|MIYASAKI, KATELYN - Desert Vista High School|
|VUONG, CONNOR - Desert Vista High School|
|MIRANDA, BRITTANY - Estrella Mountain Community College|
|STEELE, BRONWEN - Estrella Mountain Community College|
|NATH, RACHNA - Arizona State University|
Submitted to: Journal of Comparative Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/28/2015
Publication Date: 2/1/2016
Citation: Brent, C.S., Katelyn, M., Connor, V., Brittany, M., Bronwen, S., Brent, K.G., Rachna, N. 2016. Regulatory roles of biogenic amines and juvenile hormone in the reproductive behavior of the western tarnished plant bug (Lygus hesperus). Journal of Comparative Physiology. 186(2):169-179.
Interpretive Summary: Although the western tarnished plant bug is an important pest of field and horticultural crops in the western U.S., the physiological mechanisms controlling mating and reproduction in this species remain poorly known. The male plant bug transfers a packet of material to the female during mating. For about a day thereafter, the male abstains from mating again while these materials are replenished. Newly mated females also become unreceptive to re-mating, but for several days, during which the rate of egg laying is increased. In other insects, such changes are controlled by neurotransmitters known as biogenic amines. To better understand the regulation of these behavioral changes in plant bugs, levels of four biogenic amines (dopamine, octopamine, serotonin, and tyramine) were examined in the brains of female and male bugs at various times after mating. Levels of dopamine changed in response to mating, but injection of this material did not influence mating or egg laying. Although mating did not produce demonstrable changes in octopamine levels, injection of this material caused egg laying to decrease. Neither serotonin nor tyramine were influenced by mating, and injection of these materials produced no response. The results suggest a brief decline in octopamine immediately after mating may be necessary to promote egg laying. Although dopamine does not appear to have immediate effects on plant bug mating, it may influence levels of the hormones that control egg and sperm production, which could indirectly influence willingness to mate. These findings provide key insights that contribute to better understanding the physiological mechanisms controlling reproduction in this important pest insect.
Technical Abstract: Mating induces behavioral and physiological changes in the plant bug Lygus hesperus Knight (Hemiptera: Miridae). Males enter a post-mating refractory period, lasting 24 hrs, during which they replenish the contents of their accessory glands and seminal vesicles. Females experience a similar loss of sexual receptivity, but it lasts for several days during which they enhance their rate of egg laying. In other insects, such changes are orchestrated by shifting neurotransmitter levels. To better understand the regulation of these behavioral changes in L. hesperus, levels of four brain biogenic amines were examined in female and male at 5 min, 1 hr and 24 hrs after copulation and compared to levels in virgins using high-performance liquid chromatography coupled with electrochemical detection. Mating significantly influenced dopamine (DA), causing an increase in females and a decrease in males at 24 hrs. Octopamine (OA) appeared lower in females and males at 5 and 60 min post-mating, although the effect was not significant. Neither serotonin nor tyramine changed with mating in females or males. Virgin females were injected with one of four amines directly into the hemocoel to determine how these amines might influence sexual receptivity or egg laying. Only an increase in OA had a demonstrable effect, decreasing oviposition during the 24 h following injection. The results suggest the brief decline in OA observed immediately after mating may be necessary to promote egg laying. DA does not appear to have immediate and direct effects on L. hesperus reproductive behavior. However, DA may influence levels of the gonadotropins or could play a role in post-mating gamete production and sexual receptivity, although such effects were not captured in the limited duration of this study.