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Short communications

Development of Tribolium anaphe irradiated as larvae of various ages with gamma rays

M a h b u b H a s a n , M. K h a l e q u z z a m a n & A t a u r R a h m a n K h a n

Department of Zoology, Rajshahi University, Rajshahi 6205, Bangladesh

Accepted: June 13, 1989

Key words: Tribolium anaphe, g a m m a radia t ion, deve lopmen t

Introduction

Tribolium anaphe H i n t o n (Co leop te ra : Tenebr io- nidae), or iginat ing in E th iop ia (Hin ton , 1948), is

one o f the m o s t des t ruct ive pests o f cereals and their p roduc t s , and is c o s m o p o l i t a n in distr ibu- tion. A g o o d n u m b e r o f works have been conce rn -

ed with radia t ion effects on Tribolium species (Cork, 1957; Sokoloff , 1961; Yang etal., 1970;

M c K i b b e n & Mills, 1972; Bhat ia & Sethi, 1980; Bha t etal., 1981; Bong i rwar etal., 1981; Wool , 1982). Unfo r tuna t e ly there seems to be no pub- lished da t a available on T. anaphe which led us to unde r t ake this investigation.

Materials and methods

Insects used in this study were originally received from Slough Laboratory, MAFF, England, and had been cultured on wholemeal flour in the Dept. of Zoology, Rajshahi University. Adults were placed on a thin layer of fine wholemeal flour in a Petri dish and on the next day eggs were collect- ed by sieving the contents. Eggs were incubated in a Petri dish for hatching. Gamma-radiation (Source Co6~ 75 Krad/hr) was administired to larvae (1-, 8- and 14-day-old) at doses of 1, 2, 4 and 6 Krad. The insects were reared in glass jars (22 x 9cm) containing 250g standard food media (Park & Frank, 1948), and each treatment contained 200 larvae. Mature larvae were retriev- ed and put on Petri dishes for pupation. The number of insects pupated in each treatment and their larval periods were carefully noted. Newly- formed pupae were retained in Petri dishes for adult emergence. The number of adults emerged and the pupal periods were then recorded. All the experiments were conducted at 30 ~

Results

Significantly (P < 0.001) lengthened larval and pupal periods were observed in treated larvae (Table 1). Significantly (P < 0.001) lower pupal

93

Table I. Mean developmental periods of irradiated T. an- aphe (days)

Dose 1-day 8-day 14-day (Krad)

0 19.15 + 0.57* 20,06 + 0.71 19.98 _+ 0,62 (control) 5.18 + 0.46** 5.41 + 0.32 5.34 _+ 0,27

l 23.40 + 1.87 23.37 + 1 .71 26.65 +_ 2,27 5.96 +_ 0.76 5.69 + 0.62 6.01 + 0,89

2 26.87 +_ 3.77 24.32 + 1 .57 27,78 +_ 2,67 6.31 + 1.09 6.54 +_ 0.75 6.81 + 0,70

4 27.60 +_ 0.89 26.50 +_ 2.30 28.28 + 3,18 6.45 +_ 0,97 6.78 +_ 0.66 7.09 + 0.99

6 - 27.22 + 2.00 29.17 _+ 2.93 6.90 + 0,74 7.12 _+ 1.06

* Larval and ** Pupal periods

and adult recoveries were recorded in irradiated insects (Table 2). The production of adults was significantly reduced (P < 0.001) at all the doses compared with that of the control. The proportion of malformed adults to normal adults increased with increasing doses.

Discussion

The lengthened developmental period in irradiat- ed insects was also observed by Blotchly (1962)

Table 2. Pupal and adult recovery in irradiated T. anaphe (%)

Dose 1-day d-*** 8-day d- 14-day d-

(Krad) values values values

0 85,00* - 86.00 - 84.00 - (control) 82.50** - 84.00 - 81.50 -

1 82.00 0.73 84.00 0.52 81.00 0,72 65.00 3.40 63.00 4.08 65.50 3.12

2 77.00 1.81 80.50 1,34 79.50 1,05 38.00 7,04 57.50 4,89 61.50 3.76

4 44.00 6.83 70.50 3.32 73.50 2.28 37.00 7.15 18,00 9.43 32.50 7.49

6 - - 25.00 9.14 22.50 8.99 - - 2.50 10.82 8.00 9.91

* Pupae and ** Adults; *** d = Standardized normal deviate No. of larvae: 200 in each treatment

94

and Rahman et al. (1975). The older larvae were more resistant to treatments than the younger ones at all the doses. A general decrease in feeding with an increase in doses was noted. After expo- sure to 6 Krad, 1-day-old larvae became mori- bund on the 6th day and all died on the 13th day. These findings indicate a close conformity with the results of Brown et aL (1972) and Dawes et aL (1987). Reduction of adult production by irrad- iation has also been recorded by several workers working with beetles (Blotchly, 1962; Tilton et al., 1966; Burgess & Bennett, 1972; Brown etal. , 1972; Rahman etal. , 1975; Ratti & Cavalloro, 1982 and Bughio, 1983). Cornwell & Bull (1960) stated that insect populations in stored products can be controlled by producing immediate mortality or by producing sterility of the irradiated insects. Considerable variation in results may occur when factors like radiation dose rate and age of the individuals are not considered (O'Brien & Wolfe, 1964; Brown & Davis, 1973).

It is hoped that the findings obtained in the present investigation can be useful in control measures for stored products tenebrionids, among others. However, more detailed studies are needed.

Acknowledgements

The authors are most grateful to the Slough Labo- ratory, MAFF, England, for supplying the experi- mental insects; the Chairman, Bangladesh Atom- ic Energy Commission, for radiation facilities and the Chairman, Dept. of Zoology, Rajshahi Univ- ersity, for necessary laboratory facilities. Thanks must go to Laila Arjumand Banu, an M.Sc. stu- dent, for her help.

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