倍数性単爲生殖型ゾウムシ2種の染色体の補足研究
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(2) Journal of Hokkaido University of Education (Section II B) Vol. 29, No. 1 September 1978. MitCT^WM (^ 2^B) ^ 29^ ^ 1'-^- ' ' TO 53 ^ 9 ^. A Further Chromosome Study on Races of Two Reportedly Japanese. Polyploid Parthenogenetic Weevils (Coleoptera:Curculionidae). Yasushi TAKENOUCHI Biological Laboratory, Sapporo College, Hokkaido University of Education Sapporo 064. ^ I^J ^ : ^l?-N3^M5uy^ A ^ 2 ItcD^^cD^^g «itCT^'iNL?m»'^i^. Abstract The oogonial chromosomes of a hexaploid parthenogenetic race of Blosyrus japonicus Sharp and the chromosomes of oocyte maturatioh metaphases of a tetraploid parthenogenetic race of. Callirhopalus (= Pseudocneorhinus) obesus Roelofs were investigated. The former showed 66 chromosomes and the latter, 44, 43, and ca40. These results correspond to the number of. chromosomes obtained in both species in other localities. The fact strongly supports the propriety of previous findings.. In my earlier papers (Takenouchi, 1972, 1974, 1976a,b) I reported that two Japanese weevil species, Blosyrus japonicus Sharp and Callirhopalus obesus Roelofs, were partheno genetic. The former species has three parthenogenetic races : a hexaploid (6x = 66), a pentaploid (5x = 55), and a tetraploid (4x = 44) as well as a diploid bisexual race (2n = 22), and the latter species has two partheno genetic races, i.e., a hexaploid (6x = 65) and a tetraploid (4x = 44). These chromosome numbers were obtained in either oogonial or maturation divisions. This report provides some supplemental results to my earlier incomplete investigations.. Materials and Methods Four specimens of Blosyrus japonicus Sharp were collected at the foot of Mt. Moiwa in Sapporo in the early part of April, 1974. One specimen of Callirhopalus (= Pseudocneorhinus) obesus Roelofs was captured in Toyama in Mid-July, 1973 and seven specimens from a small. bushy sand bank of the Toyohira River in the early part of May, 1974. All localities are in the Sapporo area. Dissection shows that they were all females, no males being observed. Mature eggs were fixed in a modified Allen-Bouin's solution and sectioned to obtain oocyte chromosomes in the maturation division. Slides were stained with Heidenhain's iron-haematoxylin. To. secure oogonial metaphases their ovarioles were squashed according to Smith's (1943) method and. (D.
(3) Y.TAKENOUCHI. stained in basic fuchsin-methyl green (Smith and Takenouchi, 1969). Observations. Blosyrus japonicus Sharp Only four oogonial metaphases were found in in a squash slide from a single specimen, and the best one is shown in Fig. 1. One of them showed exactly 33 chromosomes, another ca40, and the remaining one, 44 chromosomes. The best oogonial cell showed exactly 66 chromosomes. The karyotype of this specimen is constituted by chromosomes of various sizes, mostly meta- or submetacentrics. The size difference of the chromosomes is gradual.. Callirhopalus (= Pseudocneorhinus} obesus Roelofs Fortunately, the only Toyama female provided two countable oocyte maturation metaphases in sectioned slides. Both cells showed exactly 44 chromosomes, respectively. The best one is. <ft». ^ -. ^"' 'f'^ Fig.l. Oogonial metaphase of Blosyms japonicus (Mt. Moiwa) showing 66 univalent chromosomes. Fig. 2. Oocyte maturation. metaphase of Callirhopalus obesns (Toyama) showiog 44 chromosomes. Fig.3. Oogonial metaphase of C. obesns (Toyohira River) showing 44 chromosomes. X 3,600.. (2).
(4) Hexaploid and Tetraploid Parthenogenetic Weevils shown in Fig. 2. The chromosomes are of univalent nature and most of them have a constriction near the middle. The size difference of the chromosomes is gradual.. A single female obtained from the sand bank of the Toyohira River showed an excellent oogonial metaphase in a squash slide. The oogonial metaphase is constituted of 44 chromosomes of various sizes and shapes, as seen in Fig. 3. All elements are meta- or submetacentric.. Discussion. B. japonicns is the weevil species which has a parthenogenetic race being the first found with the highest degree of polyploidy, hexaploid (6x), with 66 chromosomes. The basic chromosome number is n -=- 11 like that of most other polyploid partheno genetic weevils so far studied cytologically. According to my careful investigation in the race the number of chromosomes varies. 61—68 (Takenouchi, 1972a,b, 1975). Such a phenomenon is quite common in the polyploid parthenogenetic weevils studied so far (Mikulska,1960; Seller, 1947; Suomalainen, 1969; Suomalainen, Saura, and Lokki, 1976; Takenouchi, 1969, 1970a,b, 1972,1974, 1975, 1976a,b). But these numbers of chromosomes have been obtained from oocyte maturation divisions only and a study of oogonial chromosomes of this race has keenly been waited for. The oogonial metaphase here studied showed exactly 66 chromosomes. The fact means that no reduction division takes place in. this race as in the case of other cytologically known polyploid parthenogenetic curculionid weevil species or races. Therefore, the race is no doubt a real hexaploid one. The ovarioles have other cells with different chromosome numbers : one is 33, one, ca 40, and one, 44. The fact means that. the female may produce triploid and tetraploid eggs (progenies). Although no triploid parthenogenetic race (3x=33) is found in this species a tetraploid race (4x=44) coexists with hexaploid and pentaploid (5x=55) females in the small sand bank of the Toyohira River (Takenouchi, 1972). From another point of view, such a situation may be caused by floods. Namely, these three. different parthenogenetic races with different degrees of polyploidy drifted to the small sand bank from localities situated upstream.. The chromosomes of the oocyte maturation metaphases of a tetraploid race of C. obesus are. also so far unknown though it was established as a tetraploid from the oogonial metaphases having 44 chromosomes in Tsukisamu specimen (Takenouchi, 1972b). According to this investigation it is revealed that a tetraploid race of this species also has 44 chromosomes in oocyte maturation divisions. The fact means that in the race no reduction division takes place as usual and the race reproduces parthenogenetically. Further, the investigation shows that the species is a tetraploid. and parthenogenetic in Toyama and the River Toyohira districts in Sapporo. Acknowledgements. I am grateful to Dr. K. Morimoto, Department of Entomology, Faculty of Agriculture, Kyushu University, for identification of species. My thanks are also due to Dr. K. Baba, Director of Kurokawa Hospital, Niigata Prefecture, for his invaluable advice, and to Mr. N. Ikahata, for. (3).
(5) Y.TAKENOUCHI. collecting the materials.. References. Mikulska, I. 1960. New data to the cytology of the parthenogenetic weevils of the genus Otiorrhynchus Germ.. (Curculionidae, Coleoptera) from Poland. Cytologia (Tokyo). 25 : 322-333. Seiler, J. 1947. Die Zytologie eines parthenogenetischen Russelkafers, Otiorrhynchus snlcahis F. Chromosoma. (BerL). 3 : 88-109. Smith, S. G. 1943. Techniques for the study of insect chromosomes. Can Entomol. 75 : 21—34. Smith, S. G., and Takenouchi, Y. 1969. Chromosomal polymorphism in Pissodes weevils : Further on incompatibility in Pissodes terminalis. Can. J. Genet. Cytol. 11 : 761—782. Suomalainen, E. 1969. Evolution in parthenogenetic Curculionidae. In Evolutionary Biology 3 (Th. Dobzhansky, M. K. Hecht, and W. C. Steere, eds.). pp. 251-296. North-Holland Publ. Co., Amsterdam. Suomalainen, E., Saura, A., and Lokki, J. 1976. Evolution of parthenogenetic insects. Evolutionary Biology, 9 (Hecht, Steere, and Wallace, eds.). pp. 209-257. Takenouchi, Y. 1969a. A further study on the chromosomes of the parthenogentic weevil, Listroderes costirostris Schonherr,from Japan. Cytologia (Tokyo). 34 : 360—368. Takenouchi, Y. 1969b. On the chromosomes of the parthenogenetic weevil, Listroderes costirostris Schonherr,from Nagasaki Prefecture. Chrom. Inform. Serv. 10 : 3—4. Takenouchi, Y. 1970. Three further studies of the chromosomes of Japanese weevils (Coleoptera : Curculionidae). Can. J. Genet. Cytol. 12 : 273-277. Takenouchi, Y. 1971. A bisexual race of the reportedly parthenogenetic Japanese weevil Catapiomis gracilicornis Roelofs (Coleoptera : Curculionidae). J. Hokkaido Univ. Educ. Sect. IIB, 22 : 1—17. Takenouchi, Y. 1972a. Chromosome numbers of Japanese weevils of Curculionoidea (Coleoptera). KontyQ40 : 123— 132. Takenouchi, Y. 1972b. A chromosome study on two hexaploid parthenogenetic weevils (Coleoptera : Curculionidae). IVth Intern. Chrom. Conf. at Jerusalem. Chromosomes Today, 4 (J. Wahrman and K. R. Lewis. eds.). p. 432. Israel Universities Press, Jerusalem, and John Wiley & Sons, New York. Takenouchi, Y. 1974. A chromosome study on two new Japanese polyploid parthenogenetic weevils (Coleoptera : Curculionidae). Vth Intern. Chrom. Conf. at Leiden. Chrom. Today, 5 (P. L. Pearson and K. R. Lewis, eds.). pp. 341—348. Israel Universities Press, Jerusalem, and John Wiley & Sons, New York. Takenouchi, Y. 1975. A hexaploid parthenogenetic weevil, Blosyrus japonicus Sharp with 68 chromosomes (Coleoptera : Curculionidae). Chrom. Inform. Serv. 19 : 24—26. Takenouchi, Y. 1976a. On the chromsomes of parthenogenetic curculionid weevils in Japan. Proc. Jap. Acad. 52 : 126-129.. Takenouchi, Y. 1976b. A study of polyploidy in races of Japanese weevils (Coleoptera : Curculionidae). Genetica 46 : 327-334.. (4).
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