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Effects of Gamma Radiation on Melanization in the Larvae of Melon Fly Bactrocera Cucurbitae (coq.) (diptera : Tephritidae)

MD. HASANUZZAMAN
Department of Zoology, University of Dhaka, Dhaka-1000, Bangladesh

ANWARA BEGUM
Department of Zoology, University of Dhaka, Dhaka-1000, Bangladesh

REZA MD. SHAHJAHAN
Radiation Biology (IFRBJ, Atomic Energy Research Establishment (AERE), GPO Box No. 3887, Dhaka-1000, Bangladesh.

FARZANA YESMIN
1Radiation Entomology and Acarology Division, Institut e of Food and Radiation Biology (IFRBJ, Atomic Energy Research Establishment (AERE), GPO Box No. 3887, Dhaka-1000, Bangladesh.

Abstract/ Executive Summary:

The effects of gamma radiation (at different doses) on the melanization activity in larvae of Bactrocera cucurbitae were examined. The degree of melanization was observed by ionizing radiation measuring the increa se/decrease of melanin in the larvae killed by freezing. The eggs (24 hr old) and larvae (48 hr old) of this pest species were irradiated at doses of 10, 40 , 70, 100, 130 and 160 Gy. At dose of 10 Gy, low and high degree of melanization were observed in 24 hr old egg and 48 hr old larvae, respectively. In unirradiated (control) larvae, melanization activity can be detected on day 4 (96 hr old , late 2nd instar ), and the activity continues to accumulate through day 7 (168 hr old, late 3rd instar ). The accumulation of melanin was not observed when larvae were irradiated with a minimum dose of 40 Gy. These results indicate that the degree of melanization in B. cucurbitae larvae is a reliable indicator of irradiation treatment and can be used to prevent the introduction of harmful exotic pest species in any quarantine station.

Keywords: Quarantine treatment, Melanization, Gamma radiation, Bactrocera cucurbitae

Location: Department of Zoology, University of Dhaka, Dhaka-1000, Bangladesh

Start Date:

End Date:

Program Area: Pest Management

Commodity: Insects

Objectives:

To determine the Effects of Gamma Radiation on Melanization in the Larvae of Melon Fly Bactrocera Cucurbitae (Coq.) (Diptera : Tephritidae)

Methodology:

Sample preparation : Eggs of Bactrocera cucurbitae were collected in pieces of sweet gourd by placing some of them in the adult cages. The eggs hatched in the pieces of sweet gourds and these were irradiated after 24 and 48 hrs of egg laying, at doses of 10, 40 , 70, 100, 130 and 160 Gy, respectively. Irradiation was done in a 60Co source. Then they were placed in the pupation cages. Larvae were washed out of the rearing medium, dried on a filter paper, placed in vials and frozen at - 20°C until they were used in the experiment . Test of melanization activity : Melanization tests were done in term s of body colour change in the larva e which w ere irradiated at different doses. At first, larvae were removed from the freezer and placed at room temperature ( 27 ± 2°C) on a whit e back ground for observation of body colour change. The colour changed (darkening) due to melanization reaction occurring in the larva e at different magnitude at different doses of irradiation treatment, and compared to those of unirradiated (control) ones. This was recorded photographically after 30 minutes post freezing exposure at room temperature.

Source of Information: Dhaka Univ. J. Biol. Sci . 12(2): 123-129, 2003 (July )

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

In quarantine treatment, the suggested radiation dose does not necessarily cause immediate death, but only prevents completion of development to the adult stage. Consequently, if a living larva is detected in shipment, it is very important to determine if it has been irradiated. Several studies have been done to distinguish irradiated larvae from those not irradiated. Results on the effects of gamma irradiation on the melanization process in larvae killed by freezing has been discussed in the present study. In addition, it also presents a fast and simple procedure for identifying irradiated larvae to detect previous exposure of the larvae to ionizing radiation. In unirradiated (control) larvae, melanization activity can be detected on day 4 (96 hr old , late 2nd instar ), and the activity continues to accumulate through day 7 (168 hr old, late 3rd instar ). The accumulation of melanin was not observed when larvae were irradiated with a minimum dose of 40 Gy. These results indicate that the degree of melanization in B. cucurbitae larvae is a reliable indicator of irradiation treatment and can be used to prevent the introduction of harmful exotic pest species in any quarantine station.

Knowledge Management: Journal