Abstract
A cytogenetic study of bisexual species belonging to the genera Cirrorhynchus, Dodecastichus and Otiorhynchus is presented in order to confirm their taxonomic position. The karyotype characterization was accomplished by an analysis of mitotic and meiotic chromosomes after differential staining, namely by C-banding, silver impregnation, DAPI and CMA3. A review of the cytogenetic data for the tribe Otiorhynchini contributed to knowledge of chromosomal evolution in this group. An investigation of five of the species studied showed some similarities such as a sex chromosome system of "parachute type" (Xyp), the presence of 10 autosomal bivalents (2n = 22) and heterochromatin localized around centromeres. These observations are similar to those already described for Otiorhynchini species, and confirm the karyological conservatism of this weevil group. In contrast, another species Cirrorhynchus kelecsenyi has an additional four autosomal bivalents (n% = 14 + Xyp, 2n = 30), which differs considerably from the chromosomal homogeneity of the other genera. Karyotypic evolution in this species was achieved most probably by increasing the number of chromosomes by centric fissions, resulting in variation in the number of acrocentric chromosomes. DAPI-positive and CMA3-negative reactions of heterochromatic DNA in all the species studied suggest that it has an AT-rich composition. Impregnating chromosomes with silver nitrate reveals NORs on one pair of autosomes, and probably argentophilic material in the interspace between the X and y sex chromosomes. The karyological findings support the taxonomical revision of Otiorhynchini based on morphological characters.
Highlights
The Curculionidae is one of the largest beetle families with some 50,000 described species (Lawrence & Newton, 1995)
The karyology of about 600 species of Curculionidae has been investigated, the great majority of the cytogenetic findings reported for weevils only refer to male chromosome numbers and sex determination system at meiotic metaphase I
The chromosomal results for the six species are assessed in order to see whether there is an agreement with the proposed taxonomy
Summary
The Curculionidae is one of the largest beetle families with some 50,000 described species (Lawrence & Newton, 1995). The karyology of about 600 species of Curculionidae has been investigated, the great majority of the cytogenetic findings reported for weevils only refer to male chromosome numbers and sex determination system at meiotic metaphase I. There are many species-rich genera in which chromosomal composition has not yet been determined. Ten species of Otiorhynchus have been introduced into North America. Numerous species are apterous, characterized by nocturnal activity (Arnoldi, 1975; Dieckmann, 1980; SmreczyĔski, 1966). This group of weevils is well known for having a large number of parthenogenetic lineages, which have a much broader distribution than their sexual counterparts (Suomalainen et al, 1987).
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