ARS | Publication request: Immunohistological localization of serotonin in the CNS and feeding system of the stable fly stomoxys calcitrans L. (Diptera: muscidae)

Submitted to: Archives of Insect Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 2, 2011
Publication Date: June 15, 2011
Citation: Liu, S.S., Li, A.Y., Witt, C.M., Perez De Leon, A.A. 2011. Immunohistological localization of serotonin in the CNS and feeding system of the stable fly stomoxys calcitrans L. (Diptera: muscidae). Archives of Insect Biochemistry and Physiology. 77(4):199-219.

Interpretive Summary: The stable fly, Stomoxys calcitrans (L.) (Diptera: Muscidae), is one of the most significant blood-feeding flies affecting cattle. Larvae feed on a solid diet made of cattle manure, hay, and other organic materials on the ground, while the adults are obligate blood feeders of animals and humans. Due to their breeding and feeding habits, stable flies cannot be effectively controlled with currently available insect control technologies, including chemical insecticides. Understanding the physiological and molecular mechanisms of several key behaviors, including blood-feeding, in the stable fly may lead to discovery of new targets for developing novel insecticides or behavioral modifying compounds, such as anti-feedants. Serotonin is a neurotransmitter and neuromodulator reported to play a role in insect feeding behavior. A study was conducted to detect the presence of serotonin in the stable fly central nervous system (CNS) and feeding related systems. Various immunohistochemical techniques were used to detect and localize serotoninergic neuronal processes in the larval and adult stages of the stable fly. The muscular structure of the stable fly feeding-related systems, particularly the cibarial pump, a key structure responsible for blood ingestion, was also described. Many serotoninergic neurons were found in the stable fly CNS and some of them were found to innervate the cibarial pump muscles and the gut, which are essential for feeding. This is the first report describing neuromuscular structures of the stable fly feeding system. The results indicate additional studies are required to characterize the roles serotonin and it's receptors play in stable fly feeding behaviors.

Technical Abstract: Serotonin, or 5-hydroxytryptamine (5-HT), plays critical roles as a neurotransmitter and neuromodulator that control or modulate many behaviors in insects, such as feeding. Neurons immunoreactive (IR)to 5-HT were detected in the central nervous system (CNS) of the larval and adult stages of the stable fly, Stomoxys calcitrans, using immunohistological techniques. The location and pattern of the 5-HT IR neurons were described and compared between these two different developmental stages. Anatomical features of the fly feeding system were analyzed in third instar larvae and adult flies using a combination of histological and immunohistological techniques. In third instar larvae, the cibarial dilator muscles were observed within the cibarial pump skeleton and innervated by 5-HT IR neurons in nerves arising from the brain. There were four pairs of nerves arising from the frontal surface of the larval brain that innervate the cibarial pump muscles, pharynx, and muscles controlling the mouth hooks. A strong serotoninergic innervation of the anterior stomatogastric system was observed, which suggests 5-HT may play a role in the coordination of different phases of food ingestion by larvae. Similarly, many 5-HT IR neurons were found in both the brain and the thoracico-abdominal ganglia in the adult; some of these neurons innervated the cibarial pump dilator muscles and the stomatogastric muscles. This is the first report describing neuromuscular structures of the stable fly feeding system. The results reported here suggest 5-HT plays a critical role in feeding behaviors of stable fly larvae and adults.