Temporal and Spatial Patterns of Mating in Rhodnius prolixus

Abstract

The kissing bug Rhodnius prolixus is a nocturnal species; however, its temporal mating patterns remain unexplored. Copulation lasts about fifty minutes, during which time the couple remains almost motionless. We hypothesized that R. prolixus copulates within shelters to reduce its vulnerability. To test this, we examined the spatial and temporal patterns of its copulation, as well as the potential endogenous regulation of its circadian rhythm, under three conditions: a light:dark cycle (L/D), constant light (L/L), and constant darkness (D/D). Over ten days, the number and the timing of copulation of pairs in arenas containing a shelter were video-recorded. Under the L/D cycle, the pairs mated mainly during daylight hours. This rhythm persisted under the D/D cycle, with a peak extending from the first half of the subjective day to the first half of the subjective night. No rhythm was observed under the L/L cycle. A greater proportion of mating occurred within the shelters during the L/D and L/L cycles, whereas its spatial distribution was random under the D/D cycle. Our results reveal an endogenously controlled circadian rhythm of mating behavior, with mating activity mainly occurring during daylight hours. Additionally, we showed that the pairs copulated inside the shelters. These results provide new insights into the reproductive behavior of R. prolixus.

Keywords: circadian rhythms; endogenous control; sexual behavior; shelters; triatomines.

Figure 1

Diagram of the experimental arena. The shelter, which consists of a corrugated cardboard floor and a red acetate ceiling, occupies one half of the arena. A male and female R. prolixus (shown inside the shelter) are enclosed inside the arena and can interact freely. A removable lid covers the arena and prevents the insects escaping.

Figure 2

Number of matings for each time interval over ten days (mean ± SE) under (A) L/D, (B) D/D, and (C) L/L regimes. For each photoperiod, different lowercase letters represent significant differences between time intervals (p < 0.05). Dark and white horizontal bars indicate the periods of the lights being off and on, respectively. EP: early photophase. LP: late photophase. ES: early scotophase. LS: late scotophase. ESD: early subjective day. LSD: late subjective day. ESN: early subjective night. LSN: late subjective night. (n = 24 for each photoperiod).

Figure 3

Proportion of mating inside the shelter over total mating (mean ± SE) for each photoperiod. The hatched line (y = 50) represents the expected point for a random distribution in this binary variable (inside/outside). Asterisks represent significant differences from the expected distribution (p < 0.05). n.s.: non-significant differences from the expected distribution (p > 0.05). Different lowercase letters represent significant differences in the proportions obtained between photoperiods (p < 0.05). (n = 24 for each photoperiod).

Figure 4

Number of matings per couple (mean ± SE) for each photoperiod. n.s.: non-significant differences (p > 0.05). (n = 24 for each photoperiod).

Figure 5

Number of matings for each day interval (mean ± SE) under (A) L/D, (B) D/D, and (C) L/L regimes. For each photoperiod, different lowercase letters represent significant differences between time intervals (p < 0.05) (n = 24 for each photoperiod).