Evidence for lock‐and‐key mechanisms in the internal genitalia of the Apamea moths (Lepidoptera, Noctuidae)

Abstract

Abstract. Fifty of the fifty‐six species of the genus Apamea known from North America and three Palaearctic species were analysed for lock‐and‐key characters in their internal genitalia, mainly in the male vesica and the female bursa copulatrix. There were an average of 4.5 such characters per species, structurally corresponding in the two sexes. Anatomically they form a postcopulatory but prezygotic isolation mechanism. In some closely related species, the internal genitalia are very similar, but these species have a precopulatory isolation mechanism in the presence or absence of male abdominal coremata. Closely related species did not have more lock‐and‐key characters than unrelated species, which is taken to indicate absence of character displacement. The anatomical distribution of the lock‐and‐key characters was examined and the organs of eight species are illustrated. The lock‐and‐key hypothesis has been abandoned by several earlier authors but mainly on consideration of external genitalia. In Apamea the invariable functional correspondence between sexes in the sperm transferring organs, and the overall species‐specifity of characters but non‐existence of interspecific differences under a precopulatory mechanism indicate that (a) lock‐and‐keys are functioning and (b) they act as isolation mechanisms. Alternative hypotheses of genitalic evolution are reviewed.

African-Arabian and Asian-Pacific "Mocis frugalis": Two distinct species (Lepidoptera: Noctuidae)

“…As diagnostic features of major importance are often found in the vesica (= endophallus) (cf. Hardwick, 1950;Lafontaine, 1987;Mikkola, 1992) particular emphasis was given to the study of its configuration. Vesicae were everted by cutting the ductus ejaculatorius at its junction with the aedeagus with sharp microsurgical scissors; distilled water was then pumped into the aedeagus with a hypodermic syringe while immersed in distilled water, aedeagus and needle being held with a pair of fine forceps.…”

The lock-and-key mechanisms of the internal genitalia of the Noctuidae (Lepidoptera): How are they selected for?

“…My analysis of the internal genitalia of 50 species of Apamea of the 56 occurring in North America (Mikkola, 1992) indicates that there is an average 4.5 lock-and-key characters in each species. Except for the two species pairs cited above, and a few other exceptions, the LKMs are species-specific.…”

“…(1) Among the North American species of Apamea, those with close relatives have, on average, the same number of lock-and-key characters as those without such relatives (4.4/4.7, respectively;Mikkola, 1992). Thus, no character displacement has occurred.…”

“…The carina near the tip of the aedeagus and the corresponding fold in the female indicate that during copulation the aedeagus penetrates the entire length of the ductus bursae (cf. Mikkola, 1992: Figs 1 and 3). Only thereafter does the vesica have the space to expand and produce the spermatophore.…”

“…Fänger & Naumann (1997) refer to "the mechanical correlation" in the Zygaenidae between the spiny and rough external parts of male and female genitalia as "rather loose", but that between the internal parts "seems much more specific". Lafontaine & Mikkola (1987) and Mikkola (1992) list the anatomical correspondences in the Noctuidae when male and female internal genitalia couple: (1) the diameter, length and shape of the male 15 Fig. 2.…”