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Mitotic and meiotic studies of seven Caribbean weevils: difference of sex bivalent compaction at pachynema between Curculionidae and Dryophthoridae (Insecta: Coleoptera) species

Dutrillaux A.M., Xie H., Dutrillaux B.

Abstract. The mitotic and meiotic karyotypes of seven species of Caribbean weevils are reported. Three species belong to the Dryophthoridae and four to the Curculionidae families. All are considered as pests for agriculture, and were formerly classified among Curculionidae. The three mitotic karyotypes of the Dryophthidae species differ in their chromosome number and morphology while those of the four Cuculionidae species are fairly similar and can be distinguished by heterochromatin variations or NOR location only. Diakineses/Metaphases I of all species exhibit a parachute sex bivalent and the same range of autosomal bivalent compaction. At contrast, at the pachytene stage, bivalents appear less compact in Curculionidae than in Dryophthoridae species, and this difference is particularly clear for the sex bivalent: at early-mid pachytene stage, chromosomes X and Y are elongated and in end-to-end association in Curculionidae while they form a rounded dense body in Dryophthoridae species. In both conditions, the sex chromosomes are embedded in argyrophilic proteins. The different compactions of the sex chromosomes do not depend on NOR location, either on the X or autosome(s). Thus, bivalent compaction kinetic and/or structure at pachynema may be a taxonomic character, which would give arguments for the split of Curculionidae into two families.