Effects of the juvenile hormone mimic NC-184 on the development of the reproductive organs and mating behaviour of nymphs of the desert locust, Schistocerca gregaria (Orthoptera: Acrididae)

Satoshi Hiroyoshi,Gadi V.P Reddy,Shigemi Yagi,Sai Mettupalli,Elizabeth Kokwaro,Takayuki Mitsunaga

doi:10.14411/eje.2019.049

Abstract

The insect growth regulator NC-184, a juvenile hormone mimic, prevents moulting to the adult stage in the desert locust, Schistocerca gregaria (Forskal) (Orthoptera: Acrididae). Male nymphs treated in the penultimate or final nymphal instar with NC-184 exhibit precocious mating behaviour in the final instar. We examined whether this chemical affects the development of the internal reproductive organs of crowded nymphs. In treated males, both accessory glands and seminal vesicles were underdeveloped, and no sperm was found in the seminal vesicle, whereas these organs in control individuals had greatly increased in size 10 days after treatment, when all the insects had moulted to adults. Testis size in treated males was similar to that in controls, regardless of their smaller body size due to the inhibition of moulting. Oogenesis and development of spermatheca in females treated with NC-184 continued to some degree, but no eggs matured, unlike what occurred in the control. In conclusion, treatment of S. gregaria nymphs with NC-184 resulted in changes in the reproductive organs in both sexes.

Highlights

The desert locust Schistocerca gregaria Forskål (Orthoptera: Acrididae) exhibits remarkable phase polyphenism, i.e. gregarious and solitary phases that differ considerably in behaviour, physiology and morphogenesis (Applebaum et al, 1997; Rogers et al, 2014)
We investigated the effects of NC-184 on the development of testis of S. gregaria (Fig. 1A and B)
We investigated the effects of NC-184 on the development of spermatheca of S. gregaria relative to whether the nymphal females accept mates or not (Fig. 5)

Summary

Introduction

The desert locust Schistocerca gregaria Forskål (Orthoptera: Acrididae) exhibits remarkable phase polyphenism, i.e. gregarious and solitary phases that differ considerably in behaviour, physiology and morphogenesis (Applebaum et al, 1997; Rogers et al, 2014). These phases are determined by crowding, chemotactic and olfactory cues, tactile and visual stimuli and maternal effects, and this insect is able to transform reversibly between the two phases (Hassanali et al, 2005). The process of trans-generational changes involves various changes in behaviour, body colour, morphology, physiology and biochemistry (Maeno & Tanaka, 2012). The behavioural response to adult aggregation pheromone is age and juvenile hormone dependent (Ignell et al, 2001)

Methods

Results

Discussion

Conclusion