良好。取不同粒度周口店土样做对比实验,粒径小于710 mm的原始样元素碳回收最高。同时对元素碳的来源、测定方法、研究意义进行了初步探讨。     

Darkened Xenopus tadpoles appeared with neurochemical agents

Skin darkened tadpoles sometimes appear spontaneously. Darkened was artificially induced in Xenopus larvae by yohimbine or chlorpromazine. These phenomena look like that are seen at pinealectomized or hypothalamus separated Xenopus larva. In this experiment, such a morphological color changed Xenopus larva is suggested by cause of inhibition of alpha2-adrenargic receptor or dopamine receptor from gastrula stages.     

高职《园艺产品贮藏加工》学生创新能力研究与实践

为培养学生创新能力,结合《园艺产品贮藏加工》教学,通过改革传统的教学模式,构建理论为实践服务的实践教学主体教学体系;理论教学融入创新教育,培养学生的创新意识;实验实训,提高学生熟练的操作能力;设计综合实验、培养学生创新能力;结合科学研究、培养学生创新能力.结果表明,能较好地提高学生的综合开发及创新能力.     

Experimental study on acute effects of the combined exposure to temperature increase and chlorination upon the marine copepod Acartia omorii

The acute effects of combined exposure to temperature increase and chlorination on a neritic marine copepod, Acartia omorii Bradford (collected offshore of Onjuku, Japan in 1982), were investigated in the laboratory. Continuous flow exposure and batch exposure modes were compared. Based on the results of continuous flow experiments, the 24-h median lethal concentration (24-h LC₅₀, in mg l^-1) of total residual chlorine was estimated using the multiple regression equation below, with a multiple correlation coefficient of 0.955: 24-h LC₅₀=2.988-0.034 dT-1.611 log₁₀ t where dT is temperature rise (°C) and t is exposure duration (min). In batch experiments, the predictive power of the multiple regression equation was reduced, probably due to variations in chlorine concentration during exposure duration.