フタトゲチマダニ属に属する単為生殖型ダニ2種類の染色体研究

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(1)Title. フタトゲチマダニ属に属する単為生殖型ダニ2種類の染色体研究. Author(s). 竹内, 恭; 椎津, 徹; 利岡, 静一. Citation. 北海道教育大学紀要. 第二部. B, 生物学,地学,農学編, 20(2): 45-50. Issue Date. 1970-01. URL. http://s-ir.sap.hokkyodai.ac.jp/dspace/handle/123456789/6285. Rights. Hokkaido University of Education.

(2) Vol. 20, No. 2 Journal of Hokkaiclo University of Education (Section II B) January 1970. A Chromosome Study on Two Parthenogenetic Ticks, Haemaphysalis bispinosa Neumann and H. longicornis. Neumann (Acarina : Ixodidae). Yasushi TAKENOUCHI, Toru SHIITSU and Seiichi TOSHIOKA* Biological Laborsttpry, Sapporo College, Hokkaido University of Education. Received October 16, 1969. /!/lfi ^ • UN; %: 7 y- h y^- -^ ^- ^ M^Nt % E^Â%a ^ ^ 2 SSio^fa ??M-^. Haemaphy sails bispinosa Neumann has both bisexual and parthenogenetic races, and sometimes male animals come out from unfertilized eggs (a parthenogenetic strain) (Toshioka, unpublished), whilst, another species Haemaphysalis longicornis Neumann reproduces parthenogenetically. So far as the authors are aware of, no cytological reports of the former species have been published yet, however, recent detailed cytological study was carried out on the latter species by Oliver and Bremner (1968). However, they failed to determine the mechanism of the parthenogenetic reproduction of the species. The present paper reports the results of a chromosome survey on the above two species and contributes to prove the mechanism of the parthenogenesis of Hae map hy sails longicornis.. Material and Methods Many nymphs of Haeinaphysalis bispinosa hatched from unfertilized eggs laid from parthenogenetic females were provided from the laboratory stock of 406 ML. The original ticks were obtained from goats in Asli Orang Kampong (=Aborigine village), West Malaysia, on December 13, 1967. From these nymphs, both male and female animals were moulted. They were reared to their adulthood on the skin of rabbits' ears in an incubator and used for this study. Nymphs from the laboratory culture stock of parthenogenetic Haemaphysalis longicornis originating from the ticks collected from cows in Sanbe, Shimane Prefecture, on July 13, 1966, and from cows in Aogashima, Tokyo, on July 26, 1967, were also provided from 406 ML. The females obtained from these nymphs were also reared and used for this study. Specimens from both male and female embryos and testes of adult males of Haemaphysails bispinosa which had infested rabbits from 2 to 3 days at 24°C were squashed with 10% acetic gentian violet; and then temporary squash preparations were made. For the study of * Department of Entomology, 406th Medical Laboratory, APO 96343, San Francisco. Present Address: The Japan Snake Science Institute, Yabuzuka, Gumma Prefecture, JAPAN..

(3) Yasushi Takenouchi, Tom Shiitsu and Seiichi Toshioka female meiosis of both species, ovaries of adults from 2 to 3 days after the infestation at 24°C, oviducts with mature eggs and eggs from 0 to 1 hour after oviposition were fixed in a modified Allen-Bouin's solution after Momma (1954) and the routine paraffin method was adopted ; sections were cut into seven microns thick, and stained with Heidenhain's iron-haematoxylin. In addition, the ovaries of females of both species from 2 to 3 days after infestation were dissected and temporary squash preparations, as stated above, were made.. The investigation was carried out from June, 1968 to February, 1969.. C®Ss. ^J. î "^. ^ ^. Figs. 1-5. Chromosomes of Haemaphysalis bispinosa. Fig. 1. Metaphase plate of early cleavage in the female. Fig. 2. Metaphase plate of early cleavage in the male. Fig, 3. Oogonial metaphase. Figs. 4 and 5. Spermatogonial metaphases. Fig, 4 corresponds to Fig. 5..

(4) A Chromosome Study on Two Parthenogenetic Ticks. Results Haemaphysalis bispinosa Neumann Female somatic chromosomes : The female somatic number of chromosomes was determined to be 22 at metaphase in the early cleavage nuclei (Fig. 1). The chromosomes are comparatively larger in size, however, 2 elements are extremely large ; 8, large ; and the others gradually diminishing in size. Most of the elements are of acrocentric nature, but some are metacentric or submetacentric. The largest 2 elements are X-chromosomes.. Male somatic chromosomes: Cleavage-nuclei deriving from male embryo showed 21 chromosomes at metaphase (Fig. 2). The chromosome set consists of one extra large, îght large, and '12 tnedium- sized chromosomes. Approximately 4 elements might be metace^tric. The largest, chromosome is the X-chromosome.. Chromosomes of female germ cells : Oogonial metaphases showed 22 chromosomes without exception (Fig. 3). In sectioned slides, the condensed chromosomes are so small that the details are obscure, but 10 of them are clearly larger than the others. <B.. I. r. j • •. î. *». -^ •i. ^. '. -a. Figt. 6-10. Chromosomes of Haemaphysalis bispinosa, Fig. 6. Prophase plate of the first meiotic division in the male. Figs, 7 and 8. First meiotic metaphases in the male. Fig. 9. Second metaphase, X-class. Fig. 10. The same, no X-class.. I.

(5) Yasushi Takenouchi, Tom Shiitsu and Seiichi Toshioka Chromosomes of male germ cells : Twenty-one chromosomes were seen in the spermatogonial metaphase as shown in Figs. 4 and 5. As the seriation of the chromosomes is gradual in size, so it is difficult to detect a special element as sex-determining. The first spermatocyte at metaphase clearly showed well distributed 10 autosomal bivalents and an X-chromosome which is easily distinguishable due its strong affinity to stain (Figs. 7 and 8). At anaphase of the first division, the X precedes one of the poles (Fig. 8). Thus, two sorts of secondary spermatocytes result from the first division. One of them contains 10. 12. ^ r^. s&ii?. Figs. 11-15. Chromosomes of Haemaphysalis longicornis. Figs. 11-13, Oogonial metaphases, showing 33 chromosomes in each. Fig, 11 corresponds. to Fig. 12 (squashed slide). Fig. 13 (sectioned slide). Figs. 14 and 15. Metaphase plates of maturation division, 33 chromosomes.. 15.

(6) A Chromosome Study on Two Parthenogenetic Ticks. autosomal dyads only (Fig. 10), the other possesses 10 autosomal dyads plus the X (Fig. 9), though it is impossible to detect the X-chromosome at this stage.. Haemaphysalis longicornis Neuman A number of larvae of this parthenogenetic species were reared to the engorged nymphal stage on rabbit ears. The dissection revealed that no males were found in 435 adult ticks moulted from the nymphs. The eggs laid by these females hatched without fertilization. Cytological study was carried out on ovaries of 336 adult females and a large number of mature eggs.. Chromosomes of female germ cells : Oogonial metaphases consistently showed 33 chromosomes of various sizes and shapes. It seems likely that most of them are of acrocentric or telocentric nature (Figs. 11-13). A few complete metaphase plates of the first maturation division were obtained. The primary oocytes were found to have also 33 chromosomes of univalent nature (Figs. 14 and 15). They were condensed rod-shaped elements. Neither chromosome conjugation nor reduction division was found in the course of the maturation division. Here the obtained results indicate apomictic parthenogenesis.. Discussion The chromosome knowledge of 48 tick species hitherto has been accumulated. Of these, 34 species belonging to the family Ixodidae and 14 species are of the Argasidae (Oliver, 1968). In the genus Haemaphy sails, so far as the authors are aware of, no report was found on the chromosomes but that Kahn's paper (Kahn, 1964), in wlch he reported the chromosome number, 22 and 21 (females and males, respectively), and the sex-determining mechanism. (XO in male) of Haemaphy sails leporis palustris (Packard). In the present study, it was observed that Haemaphysalis bispinosa had the typical chromosome numbers of the Ixodoiclea, i.e. 22 in females and 21 in males. Both were obtained in gonial and cleavage-cells. The first spennatocyte has 10 autosomal bivalents and the largest X-chromosome, whilst, female animals have a similar autosomal set plus 2X. Thus, it is revealed that the species has XO sex-determining mechanism in the male. However, in the present study the method of parthenogenetic reproduction of this strain was not studied due to the shortage of ticks. In his preliminary observations on the cytology of Haemaphysalis longicornis (formerly bispinosa') from Mt. Tamborine, Queensland, Bremner (1959) suggested that the species is triploid and described as follows : Suomalainen (1950) has pointed out that constant triploid parthenogenetic forms can arise naturally only in animals exhibiting an ameiotic type of parthenogenesis, and it would therefore appear unlikely that chromosomal reduction divisions occur during the oogenesis in the strain of Haemaphysalis longicornis. And recently, Oliver and Bremner (1968) have succeeded in detecting the chromosome number of Haemaphysalis longicornis from Mt. Tamborlne, Queensland, as 32 and 33 in oogonia. They did not determine whether Haemaphysalis longicornis females were apomictic or automictic but they suggested that the species would be found to be apomictic in reference to Suomalainen (1962).. C 49).

(7) Yasushi Takenouchi, T6ru Shiitsu and Seiichi Toshioka The females of the Japanese Haemaphysalis longicornis brought from Aogashima, Tokyo, and Sanbe, Shimane Prefecture, have 33 chromosomes which coincide with the theoretical number of triploid, as the basic number of the genus Haemaphysalis is 11. The first oocyte at metaphase again shows 33 chromosomes. The fact, confirmed in this study, indicates that no reduction of chromosomes takes place in this species. No chromosome pairing was observed in any stage of the prophase of the first maturation division. The results revealed that the species of both regions reproduce by apomictic parthenogenesis.. ABSTRACT Chromosomes can be found in cleavage cells as well as in germ cells of a Malaysian hard tick, Haemaphysalis bispinosa Neumann and in germ cells of a Japanese hard tick, Haemaphysalis longicornis Neumann. Special emphasis was given to prove the mode of parthenogenetic reproduction of the latter species. The diploid number of Haemciphy sails bispinosa was 22 in females and 21 in males, and the species possessed an XX : XO sex-chromosome mechanism. Thirty-three chromosomes were observed in both oogonla and the primary oocyte of Hae'maphy sails longicornis. The cytological findings reveal that it is evident that the species reproduces by apomictic parthenogenesis. The evidence obtained here is the first to prove the mechanism of parthenogenesis of ticks.. References Bremner, K. C. 1959. Observations on the biology of Haenwphysalis bispinosa Neuman (Acarina : Ixodidae) with particular reference to its mode of reproduction by parthenogenesis. Australian Jour. Zool. 7: 7-12.. Kahn, J. 1964. Cytotaxonomy of ticks. Quart. Jour. Microscop. Sci. 105: 123-137, Momma, E. 1954. Drosophila survey of Hokkaido, II. Chromosomes of seven wild species. Jour. Fac. Sci. Hokkaido Univ., Ser. VI. Zool. 12: 200-208. Oliver, J. H. and Bremner, K. C. 1968. Cytogenetics of ticks. III. Chromosomes and sex determination In some Australian hard ticks (Ixodidae). Ann. Entomol. Soc. Amer, 61:837-844. Suomalainen, E. 1950. Parthenogenesis in animals. Adv. Genet. 3 : 193-253. 1962. Significance of parthenogenesis in the evolution of insects. Annu. Rev. Entomol. 7 :349-366,. ( Kn\.

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