Insemination and fertilization in the seed bug Lygaeus simulans (Heteroptera: Lygaeidae)

Abstract

Abstract. In the laboratory, not all females of the seed bug Lygaeus simulans Decked, 1985, produced fertilized eggs after copula tion: 26.7% of the females were not inseminated and 5% were inseminated but did not lay fertilized eggs; only in 40% of the couples did copulation result in fertile eggs. The remaining 28.3% of couples refrained from mating. Duration of copulation was associated with insemination and fertilization: (i) fertile eggs were produced by only one couple that copulated for less than 60 min and all those that copulated for more than 360 min, (ii) probability of fertilization increased steadily with duration of copulation between 60 and 360 min, and (iii) duration of copulation was significantly different for couples that showed different insemination status.A possible morphological explanation for this time dependency was revealed by examining the genitalia of 69 couples freezefixed in copula after different periods in copulation. Because of the intricate structure of the genitalia in L. simulans, a male takes a long time to manoeuver its intromittent organ into the narrow insemination duct of the female. Only if completely inserted is the tip of the intromittent organ close enough for successful ejaculation of sperm into the spermatheca. The freeze-fixing experiment re vealed that it usually took the male more than 30 min to locate the entrance to the insemination duct and another 30 min for full penetration. This explains why copulations that lasted less than 60 min failed, since insemination began only after intromission was complete.The experiments, therefore, indicated that there is a relationship between the complex morphology of the genitalia and the low rates of insemination and fertilization in L. simulans.

Experimental reduction of intromittent organ length reduces male reproductive success in a bug

“…Dishes were observed continuously for 2 h, and then checked every 10 min for a further 8 h. If a copulation ended during the trial, the pair were separated so as to restrict the female to a single mating. This was done for any copulation that lasted 15 min: pairs that copulated for less than this time were not separated as sperm transfer is not possible (sperm transfer has been shown to take at least 30 min [34]). Copulations that did not end during the trial were separated manually using a fine paintbrush (this does not damage the male or female).…”

“…The positions of the male aedeagus and processus within the female bursa have not previously been reported, and physical dissection invariably causes distortion of the natural shape of the bursa, which is very fragile; consequently, this virtual approach was an ideal way of imaging these structures in situ. It appears that the processus is coiled inside the bursa for slightly more than half of its length and performs one and a half turns once in the spermathecal duct (figure 1b,c) [34]. Furthermore, the high resolution of the scans (down to about 5-7 mm) meant that very fine-scale anatomical features could be detected, such as the tight corkscrew region at the entrance to the spermatheca (point D in figure 1b) [41].…”

Mate-guarding in a promiscuous insect: species discrimination influences context-dependent behaviour

“…However, the genitalia of many Lygaeidae, including L. equestris, are elongate and complex (Bonhag and Wick 1953;Gschwentner and Tadler 2000;Micholitsch et al 2000;Higgins et al 2009;Aspiras and Angelini 2011) and the delay in insemination may be a result of the time taken for the male processus to traverse the female reproductive tract to reach the spermatheca. This, combined with the high levels of mating failure observed in this group (Tadler et al 1999;Gschwentner and Tadler 2000;Micholitsch et al 2000), suggests that males may make significant investment in copulation duration due to processes of post-copulatory sexual selection (or ''cryptic female choice'': Eberhard 1996). As such, even if other females are in the environment, minimum copulation duration may still represent a significant time investment for males.…”

The extent and costs of reproductive interference among four species of true bug

“…Mature female L. equestris (Dolomites population) were placed in new 300 cc boxes with an arbitrarily chosen conspecific male from the same population and were oncemated (females have greatly restricted oviposition if they remain unmated). Copulations of over 1 h were treated as a first mating as sperm transfer is likely to have occurred in that time (Sillén-Tullberg 1981; see also Micholitsch et al 2000 for the closely-related L. simulans). The male was removed and females were then placed into one of the experimental treatments after copulation.…”