THE CHROMOSOMES OF AN , FORFICULA SCUDDERI BORM.r) A. B. MISRA TheBenares Hindu University, India (From the Zoological Institute, Faculty of Science, Hokkaido Imperial University, Japan) ReceivedJanuary 28, 1937

The chromosomes of Dermaptera have been favourite objects of study since the works of CARNOY('85) and ST. GEORGE('87). They were followed by a number of other investigators, who studied the chromosomes in several of , but our knowledge of the subject remains incomplete and unsatisfactory as is shown to be the case by the summaries of the subject presented by SCHRADER('28) and HARVEY('16). Soon after the publication of SCHRADER'Streatise in 1928, MORGAN('28) added considerably to our knowledge of the subject by publishing the results of his studies on five species of earwigs. He found the diploid numbers of chromosomes in the males of Labidura bidensand of minor to be 12 and 14 respectively, both having an X-Y complex in which the X is a single chromosome. According to him, Anisolabis annzulipesand Anisolabis mari- tima, however, possess the diploid number of 25 (or I 1 pairs of autosomes plus an XX-Y complex). The full complement of chromosomes in the male of Forfzczzlaauriczclaria is 2a or 25, depending upon the degree of fusion, or separation, of the two X components in different individuals. MORGAN('28) also pointed out that the discrepanciesin the results of the previous students of the chromosomes of Forficzzlaauricularia were due to their inability to understand the irregular behaviour of the XX-Y complex, and suggested that the X chromosome in earwigs was either fragmenting from a large element into two small daughter chromosomesin some cases, or else two small chromosomes were fusing to form a large X chromosome,and that the differencesin the observed diploid and haploid numbers given by earlier workers were accountable on this basis. Recently, SUGIYAMA('33) has published some observations on Anisolabis marginalis and ASANAand MAKINO('34) have reported upon Labidzzrariiaria. i) ContributionNo. 116 from the Zoological Institute, Faculty of Science, Iokkaido Imperial University,Sapporo. 172 THE JAPANESEJOURNAL OF GENETICS, VOL. XIII, Nos. 3-4

According to SUGIYAMA('33), there are 25 chromosomes in the sperinatogonia of Anisolaois marginalis, 12 in the primary spermatocytes, and I2 or I3 chromosomesin the secondary spermatocytes. He seems to accept MORGAN's interpretation of the sex chromosomes being an XX-Y complex because he says that " the number of the heterochromosomes may be counted to be as many as three." ASANAand MAKINO('34) have recorded 14 chromosomesin the case of Labidura riparia. The male in this case has an X-Y complex, the female X-X. No numerical deviations in the number of chromosomes were noticed nor were lagging chromosomes observed by them in this case.

1 2 3

5 7 9

Figs. 1-9. The chromosomes of Forficula scudderi. (1/12 oil imm. and K. 20 X ocular). FLEM- MING's fixation and HEIDENHAIN'Sstain. I-2 , metaphase polar view of spermatogonia. 3-4, metaphase polar view of primary spermatocyte . 5, side view of primary spermatocyte metaphase. 6-7, daughter complexes of primary spermatocyte anaphase . c, chromatoid body. 8, metaphase polar view of secondary spermatocy X-class. 9, the same, Y-class. During my stay in Sapporo, specimens of Forficula scuddcri BoRM. came to hand, and, in view of the conflicting opinions expressed by several of the workers on forficulid chromosomes Fig. 10-11 , it seem- ed worthwhile to investigate the chromo- somes of this species . This work was carried out in the Zoo- logical Institute of the Hokkaido Imperial University under the supervision of Prof . 10 11 KAN OGUMA to whom the author is greatly Figs. 10-11. Photomicrographs of XY complex in the first division. indebted for suggestions and correction of t he manuscript. The author is also grateful to Dr. S. MAKINO for much friendly assistance and helpful advices .

446 Misra-The chromosomesof Forficulascudderi 173

Observations Forficula scudderi shows 24 chromosomes in the metaphase of the spermatogonium,including the X and Y elements (Figs. 1-2). The chromo- somes have the form of simple rods or ovals. In the primary spermatocytes, 12 bivalent chromosomes are clearly recognizable, as seen in Figs. 3-4. In the metaphase of the primary spermatocytes, in side view, the chromosomes present dumbbell-shaped appearance, and the XY bivalent lies at the periphery of the spindle, the X chromosome being, of course, larger in size than its mate, Y (Fig. 5). In the anaphase, the X and Y chromosomes separate, going to oppositepoles of the spindle as shown in Figs. 6 and 7, thereby giving rise to two kinds of secondary spermatocytes which are represented in Figs. 8 and 9. The chromosomesof Forficula scudderi did not show variation in number, or any other kind of irregularity. In view of the discrepancies in the sex-chromosomes of earwigs as noted by MORGAN('28), Prof. OGUMAadvised me to pay particular attention to the sex-chromosomes of F. scudderi with a view to detect splitting or fragmenta- tion, if any, in its X chromosome or any sign of compositeness. The X chromosome of F. scudderi was, therefore, carefully examined, but no split or tendency to fragment could be detected in it. Figures io and I I represent photomicrographic enlargements of the XY-complex in the meta- and the anaphases of the primary spermatocytes. It will be seen that the X chromo- some is a completely spherical body, and its partner, Y, is associated with it in the characteristic manner. These photographs, therefore, clearly demon- strate the simple nature of the X chromosome in this species.

Discussion

On referring to the literature, it becomes evident that two types of sex-chromosome complexes exist in the Dermaptera, viz., X-Y and XX-Y. It is very difficult to say, in the present state of our knowledge, whether XX-Y type is the result of the fragmentation of the X chromosome in an original simple X-Y complex, or whether the X-Y complex has been derived from the fusion of the two X's represented in the XX-Y complex into a single one. Forficula scudderi has an X-Y complex, and in this respect, resembles Labidura riyiaria, Labidura bidens and Labia minor more than any other Dermapteran species so far studied. Curiously enough, the chromosomal complex of Forficula scudderi differs considerably from the only other worked out species belonging to this genus--in which, accord- ing to MORGAN,XX-Y complex exists. The two species of Forfuula are, 174 THE JOURNALOF JAPANESE GENETICS, VOL, XIH, Nos. 3-4 therefore, dissimilar in respect of the type of the sex-chromosomes. Forficula scudderi also resembles Labidura riparia in that there is no fluctuation in the chromosomal number, nor any other kind of irregularity in its meiotic divisions.

Literature cited ASANA,J. J. andMAKINO, S. 1934. The idiochromosomesof an earwig,Labidura ritaria. Journ. Morph.,56. CARNOY,J. B. 1885. La cytodierPsechez les Arthropodes.La Cellule,i. HARVEY,E. B. 1916. A reviewof the chromosomenumbers in the Metazoa.Pt. i. Journ.Morph., 28. MORGAN,W. P. 1928. A comparativestudy of the speamatogenesisof five speciesof earwigs. Journ. Morph.,46. SCHRADER,F. 1928. Thesex chromosomes Berlin. St. George,LA VALLTTE 1887. Zeilteilungand Samenbildungbei Forfzculaauricularia. Festschrift fur I{olliker. SUGIYAMA,M. 1933. Behaviorof thesex-chromosomes in the spermatogenesisof Japaneseearwig , Anisolabismargiualis. Journ. Fac. Sci.Tokyo Imp. Univ., Sec . IV, 3.

ハ サ 三 ム シ の 一 種F・ γ愈駕iα5c醐d師 の 染 色 髄 工 一。ピー・ミスラ(A・B・MISRA)

摘 要 札 幌 にて 採 集 せ る ハ サ ミムシ の一 種 乃 吻'磁 ∫砺巌%の 雄 の生 殖 細 胞 に て染 色 膣 を研究 せ る に次 の結 果 を得 た ・自ロち精原 細 胞}こはXYを 含む ・4個の 染 色 膿 が 観 察 せ られ(・一2囲) 細 胞 、第一精母 に は12個 の二 便 染 色瞠 現 は る(3-5圖)。 其 内1個 はX-Y染 色 燈 で あ る。第 二 精 母 細 胞 は何 れ も12個 の 染 色膿 を 含 め ど も、X及Yの 存 在 に よ り2種 に匿 別 さる(6-g圖) 。以 上 よ りして此 の種 に見 られた性 染 色 膿 型 は 既 に 研 究 さ れ た る ハサ ミム シの 数 種 例 へ ば ∠・∂勧駕 吻4痂 , ∠α∂劾〃η∂敏郷,Z;α勉 痂'岬 等 と同様 にX-Y型 な れ ど 、同一 厨 の一 種 乃 吻 蜘 劒 舵 痂 癩(此 の種 に て はXX-Y型)と 異 るは 奇 異 な る事 實 で あ る 。