Influence of Nutrition on Courtship and Mating in the ScorpionflyPanorpa cognata(Mecoptera, Insecta)

Abstract

Scorpionflies have been used as model organisms for the study of alternative male mating tactics as well as sexual conflict and coercive mating. Here we describe the courtship and mating behaviour of the scorpionfly Panorpa cognata at different levels of nutrition. Alternative mating tactics in scorpionflies involve nuptial food gifts, and we expected an effect of nutrient availability and male individual condition on the relative frequency of these mating tactics. Subsequent to female attraction by means of male pheromonal emission (calling) and a conspicuous pairing prelude, the majority of matings were initiated by male secretion of one relatively large salivary mass on which females feed during copulation. Usually, males produced only a single salivary mass per mating, and the copulation was terminated after the female had consumed the salivary mass. Alternatively, in 40% of the copulations, males offered females a dead arthropod as nuptial gift. However, these matings were neither preceded by male calling nor by the pairing prelude. Copulations with no gifts were extremely rare, and forced copulations were absent. The manipulation of the clamp‐like notal organ used by male scorpionflies in coercive matings had no effect on the duration of copulation, suggesting that P. cognata males are not able to enforce longer matings. Copulations involving salivary mass gifts were significantly longer than copulations with prey provided as gifts. Although contrary to our expectations, nutrition had no effect on the relative frequency of the different male mating tactics, it had several effects on courtship and mating. First, well‐fed individuals copulated significantly more often, both with prey and salivary secretions, than individuals with limited nutrient resources available. This was true for both sexes, although the effect was stronger for males. Higher availability of nutrients decreased the time until male and female sexual maturity and increased male calling duration per day. Furthermore, high nutrient availability decreased the duration of the pairing prelude, and consequently pairs started copulating earlier at night in the high nutrient treatment.

Nuptial food gifts influence female egg production in the scorpionfly Panorpa cognata

“…In this study, the estimate of female nutritional benefits from salivary mass consumption, and thus additional matings, is in the magnitude of four or five eggs, or roughly 8%. Mean estimates of the lifetime fitness increase of polyandrous females due to salivary mass consumption, which take both the lifetime number of female matings (see Engqvist & Sauer, 2003b ) and the relative fitness increase per mating into account, would therefore be in the magnitude of slightly more than 30% for females subjected to a highly restricted diet as in the present study and approximately 20% for females in populations with ample food abundance. These estimates are thus slightly lower than the average direct benefit of multiple mating in insect species with nuptial gifts ( Arnqvist & Nilsson, 2000 ).…”

“…The males that were used in these matings were well fed (a one-segment piece of a mealworm every third day) and between 14 and 25 days old. Furthermore, only males that were obviously emitting pheromones and thus 'calling' for females were used (see also Thornhill, 1979;Engqvist & Sauer, 2003b ). Before every mating trial, females were weighed to the nearest 0.1 mg.…”

“…Previous studies on P. cognata have shown that during their lifetime, females copulate several times but refuse to mate with males without receiving a nuptial gift ( Engqvist & Sauer, 2003b ). Furthermore, by increasing the size of the secretion males achieve longer copulations ( Engqvist & Sauer, 2001 ) and transfer more sperm ( Engqvist & Sauer, 2003a ).…”

Nuptial gift consumption influences female remating in a scorpionfly: male or female control of mating rate?

“…In this species, females typically mate with multiple males (Engqvist and Sauer 2003b) and benefit in several ways from polyandry. First, female scorpionflies often receive nuptial food gifts in form of salivary secretions at mating (Mercier 1915;Byers and Thornhill 1983;Sauer et al 1998;Engqvist and Sauer 2003b;Engqvist 2006), and as showed for P. cognata, females derive nutritional benefits that increase their fecundity by consuming these gifts (L. Engqvist, unpublished data).…”

“…In this species, females typically mate with multiple males (Engqvist and Sauer 2003b) and benefit in several ways from polyandry. First, female scorpionflies often receive nuptial food gifts in form of salivary secretions at mating (Mercier 1915;Byers and Thornhill 1983;Sauer et al 1998;Engqvist and Sauer 2003b;Engqvist 2006), and as showed for P. cognata, females derive nutritional benefits that increase their fecundity by consuming these gifts (L. Engqvist, unpublished data). In addition, P. cognata females benefit due to an increased egg-hatching rate by mating with different males (Engqvist 2006), possibly by avoiding genetic incompatibility (for reviews see Tregenza and Wedell 2000;Zeh and Zeh 2003;Simmons 2005).…”