摘要:

SummaryThe food of the larvae of two New Zealand Trichoptera,Hydrobiosis parumbripennisandHydropsyche colonica, was investigated between March and November 1971 at the Wainui Valley Stream, Canterbury, New Zealand. Most samples were collected from an experimental channel constructed in the stream in 1970. The first three instars ofH. parumbripenniswere mainly detrital feeders, whereas the two later instars were exclusively carnivorous. In contrast,H. colonicawas omnivorous. The main prey taken byH. parumbripenniswere larvae of a simuliid,Austrosimulium tillyardianum, Chironomidae (subfamily Orthocladiinae), and an ephemeropteran,Deleatidiumsp. The first three instars appeared to select chironomids in preference to simuliids, whereas the converse was true for the final two instars. The main prey taken byH. colonicawasA. tillyardianum. The size of prey and the mean number of prey found per larva ofH. parumbripennisincreased with each instar. Forage ratios indicated thatH. parumbripenniswere eatingA. tillyardianumat the same relative frequency as their abundance in the fauna, but that the chironomids andDeleatidiumsp. were being preferentially selected as prey. Cased caddis larvae were avoided as food items, as was the molluscPotamopyrgus antipodarum. AlthoughH. parumbripenniswas the most important predator ofA. tillyardianumin the stream, it is considered that it has little effect on the simuliid population.

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1975.tb00124.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SummaryNucleic acid concentrations show large variations between different planktonic species. RNA concentration is much higher in phytoplankton than in zooplankton. DNA varies to a considerable extent, being five to six times higher in copepods than in cladocerans. InDaphnia hyalina, nucleic acid contents are proportional to dry weight during the whole life cycle except in newbornDaphniawhere DNA concentration is abnormally high. Seasonal variations affect, to a large extent, nucleic acid concentrations. These results rule out the possibility of using nucleic acids as indicators of biomass in mixed planktonic populations.

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1975.tb00125.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Summary(1) An analysis of the metazoan fauna of Nahal Soreq was made at several sampling stations from October 1970 to August 1971. Relative abundance of each species or group of species was estimated by semi‐quantitative sampling, and population structures are given here in the form of percentage tables. (2) A succession of three zones, indicating three degrees of pollution, were recognized: a ‘Nematode zone’ in the most polluted waters, a ‘Chironomus zone’, where purification has progressed a little, and a ‘Proasellus(and ostracod) zone’, where purification is nearing completion. (3) These zones of indicator organisms roughly correspond to three zones classified in a ‘Saprobien System’ manner: a polysaprobic zone (Nematode zone), a mesosaprobic zone (Chironomuszone), and an oligosaprobic zone (Proaselluszone). A state of complete purification or recovery is not reached, and the purification process is stopped in the oligosaprobic condition by the disappearance of the stream underground. The other invertebrates characterizing these three zones are given. (4) A comparison is made of the saprobic zones and their corresponding fauna with findings reported elsewhere‐‐‐Europe, North America and South Africa. The successional changes are generally similar to European findings with some notable absentees, and there are also some similarities with polluted South African streams. (5) Seasonal changes in species composition and the position of these species along the stream are discussed. There are small changes which appear to be a result of life cycle habits in some air‐breathing dipterans and a slight change in the position of chironomids downstream, which is correlated with the winter rain floods. (6) The faunal types and numbers occurring downstream are compared with the increase in algal species diversity, dissolved oxygen and coli bacterial counts. It is suggested that the degree of pollution is the primary factor in the establishment and population build‐up of any particular species, but that presence of suitable substrates, availability of food and presence of predators play a larger part

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1975.tb00126.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SummaryThe salinity tolerance and osmoregulatory ability ofGalaxias maculatuswere investigated. In the field this species has been recorded from salinities of less than 1‰ to 49‰. In the laboratory, upper L.D.50salinity values of 62‰ after gradual acclimation and 45‰ after direct transfer were established. Within the salinity range of its field occurrence the species is a powerful osmoregulator, being able both to hypo‐ and hyper‐o

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1975.tb00127.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SummaryThree species of Corixidae (Hemiptera : Heteroptera) were studied in thirty montane, sub‐alpine, and alpine ponds in Western Colorado.Callicorixa audeniHung, had the widest altitudinal range (2800‐3400 m).Cenocorixa bifidaHung, was most common in montane ponds.Arctocorisa lawsoniHung, was found only above 3100 m.C. audeniwas significantly associated withC. bifidaandA. lawsoni. Habitat selection was studied in two montane (2900 m) and one alpine (3480 m) pond.C. audeniutilized both mud and emergent sedges as perching and feeding sites, occurring more frequently in the sedges in the montane ponds.C. bifidawas confined to the mud. In the alpine pond,A. lawsoniwas most abundant on the mud;C. audenioccurred equally on the mud and in the sedges. All three species preferred shallow water (less than 0·5 m).A. lawsonioccupied deeper water more often thanC. audeni. In substrate selection experimentsC. audenioccupied emergent sedges more thanC. bifida, confirming field observations.C. bifidaoccurred in sedges in the aquaria, but not in the montane ponds, suggesting that an interspecific interaction may be excludingC. bifidafrom the sedges in na

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1975.tb00128.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SummaryIn laboratory experiments with full‐grown larvae of three Trichoptera species (Limnephilus rhombicus, Potamophylax rotundipennisandSericostoma pedemontanum) in an artificial stream, four types of bottom material were provided in combination with various currents. OnlyL. rhombicusreacted to low current speed (9 cm/sec), moving downstream when a bottom current was present.L. rhombicusandP. rotundipennisshowed a distinct preference for pebbles over sand and for coarse pebbles over crushed brick.S. pedemontanumburrowed under pebbles or stones.L. rhombicusshowed a distinct tendency to climb onto the dividing gauze or vertical sticks. All three species preferred shaded parts of the experimental stream to the illuminated parts.The results are related to field observations.Limnephilus rhombicusoccurs in stagnant and slow‐running waters.Potamophylax rotundipennisis restricted to rather fast‐running streams with a perpetual flow, whileSericostoma pedemontanumoccurs in the same type of s

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1975.tb00129.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SummaryDiatoma elongatumhas been observed in Tjeukemeer (The Netherlands) from time to time. Its intermittent presence is probably a consequence of the local hydrology. In early 1972, besides the usual increase ofMelosiraspp. and of unicellular centric diatoms, a development ofD. elongatumtook place. Its maximum was found 5‐6 weeks later than those of the centric diatoms. Possible factors causing the decrease in number of cells are discusse

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1975.tb00130.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SummaryThe invertebrate community of a small stream system in western Ireland is described from the results of two sampling programmes. The investigation was conducted at four sites which occurred within the same range of altitude (between 60 and 130 m O.D.) and the greatest differences between them were rock size, current intensity and the amount and type of detritus in the substratum. Approximately 60,000 invertebrates were identified and almost 100 taxa were listed. Attempts which were made to relate the occurrence of certain taxa to three factors (rock size, current intensity and detrital content) showed that detrital content was the most significant. Using empirical clustering techniques efforts were made to demonstrate zonation of the invertebrates taken during one of the two sampling programmes and the groups which were so obtained were further amalgamated subjectively. The resemblance of the resulting pattern to lotic zonation is briefly discussed.

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1975.tb00131.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SummaryThe number of perch caught weekly in traps set in Slapton Ley, Devon has been considered. Five traps were laid in each of six regions during 1970 and 1971. The numbers caught in each region were averaged for eight lifts during 8 weeks and the logarithms of these numbers calculated. The figures obtained showed marked seasonal trends in the catch of the traps and these trends were consistent when both years were compared. If single traps were considered there was marked variability at one time which was attributed to differences in habitat. However, the combined data from each region did give a good comparison of the density of perch between regions.

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1975.tb00132.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SummaryThe Plecoptera community of a small woodland stream in Oregon was studied by examining density and species composition. Four sites were studied using benthos sampling for larvae and emergence trap collections for adults. Sixteen genera and forty‐three species were identified with most species occurring in relatively low numbers. A comparison with the species list from an earlier study suggested that the species composition has not changed markedly in 40 years but there were several changes in relative abundance.Species diversity of stoneflies decreased with distance from the headwaters. These changes were correlated with decrease in habitat complexity, decrease in stability of the substrate, and increase in water depth. Examples of longitudinal succession are given as a method enabling the large number of species to partition the habitat. Concurrent benthos and emergence sampling demonstrated differences in emergence success that were correlated with habitat suitabilit

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1975.tb00133.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY