新たに発見された単為生殖型ゾウムシ，ニセチビヒョウタンゾウの染色体
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(2) Journal of Hokkaido University of Education (Section II B) Vol. 31, No. 2 gg% 56 ^ 3 ^. »®grS:^'!N3^ (^ 2 SISB) ^ 31 ^ ^ 2^- March, 1981. A Chromosome Study on the New Parthenogenetic Weevil, Myosides. pyrus Sharp (Coleoptera : Curculionidae). Yasushi TAKENOUCHI Biological Laboratory, Sapporo College, Hokkaido University of Education, Sapporo 064. ^ ^ ^:IJr^::m^^-N3^^?/r>A'>, -^ -fef-brb 3 rj7^>y"r>^^fa^. »?tCT±'iNL^^f^|^. Abstract The chromosomes of the weevil species Myosides pyrus Sharp 1890, obtained from Murakami City, were studied in female germ line cells in squash slides. The chromosome number was confirmed as being exactly 33 in oogonial divisions. It is therefore concluded that in Murakami City Myosides pyrns is a parthenogenetic triploid. Introduction Since the pioneer work of Suomalainen (1940), chromosome knowledge of thecurculionid weevils has been rapidly accumulated. To date, the chromosomes of more than 500 species. have been studied. It is especially interesting to note that the family includes parthenogenetic (apomictic or thelytokous) species or races, and 63 parthenogenetic taxa having been reported so far. This time I have had a chance to study the chromosomes of a new parthenogenetic weevil species. This paper reports the details.. Materials and Methods Myosides pyms Sharp 1890 is a member of the tribe Ptochini of the subfamily Otiorrhynchinae. A single female was obtained in the bushy garden of IVIurakami Hospital, Murakami City, Niigata Prefecture, in late May, 1977. Her ovarioles were squashed according to Smith's method (Smith, 1943) and stained with an aqueous solution of 0.6% methyl green and 0.15% basic fuchsin (1 : 1). The camera-lucida drawings were made at about X 3,600.. (55).
(3) ^ fi ^ Observations A single excellent oogonial metaphase was found in the squash slide. It showed exactly 33 univalent chromosomes. The karyotype of this species consisted of chromosomes of various sizes, mostly meta- or submetacentrics. The size difference of the chromosomes is gradual. No sex-chromosomes were observed. The chromosome number, 33, establishes that. this specimen is undoubtedly triploid, which, according to the recent cytological investigations of the Curculionidae, indicates parthenogenetic reproduction. Discussion. So Far, 63 species or races belong to the closely allied 6 subfamilies ; Otiorrhynchinae, Brachyderinae, Eremninae, Leptopinae, Cylindrorrhininae, and Curculioninae (Lissorhoptrinae), are parthenogenetic. These parthenogenetic taxa are usually connected with polyploidy with the exception of three diploid parthenogenetic forms with 2x=2n=22 : the one is the European Polydrosus mollis (Strom 1976) and the other two are the Japanese Scepticus insularis Roelofs 1873 and Catapionus gracilicornis Roelofs 1873 (Suomalainen, 1969 ; Takenouchi, 1968, 1978, in press). Of the other polyploid parthenogenetic taxa hitherto reported, 2 are hexaploid (6x, 66), 6 pentaploid (5x, 55), 16 tetraploid (4x, 44) and 36 triploid (3x, 33 or 30). Although there are found some numerical differences in several species or races, the commonest chromosome. number is an exact multiple of the basic number of 11 (M^ikulska, 1953, 1960 ; Suomalainen, 1969 ; Takenouchi, 1969, 1970, 1978, 1981). Among triploid forms only three species, Liophloeus tessulatzts (Ntuller 1776), Eusomus ovulum Germer 1824, and Listroderes costirostris Schonherr 1826, have 30 chromosomes suggesting the basic number of 10. As mentioned above, weevil species or races with 33 chromosomes so far known are all triploid parthenogenetic. The fact strongly suggests that M. pyrus is a triploid parthenogenetic species. In the genus Myosides, M. seriehispidus Roelofs 1873 is also a parthenogenetic triploid in both Sengen and Hakodate, Hokkaido, and M^orioka City, Iwate Prefecture in Honshu (Japan Hondo) (Takenouchi, 1972).. » - •^£f». •:v»^ ^. - .t^'v. ^ 1^. Fig. 1. Oogonial metaphse of Myosides pyrus, showing 33 ehromosomes.. X 3,600.. (56).
(4) Chromosomes of a New Parthenogenetic Weevil. Acknowledgements I am grateful to Dr. Kintaro Baba, the director of Kurokawa Hospital, Niigata Prefecture, for invaluable help in collecting the material. My thanks are also due to Dr. Katsura Morimoto, Entomological Laboratory, Faculty of Agriculture, Kyushu University, for identification of the species and for invaluable advice. 6 Literature Mikulska, I. 1953. The chromosomes of parthenogenetic and thelytokian weevil Eusomzis ovulum Germ. (Curculionidae, Coleoptera). Bull. Acad. Pol. Sci. Lettr., Ser. B II, 1951 : 293-307 ; Cracovie/Poland.. Mikulska, I. 1960. New data to the cytology of the parthenogenetic weevils of the genus Otiorrhynchns Germ. (Curculionidae, Coleoptera) from Poland. Cytologia, 25 : 322-333 ; Tokyo. Smith, S. G. 1943. Techniques for the study of insect chromosomes. Can. Entomol. 75 : 21-34 ; Ottawa/ Ontario. Suomalainen, E. 1940. Polyploidy in parthenogenetic Curculionidae. Hereditas, 26 : 51-64 ; Lund. Suomalainen, E. 1969. Evolution in parthenogenetic Curculionidae. In Evolutionary Biology, Vol. 3 Edited by T. Dobzhansky, M. Hecht and W. Steere. Appleton-Century-Crofts, New York, pp. 261-296 ; New York. Takenouchi, Y. 1968. A chromosome study on bisexual and parthenogenetic races of Scepticns insularis Roelofs (Curculionidae : Coleoptera). Can. J. Genet. Cytol. 10 : 945-950 ; Ottwa/Ontario. Takenouchi, Y. 1969. A further study on the chromosomes of the parthenogenetic weevil, Listroderes costirostris Schonherr, from Japan. Cytologia, 34 : 360-368 ; Ttkyo. Takenouchi, Y. 1970. A further chromosome study in bisexual and parthenegenetic races of the weevil, Catapionus gracilicornis Roelofs (Curculionidae : Coleoptera). Jap. J. Genet. 45 : 457-466 ; Tokyo. Takenouchi, Y. 1972. A chromosome study on two new Japanese parthenogenetic weevils (Coleoptera : Curculionidae). Jap. J. Genet. 47 : 19-22 ; Tokyo. Takenouchi, Y. 1978. A chromosome study of the parthenogenetic rice water weevil, Lissorhoptrus oryzo-. philns Kuschel (Coleoptera : Curculionidae), in Japan. Experientia, 34 : 444-445 ; Basel/Schweiz. Takenouchi, Y. 1979. The chromosomes of new polyploid races of two Japanese weevils. At 50th Conf. Zool. Soc. Jap. Nov. 18, 1979, at Tokyo Univ. Zool. Mag. 88 : 602 ; Tokyo. Takenouchi, Y. 1979. A diploid parthenogenetic race of the reportedly Japanese weevil Catapionus gracilicornis Roelofs (Coleoptera : Curculionidae). Entom. Gen. (in press) Takenouchi, Y. 1981. A further chromosome survey on a parthenogenetic weevil, Callirhopaliis bifasciatus. Roelofs (Coleoptera : Curculionidae). Genetica (in press). (57).
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