Satyrization without evidence of successful insemination from interspecific mating between invasive mosquitoes

Abstract

Previous research has documented low frequencies of interspecific mating in nature between the invasive vectors Aedes aegypti and Aedes albopictus. It is also known that heterospecific male accessory gland substances transferred during mating sterilize A. aegypti but not A. albopictus females, leading to satyrization, a form of reproductive interference. This paper demonstrates that satyrization of A. aegypti by A. albopictus may occur without evidence of successful insemination. Our results show that A. aegypti females, previously exposed to A. albopictus males, are rendered refractory to subsequent conspecific mating even though their spermathecae contain no heterospecific sperm. Additional experiments demonstrating transfer of labelled semen from A. albopictus males to A. aegypti females and low production of viable eggs of females housed with conspecific males, following exposure to A. albopictus males, confirm higher incidences of satyrization than expected, based on heterospecific insemination rates. We conclude that frequencies of satyrization based on detection of interspecific sperm in spermathecae may underestimate the impact of this form of reproductive interference.

Keywords: Aedes aegypti; Aedes albopictus; empty spermathecae; reproductive interference; satyrization.

Figure 1.

δ¹⁵N values of A. aegypti females exposed to A. albopictus males and control females. Each point represents a female mosquito. Females negative for heterospecific sperm in spermathecae (circles), females positive for heterospecific sperm in spermathecae (triangles), control females (diamonds) and positive control females (crosses). Females above the threshold (dotted line) are considered labelled with ¹⁵N.

Figure 2.

(a) Aedes aegypti bursa contains A. albopictus semen yet the spermathecae are empty. (b) Dissected terminalia of the same female showing sperm in the dissected bursa and the empty spermathecae. (Online version in colour.)