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关键词： 海洋浮游动物   新动向   磷虾   南极海   海洋浮游生物   挠足类   浮游生物学  

摘要： 蓝色的海洋蕴藏着丰富多采的水产资源,浮游生物就是水产资源的重要组成部分,不但数量大①,种类多,并且分布广,遍及世界各海。它的营养和经济价值不亚于鱼类——它既是经济鱼、虾类的饵料基础,又是人类的食物来源之一。我国沿海盛产的海蜇(Rhopilema)(图1)和毛虾(Acetes)(图2c)两种浮游动物就是普遍食用的海产品。随着世界人口的不断

关键词： 底栖动物   采样点   生态学   渡口   底栖生物   生物指数   耳萝卜螺   沈阳市   生物学  

摘要： 前言浑河是沈阳市的主要河流起源于清原县,流经抚顺市、县、沈阳市,辽中县至韭菜台附近入辽河,再由营口入海。由于沿途各县、区工业废水的排放,几乎使整个河道都受到了不同程度的污染。浑河流经沈阳市区的南侧,又是沈阳地区水系的主体,还有许多支流和明渠,构成了沈阳地区的河水网。为了摸清沈阳市水体污染程度,在沈阳市环境保护研究所的主持下,开展对沈阳市环境质量评价的研究,我们承担了《用底栖动物对沈阳市水体污染的

关键词： Median Survival   Life Span   Natural Habitat   Polychaete   Reproductive Biology  

摘要： Specimens from a presumably hybrid population of Autolytus spp., with A. prolifer and A. brachycephalus as extreme phenotypes, and including all intermediates inbetween, were used throughout this investigation on reproductive biology and ontogenesis. Laboratory culture of larvae, juvenile and adult individuals was successful, using laboratory-bred Eirene viridula (Hydrozoa) as food instead of Dynamena pumila on which this genus feeds in its natural habitat. Schizogamous reproduction of the asexual nurses by formation of sexual stolons was studied in detail. The observed mode of stolon formation was not consistent with earlier descriptions: it could neither be termed strictly scissiparous nor gemmiparous. Not only stock setigers but also, segments added by the prepygidial proliferation zone contribute to the very 1st stolon and also to some of the subsequent stolons. Incorporation of stock setigers into stolons led to size-reduction of the nurses. Gemmiparous stolons were formed intermittently. Contrary to earlier reports, a proliferative segment which produces all stolons except for the 1st of a stolon chain was never observed. A separate proliferation zone was generated for each new gemmiparous stolon. The further differentiation of stolons was observed, setiger formulae for stolons of both sexes were established and a sex-specific pattern of development of stolonial head appendages was detected. Oocytes are produced in the terminal setigers of the nurse and are transferred to the adjacent stolon after its head has begun to develop. Testes and sperm were found exclusively in the anteriormost setigers of the stolons. Mating and egg-laying of stolons was observed and ontogenesis of 99 larvae, hatched from the egg sac of 1 single female, was studied. No larval or deutometameres were simultaneously formed, but setigers were produced one by one. No setigerous segment was ulteriorly integrated into the peristomium as in nereid larvae. Stolons were formed at the earliest

关键词： Crustaceans   Integers   Seasons   Estuaries   Female animals   Plankton   Salinity   Cooling  

摘要： Changes in the abundance and composition of crustacean populations in the plankton of the Severn Estuary (England) were followed for 25 mo. (1973-1975). The collections were made primarily near shore from the cooling intake of the Oldbury nuclear power station. Neomysis integer overwintered at comparatively low densities with all specimens measuring more than 5 mm in length. Inshore swarms of this species were detected early in the summer and most females carried either eggs or embryos. Praunus flexuosus invariably occurred less frequently than N. integer. During the summer, inshore aggregations of adults were probably formed and, although large numbers of berried females were observed at this time, the release of young possibly never occurred in the Oldbury region. Eurytemora affinis was observed only during periods of low salinity in winter with maximum reproductive activity taking place in Dec. The highest density of Eurydice pulchra occurred early in the summer due to the recruitment of young while, at other times, this species remained comparatively rare. The same pattern was observed in Gammarus salinus but since only a few females carried eggs at any 1 time reproduction must take place outside of the study area. Crangon crangon maintained greatest numbers during the summer and fall, being almost absent during part of the winter. The growth rate, size at maturity and period of reproductive activity of this species different from earlier accounts on Severn populations.

关键词： Hearing   Sound discrimination   Acoustic pattern recognition   Acoustics   Agroacoustics  

摘要： The sense of hearing has become highly developed and specialized in the mammals relative to the other tetrapods. Increases in absolute sensitivity to acoustic stimuli and in the audible frequency range, and enhanced differential acuity to the different dimensions of auditory stimuli such as frequency and intensity have contributed to the success of the mammals as a group. Evolutionary changes in the structure of the middle ear conducting system, in the cochlea, and, to a lesser extent, in the central nervous system are presumed responsible. The considerable variation in auditory capabilities in the various orders and families reflects the different selective pressures which have played a major role. In some mammals, orientation and navigation have emphasized extended high‐frequency sensitivity, while in others the obvious adaptive value of a tightly knit social organization has placed a premium on the fine discrimination of the small but significant changes in the acoustic patterning of intraspecific communication sounds. Some of the factors thought to be responsible for the evolution of hearing in the early mammals will be discussed, and a comparative analysis of mammalian hearing in living species will be presented. [Research supported by NSF.]

关键词： Science   Humanities and Social Sciences   multidisciplinary  

摘要： TWO international meetings devoted entirely to echinoderm biology have taken place this year : in March, the Third International Echinoderm Conference was held at the Australian Museum, Sydney, and in July a meeting was organised principally for European workers at Bedford College, *** both meetings this year, the proportion of papers offered on the various groups of echinoderms was remarkably similar: notably, about a quarter at each were devoted to starfishes, and a tenth to palaeontological aspects. A major difference in the coverage was that at Sydney about a quarter of the papers were taxonomic, reflecting perhaps the present concentration on this type of work in the Australasian area, while in London only a single paper (by an Australian) was *** would have been all too easy for the Sydney meeting to have been dominated by papers on the coral-devouring Crown-of-Thorns Starfish, but the convener, F. W. E. Rowe (Australian Museum), wisely rationed this subject to three papers. One of these referred to the possible cyclic occurrence of population explosions in this starfish. Elderly fishermen have said that they recall abnormally large numbers of Acanthaster being present on the Great Barrier Reef at about the turn of the century, and E. Frankel (University of Sydney) has examined cores taken from the reef talus in several areas to see if he can identify abnormally high concentrations of the disarticulated skeletal ossicles of this starfish among the broken coral and other material through the cores. He has assumed that the relative occurrence of these ossicles at the various levels in the cores might reflect the relative abundance of the starfish at the time the debris was being abraided from the reef. So far, Frankel has gone back 900 years, and, while not yet recording evidence of a plague 70 or 80 years ago (at the turn of the century), he has recorded higher-than-normal incidences of remains of Acanthaster at 110, 185 and 450 years *** conv

关键词： 嗜温菌   微生物分析   食品   好气菌   动物饲料  

标准号: NF V08-201-1978

摘要： La présente norme décrit des méthodes d'examen microbiologique concernant les produits destinés à l'alimentation des *** comprend :- la préparation de l'échantillon pour essai, de la suspensionmère et des dilutions décimales.- les conditions d'adaptation de la norme V 08-011 "directives générales pour le dénombrement des germes aérobies mésophiles".Elle sera complétée ultérieurement au fur et à mesure de la mise au point des autres normes de directives générales.

关键词： Science   Humanities and Social Sciences   multidisciplinary