SYNAPTONEMAL COMPLEXES IN FEMALE AND MALE MEIOTIC PROPHASE OF EPHESTIA-KUEHNIELLA (LEPIDOPTERA)

Synaptonemal complex (SC) complements of oocyte and spermatocyte pachy tene 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 morp hological landmarks; one SC has a prominent knob and two SCs have nucl eolus organizer regions. In a later stage of SC development in oocytes , the two nucleolar SCs displayed electron dense terminal modification s of the lateral elements. In some oocytes, the sex chromosome bivalen t was inconspicuous but in the majority it was recognized by heterochr omatin tangles associated with the W chromosome, a shorter W chromosom e axis and/or incomplete pairing. Male synaptonemal complexes in contr ast to female ones contained recombination nodules (RNs). Almost every bivalent was associated with one RN, rarely none or two RNs. Along th e SCs, RNs were preferentially located in distal positions. The presen ce 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 wa s greater in males than in females, but in both sexes, variation was c onsiderable. We assume that male SCs become longer with progression of the pachytene stage while in female SCs a period of elongation is fol lowed by a period of shortening.