摘要:

SummaryErosion from a tributary of the River Camel deposited an estimated 10,000 m3of sand in the main river over a period of 2 years. The poor incidence of plants and macro‐invertebrates from the river was associated with the unstable shifting nature of the sand deposits, rather than turbidity or abrasion caused by particles in suspension. Sand deposition accounted for the low diversity of invertebrate species below the tributary, and resulted in the elimination of several species which were frequent upstream. Baetis rhodani, Rhithrogena semicolorata, and Tubificidae were abundant where sand deposition had occurre

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1972.tb00047.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SummaryA new freshwater hoplonemertean from Campbell Island, to the south of New Zealand, i s described and named Campbellonemertes jolinsi gen. et sp. nov. The morphology of this tiemertean relates it with the family Prosorhochmidae and the occurrence of this form, the second freshwater prosorhochmid genus from the Antipodes, strongly supports an earlier hypothesis on the evolution of freshwater hoplonemerteans.

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1972.tb00048.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SummaryStock SL Pinkster (1970) erected two subspecies of Gammarus duebeni primarily on the basis of a difference in the relative dimensions of the merus on the fifth walking leg. The diagnostic feature was given as the ratio of merus length/width, with ratio2 in G. duebeni celticus. It is shown here that the ratio varies with the size of the animal, and this particular ratio is therefore not valid as a taxonomic character.Regressions of log merus width on log merus length were made on large samples of G. duebeni assumed to belong to subspecies celticus and duebeni respectively. The regressions were significantly diiferent and were used to predict that the ratio log merus width/log merus length is relatively constant in both subspecies. Diagnostic values for this ratio were 0.71–0.73 in celticus and 0.74–0.77 in duebeni. The ratio was also determined in small samples of G. duebeni from other localities in western Britain.The morphological difference which characterizes celticus and duebeni was not associated with habitat salinity or with previously determined physiological characteristics. It may be an instance of cHnal variation reinforced by geographical isolation.Regressions of merus length against cephalic length suggest that the relative growth rates of the merus may also differ in the two subspec

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1972.tb00049.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SummaryThe heterotrophic planktonic bacteria in two high‐arctic lakes were studied by direct microscope count and the enzymatic uptake of14C labelled glucose which generally conformed to Michaelis‐Menten kinetics. Bacterial numbers and activity in oligo‐trophic Char Lake ranged from 0.1 to 2.0×10−3bacteria/l and a maximum uptake velocity (Vmax) of 1.8 × 10−3μg glucose l−h−1. Nearby Meretta Lake received waste water from the Department of Transport Base at Resolute and this eutrophication was reflected in higher bacterial numbers of 2‐80 × 108/1 and Kmax of 0.1 × 10−1‐7.5 × 10−1fig glucose l−1h−1The Kmax per cell in Char Lake was 3 × 10−11μg glucose l−1h−1and changed little between the period of solid ice cover in May and ice‐free conditions in August. Bacterial cycles could not be related to phytoplankton cycles in either lake. Comparison of kinetic data from several lakes suggests a relationship between the bacterial uptake rate of glucose and phytoplankton production. Both bacterial numbers and activity in Char Lake may be very close to the minima to be expect

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1972.tb00050.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SummaryWeekly observations were made of the South Winterbourne from October 1970 to December 1971. Flow commenced in November 1970 and ceased in July 1971, a maximum flow of 1.51 m3s−1being recorded in January 1971.The chemical composition was not very variable, but nitrate showed a positive correlation with flo

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1972.tb00051.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SummaryIt this study the use of Sephadex G‐25, Sephadex LH‐20 and CPG‐10‐75 for the separation of soluble humic compoutids frotn fresh water is tested.It is shown by Sephadex G‐25 gel filtration that differences in molecule‐size distribution of soluble humic compounds in one lake at different titnes and between lakes can be predicted by E250and E365m

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1972.tb00052.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SummaryThe eggs of Baetis rhodani were collected from natural conditions just after laying and incubated at different constant temperatures (from 7‐5°C to 27‐5°C) with a constant photoperiod. The incubation period was shorter at higher temperatures up to 25°C (8 days); above this eggs no longer hatched. The slowest development (determined by extrapolation) was at about 3°C (theoretically 130 days). The hatching period was always very short (about 3‐5 days). Fewer eggs hatched at higher tem

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1972.tb00053.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SummaryMacrostomwn johni sp. nov. from Llyn Cwellyn, N. Wales is described. The species has been recorded from the vegetational littoral in December and February only. The main distinguishing criterion is the penis stylet which consists of a funnel, about 80‐98 μm in length in slightly squashed specimens, curved in two planes and with a sub‐terminal distal opening, the distal end is blunt and cowl (hood) shaped. Other features include the presence of sensory hairs and rhabdoids all over the body, ‘Haft‐papillen’, and eyes. Rhammite tracks are weakly developed. The testes are elongate and the ovaries are compact, though slightly indented, and smaller than the testes. A very short ductus intervesicularis is present. The vagina is short. A ‘Verschlussap‐parat’ is present but

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1972.tb00054.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SummaryUsing Surber‐type samplers and dip‐net samplers, we assessed the efficiency of nets having pore sizes of 720 μm and 320 μm for determining standing crop and percentage composition of the stream fauna, and for collecting representative size‐class specimens of Ephemeroptera and Plecoptera to be used in life‐cycle studies. Except for one species, samples collected with either the 720‐μm or 320‐μm dip‐net led to the same general inferences about the species' life cycle. Of fifty possible sample comparisons, there were twelve samples where the size‐class frequencies of particular species collected in the 720‐μm dip‐net were significantly different from the size‐class frequencies of the 320‐μm dip‐net; for five of these samples a deficit of large nymphs (>5.0 mm) in the 320‐μm net mainly contributed to the significant χ2values. On one date, we used double‐bag samplers with both th e 720‐μm and 320‐μm nets attached to either the Surber or dip‐net sampler. Approximately 50% of the insects by numbers passed through the 720 fxm mesh ofeach sampler, but only 5% by volume‐biomass. Shape of the insect as well as body length was important in assessing mesh‐size efficiencies. The 720‐μm mesh of the double‐bag dip‐net sampler retained most of the Nemoura dnctipes (having stout appendages) and Epeorus longimanus (flattened) nymphs 2.0 mm in body length and larger; whereas most Baetis (streamlined) nymphs smaller than 3.0 mm and all Paraleuctra (

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1972.tb00055.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SummaryData is presented on the life cycles of Leptopblehia vespertina (L.) and L. marginata (L.) in Llyn Dinas, an oligotrophic North Wales lake. Both species are univoltine and growth continues throughout the winter although somewhat retarded. Except during July and August there is a clear size separation of the two species, L. marginata being larger and emerging earlier. The egg incubation period was determined directly from laboratory studies. The results are discussed in relation to previous research in the English Lake District.

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1972.tb00056.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY