نوع مقاله : مقاله پژوهشی
نویسندگان
گروه گیاهپزشکی، دانشکده کشاورزی، دانشگاه تهران، کرج، ایران
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسندگان [English]
Bumblebees are valuable assets in terms of pollination services in wild plants and greenhouses. The most well-studied species of bumblebees is Bombus terrestris which is commercially reared and sold on a large scale worldwide. Even though the artificial rearing of bumblebees started in the 1950s, there are still some problems in the mass-rearing process of them. One of the main problems is the low rate of gyne production in the late phase of the colony, to start the new colonies. So, the main objective of this study was to increase the number of produced gynes in the B. terrestris colonies by changing the caste of the larva from worker to queen. For this purpose, we used pyriproxyfen which is a juvenile hormone analogue compound. The first and early second-stage larvae were treated with 1,3 and 6 ppm of pyriproxyfen and the onset time of emergence, number, weight, mating succession, and diapause survival of new gynes were recorded. The results showed that the 3 ppm treatment had the highest number of the produced gynes, and also the shortest onset time of emergence. There was no difference in mating succession and diapause survival among the treatments. Based on the experiment results, we concluded that using a 3 ppm concentration of pyriproxyfen compound on young larvae of B. terrestris can induce the juvenile hormone effect and increase the number of produced gynes in the colony. We suggest that pyriproxyfen as a juvenile hormone analogue, regarding the concentration, type, and time of application on the young larvae, can be used to increase the number of produced gynes in the bees’ colony.
کلیدواژهها [English]
Extended Abstract
Introduction
Farmers worldwide are using commercial pollinators to increase their product amount and quality. Many greenhouse products pollinated with the help of commercial colonies of bumblebees especially Bombus terrestris (Hymenoptera: Apidae). Even though the laboratory-rearing of these bees started in the 1950s, there are still problems in its mass production process. One of the most important limitations in the mass rearing of bumblebees is the number of newly produced gynes to start new colonies. There are two female castes in a bumblebee’s colony; queen and worker, which are genetically the same. It is shown that caste determination in B. terrestris happens in the early days of larval stage and juvenile hormone plays an important role in it. The juvenile hormone is a gonadotropin that regulates many pathways of reproduction, domination hierarchy, and caste determination. It could be suggested that manipulating the juvenile hormone titer in a diploid (female) larva could lead to producing a gyne instead of a worker. However, the use of juvenile hormone is limited due to its instability and the need to keep it continuously at -18 Celsius, as well as being expensive. Therefore, to measure our goal in this research, we decided to introduce a synthetic compound into the experiments equivalent to this hormone in the form of a juvenile hormone analogue with the chemical name pyriproxyfen. Pyriproxyfen is one of the juvenile hormone analogues, which is currently used in Europe as an insecticide and is also reported as a safe compound for B. terrestris since there is no mortality reported due to its application on bumblebees. So, the main objective of this research is to find a way to produce more gynes in a B. terrestris colony by manipulating the juvenile hormone.
Materials and Methods
In this study, we used 12 naturally reared queen right colonies at the 10-workers stage, We used 1,3 and 6 ppm of pyriproxyfen as treatments and applied it to the first and early second larval stage in the queen-right colonies. In the first experiment, the onset time of emergence, number, and weight of new gynes were recorded. In the second experiment, we tested the mating succession and diapause survival of the new gynes. All the experiments were performed in the red light and the colonies were at the same age.
Results and Discussion
The results showed that using 3 ppm of pyriproxyfen on the first and early second larval stage of B. terrestris mimics the juvenile hormone role since the 3 ppm treatment had the shortest onset time of gyne emergence and also the highest number of produced gynes. Although the produced gynes in the 3 ppm pyriproxyfen treatment had lower weight than the control, there was no significant difference in mating succession and diapause survival among the treatments. We observed no difference between the results of the 1 ppm treatment and control in this experiment, however, the 6 ppm treatment showed some differences in onset time of emergence, weight, and number of produced gynes. This finding confirms that juvenile hormone titer in the larval stage is crucial in caste determination of B. terrestris and also shows that manipulating the JH with pyriproxyfen as a juvenile hormone analogue is a possible and concentration-sensitive process.
Conclusion
Based on the results, we concluded that pyriproxyfen as a juvenile hormone analogue, regarding the concentration, type, and time of application on the young larvae in the queen right colonies of B. terrestris, can be used to reduce the onset time of emergence and increase the number of produced gynes in these bees’ colonies.
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