BIOTROPIA No. 5, 1991/1992: 26-40 

EFFECTS OF CARBOFURAN ON THE REPRODUCTIVE CAPACITY OF A 

FRESHWATER SNAIL, RADIX QUADRASI, 

UNDER LABORATORY CONDITIONS 

IMELDA F. PAGULAYAN, GLORIA L. ENRIQUEZ 

and VIRGINIA S. CARING 
College of Science, University of the Philippines 

Diliman, 1001 Quezon City, Philippines 

ABSTRACT 

The effects of 4 sublethal concentrations of carbofuran (250, 500, 1000 and 2000 ppm) on the 

reproductive capacity of R. quadrasi was determined. Results showed that incubation period is delayed and 

inhibited by 1000 and 2000 ppm carbofuran but not by lower concentrations. The hatching period is longer in 

treated snails and not all eggs hatch in the 1000 and 2000 ppm treatment. The percentage of hatching is 

inversely proportional to the carbofuran concentration. 
Oviposition was delayed in all the treated stages and at all dosages. The higher the carbofuran 

concentration, the later the onset of oviposition. The reproductive period is shortened. Fecundity was 

decreased in snails treated at EMB and SM. However, only the 2000 ppm carbofuran concentration showed an 

adverse effect on the snails exposure at PSM. 

INTRODUCTION 

Pesticides are continuously finding widespread use and increasing amounts are 

being introduced into the aquatic environment. Researchers worry that this increasing use 

of pesticides and the farming industry's dependence on it may eventually lead to health 

problems for both consumers of farm products and farm workers (Allmon 1985). 

Moreover, this will pose a potential hazard not only to human beings but also to aquatic 

organisms of economic importance (Mane et al. 1979). 

Invertebrates constitute a very large portion of the fauna in both the aquatic and 

terrestrial system. From an ecological viewpoint, these animals play an important role in 

the energy flow in these ecosystems. The feeding habit of invertebrate animals varies 

from detritus feeding to herbivorous and carnivorous food consumption. Disruptions 

caused by pesticide stress in one or more organisms may directly interfere with other 

inter-dependent components of the food chain (Gunther et al. 1968). 

Carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofuranyl-N-methylcarbamate) 

developed by the Niagara Chemical Division of FMC Corporation is commercially known 

as Furadan. It is a systemic insecticide, nematicide with broad spectrum activity (Metcalf et 

al. 1968; Yu et al. 1974; Cremlyn 1980; Handa 1980) although hydro- 

26 



Antioxidant metabolism in water stressed peanut - G.C. Rivero & D.M. Orcutt 

lyzed rapidly in water. It is an effective contact toxicant and is non-corrosive and 

compatible with other pesticides (Rangaswany et al. 1976). Carbamate insecticide is a 

popular choice since it is less toxic, less persistent and has lower residual effects in animals 

than other classes of pesticides. Nevertheless, it is accumulated to a certain extent. 

This work aims to determine the levels of carbofuran concentrations that are toxic 

or deleterious to the embryonic (EMB), presexually mature (PSM), and sexually mature 

(SM) R. quadrasi; to determine the effects of sublethal concentrations of carbofuran on the 

fecundity and reproductive period of the snail; and to determine the particular age group 

that is most sensitive to carbofuran. 

MATERIALS AND METHODS 

Organism 

Radix quadrasi, (Fig. 1) the snail used in this study, were obtained from stock 

cultures started in 1981 and have been maintained and reared continuously in the 

Snail Room of the Natural Sciences Research Institute, University of the Philippines, 

Diliman, Quezon City. 

 

27 

Figure 1. Radix quadrasi 



BIOTROPIA No. 5, 1991/1992 

Laboratory maintenance and culture of snails, maintenance of eggs and young snails 

followed that of de Lara and Enriquez (1981) and Pagulayan and Darvin (1986). 

Preparation of Working Solutions 

Carbofuran in the form of 3G was prepared by dissolving the granules first in 

acetone before adding distilled water. The solution was aerated overnight before use. 

Concentration parts in per million (ppm) were used. 

All glasswares and plastic containers were acid washed and rinsed with de-ionized 

water. Petri dishes were oven-dried before use. 

Experimental Set-up 

Thirty egg masses were used as the source of snails that were observed for 

fecundity and reproductive period. Ten of these egg masses were allowed to hatch under 

normal conditions (control). The other experimental groups consisting of 10 egg masses 

each were treated with 250 ppm and 500 ppm carbofuran for a period of one week in 

separate petri dishes. Two-week treatment durations and 1000 and 2000 ppm 

concentrations were not used because preliminary work showed that survival of 

experimental snails would be less than 50%. 

A. Treatment at the Larval Stage 

Two weeks after the eggs hatched into young snails, 48 snails were taken at 

random from the untreated egg masses and were placed in groups of four in 12 separate 

basins. The same was done for egg masses treated with 250 and 500 ppm. The average 

size and age of the snails at first and last oviposition were recorded. The total number of 

egg masses laid per group were recorded weekly in the entire length of the reproductive 

period. The length of the reproductive or egg laying period was recorded. 

B. Treatment at Week Four (PSM) 

Forty five newly hatched snails from egg masses under normal laboratory conditions 

were separated at the age of two weeks. They were placed in 9 separate basins in groups of 

five. The above procedure was followed. However, the snails were exposed to the four 

carbofuran concentrations applied at the end of the 4th week to the end of the 6th week 

after hatching. 

28 



Effects of carbofuran on the reproductive capacity - Imelda F. Pagulayan et al. 

C. Treatment at Week Seven (SM) 

The same procedure was followed except that the snails were treated at the end of 

the 7th week to the end of the 9th week after hatching. 

In the two-week duration of treatment, the medium was changed after the first 

week. Possible toxic material in the medium like the feces were removed regularly. 

RESULTS 

Effects of Fecundity 

Fecundity is the total number of the eggs produced by the individual during its 

reproductive period. Reproductive period, on the other hand, is defined as the number 

of days from the first to the last day of egg-laying. 

A. Treatment at Embryonic Stage (EMB) 

Table 1 shows the size range and average at the onset and end of oviposition, the 

reproductive capacity and the reproductive period of R. quadrasi that were hatched 

from untreated embryos and embryos exposed to 250 and 500 ppm concentrations of 

carbofuran. The average size length: 10.62, 10.56 and 10.45 mm for the control, 250 ppm 

and 500 ppm treatment respectively, are not significantly different from each other. 

However, the age range and average in days of the treated snails differ greatly from the 

untreated. The earliest oviposition took place in the control at day 29, although the 

average age was 39 days. The earliest oviposition for both treatments was 43 days with 
an average age of 49.5 days. The treated snails oviposited at a much older age but the 

size of the snails were almost the same as that of the untreated ones. 

The average size length at last oviposition differ between the control and the treated 

snails; for the control it took place at an older age range with an average of 224 days. 

Oviposition stopped at an average age of 196.5 days for the 250 ppm treatments; and 193 

days as average age for the 500 ppm treatment. There is no significant difference in the 

size and average for the two treatments. 

The number of egg masses, number of eggs (Table 1 and Fig. 2) and average 

number of eggs per egg mass are highest in the control followed by the 250 ppm and 

lowest in the 500 ppm treatment. The reproductive period was shorter in the treated 

snails. 

29 



BIOTROPIA No. 5, 1991/1992 

 

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Efects of carbofuran on the reproductive capacity – Imelda F. Pagulayan et al. 

 

 

 

 

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BIOTROPIA No. 5, 1991/1992 

B. Treatment at Week 4, Pre-Sexual Maturity (PSM) 

Table 2 shows the effect on the size and age of the snails treated at the end of week 

4 to the end of week 6 at the onset and end of oviposition. The total number of egg masses, 

eggs (Fig. 3) and the average eggs per egg mass observed during the entire reproductive 

period is also shown in the table. 

With the exception of the 2000 ppm treatment wherein the average snail size at 

initial oviposition is smaller, the size average of the rest of the treatments and control are 

not significantly different from each other. The average age for initial oviposition in the 

control is 40.44 days, while the treated snails at 4 carbofuran concentrations are 53.36, 55.0, 

56.5 and 55.84 days. This is an indication that treated snails oviposited at an older age. 

The average size in the last oviposition of the treated snails is smaller than in the 

control except in the 2000 ppm treatment. The average age at last oviposition is higher in 

the control and significantly lower in the treated. The 500, 1000 and 2000 ppm 

treatments were not significantly different from each other but significantly different 

from the 250 ppm group. 

The number of egg masses and eggs in the snails exposed to 2000 ppm is significantly 

low. There is no significant difference though in the total number of eggs and egg masses 

among the other experimental set-ups including the control (Fig. 3). The reproductive 

period is longest in the control, and decreasing with higher concentrations. Those 

exposed to 500, 1000 and 2000 ppm are lower but not significantly different from each 

other. 

C. Treatment at Week 7, Sexual Maturity (SM) 

Table 3 shows the effect of the 4 carbofuran concentration on the size of the snails 

treated at week 7 at the onset and end of oviposition. The total number of egg masses 

laid and the total number of eggs for the entire reproductive period is also shown (Fig. 4). 
The average number of eggs per egg mass at the end of the observation period is likewise 

indicated. 

It is shown in Table 3 that untreated snails start to oviposit at an average length 

of 9.6 mm. The average size of the snails at the onset of oviposition in all four treatment 

groups as well as in the control does not significantly differ from each other. The average 

age, however, was older in the treated snails, indicating that while sizes are more or less 

the same, oviposition occurred at an older age. There are snails in the untreated that 

oviposited in as early as 35 days of age, while the youngest snail that oviposited in the 

experimental group was 45 days old, or a difference of 10 days. Some snails did not 

oviposit: 1 snail in the untreated, 10 in the 250 ppm treatment, 8 in the 500 ppm treatment, 

6 in the 1000 ppm treatment and 

32 . 



Effects of carbofuran on the reproductive capacity – Imelda F. Pagulayan et al. 

                                                          

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BIOTROPIA No. 5, 1991/1992 

 

 

 

 

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BIOTROPIA No. 5, 1991/1992 

7 in the 2000 ppm treatment. Average age at first oviposition in the untreated is 42 days, 

while in the treated the range is from 58.4 to 60.73 days (Table 3). 

The average size of the snails at last oviposition was smaller in the treated but not 

significantly different from control and from each other. The average age at last 

oviposition, however, is highest in the control (169.42 days) and lowest in the 2000 ppm 

treatment (120.36 days) in a decreasing order with increasing concentration. 

The total number of egg masses and eggs was highest in the untreated snails, 1284 

and 76559, respectively. The number of egg masses and eggs produced in the treated 

was lower and significantly different from the control but not significantly different from 

each other. The average number of eggs per mass is highest in the control and lower in the 

treated. The numbers of snails that reached the stage of oviposition in the treated set-ups 

were reduced. 

The reproductive capacity of the treated snails increases weeks after treatment. 

The observation is more evident in the treated than in the untreated snails. However, the 

above increase is still not enough to equal the number of egg masses and eggs produced 

by the control group. The reproductive period in the treated snails is significantly lower 

than in the control. 

D. Comparative Fecundity Results in the Three Designated Stages (EMB, PSM, SM) 

Table 4 is the summary of the effects of all the treatments on the size and age at 

the onset and end of oviposition, on the reproductive capacity and length of the 

reproductive period in the three stages of treatment. 

The size range in days at the start of oviposition was 29 - 50 days for the EMB control; 

35 - 52 days for the PSM control; and 35 - 50 days in the SM control. The total range 

using 138 snails was from 29-52 days. 

The smallest in size average at the same time oldest in average for the initial 

oviposition in all the treatments was on the SM treated snails, followed by the PSM and the 

largest but the youngest to oviposit was in the EMB. While Table 4 shows that the PSM 

group is the earliest to stop ovipositing, it cannot be concluded that it is the most 

sensitive to the treatment since the control group follows the same trend. The 

reproductive capacity is highest in the EMB treated snails. While SM treated snails had a 

longer reproductive period than the PSM, their reproductive capacity is very much less. 

36 



Effects of carbofuran on the reproduction capacity – Imelda F. Pagulayan et al 

                 

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BIOTROPIA No. 5, 1991/1992 

DISCUSSION 

The results of previous work (de Lara and Enriquez 1981) gave a range of 35 -42 days 

under controlled condition as the start of oviposition. In the current work, however, the 

total range in these 138 snails was 29-52 days. The current results did not exactly 

sustain the earlier findings, perhaps because of the effect of cold temperature when these 

experiments were done, since the expected oviposition periods coincided with the cold 

months of December and January. Boray (1964) observed in his work that no copulation 

occurred in L. tomentosa in temperatures below 16°C in the laboratory cultures or in the 

field. The variations apparently reported in the reproductive biology of lymnaeids in 

general may be due to the different culture methods used. However, Remigio and 

Pagulayan (1984) contradict this finding. 

Start of oviposition was delayed in all the treated snails while size range and 

average do not differ much in both the untreated and treated snails in the initial 

oviposition. The treated snails are older which means that it took a greater number days to 

reach the ovipositing size. It seems that it is more the size rather than age that 

determines the onset of oviposition. This is true in all the 3 age treatments. Since growth is 

delayed by the treatment, delay in the oviposition could be attributed to it. It can be 

stated that the higher the concentration, the later is the start of oviposition. This could 

also be due to a delay in the rate of gonadal maturation. The higher the concentration, the 

earlier the cessation of oviposition. 

The number of egg masses and eggs produced at initial oviposition is highest at the 

control and lowest at the 2000 ppm treatment. The treatment not only delayed but also 

inhibited the reproductive capacity of most of the snails. Inhibition increased with 

increasing carbofuran concentration. However, the actual number of egg masses- at first 

oviposition could not be correctly determined. The fact that the number of egg masses at 

its first appearance is less than the number of snails clearly indicates that not all 

oviposited. There is no way of determining which of the snails in the basin did or did not 

oviposit since they are in groups of 4's and 5's. It is possible that the first oviposition in 

some may have been included in later weeks and counted as later ovipositions. While it is 

true that there is no accurate method of counting the number of egg masses for first 

oviposition, there is no other way, unless observations will be done on individual snails 

cultured in separate basins; such condition, however, is not conducive to fecundity. 

The results showed that the carbofuran maybe more effective in a particular age 

group, and the results could have altered the individual's competitive ability, i.e. food 

getting, mating. This could be the reason for the decreasing fecundity with increasing 

concentration in the EMB; there was a drastic effect only 

38 



Effects of carbofuran on the reproductive capacity - Imelda F. Pagulayan et al. 

of the 2000 ppm on the egg laying capacity of the PSM treated snails, and a drastic effect 

of all the treatments on the egg laying capacity of the SM treated snails. It may also be 

possible that the PSM treated snails could have recovered after the effect of the 250, 

500 and 1000 ppm carbofuran concentrations had diminished. Recovery brought them 

back on equal footing with the untreated ones, thus the egg production was higher, 

counteracting the low egg production at the start. The initial effect, therefore, seems 

to be delaying in this particular stage instead of totally inhibiting with the exception of 

the 2000 ppm which partially inhibited the egg laying capacity. Godan (1983) stated that 

the periods of greatest sensitivity occur when the gastropods are very young and again 

when they are adults, at the peak of their reproductive activity. Resistance is greatest 

among juveniles before the onset of sexual maturity. This reinforces the results of this 

work, as shown by the effect on fecundity of the SM treated snails. Sexual maturity is the 

most critical stage to carbofuran treatment when it comes to reproductive capacity. 

The reproductive period is shorter in the treated snails and is again inversely 

proportional to the carbofuran concentration. The snails had to attain a bigger size 

and older age before oviposition took place. 

The snails used as control in the EMB, PSM and SM treatments had a wide range 

of variation for the first oviposition. The said control set-ups were not done at the same 

time. That could explain the wide variation in 29 - 50 for the EMB control; 35 - 52 for the 

PSM control; 35 - 50 for the SM control. The final average, though, for all the control is 

still 40.48 days which still supports the upper range of the results of earlier works, 

35-42 days (de Lara and Enriquez 1981). 

The pesticide decreased the reproductive capacity of the snails and shortened the 

reproductive period. Unlike its effect on growth, the SM treated snails were the ones 

adversely affected. There were snails that did not oviposit at all and a great number did not 

reach the size/age of oviposition. The carbofuran, depending on the concentration 

and/or the stage of application must have direct and subtle impacts on behaviour that 

influences the snail's competitive success i.e. small changes in courtship or mating rituals 

induced by the carbofuran may lead to mating failure, thus affecting the reproductive 

capacity and period. 

REFERENCES 

ALLMON, F. 1985. Pesticides and unhealthy dependence. Science  6(8): 14. 

CREMLYN, R. 1980. Pesticides: preparation and mode of action. John Wiley and Sons, New York.  

DE LARA, A.V. and G.L. ENRIQUEZ. 1981. Life history of laboratory reared Radix quadrasi (Gastropoda: Pulmonata). 

Kalikasan 10(2-3): 242-254. 

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BIOTROPIA No. 5, 1991/1992 

GODAN, D. 1983. Pest slugs and snails, biology and control. Springer-Verlag, Berlin. 

GUNTHER, F.A., W.E. WESTTAKE and P.S. JAOLAN. 1968. Reported. 

HANDA, S.K. 1980. Spectrophotometric determination of carbofuran residues in water. Assoc. Chem. 64(2): 

200-201.  

MANE, U.H., M.S. KACHOLE, and S.S. PAWAR. 1979. Effect of Pesticides and Narcotants on Bivalve Mollusks. 

Malac. 18: 347-360.  

METCALF, R.L., T.R. FUKOTO, C. COLLINS, K. BERCK, S. ABD EL-AZIZ, R. MUNOZ and C.C. CESSRL. 1968. Metabolism of 

2,2-dimethyl-2,3-dihydrobenzofuranyl-7-N-methyl carbamate (Furadan) in plants, insects, and mammals. 

J. Agr. Food. Chem. 16(2): 300-311.  

PAGULAYAN, I.F. and D. DARVIN. 1986. The systematic relationship of Radix quadrasi and Mixas cumingiana 

(Pulmonata: Lymnaeidae). Part III Genetics and Part IV Ecology. Final Report on a Research Project 

submitted to the Natural Sciences Research Institute, Diliman, Quezon City.  

RANGASWANY, J.R., Y.D. VIJAYASHANAKAR, and S.R. PRAKISH. 1975. A simple Spectrophotometric method for the 

determination of carbofuran residues. J. AOAC 59(6): 1276-1278.  

Yu, C., G.M. BOOTH, D.J. HANSEN, and L.R. LARDEN. 1974. Fate of carbofuran in a model ecosystem. J. Food 

Chem. 22(3): 431-434. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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