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United States Department of Agriculture

Agricultural Research Service

Research Project: Chemical Biology of Insect and Plant Signaling Systems

Location: Chemistry Research Unit

Title: Precocene-I inhibits juvenile hormone biosynthesis, ovarian activation, aggression and alters sterility signal production in bumble bee (Bombus terrestris) workers

Authors
item Amsalem, A -
item Teal, Peter
item Grozinger, C -
item Hefetz, A -

Submitted to: Journal of Experimental Biology Online
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 17, 2014
Publication Date: August 11, 2014
Citation: Amsalem, A., Teal, P.E., Grozinger, C.M., Hefetz, A. 2014. Precocene-I inhibits juvenile hormone biosynthesis, ovarian activation, aggression and alters sterility signal production in bumble bee (Bombus terrestris) workers. Journal of Experimental Biology Online. 217:3178-3185.

Interpretive Summary: Although insect juvenile hormone (JH) has been shown to be an important hormone in regulating reproductive development in many insects little is known about the function of JH in adult bumble bees. Scientists at the Department of Biology, Tel Aviv University, Israel, Department of Entomology, Pennsylvania State University and the Center for Medical, Agricultural and Veterinary Entomology, USDA-ARS in Gainesville Fl studied the role of JH in regulation of adult reproductive status and behavior. The used a chemical called Precocene to poison chemically the gland that produces JH in adult bumble bees and monitored ovary development and behavior of the bees. The results showed that production of JH was low in workers treated with Precocene and that ovarian development was inhibited. Rescue therapy in which JH was given to these bees showed that ovaries were stimulated to develop when JH was applied. Additionally, the results showed that bees treated with Precocene were much less aggressive than untreated bees. These results show that JH plays a significant role in both reproductive development and behavior in bumble bees.

Technical Abstract: Juvenile hormone (JH) is an important regulator of development and physiology in insects. While in many insect species, including bumble bees, JH function as gonadotropin in adults, in some highly eusocial insects its role has shifted to regulate social behavior including division of labor, dominance and aggression. Studying JH functions across social insect species is important for understanding the evolution of sociality; however, these studies have been limited due to inability to reduce JH levels without surgically removing its glandular source, the corpora allata. Precocene is known to inhibit JH biosynthesis in several non-social insects, but was hardly studied in social insects. Here, we tested if precocene-I can effectively reduce JH levels in Bombus terrestris workers, and examined its effects on their physiology and behavior. Precocene-I treatment of 3-workers groups decreased JH titer and ovarian activation, irrespective of the bees' dominance rank within the group, and was remedied by JH replacement therapy. Precocene-I also decreased aggressiveness and increased ester-sterility-signal production that was rank-dependent, affecting mainly in the most reproductive and the least aggressive workers, respectively, and could not be remedied by JH replacement therapy. These results clearly confirm the role of JH as a gonadotropin and mediator of aggression in B. terrestris, and that JH effects are associated with worker dominance rank. The ability to chemically reduce JH titer provides us with a non-intrusive method to probe the evolutionary changes associated with JH and the hormonal mechanisms that are associated with reproduction and behavior in social insects.

Last Modified: 11/28/2014
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