A description of male and female genitalia and a reconstruction of copulatory and fertilisation events in Calopteryx haemorrhoidalis (Vander Linden) (Odonata: Calopterygidae)

The genitalia have a “design” remarkably similar to those of other representatives of the family. The main 5 structures are the bursa copulatrix, a T-shaped spermatheca, a pair of vaginal plates bearing a variable number of mechanoreceptive sensilla, and a ganglion located at the VIII abdominal segment. The 6 intromittent organ is a curved, sclerotised aedeagus that ends in a distal penis head. This latter structure bears 2 lateral appendages which are covered by recurved spines, A construction of the fertilisation and copulatory events is proposed based on descriptive and experimental evidence in other zygopterans as well as in this species. The female genital anatomy suggests fertilisation occurs in the manner proposed for other odonates. Experimental evidence shown in this work suggests that, during fertilisation, the egg stimulates the mechanoreceptive sensilla and elicits contractile activity of the muscles that surround the sperm storage organs (SSOs). The contractile activity is likely to be mediated by the VIII abdominal segment ganglion. As a consequence of the muscular contractions, the SSOs eject sperm which arrive to the site where the egg is and fertilise it. During copulation, the aedeagus “imitates” the presence of an egg in the vaginal plates and stimulates the mechanoreceptive sensilla inducing spermathecal sperm ejection. It is likely that spermathecal sperm is ejected to the bursa copulatrix where it is removed by the penis head and lateral appendages. After this sperm displacement process, the copulating male’s sperm, stored in the seminal vesicle, is transferred, through a canal-like passage, by the aedeagus to the SSOs, Since $ 5 exhibit a considerable intra- and inter-individual variation in sensillum distribution and number on the plates, it is discussed whether this may have an adaptive significance in terms of retaining more control over stored sperm for $ $ during <5 stimulation.