Cytological Studies in Six Species of Pill-Millipedes (Diplopoda-Myriapoda)

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1 Caryologia International Journal of Cytology, Cytosystematics and Cytogenetics ISSN: (Print) (Online) Journal homepage: Cytological Studies in Six Species of Pill-Millipedes (Diplopoda-Myriapoda) B.N. Chowdaiah & Rani Kanaka To cite this article: B.N. Chowdaiah & Rani Kanaka (1974) Cytological Studies in Six Species of Pill-Millipedes (Diplopoda-Myriapoda), Caryologia, 27:1, 55-64, DOI: / To link to this article: Published online: 30 Jan Submit your article to this journal Article views: 72 Citing articles: 12 View citing articles Full Terms & Conditions of access and use can be found at

2 CYTOLOGICAL STUDIES IN SIX SPECIES OF PILL-MILLIPEDES (DIPLOPODA-MYRIAPODA) B.N. CHOWDAIAH and RANI KANAKA * Department of Zoology, Bangalore University, Bangalore, India INTRODUCTION Received: 4th January 1973 Interest in the studies of diplopod cytology has increased considerably during the recent years. A few important earlier contributions to this field of study include those of OETTINGER (1909), SoKOLOFF (1914), BESSIERE (1948) and a few recent ones include those of NATARAJAN (1959), CHOWDAIAH (1966a, b, c 1967, 1969) and CHOWDAIAH and KANAKA (1969). The present paper reports on the chromosome cytology of six species of South Indian Pill-millipedes investigated for the first time. MATERIALS AND METHODS Adult male specimens of six species of Diplopoda, belonging to the genus Arthrosphaera of the family Sphaerotheridae collected from various parts of South India constituted the material for the present study. They include Arthrosphaera gracilis, Arthrosphaera disticta, Arthrosphaera dalyi, Arthrosphaera craspedota, Arthrosphaera bicolor and Arthrosphaera hendersoni. The testes were dissected out in normal saline and fixed in Allen's modified Bouin's fluid and acetic alcohol (3: 1 ). Pretreatment of the testes with 1% sodium citrate solution for fifteen minutes yielded better results. Acetacarmine and Feulgen squashes were made. Sections of paraffin embeded material were cut at thicknesses varying from 8 j..l. to 12 j..l. and stained in Heidenhain's haematoxylin. Observations were made with a 45 X achromatic objective and a 10 X ocular. Drawings were made at table level with the aid of a Carl Zeiss camera lucida using a 100 X achromatic objective and a 15 X ocular. *Present address: Department of Physiology, St John's Medical College, Bangalore , India. [Caryologia, Vol 27, n. 1, 1974

3 56 CHOWDAIAH and KANAKA OBSERVATIONS The spermatogonial metaphases of both Arthrosphaera gracilis and Arthrosphaera disticta reveal a diploid chromosome number of 28 (Figs. 1, 9); and those of Arthrosphaera craspedota, Arthrosphaera bicolor, Arthrosphaera hendersoni and Arthrosphaera dalyi a diploid chromosome number of 30 (Figs. 18, 27, 34, 41). In each case all the chromosomes appear to be acrocentric and at metaphase are found arranged radially on the equator. A pair of large chromosomes disposed at the periphery is the sex-pair (XY) which is conspicuous and the seriation of the remaining chromosomes is gradual. Even in the late diakinesis the terminalization of chiasmata in the large pair of chromosomes is found to be incomplete as clearly seen in Arthrosphaera gracilis (Fig. 2) and in Arthrosphaera craspedota (Fig. 20). In metaphase I, the bivalents appear either completely spherical as in Arthrosphaera gracilis (Fig. 3 ), Arthrosphaera disticta (Fig. 11 ), Arthrosphaera craspedota (Fig. 21) and Arthrosphaera dalyi (Fig. 43 ); or both dumbbell shaped and spherical as in Arthrospaera bicolor (Figs. 28, 29) and in Arthrosphaera hendersoni (Figs. 35, 36). In all the species investigated, the sex-chromosomes exhibit lagging during the first meiotic division (Figs. 5, 14, 23, 30 37, 46) which is reductional for all the chromosomes (Figs. 6, 15, 24, 31, 38, 47). However, in all the species, the behaviour of the sex-chromosomes is normal during the second meiotic division (Figs. 8, 17, 26, 33, 40, 48) which is equational for all the chromosomes (Figs. 7, 16, 25, 32, 39) In addition, the clumping of first metaphase chromosomes in Arthrosphaera disticta (Fig. 12) and in Arthrosphaera dalyi (Fig. 44) and a regular zygotene ' bouquet ' formation in Arthrosphaera craspedota (Fig. 19) have been observed. DISCUSSION The present knowledge of the Diplopod cytology which is as yet very scanty is concerned mostly with a few species of the Indian subcontinent. This paper is a further contribution to the understanding of the chromosomal cytology of some more species of Indian Diplopoda. The cytological studies of six species of Pill-millipedes presented here reveal some interesting features similar to those described earlier in two other species of Pill-millipedes (CHOWDAIAH 1966c). Thus in keeping with what appears to be common in members of the genus Arthrosphaera, the Pill-millipedes investigated thus far are known for unusual but symmetrical karyotypes. They exhibit the highest diploid chromosome number recorded for the group and all chromosomes are acrocentric in each case.

4 .J;.!, X ~ ~, ' c ' 1 3 ' : 4.. I 2 ',)oxv 0 a ' Figs Meiosis in Arthrosphaera gracilis. Fig Spermatogonial metaphase (2n=28). Fig Late diakinesis; the chiasmata still persist in the large sex-bivalent. Fig Fig Polar view of metaphase I. Polar view of anaphase I. Fig Side view of telophase I, showing the lagging sex-chromosomes. Fig Polar view of metaphase II. Fig Polar view of anaphase II. Fig Side view of telophase II, showing the normal type of segregation.

5 .,.,. y X 9 '., :..,~ -.,,. 10 XY Figs Meiosis in Arthrosphaera disticta. Fig Spermatogonial metaphase (2n=28). Fig A late diakinetic nucleus showing the entire chromosome complement. Fig Polar view of metaphase I. Fig Metaphase I showing the clumping of chromosomes. Fig Fig Polar view of anaphase I. Side view of telophase I. Fig Metaphase II, polar view. Fig Anaphase II, polar view. Fig Side view of telophase II, showing the normal type of segregation.

6 X~,. ee' fll'j t~' ~ -'XY,_,\.., \ ' , 1:. 22 'I 25 ('. ~ 21 v~ Figs Meiosis in Arthrospbaera craspedota. Fig Spermatogonial metaphase (2n=30). Fig Zygotene nucleus, showing the 'bouquet' formation. Fig A late diakinetic nucleus: the chiasmata still persist in the two large bivalents. Fig Polar view of metaphase I. Fig Polar view of anaphase I. Fig Side view of telophase I, showing the lagging sex-chromosomes. Fig Polar view of metaphase II. Fig Polar view of anaphase II. Fig Side view of telophase II, showing the normal type of segregation. 26

7 60 CHOWDAIAH and KANAKA.vtt... ~, X-A e.-.. '...,,, ; \ Figs Meiosis in Arthrosphaera bicolor. Fig Polar view of spermatogonial metaphase (2n=30). Fig Side view of metaphase I, showing the dumb-bell shaped bivalents. Fig Polar view of metaphase I. Fig Side view of telophase I, showing the lagging sex-chromosomes. Fig Polar view of metaphase II. Fig Anaphase II, Polar view. Fig Side view of telophase II, showing the normal type of segregation.

8 . \fx...,.... ~ -'.~ ~,._~..., ~. 34 = , ~ c.~ ~ " ~ " 4j XY ea \ e~ I? ~~ ~~,\ '... ~ Figs Meiosis in Arthrosphaera hendersoni. Fig Spermatogonial metaphase (2n=30). Fig Side view of metaphase I, showing the dumb.bell shaped bivalents: The co-orientation of the X and Y is seen. Fig Metaphase I, polar view. Fig Side view of telophase I, showing the lagging sex-chromosomes. Fig Metaphase II, polar view. Fig Anaphase II, polar view. Fig Side view of telophase II, showing the normal type of segregation.

9 62.,.. X 41 v-,... : \XY e e CHOWDAIAH and KANAKA Figs Meiosis in Arthrosphaera dalyi. Fig Spermatogonial metaphase (2n=30). Fig A diakinetic nucleus showing the entire chromosome complement. Fig Metaphase I, polar view. Fig Metaphase I, showing clumping of chromosomes. Fig Anaphase I, polar view. Fig Side view of telophase I, showing the lagging sex-chromosomes. Fig Metaphase II, polar view. Fig Side view of telophase II, showing l,.e normal type of segregation XV II a- --~ ~ 48 45

10 CYTOLOGICAL STUDIES IN DIPLOPODA-MYRIAPODA 63 However, the chromosomal pairs in the complement fall mainly in to two size classes - large and small. The decrease in chromosome size has probably cased the problem of accomodating the increased number of chromosomes on the spindle as suggested by LEWIS and JoHN (1963 ). As in the case of most other cytologically known species of diplopods, the male pill-millipede is the heterogametic sex and the sex-mechanism is of the XY type. It is characteristic of the sex chromosomes to segregate in the first meiotic division and to divide equationally in the second. Again, the sex-chromosomes, which form the largest pair in the complement are easily recognized by their heteromorphic nature and behaviour during meiotic divisions. The presence of unusually large sized sex chromosomes among the large number of small autosomes is a striking feature in the cytology of Pill-millipedes and furnishes an example of the adaptation of the spindle mechanism. An attempt has been made to correlate the cytological findings with the morphological observations among these Pill-millipedes (KANAKA and CHOWDAIAH 1972). However, intensive cytotaxonomic investigations of a large number of diplopod species are very much warranted before drawing any conclusions as to the phylogeny and evolutionary history of this ancient group. Acknowledgement. - One of us (R.K.) wish to acknowledge the award of a Research Fellowship from the Bangalore University during the tenure of which this work was completed. REFERENCES BESSIERE cl., La spermatogenese de quelques Myriapodes. Arch. Zool. Expt, 85: CHOWDAIAH B. N., 1966a. - Cytological investigations on some Indian Diplopoda (Myriapoda). Nature, 210: , 1966b. - Cytological studies of some Indian Diplopoda (Myriapoda). Cytologia, 31: c. - Chromosome studies in two species of Pill-millipedes (Diplopoda- Myriapoda). Caryologia, 19: , Chromosome studies in Diplopoda (Myriapoda) A note on the abnormal sexchromosome behaviour in the male of Thyropygus sp. Curr. Sci, 36: , A note on the occurrence of chromatid bridges in the male of Arthrosphaera Sp. A Pill-millipede. Curr. Sci, 38: CHOWDAIAH B. N. and KANAKA R., Cytological studies of Indian Diplopoda II (Myriapoda). Bull. Mus. Nat. D'His. Naturelle, (Suppl), 41: KANAKA R. and CHOWDAIAH B. N., Studies on the male reproductive pattern in some Indian Diplopoda (Myriapoda). Proc. II Int. Cong. Myriapodology. Manchester, (in press). LEWIS K. R. and JoHN B., Chromosome Marker. London: Churchill. NATARAJAN R., Cytological studies in Diplopoda (Myriapoda). J. Zool. Soc. India, 11: OETTINGER R., Zur Kenntnis der Spermatogenese bei den Myriapoden. Archiv. fiir Zellfors, 3: SoKOLOFF J., Vber die Spermatogenese bei Polyxenus sp. Zoo!. Anz, 44:

11 64 CHOWDAIAH and KANAKA SUMMARY The chromosome studies in six more species of Indian Pill-millipedes have been made for the first time. The species investigated reveal a highest diploid chromosome number for the group (2n=30) and an XY sex-chromosome mechanism in the male. The sex-bivalent is the largest pair in the complement.