摘要:

SummaryThe seasonal and depth distribution of phytoplankton in Gull Lake, a moderately large, temperate, dimictic, recreational lake in southern Michigan, U.S.A., is described and discussed. Diatoms (Fragilaria crotonensis, Cyclotella michiganiana, Asterionella formosa, andSynechococcus) grow mainly in summer. Diatoms grew under the winter ice, and objections are lodged to the classic explanation of seasonal growth in temperate lakes, and to a recent hypothesis concerning the `paradox of the plankton'. Two raphe‐bearing large diatom species were considered to be truly planktonic. ASynechococcusspecies was similar to that described previously only from Loch Leve

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1972.tb00371.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SummaryEvidence is presented, from studies on deoxygenation of the hypolimnion and from examination of the diatom frustules in a surface mud core, that Gull Lake is becoming progressively more fertile. This appears to be a recent phenomenon, having begun in the last century. Phosphate is identified, from bioassay experiments, as the key nutrient limiting to algal growth. Probable future changes in the lake are discussed, and the existence of `natural' eutrophication is denied.

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1972.tb00372.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SummaryNecessity of a thorought study of hybridization, following the breakdown of reproductive isolating mechanisms between naturally occurring populations, has been felt by biologists in geneeral and ichthyologists in particular. In this connection a formula for ‘hybrid index’ developed mainly by Hubbs&Kuronuma (1942) and Hubbs, Hubbs&Johnson (1943) has widely been in use, to test the assumption of hybridity and to study the mode of inheritance. Misra, Bateson&Keenleyside (1970) gave statistical methods of analysing hybrid indices estimated for characters of the ‘continuous’ type, and also provided a numerical example. Recently Misra (1971) gave a method of doing similar analysis for hybrid indices estimated for meristic characters, but no example was provided, as data were not available to him. This paper presents a study of hybridization in the sunfishes (genusLepomis) of Pinehurst Lake, Ontario, Canada, based on the number of scales below the lateral line; the primary purpose of the study is to show the complete computational procedure involved in the application of the method of Misra (1971), so that those users of the method who are mainly interested in the applied aspects of the method, can bypass the mathematics

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1972.tb00373.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SummarySunfish specimens (genusLepomis) collected from Pinehurst Lake, Ontario, Canada, were identified as bluegill (L. macrochirus), pumpkinseed (L. gibbosus) and their hybrids. Hybridization was studied on the basis of the constants of cross‐sectional allometry as, to the best of our knowledge, no attempt has ever been made to study hybridization quantitatively from the relative growth aspect. Two sets of data‐‐‐one on the pair Y1/X (head length/standard length) and the other on the pair Y2/X (body depth/standard length)‐‐‐ were analysed, with the following objectives: (i)A statistical method of analysing hybrid index based on cross‐sectional allometry was first presented and then Y1/X‐data analysed by this method, and (ii)data Y2/X were analysed to show that in some particular situations analysis for hybridization by methods other than the hybrid index appraoch may be more appropriate. Results of the analys

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1972.tb00374.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

RésumeLa fécondité deBaetis rhodaniPictet a étéétudiée sur tout un cycle saisonnier dans le lissurage, ruisseau du Sud‐Ouest de la France.La variation de la fécondité suit celle de la taille; les femelless les plus grandes sont les plus fécondes et pondent les plus gros oeufs. Le maximum est atteint en hiver; le minimum estival résulte à la fois d'une diminution du nombre d'ovarioles et d'ovules produits par ovariole.Des lignes de régression ont étéétablies entre la fécondité et plusieurs mensurations larvaires et adults, elles ont permis de calculer chaque mois le potentiel de reproduction de la population d'après des prélèvements quantitatifs de larves au dernier stade.Une relation nombre d'oeufs pondus‐‐‐numbre de larves au dernier stade qui en sont issues a fourni a base d'une estimation de la production de la génération printanière en utilisant la méthode de la courbe d'Allen. La part prise par les jeunes stades non capturables dans la production de cette cohorte a été calculée è partir de cetteestimation.SummaryThe fecundity ofBaetis rhodanithroughout a seasonal cycle is measured and the production by the spring generation is calculated from the figures obtained. Females ofB. rhodanicannot be identified with certainty and therefore they were not cauht wild but bred from mature nymphs in the laboratory. Various measurements were made(Fig. 1). Eggs range in number from 4500 in February and March to 200 per female in July. This decrease coincides with a diminution in size and a rise in temprature (Fig. 2). In summer there are about 200 fewer ovarioles per female and production per ovariole is about half what it is early in the year. Smaller females produce not only fewer eggs but also smaller eggs (Fig. 3).The relation between certain dimensions and number of eggs is found to remain close (Table 4), and it is therefore possible to predict how many eggs will be laid per square metre from a quantitative sample of full‐grown nymphs that have been measured (Table 6). Continuous sampling and measuring therefore make it possible to calculate the number of eggs at the beginning of a given generation and the number of adults that ultimately emerge. Calculation of production is based on the assumption that mortality follows the Allen curve (Fig. 10). It is shown that the very small nymphs, ignored in many other calculations of production could contribute up 18% to the tot

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1972.tb00375.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SummaryFive new British records of freshwater Microturbellaria are illustrated:Gieysztoria infundibuliformis, Castrada lanceola, Castrada neocomensis, Castrada viridisandStrongylostoma elongatum. These species together with a new species,Macrostomum johnidescribed by Young (1972), are woven into the fabric of the existing key for the group (Young, 1970). All six species were recorded from the littoral zone of lakes in Caernarvonshire, N. Wales. The times of the recordings are indicated.

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1972.tb00376.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Summary(1)Where grinding or maceration of plant tissue is impractical, immersion in methanol should be used.(2)The adaption to aqueous methanol of existing techniqus for distinguishing chlorophyll and phaeophytin in aqueous acetone was studied in detail. In methanol the spectra of both phaeophytinaandbwere found to be pH sensitive. A method developed involving changes in absorbance at 665 nm is less precise than similar methods using acetone.(3)The spectra of phaeophytinbin methanol at different pH levels are anomalous. Changes in absorbance between 440 and 410 nm cannot be used for the estimation of phaeophytin.(4)Plant pigments can be transferred from methanol to aqueous acetone without degradation of chlorophyll. Modified standard techniques may then be used to measure chlorophyllaand phaeophytinacontent.

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1972.tb00377.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SummaryThe properties of waves on a lake surface and the influence of water depth on these properties are discussed.The method, derived by the Beach Erosion Board, of predicting wave characteristics if the wind speed and fetch are known is outlined and the validity of the method in Loch Leven, Scotland, is confirmed.This prediction technique is then combined with the equations of classical hydrodynamics to form a method of assessing the nature and extent of wave action in lakes without direct measurement. The value of the ratio of the wave‐mixed volume to the total lake volume as a meausre of hydraulic conditions in lakes is suggeste

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1972.tb00378.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SummaryA new type of Ekman Grab is described in which the need for a messenger weight is eliminated, improving its operation under non‐static condition

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1972.tb00379.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Books Reviewed in this Article:Flössner, Dietrich (1972).Krebstiere, Crustacea. Kiemen‐ und Blattfüsser, Branchiop

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1972.tb00380.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY