Synaptonemal complexes in female and male meiotic prophase of Ephestia kuehniella (Lepidoptera)

Abstract

Synaptonemal complex (SC) complements of oocyte and spermatocyte pachytene nuclei in the Mediterranean flour moth, Ephestia kuehniella, were investigated using a microspreading technique and electron microscopy. In both sexes, three autosomal SCs could be identified by their morphological landmarks; one SC has a prominent knob and two SCs have nucleolus organizer regions. In a later stage of SC development in oocytes, the two nucleolar SCs displayed electron dense terminal modifications of the lateral elements. In some oocytes, the sex chromosome bivalent was inconspicuous but in the majority it was recognized by heterochromatin tangles associated with the W chromosome, a shorter W chromosome axis and/or incomplete pairing. Male synaptonemal complexes in contrast to female ones contained recombination nodules (RNs). Almost every bivalent was associated with one RN, rarely none or two RNs. Along the SCs, RNs were preferentially located in distal positions. The presence of RNs in male SCs and their absence in female SCs corresponds with the presence of crossing over and chiasmata in male meiosis and their absence in female meiosis. The mean total length of SC complements was greater in males than in females, but in both sexes, variation was considerable. We assume that male SCs become longer with progression of the pachytene stage while in female SCs a period of elongation is followed by a period of shortening.

Organization and Behavior of the Synaptonemal Complex during Achiasmatic Meiosis of Four Buthid Scorpions

“…Similar results were sporadically recorded for species of other taxa that possess both holocentric chromosomes and achiasmatic meiosis, e.g. Lepidoptera, Mantodea and Trichoptera [Gassner, 1969;Rasmussen, 1977;Rasmussen and Holm, 1979;John, 1990;Marec and Traut, 1993;Wolf et al, 1997]. In Scorpiones, the maintenance of SCs in late meiosis I likely provides the connection required for the correct and balanced segregation of bivalent-like elements and chromosome chains during meiosis I, such as suggested by Rasmussen [1977] for Bombyx mori (Lepidoptera).…”

Karyotype, sex chromatin and sex chromosome differentiation in the carob moth,Ectomyelois ceratoniae(Lepidoptera: Pyralidae)

“…Similar to another pyralid moth, Ephestia kuehniella (n = 30), two autosomal NOR-bivalents were observed in pachytene complements (cf. Marec and Traut 1993). On the contrary, a single NOR-bivalent was reported in several other lepidopterans.…”

Inherited Sterility in Insects

“…They concluded that crossing-over contributes to the sterility in F 1 males mostly through the formation of multiple translocations. Since female meiosis is achiasmate during oogenesis, this factor cannot play a role in the sterility level of F 1 females (Rasmussen 1977, Traut 1977, Nokkala 1987, Marec and Traut 1993b). …”