ZoologtcalJuurnal of the Linnean Society, 64: 59-62

September 1978

The effect of five organophosphorus insecticides on survival and temperature tolerance in the copepod, Macr&ycloPs albidus (Copepoda: Cyclopidae)

CLIFFORD RAY JOHNSON

Diuision of Biological Control, University of Calfornia, Berkeley, I050 San Pablo Avenue, Albany, Calfornia 94706, U.S.A.

Accepted for publication February 1977

Macrocyclops albidus were exposed for 24 hours to ABATE', fenthion, malathion, methyl parathion, and chlorpyrifos at concentrations of 1 , 5, 10, 25, and 50 parts per billion (ppb). Exposure to chlorpyrifos resulted in the greatest mortality to M . albidus; concentrations of 25 and 50 ppb caused 100% mortality. The thermal tolerance was lowered significantly by all chemicals at concentrations from 1 to 50 ppb.

KEY WORDS:-thermal tolerance-organophosphorus insecticides-copepod-Macroqclops albidus.

CONTENTS

introduction . . . . . . . . . . . . . . . . . . . . . . . 59 Methods and materials . . . . . . . . . . . . . . . . . . . . 60 Results and discussion . . . . . . . . . . . . . . . . . . . . . 60 Acknowledgements . . . . . . . . . . . . . . . . . . . . . 6 1 References . . . . . . . . . . . . . . . . . . . . . . . . 62

INTRODUCTION

Although much literature exists on acute toxicity of pesticides to organisms, few investigations have been concerned with sublethal effects. The majority of the latter studies have dealt primarily with the sublethal effects of DDT exposure on salmonid fishes (see review by Johnson & Prine, 1976). Recently there has been a renewed emphasis on such studies (Cooke, 1970, 1972, 1973; Weis, 1975; Johnson & Prine, 1976; Johnson, 1976). This study ispart of a more com- prehensive investigation to access the nature of the effects of pesticides at sublethal levels on physiological functions and survival on non- target and target organisms.

0 1978 The Linnean Society of London 59 0024/4082/78/090059-04/$02.00/0

6 0 C . R . ~ J O H V S O Y

Table 1. Trade name, formula, and field applied dosage rates as recommended in California for mosquito control for the chemicals used in this study

(,oI1IpOund Scientific name Dmage rates

(rcc oinrnendcd in Califoi-nia)*

0.0, 0'0'-tetramethyl 0,O'-thiodi- p-phenylene phosphorothioate

0,O-dirnethyl 0 -[4-(rnerhyl= thiol- in-tolyll phosplio= rothioate

0,O-diethyl 0-(3,5,6-trichloro- 2-pyridyl) phosphorothioate

0 , O - dirnethyl 0, p-nitrophenyl phosphorothioate

0.0-dimethyl S-( 12-dicarbethosy) ethyl phosphoi-odithioate

0.05 Ib/acre

0.1 Ib/acre

0.05 Ib/acre

0.1 Ib/acre

0.5 Ib/acie

M E T H O D S A N D MATERIALS

.Wacrocylops albidus were cultured from a stock collected from a small permanent pond near Concord, California. After an acclimation period of 24 hours at 18OC to 19OC LD 12 : 12, the copepods were exposed for 24 hours to the insecticides ABATE@, fenthion, malathion, methyl parathion, and chlorpyrifos at the concentrations of 1, 5, 10, 25, and 50ppb. Table 1 presents the chemical name, formula, and applied rates as recommended in California for the above toxicants. The copepods were exposed in 10 litres of solution in aquaria without aeration. After the 24- hour exposure period, the copepods were removed from each toxicant and placed in a 1000 ml beaker with 800 ml ofwater. The water was heated with a 250 W infrared heat lamp at a rate on 0.3"C/min and continually stirred to prevent formation of a temperature gradient. Thermocouples were attached at different levels within the water column and temperature was recorded continually with a Comark electronic thermometer (model 1625; accuracy +O.OS°C) through a Comark selector unit (model 1698). The M. albidus were heated until death occurred and the thermal death points were recorded. Observations were made before heating on the number of dead copepods and behaviour and activity of the live individuals and these data were compared with controls treated in like manner with the exception of not being exposed to the toxicants.

RESULTS A N D DISCUSSION

Exposure to chlorpyrifos resulted in the greatest mortality to M. albidus; mortality was 100% at 25 and 50 ppb and 92.4% at 5 ppb (Table 2 ) . Hurlbert et al. I, 19 7 2 ) f&nd that populations of the copepod, Cyclops uernalis were decimated by this coinpourid during field trials. Survival was greater in the toxicants methyl parathion, malathion, ABATE@, and fenthion resulting in more than 80 to 90% survival even at higher concentrations.

The teinperature tolerance was lowered significantly (5%, non-overlap of 2Sa) b y all chemicals and concentrations (Table 2 ) . Chlorpyrifos and methyl parathion showed the greatest depression to thermal tolerance in M . albidus and

EFFECT OF INSECTICIDES O N MACROCYCLOPS 0 I

Table 2. Thermal death points and mortality of control and toxicant exposed M. albidus

Toxicant and coiicciitratiori

Thermal lethal ("C) Range N ?6 Mortality 2sx

0.15 Control clilorpyrifes

1 PPb 5 PPb

10 PPb 25 ppb 50 ppb

1 ppb 5 ppb

I 0 p p b 25 ppb

1 pph 5 ppb

10 ppb 25 ppb 50 f' pb

1 PPlj 5 PPb

50 pph

' PPb ,5 ppb

10 ppb 25 ppb

niethyl parathion

50 ppb milathion

ABATE@

10 pph 2.5 ppb

feiitliion

50 ppb

35.1 33.2-37.7 185 0.0

43.9 92.4 96.2

100.0 100.0

30.6 24.2 24.8

26.9-32.6 23.5-24.4 23.9-26.6

23 4 3

89 dead 7 2 dead

1.03 0.44 1.82

34.3 31.5 31.9 30.9 29.4

33.6-35.9 23.5-33.5 24.1-34.9 25.0-36.2 21.9-34.8

72 43 49 92 86

0.13 0.85 0.76 0.34 0.77

10.0 18.9 9.2

15.6 14.8

34.6 33.1 32.2 32.0 28.7

27.1-35.4 30.0-34.5 29.1-34.3 30.8-35.2 22.2-35.6

83 35 64 52 35

0.21 0.34 0.44 0.38 1.32

3.4 2.8 1.2 7 . 1 7 . I

34.6 33.5 33.0 32.2 29.2

34.0 - 35.2 31.2-34.6 3 1.7-34.4 26.7-34.4 22.1-35.2

60 61 43 68 39

0.1 1 0.17 0.31 0.59 1.22

3.2 4.7

12.2 10.5 17.0

34.8 33.6 33.9 33.1 31.9

33.5-35.2 25.5-34.5 26.3-35.2 31.7-33.6 23.8-35.5

54 73 59 53 53

0.09 0.50 0.37 0.16 1.09

0.0 1.4 6.3 8.6 7.0

fenthion was the least toxic. Although fenthion was the least toxic to M . albidus, exposure at 1 ppb resulted in a significant depression in heat resistance.

It has been suggested by several previous studies that other physiological responses were probably affected along with the depression of temperature tolerance (Johnson & Prine, 1976; Johnson, 1976). In these studies an alteration in behaviour and activity occurred which would suggest that other physiological responses were affected. Differences in behaviour were not noted with active M. albidus between the exposed individuals and controls. However, activity appeared to be less in individuals exposed to the mid-range con- centrations of chlorpyrifos ( 5 , 10 ppb) and to the higher concentrations ( 2 5 , 50 ppb) of the other chemicals. With those copepods exposed to the median con- centrations of chlorpyrifos and the higher concentrations of methyl parathion, many were visibly in stress at the acclimation temperatures, as noted by sporadic and uncoordinated swimming movements. Thus many of these copepods could be considered to be ecologically dead and did not appear normal in either behaviour or activity.

ACKNOWLEDGEMENTS

Jerry E. Prine and Ernst P. Zboray, State of California Department of Health, offered suggestions concerning the manuscript.

ti:! C. R. JOHNSON

REFERENCES

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COOKE, A. S., 1972. The effects of DDT, dieldrin, and 2.4-D on amphibian spawn and tadpoles. Environment Pollution, I : 5 1 - 7 1.

andPollution, 3 : 51-68, COOKE, A. S.. 1973. Response of Rana temporaria tadpoles to chronic dosrs of p,p' DDT. Copeia, 1973:

647-654. HURLBERT. S . H., IMULLA, M . S . & WILLSON, H. R., 1972. Efiects of an organophosphorus insecticide on

the phytoplankton. zooplankton, and insect populations of fresh-water ponds. Ecologzcd Momographs, 42. 269-299

J O H N S O N , C. R., 1976. Herbicide toxicities in some Australian anurans and the effect ofaubacute dosages on ternperarure tolerance. ZoologicalJournalof the Linnran Sociefy, 59: 79-83.

J O H N S O N , C. K. & PRINE, J. E., 1976. The effects of sublethal concentrations of organophosphorus insecticides and an insect growth regulator on temperature tolerance in hydratrd and dehydrated juvenile western toads, Bufo borra. Comparative Biochemistry and Physioloa, 53A: 147-149.

WEIS, J . S., 1975. The effect of DDT on tail regeneration in Rana pipiens and R. catesbeiana tadpoles. Copeia, I Y 7 S : 765-767.