Cytological characteristics of chromosome behaviour during female meiosis in Sphinx ligustri L. (Sphingidae, Lepidoptera)

Abstract

Nokkala, S. 1987. Cytological characteristics of chromosome behaviour during female meiosis in Sphinx ligustri L. (Sphingidae, Lepidoptera). ‐ Hereditas 106:169–179. Lund, Sweden. ISSN 0018–0661. Received May 26,1986 The behaviour of chromosomes was studied in female meiosis of Sphinx ligustri L. (Sphingidae, Lepidoptera) by using improved cytological methods. The haploid chromosome number is n = 28. Throughout pro‐phase from pachytene until metaphase I, bivalents consist of two chromosomes aligned in parallel, i. e., meiosis is achiasmatic. All bivalents appear to be homomorphic, thus the ZW bivalent could not be identified. In early vitellogenesis, bivalents begin to associate nonhomologously via telomeres, forming a simple chain consisting of all 28 bivalents. After secondary modifications, a more complex, branched chain is produced. The branched chain configuration of bivalents is retained throughout the time when yolk is produced, and it breaks down during prometaphase. At metaphase I, only short chains are remaining. Based on present knowledge on chromosome behaviour in female meioses in different ovary types, it is suggested that the formation of the nonhomologous associations of biVdlentS is a prerequisite for karyosome or karyosphere formation, the karyosome being meiotically a resting stage. The effects of nonhomologous associations of bivalents on segregation are discussed. Copyright © 1987, Wiley Blackwell. All rights reserved