some factors affecting the oxygen consumption of asellus

[ 7 o 6 ]

SOME FACTORS AFFECTING THE OXYGENCONSUMPTION OF ASELLUS

BY R. W. EDWARDS AND M. A. LEARNER

Water Pollution Research Laboratory, Stevenage

(Received 3 May i960)

INTRODUCTION

Asellus aquaticus is often abundant in polluted streams (Allan, Herbert & Alabaster,1958) and under certain conditions its oxygen consumption may be of significancein studies of oxygen balance. In an earlier paper (Edwards, 1958), the need forcomparative studies, using different respirometer systems, was stressed. Theexperiments described in the present paper were carried out using both a Warburgconstant-volume respirometer* and an apparatus in which the fall in dissolved-oxygen concentration of water passing through a respirometer was measured,using a polarographic technique.

Most of these experiments have been confined to a study of the effect of body size,temperature, and oxygen concentration on the oxygen consumption of A. aquaticus.Some observations have also been made on the diurnal rhythm of A. aquaticus andthe effect of oxygen concentration on the oxygen consumption of A. meridianus,a species which has not been recorded in organically polluted streams.

An extension of this study is not possible at the present time and the authorsapologize for the incomplete nature of certain aspects of the work.

MATERIALS AND METHODSAll experiments were conducted between December and March except where thetime of year is specifically mentioned.

A. aquaticus was collected from three locations:(i) Maple Lodge Sewage Effluent Channel, Rickmansworth, Hertfordshire

(G.R. SU 039910). The average dissolved-oxygen concentration at the collectionsite for the year 1953-54 was about 40% of the saturation value and during thewinter months was below 30% (Allan et al. 1958).

(ii) River Hiz, Henlow, Bedfordshire (G.R. TL 190378). Animals were collectedfrom an area 4-5 miles below Hitchin Sewage Works. Oxygen records are notavailable for this site but data have been collected for an area near the effluentdischarge (Gameson & Griffith, 1959) and here the average dissolved-oxygenconcentration was about 50 % during the winter of 1957-58.

• These experiments were carried out by Mr R.W. Edwards, whilst on the Staff of the FreshwaterBiological Association.

Factors affecting the oxygen consumption of Asellus 707

(iii) River Ivel, Stotfold, Hertfordshire (G.R. TL 223373). Collections weremade in this unpolluted and spring-fed chalk-stream about 3 miles from its source.In November 1958 a polarographic dissolved-oxygen recording machine wasplaced at the collection site and the average dissolved-oxygen concentration wasbetween 70 and 80 % for the winter period and did not fall below 60 % (Depart-ment of Scientific and Industrial Research, i960, Fig. 41).

A. meridianus was collected from a pond in Baggrave Park, Leicestershire(G.R. SK 696086).

Animals were kept in the laboratory at 200 C. (± 2° C.) in aerated water for atleast 24 hr. after collection and were allowed to feed, except in certain Warburgexperiments described later where animals were starved for 24 hr. before oxygen-consumption measurements were made. Animals used in experiments at 10° C.were acclimatized to that temperature for 24 hr. Respirometers were fitted withhoods to exclude light. The wet and dry weights of groups of animals weredetermined, but there was no change in the proportion of dry matter in thesegroups (about 20%) with an increase in size. The effect of moulting on thewet weight:dry weight ratio in individual specimens was not studied.

Warburg respirometer

The techniques used were similar to those described in an earlier paper (Edwards,1958). A. aquaticus from the Sewage Effluent Channel was used exclusively andexperiments were conducted between December 1956 and March 1957 except forthose on diurnal rhythms, which were conducted in July 1957.

Polarographic respirometer

Polarographic techniques have been employed to measure oxygen concentrationsin respirometer studies for many years (Berg, 1953). Some workers have describedtechniques which measure the dissolved-oxygen concentration continuously (Mann,1958; Bielawski, 1959). The apparatus used in the present study measures theconcentration of dissolved oxygen in the water before and after it has passedthrough the respirometer tube and records these concentrations on a strip chart.

General description.' A general diagram of the apparatus is shown in Fig. 1.Water passes from the 20 1. reservoir A, through a constant-level device B, toa 10 1. reservoir C, where it is maintained at a constant temperature and thecontent of oxygen is controlled by saturation with a predetermined mixture of airand nitrogen. From the reservoir C water passes either (a) by direct route, D,to a two-way tap G which controls the flow through the apparatus; or (b) by route E,through the respirometer U-tube F, to tap G. Both routes may be closed near thereservoir C by screw clips. From the tap G, water passes through the electrodechamber J, to a flowmeter K, and then to waste. When water is passing through thedirect route from the reservoir, water may also pass through the respirometerroute by opening tap H. The water flow in this route is controlled by tap H andmeasured at the flowmeter, /. By including an alternative route in the respirometerline the dissolved-oxygen concentration in the direct line (and hence reservoir C)

45-2

708 R. W. EDWARDS AND M. A. LEARNER

can be recorded and at the same time a similar flow of water can be maintainedthrough the respirometer route so that animals may be kept under controlledoxygen and flow conditions throughout the experiment.

The proportions of air and nitrogen in the gas mixture are controlled by the needlevalves Q. Pressure-reducing valves P maintain a gas supply at constant pressureto the needle valves, and flow meters R measure the gas flows. The two gas streamsare mixed in the chamber S before passing through a diffuser T in the reservoir.Provision is made for drawing off water samples from the reservoir for the analysisof oxygen concentration by the Winkler method by a siphon tube V.

Height ofmercury

Apparatuscontainingmercury

Fig. i. General diagram of polarographic respirometer. Items drawn in dotted lines are attached tothe outside of the constant-temperature bath.

Polarographic analysis of dissolved-oxygen concentrations. A wide-bore dropping-mercury electrode was used, similar to that described by Briggs, Dyke & Knowles(1958) with a mercury pool reference electrode. The mercury drop rate was con-trolled by the height of the mercury reservoir L above the electrode tip (24 cm.)and two lengths of capillary tubing, 60 cm. of 0-2 mm. bore (M) and about 40 cm.of O'8mm. bore (N).* The dropping-mercury electrode was kept at 1-65 V.

• For details of mercury level control and pre-treatment of capillary tubing see British PatentApplication No. 40151/59.


negative with respect to the mercury pool. The system operates on the secondoxygen plateau (Kolthoff & Lingane, 1952). In initial experiments slow currentdrifts were caused by the deposition of calcium carbonate on the tip of the dropping-mercury electrode. Addition of 3 p.p.m. (as P) of sodium hexa-meta-phosphate tothe water prevented this and high stability, lasting several days, was achieved. Thewater used in the experiments was unchlorinated tap water with a total hardness ofabout 290 p.p.m. (as CaCO3). Fig. za shows a typical calibration curve for theapparatus; unlike those of Berg (1953), Mann (1958), and others, this is not quitelinear. Fig. zb shows polarograms of the second oxygen plateau from which thiscalibration curve was constructed. The dissolved-oxygen concentrations werecalculated from the saturation values of Truesdale, Downing & Lowden (1955)and the partial pressure of gases in the gas mixture, and were checked by Winkleranalysis of bottle samples from the reservoir C. Unless different potential differenceshad been applied at different dissolved-oxygen concentrations, a truly linear rela-tion between current and oxygen concentration could not have been achieved. Theelectrode system was not temperature-compensated and all experimentswere conducted at 200 C. (±o- i°C) . Unlike the systems of Bielawski (1959)

40

30S

n

u

(a)

x Chart reading• Mlcroammeter

reading

2 4 6 8Dissolved oxygen (p.p.m.)

1-2 1-4 1-6 1-8Applied potential (V.)

2-0

Fig. 2. Calibration graph and polarograms of polarographic respirometer.

and Mann (1958), the current readings were independent of flow between60 and 170 ml./hr. The position of the dropping-mercury electrode and thedesign of the electrode chamber are important in determining the dependencyof current readings on flow rates. All experiments were conducted at flows of100-130 ml./hr.

The electrical circuit is shown in Fig. 3. Provision was made either to record thecurrent produced by the polarographic cell on a strip chart, readings being takenevery 3 min., or to read it directly on a microammeter. The microammeter in con-junction with a voltage control was useful in providing a quick check of the charac-teristics of the second oxygen plateau (see Fig. 26). A standard cell giving a currentof 5-4 micro-amp, was built into the circuit to check recorder sensitivity, but is notshown in the circuit diagram.


Procedure. Animals were placed in the respirometer and water was passed throughboth direct and respirometer routes at a predetermined rate, the dissolved-oxygenconcentration of water in the direct route passing through the electrode chamberbeing recorded. Tap H was then closed and tap G revolved, allowing water fromthe respirometer route to pass through the electrode chamber. The dissolved-oxygen concentration in water leaving the respirometer was recorded for at leasti hr. and the flow measured. Finally, the stability of the dissolved-oxygen con-centration in the reservoir was checked by returning to the direct route and record-ing the reading. This routine was repeated at different dissolved-oxygen levels(see Fig. 4). After the gas mixture had been changed it took about 1 hr. beforestable readings were achieved.

RESULTS

Warburg experiments

Fig. 5 shows the logarithmic relation between oxygen consumption per unit weightand wet weight of A. aquaticus at 10 and 200 C. Larger animals were separated intomales and females* and certain experiments were conducted with animals whichhad been starved for 24 hr. Results of analysis of covariance suggest that there isno significant difference in the oxygen consumption between the two sexes orbetween fed and starved animals (i.e. between centres of gravity of groups shown

Fig. 3. Electrical-circuit diagram of polarographic respirometer.A1 Ammeter, F.S.D. 3 A.A 2 Microammeter, F.S.D. 5 11A., resistance approximately 3000 Si.B 12 V. accumulator.Ci 5000 11F. electrolytic condenser. 6 V. working.D.M.E. Wide-bore dropping-mercury electrode.Hg pool Reference electrode (mercury pool in polarographic cell).M Microswitch operated by a cam which is driven by a synchronous clock motor. Contacts

close for several seconds every 3 min. (Synclock motors from Everett Edgcumbe & Co.Ltd., Colindale Works, London, N.W. 9).

P.P. 12 V. power pack—could be replaced by a standard battery charger capable of deliveringabout 3 A. at 12 V.

fii ofl, 18 W.Rz 50 Si, 3 W. (wire-wound).R3 190 fi, JW.R4 2500 Si, 3 W. (wire-wound).RC Recorder solenoids for printing and moving chart (chart solenoid operates on release).

They are part of REC.REC Cambridge Model B 'thread recorder' modified by manufacturer to give solenoid-operated

print and chart-movement. F.S.D. 5 fiA., resistance approximately 2000 Si. (CambridgeInstrument Co. Ltd.)

RECT Full-wave rectifier, Sentercel type B84-1-1 W. (Standard Telephone and Cables Ltd.,Edinburgh Way, Harlow, Essex.).

51 Double-pole on-off toggle switch.52 Double-pole change-over toggle switch.53 Double-pole change-over toggle switch.T Heavy-duty filament transformer with all secondaries connected in series and capable of

delivering 3 A. at 18 V. (Radiospares, 4, Maple Street, London, W. 1).V Voltmeter, F.S.D. 3 V.

* Females with brood pouches were not used in these experiments.


in Fig. 5). Although the relation between size and oxygen consumption is similar forfed and starved animals (P = o-6 at 10° C. and P = 0-9 at 200 C), it may bedifferent for the two sexes (P = 0-05 at 10 and 200 C) . Regression analyses ongrouped data gave coefficients of —0-32 ( + 0-03) at io° C. and 0-28 (±0-02) at20° C. The oxygen consumption per unit weight is proportional to these powers ofthe wet weight.

A. aquaticus consumes oxygen about 1-5 times as fast at 20° C. as at 10° C. overthe size range studied and results suggest that the Q10 value is not dependent uponsize, the difference in regression coefficients being insignificant (P = 0-3).

p.p

Fig 3. For legend see opposite page.

712 R. W. E D W A R D S AND M. A. L E A R N E R

The oxygen consumptions of several groups of A. aquaticus were determinedat four times the normal amplitude of shaking of the respirometer flasks. Thedifference between groups was not significant (P > 0-5).

Lang & Ruzickova-Langova (1951) reported a diurnal rhythm in the oxygenconsumption of A. aquaticus, throughout the year, the lowest oxygen consumptionbeing recorded around noon. It is not clear whether the animals were exposed toconstant or variable illumination, however, and experimental observations werecontinued for only 9 hr., generally between 9 a.m. and 6 p.m. Fig. 6 summarizesobservations made in the present study. At six-hourly intervals groups of maleswere placed in the dark in respirometer flasks and their oxygen consumptionswere measured for 24 hr. The interpretation of these data is difficult, but it seemsthat there is an initial decline in oxygen consumption during a period of acclimati-zation, and that there is a daily rhythm of small amplitude even under constantenvironmental conditions, with a minimum oxygen consumption around noon.A more general decline has been reported by Fox & Simmonds (1933). They foundthat the oxygen consumption on the second day of measurement in a Barcroftrespirometer was 93 % of that on the first day. The high initial rate observed inGroups II, III and IV (see Fig. 6) was not observed in Group I. This is probably dueto the coincidence in Group I of the acclimatization period (with its high oxygen con-sumption) with a period of minimal daily oxygen consumption. The experimentsdiscussed earlier in the paper correspond to Group I animals in that observationsstarted at 9 a.m. and no systematic fluctuation was observed.

Polarographic experiments

Initial experiments showed that no systematic changes occurred in the oxygenconsumption of A. aquaticus for at least 12 hr. in this apparatus under constantconditions. The coefficients of variability between hourly averages over this periodwere about 7 %. In view of the similarity of the oxygen consumption of malesand females described above, sexes were not separated for these experiments;the larger size groups were exclusively male, however. Such a grouping may becriticized on two counts: first, the oxygen consumption of males and females maybe differently affected by size, and secondly, the level of oxygen consumption maybe different when sexes are grouped. Fig. 7 shows the logarithmic relation betweenoxygen consumption per unit weight and wet weight of A. aquaticus in air-saturatedwater at 200 C, data from three areas having been grouped. The oxygen consump-tion per unit weight is proportional to -0-22 (±0-07) power of the wet weight.The effect of size on the oxygen consumption is not significantly different fromthat calculated earlier for the Warburg respirometer (P ~ 0-3); the level of oxygenconsumption determined in the polarographic respirometer is, however, signifi-cantly higher (P < o-ooi).

It will be seen from Fig. 8 that the reduction in oxygen consumption betweendissolved-oxygen concentrations of about 8-3 and 1*5 p.p.m.* is small in all groups.

• The average of the respirometer influent and effluent concentrations has been taken throughoutthis paper. Generally the conditions, for example, flow and animal numbers, were arranged so thata fall of about 1 p.p.m. could be expected.


The oxygen consumption is expressed as a percentage of that determined at thebeginning of the day in air-saturated water. Values above 100 % were sometimesobtained when animals were returned to air-saturated water at the end of a day'sobservation.

„,..- D

0 _, <

.' «•••"•••.•..•„.,'•'•••..•.•

0 .

D V

—10

Fig. 4. Typical recorder chart showing oxygen consumption of A. meridianus at 20° C. at three oxygenconcentrations (recordings were made every 3 min.). Flows at these oxygen levels were notidentical and therefore the oxygen consumption is not directly proportional to the fall in oxygenconcentration as it passes through the respirometer. Direct route = D. Respirometerroute = R.

a.

I iu

600

400

200

1008060

_

—

-

_

- 0 4

(a

A

.

A

0-8I 1 1

•

o »

1

a ca

I

•

8

Fed

Unfed

0 0 ^

<

1

i•0

• »

• °1

%

ma

UnsexedA

0-6

a.

I i3 ?

200

10080

60

( b ) .

—

2 4

• ^

I

6 10•0 m

8

20

_V

40

O

14 6 10 20Wet weight (mg.)

40

Fig. 5. Log oxygen consumption per unit weight plotted against log wet weight for A. aquaticus.The continuous lines are drawn for grouped data and dotted lines for the separate sexes,(a) at 200 C.,,6 = -0-281; (6) at io° C , b = -0-321.

R. W. E D W A R D S A N D M. A. L E A R N E R

A close inspection of charts (Fig. 4) reveals differences in the variability of thedissolved-oxygen concentration of the effluent from the respirometer at differentoxygen levels. At high dissolved-oxygen concentrations the concentration in theeffluent is variable and would be even more so were it not for mixing in the tubingand electrode chamber. At low oxygen concentrations the effluent concentration is

200

100

200

V 0 0

.2 0a. 200

100

X

o

100

IV (5)

III (S)

I (4)

I (6)

J II I I I I I

300

200

100

0 ~300 -£

200 S

100

i300

200

100

200

100

a.

e

09.00 15.00 21.00 03.00 09.00 15.00 21.0012.00 18.00 24.00 06.00 12.00 18.00 24.00

Time (G.M.T.)

Fig. 6. Oxygen consumption of A. aquaticus at 2O° C. over 24 hr. Figures in parentheses indicatethe number of groups for which the average oxygen consumption has been taken.

A. aquaticus ° River HizQ River Ivel

Sewage effluentchannelA. meridianus x

4 6 8 10Wet weight (mg.)

20 40

Fig. 7. Log oxygen consumption per unit weight plotted against log wet weight for A. aquaticusand A. meridianus measured in the polarographic respirometer. Temperature 20° C , b = — 0-22.


relatively constant. It seems likely that the greater variability in oxygen consump-tion is due to periods of locomotory activity. In the confined space of the respiro-meter, movement by one animal tends to disturb others and promote a moregeneral activity, resulting in a period of high oxygen consumption. Variations in theoxygen consumption of trout observed by Job (1955) were shown to be caused byirregular swimming activity. At low oxygen concentrations locomotion is reducedand pleopod movement becomes more regular. The effect of dissolved oxygenconcentration on pleopod movement has been studied by Fox & Johnson (1934).

120

•c-100

„ S 8000 0)

I f 6 0

S I * Mc «0 Q. 0

| - 5 120

1*5 1001 S 80

A. aquaticus,R. Ivel

X «O-S

A. aquaticus,sewage effluentchannel

120r

100

80

60

40

20I

10 0120

100

80

60

40

20

A. aquaticus,R. Hiz

10

A. meridianus,Leicestershire pond

8 10Dissolved oxygen concentration (p.p.m.)

10

Fig. 8. Oxygen consumption of A. aqnaticus and A. meridianus from different habitatsat different dissolved-oxygen concentrations.

DISCUSSION

Fig. 9 shows data on the oxygen consumption of Asellus species collected fromvarious sources. Fox & Simmonds (1933) reported differences in the oxygen con-sumption of anaesthetized A. aquaticus from a fast- and a slow-flowing stream.All the streams from which animals were collected for the present study were slow-flowing, with velocities generally less than 1 ft./sec. Other habitat differences, forexample, dissolved-oxygen levels and degree of pollution, did not influence oxygenconsumption.

Sprague (in preparation) showed that A. intermedius respires at similar rates at 10and 200 C. in a Warburg respirometer after acclimatization to these temperaturesfor one week. In the present study, A. aquaticus respires 1-5 times as fast at 20 asat io° C. after temperature acclimatization for only 1 day.

Will (1952) found the oxygen consumption of A. aquaticus at 230 C. in a darkenedWarburg respirometer to be about twice that measured in the present investigationat 200 C. in the Warburg respirometer. The temperature difference of 30 C.between the two series would seem inadequate to account for a difference of suchmagnitude and no other explanation can be offered.


Allee (1929) measured the oxygen consumption of A. communis males in bottles,analysing oxygen concentration by the Winkler method. His data have beengrouped and plotted in Fig. 9. A. communis clearly reaches a much greater sizethan the other species discussed, but assuming that its oxygen consumption/sizerelationship is comparable, its oxygen consumption is very similar.

600500

.2 2" 400

! t l 30°1 S200

' 100• 80

60

20°P(£)20°W(E) 23° W(W) ^ ° ^ W ^" ' n t e r f n e < " u s

^ 20° P(£) A. mend/anus

10° B(F) Swift

"M0°W(S)A. intermediut

10°6(F)Slow

I I08

I I I0-2 0-4 06 1 2 4 6 810

Wet weight (mg.)

12°X(A) A. communis #

J I I I I |__60 80100 20020 40

Fig. 9. Log oxygen consumption per unit weight plotted against log wet weight for species ofAsellus, collected from various sources (Allee, 1929, (A); Fox and Simmonds, 1933, (F);Sprague, in preparation, (S); Will, 1952, (W) and present authors (is1)). The respirometersreferred to in the figure are Warburg, W; Barcroft, B; Polarographic, P; and Bottle, X (see text).Data refer to A. aquaticus wherever species are not given.

The differences between the oxygen consumption as measured in the polaro-graphic and Warburg respirometers are probably associated with intensities ofactivity under rather different experimental conditions. Although sexes were notseparated in the polarographic respirometer experiments it seems unlikely that thegrouping could account for this difference, which extends over the whole size range;in both series the larger size-groups were exclusively male. Animals moved freely inboth respirometers and neither gives a measure of the 'basal metabolic rate'.A comparative analysis of activity in these respirometers has not been attempted inthe present study.

The oxygen consumptions of A. meridianus and A. aquaticus are very similar at200 C. and both species behave similarly in low oxygen concentrations. It would berash to assume, from these experiments, that the distribution of these species isnot influenced by the oxygen conditions of their habitats. The effect of oxygenconcentration on activity, growth, reproduction, etc., would need to be studiedbefore any ecological generalization could be made concerning the influence ofoxygen concentration on distribution.

The oxygen consumption of A. aquaticus and A. meridianus may be described asof the 'regulatory' or 'independent' type between oxygen concentrations of 8-3and 1'5 p.p.m., the oxygen consumption between these two concentrations beingreduced by only 15 to 20%. It seems probable from recorder-chart characteristicsand other evidence that locomotory activity decreases and pleopod activity increases(Fox & Johnson, 1934) as the oxygen concentration falls. Differences in activity


pattern have been described more fully for Chironomous plumosus (Walshe, 1950),where the proportion of time spent in feeding decreases and that spent in respiratoryirrigation increases below 3 p.p.m. Similar changes in ventilation activity havealso been described for Phryganea grandis (Van Dam, 1938). The assumption thatan ' independent' type of oxygen consumption is favourable to an organism (Berg &Ockelmann, 1959) or implies maintenance of full metabolic function is invalidwherever such changes in activity pattern take place that the 'scope for activity'(Fry, 1947) decreases. Animals with such a behaviour pattern can survive onlyrelatively short periods of exposure to low oxygen concentrations unless they canalso withstand longer periods of starvation. In the case of A. aquaticus, Warburgmeasurements suggest that the oxygen consumption was not reduced after starva-tion for 24 hr. Sprague (in preparation) has shown that A. intermedius can withstandoxygen concentrations as low as 0-3 p.p.m. for about 7 days at 200 C. when nofood is available.

SUMMARY

1. The oxygen-consumption rates of Asellus aquaticus (males and females) havebeen measured at 10 and 200 C. using a constant-volume respirometer, and theeffect of starvation for 24 hr. investigated. The oxygen consumption is approxi-mately proportional to the 0*7 power of the wet weight. The rate of oxygen con-sumption at 200 C. is greater than at io° C. by a factor of 1-5.

2. The oxygen-consumption rates of A. aquaticus and A. meridianus have beenmeasured at 200 C. in a flowing-water respirometer employing a polarographictechnique for the measurement of dissolved-oxygen concentrations. The oxygenconsumptions of A. aquaticus and A. meridianus are similar and decrease by 15-20%when the dissolved-oxygen concentration falls from 8-3 to 1-5 p.p.m.

3. The oxygen consumption of A. aquaticus is between 35 and 75 % higher in thepolarographic respirometer than in the constant-volume respirometer.

We wish to thank Prof. H. P. Moon (Leicester University) for his interest andhelp in supplying A. meridianus and Dr J. B. Sprague (Fisheries Research Board ofCanada) for his unpublished data on the oxygen consumption of A. intermedius.Mr G. Knowles, Mr R. Briggs and Mr W. H. Mason provided much help andadvice in the construction of the polarographic respirometer.

This paper is published by permission of the Department of Scientific andIndustrial Research.

REFERENCESALLEE, W. C. (1929). Studies in animal aggregations: natural aggregations of the isopod Asellus

aquaticus. Ecology, 10, 14-36.ALLAN, I. R. H., HERBERT, D. W. M. & ALABASTER, J. S. (1958). A field and laboratory investigation

of fish in a sewage effluent. Fish. Invest., Lond., Ser. I, 6, no. 2, 76 pp.BERG, K. (1953). The problem of respiratory acclimatization. Hydrobiologia, 5, 331-50.BERG, K. & OCKELMANN, K. W. (1959). The respiration of freshwater snails. J. Exp. Biol. 36,

690-708.BIELAWSKI, J. (1959). A polarographic method of measuring the intensity of respiration in aquatic

animals. Ada Biol. exp., Varsovie, 19, 41-8.

7 i 8 R. W. EDWARDS AND M. A. LEARNER

BRIGGS, R., DYKE, G. V. & KNOWLES, G. (1958). Use of the wide-bore dropping-mercury electrodefor long-period recording of concentration of dissolved oxygen. Analyst, 83, 304-11.

DEPARTMENT OF SCIENTIFIC AND INDUSTRIAL RESBARCH (i960). Water Pollution Research 1959.London: H.M. Stationery Office.

EDWARDS, R. W. (1958). The relation of oxygen consumption to body size and to temperature in thelarvae of Chironomus riparius Meigen. J. Exp. Biol. 35, 383-95.

Fox, H. M. & JOHNSON, M. L. (1934). The control of respiratory movements in Crustacea by oxygenand carbon dioxide. J. Exp. Biol. xx, 1-10.

Fox, H. M. & SIMMONDS, B. G. (1933). Metabolic rates of aquatic arthropods from different habitats.J. Exp. Biol. io, 67-74.

FRY, F. E. J. (1947). Effects of the environment on animal activity. Univ. Toronto Biol. Seriesno. 55; Publ. Ont. Fish. Res. Lab. no. 68, 1-62.

GAMESON, A. L. H. & GRIFFITH, S. D. (1959). Six months' oxygen records for a polluted stream.Wat. Waste Treatm.J. 7, 198-201.

JOB, S. V. (1955). The oxygen consumption of Salvelinus fontinalis. Univ. Toronto Biol. Seriesno. 61; Publ. Ont. Fish. Res. Lab. no. 73, 1-39.

KOLTHOFF, I. M. & LINGANE, J. J. (1952). Polarography, vol. 2, 2nd ed., 553 pp. New York:Interscience.

LANG, J. & RUZICKOVA-LANGOVA, M. (1951). Periodicity in oxygen consumption oiAsellus aquaticus.Mim. Soc. zool. Tchicosl. 15, 89-98.

MANN, K. H. (1958). Seasonal variation in the respiratory acclimatization of the leech Erpobdellatestacea (Sav.). J. Exp. Biol. 35, 314-23.

SPRAGUE, J. B. (In preparation.)TRUESDALE, G. A., DOWNING, A. L. & LOWDEN, G. F. (1955). The solubility of oxygen in pure water

and sea water. J. Appl. Chem. 5, 53-62.VAN DAM, L. (1938). On the utilization of oxygen and regulation of breathing in some aquatic

animals. Drukkerij Volharding, Groningen, 143 pp.WALSHE, B. M. (1950). The function of haemoglobin in Chironomus plumosus under natural conditions.

J. Exp. Biol. 27, 73-95-WILL, A. (1952). Korpergrosse, Korperzeiten und Energiebilanz, VI. K6rpergr6sse und 0«-

Konsum bei Schaben und Asseln (Isopoden). Z. vergl. Physiol. 34, 20-25.

some factors affecting the oxygen consumption of asellus

Documents