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Proc. Indian Acad. Sci., Vol. 81 B, No. I, 1975. pp. l-6

Chromosomes of son1e Indian tenebrionidae (Insecta : Coleoptera)

J. DASGUPTA

Department of Biology, .lawaharlal Institute of Postgraduate Medical Education and Research, Pondichcrry 605006

MS received 19 June 1974

ABSTRACT

. The diploid chr~mosome number in spermatogonial metaphaE:e, the meiotic cycle, the haploid number with the chromosome. formula and sex chromosome mechanism at primary spermatocyte division have been studied for the first time in five species of tenebrionid beetles, Platy11otus exavatus F., Gonocephalum depressum Fabr., Pachycera arta Hbst., Himatismus fasciculatus Fabr., and Hiperops coromendelensis Sol. The first, second and the last three species belong to the subfamilies Pedininae, Opatrinae and Epitraginae respectively. The Karyotypes are uniformly viewed as 2 n = 20 or n (I st div.) = 10 with sex mechanism Xy,, having the chromosome formula 9AA + Xy)J' Against the background of the previous study the modal chromosome number and the sex mechanism are discussed.

INTRODUCTION

THE family Tenebrionidae comprises a vast number of 10,000 species described morphologically, of which our knowledge of chromosome cytology is confined to 50 species only reported by Stevens (1905), Nonidez (1914, 1915, 1920), Guenin (1949, 1950, 1951 a, 1951 b, 1953, 1956), Smith (1950 a, 19§0b, 1952, 1953, 1960), Dutta (1953), Lewis and John (1957), Takenouchi (1957), Agrwal (1960), Joneja (1960), Kacker (1968).

The present study is on the chromosome complement of five species observed for the first time belonging to three subfamilies Pedininae, Opatrinae and Epitraginae. Two species of each of the subfamilies Pedininae and Opatrinae have been studied by Smith (1953, 1960) but no cytological info~mation of the subfamily Epitraginac has so far been rep0rt.;d.

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2 J. DASGUPTA

MATERIALS AND METHODS

Male specimens were collected from the Institute campus either from the ground or light-trapped during the month of November 1970. The list of species is given below.

Family-Tene brionidae

I. Subfamily-Pedininae : Platynotus exavatus F.

2. Subfamily-Opatrinae : Gonocephalum depressum Fabr.

3. Subfamily-Epitraginae : Pachycera arta Hbst., Himatismus fasci~ culatus Fabr., Hyperops coromandelensis Sol.

Aceto-carmine squash preparations and sections (10-12 microns) of testes were made. Aceto-alcohol (I: 3) was used as fixative and sectioned slides were stained in crystal violet.

1. Subfamily Pedininae

Platynotus exavatus F.

OBSERVATIONS

The diploid chromosome number encountered in large number of spermatogonial metaphase plates (figure I) confirm 2 n = 20, mostly rod­shaped or smoothly bent. The y chromosome could be ascertained by its minute dot-shaped structure taking mostly the peripheral and occasionally the central position. The X, however, could not be recognised due to lack of any differential character.

The diplotene and diakinesis are not very clear.

Primary spermatocyte polar views (figure 2) show 10 round bodies, quite often interconnected with tenuous chromatin threads. In side view (figure 3) the sex bivalent can sometimes be recognised due to its Xyp configuration occupying an accessory plate or eccentric position. The first meiotic division is reductional for the sex chromosomes in beetles and is evidenced by two types of daughter cells in the second division metaphase which in polar view show 9 autosomes plus the dot-shaped minute y chromosome or 9 autosomes plus the X chromosomes. The X, however, cannot be identified.

The Karyotype is 2 n = 20 or n (lst div.)= 10 with sex mechanism Xyp """ making the chromosome formula 9AA + Xyp.

J. Dasgupta Proc. Indian Acad. Sci., Vol. 81 B, Plate I

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FIGS. 1-15 (facing page 2)

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Chromosomes of Some lndian Tenebrionidae (lnsecta: Coieoptera) j

2. Subfamily Opatrinae

Gonocephalum depressum Fabr.

Spermatogonial metaphase plates (figure 4) clearly evince 2 n = 20 chromosomes with an average of 8 acutely or smoothly bent, IO rod-shaped and the rest two as dots. It is interesting to note that in all the metaphase plates the dot chromosomes are conspicuously clear, situated independently without any fixed position, one of which only is suggestive of Y chromosome. The X chromosome could not be identified from autosomes.

Diplotene and diakinesis show 10 elements mostly with one chiasma per bivalent with usual configurations of cross, open cross, rod and at least one ring formed due to terminalised pricentric chiasmata. The sex bivalent shows Xyp association and there is no other dot-chromosome whatsoever. This configuration does not explain the two chromatin dots seemingly Y chromosomes at mitotic metaphase stage.

Metaphase first division polar views (figure 5) clearly exhibit 10 round bodies. In side view of the spindle (figure 6) the Xyp sex bivalent is clear and mostly shows an advance movement to the autosomal group.

The Karyotype is viewed as 2 n = 20 or n (1st div.)= 10 with sex mecha­nism Xyp and the chromosome formula 9AA + Xyp.

3. Subfamily Epitraginae

Pachycera arta Hbst. and Hinzatismus fasciculatus Fabr.

Chromosome numerals and the details of the divisional stages of both the species P. art a and H. fasciculatus are identical. Spermatogonial meta­phase plates (figures 7, 10) show 2 n = 20 chromosomes.

The diplotene and diakinesis are with 10 bivalents having usual con­figurations and at least one ring; the sex bivalent forms the typical • parachute ' Xyp configuration.

Metaphase first division polar views (figures 8, 11) clearly show 10 well defind round bodies of graded size. Only in side views (figures 9, 12) at this stage the Xyp could be detected showing precocious movement from the autosomal mass.

The Karyotype in both the cases are 2 n = 20 or n (1st div.) = 10 with sex mechanism of Xyp and chromosome formula 9AA + Xyp.

Hyperops coromendelensis Sol.

The spermatogonial metaphase plates (figure 13) are abundant showing uniformly 20 chromosomes with graded size difference having 10 metacentric/

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4 .. J. DASGUPTA

submetaccntric, smoothly or acutely bent and 8 rod-shaped autosomes. Of the s•:::x chromosomes Y is always conspicuous _by its minute size and dot­shape. It is randomly placed in the metaphase plate. The X chromosome is probably a large chromosome and presumably can be singled out by its non-homologous nature.

The diplotene and diakinesis are clear and of the same type as in the preceding species but with a brushy outline and the bivalents are often inter­connected by tenuous chromatin threads.

Metaphase first division polar view (figure 14) clearly shows 10 bivalents which also may be interconnected by meterochromatic threads. In side view (Fig. 15) the sex bivalent is in the usual Xyp configuration and occupies an accessory position in the spindle.

The second division metaphase stage could not be well scored.

The Karyotype is 2 n = 20 or n (1st div.) = 10 with sex mechanism Xyp and chromosome formula 9AA + Xyp.

DISCUSSION

Tenebrionidae is highly polymorphous where the diploid number of chromosomes range from 14 to 37 having all numerals except 15, 17, 21-25, 27-33 which will also presumably be encountered on further investigation of the family. But a very high frequency of 2 n = 20 is suggestive of the type number.

As regards the sex mechanism, most of the Coleopteran varieties, e.g, Xyp, Xyr, neo-XY, XY, Xy, XO, XXXY are encountered in which the Xyp is mostly prevalent. Thus the variant chromosome numerals and sex bivalents show the most basic Karyotype as 9AA + Xyp, the archaic protocoleop­terous forms of the Triassic (Smith 1959). This suggests that extensive structural rearrangement of archaic forms resulted in establishing hypo and hypermodal numbers and the varied sex mechanism in the recent species.

In Pedininae only three species, Opatrinus aciculatus (Smith 1952 b), Blapstinus. sp. (Smith 1960) and the present one have been noted where in alLcases the diploid number 2 n=20 and the sex mechanism Xyp are uniformly existent.

Besides the present species, our knowledge of Opatrinae is limited to Opatroides vicinus (Dutta 1953), Opatrum bilineatum (Kacker 1968). The Karyotype is similar to Pedininae except in 0 vicinus where Xy sex bivalent does not assume a parachute-like association.

~. Phylogu1ctica1Iy Pedininac is supposed to be archaic to Opatrinac (Leng 1920} though the two ~pecies P. exai'atus and G. depress um, each representative

Chromosomes of Some Indian Tenebrionidae (Jnsecta: Cok:optera) · 5

of the two subfamilies in the present study, do not show any cytological difference.

The subfamily Epitraginae is explored cytologically for the first time here where the three species studied show modal Karyotype of Tenebrionidae.

The diploid and haploid numbers with chromosome formula of the five species summarised below concord with the model diploid number and typical sex mechanism.

Summary of cytological determinations in five Tenebrionid species.

Chromosome Species 9 (Q") 2 n number formula

Family-Tenebrionidae Subfamily-Pedininae

Platynotus exavatus F.

Subfamily-Opatrinae Gonocephalum depressum Fabr.

Subfarnily-Epitraginae Pachycera arta Hbst

Himatismus fasciculatus Fabr.

Hyperops coromendelensis Sol.

ACKNOWLEDGEMENT

20

20

20

20

20

(1st div.)

9AA+Xy

9AA+-Xv J • p

9AA+Xy11

9AA-LXv J .,,, p

The author is thankful to Dr. A. P. Kapur, for identification of the material. Thanks are due to Miss Arnita Chakravarti for technical assistance and to the staff of the Medical Illustration Division JIPMER, for the micro­photographs.

REFERENCES

Agrawal, U., Chromosome number and sex determining mechanism in 16 species of Indian Coleoptera. Curr. Sci. 29 140 (1960).

Dutta, M. K., Chromosome of Opatrinus vicinus Farim. (Coleoptera: Tenebrionidae). Curr. Sci. 22 278 (1953).

Guenin, H. A., L'evolution de la formule chromosomique dans le genre Blaps (Coleopt. : Tenebr.) Rev. Suisse Zoo!. 56 336 (1949).

Guenin, H. A., Chromosome et heterochromosomes de tenebrionides. Genetica 25 157-182 (1950).

OTJenin, H. A., La formule chromosomiale de Coleopteres tenebrionides; nord afd~1u1s;

!. Pim;limes et TentyrHnes. Bull. Soc. Vm1dofs~ Sci, Nmur. 6~ 7 .. )s 0951 fl).

6 J. DASGUPTA

Guenin, H. A., La formule chromosomiale de Coleopteres tenebrionides nord afrioons II. Brodiines. Rev. Suisse Zoo/. 58 471-475 (1951 b).

Guenin, H. A., Les chromosomes sexuels multiples du Blaps polychresta Forsk. (Col. Tenebr .), Rev. Suisse Zool. 69 462-466 (1953).

Guenin, H. A., Le complexe heterochromosomique du Caenoblaps nitida Schast (Col. Tenebr. Blaptinae). Rev. Suisse. Zoo!. 63 298-303 (1956).

Joneja, M. G., Chromosome number and sex-determining mechanism in twenty-five specie! of Indian Coleoptera. Res. Bull. Punjab Univ. Sci., (N.S.) JJ 249-251 (1960).

Kacker, R. K., Studies on the chromosomes of Indian Coleoptera. 3. Chromosome comple" ment and spermatogenesis in two species of b~etles of the family Tenebrionidae. Proc. Zoo/. Soc. Calcutta 21 29-34 (1968).

Leng, C. W., Catalogue of the Co/eoptera of America, North of Mexico. John D. Sherman, Jr., Mount Vernon, N.Y., U.S.A., 1920.

Lewis, K. R. and John, The organisation and evolution of the sex multiple in Blaps mucronata. Chromosoma 9 69-80 (1957).

Nonidez, J. F., Los cromosomas en la espermatogenesis del "Blaps lusitaxica" Herbst. Trab. Del. Mus. De. C. Nat. De. Madrid. Ser. Zoo/. 18 5-97 (1914).

Nonidez, J. F., Estudios sobre Jas celulas sexuales. I. Los cromosomas goniales y las mitosis de maduracion en B/aps lusitanica y B. waltli. Mem. R. Soc. Esp. His. Nat. 10 149-190 (1915).

Nonidez, J. F., The meiotic phenomena in the spermatogenes1s of Blaps, with special reference to the X-Complex. J. Morphol. 34 69-117 (1920).

Smith, S. G., Evolutionary changes in the sex chromosomes of Coleoptera. IL Flour beetles of the Genus Tribolium. Genetics 35 693 (1950 a).

Smith, S. G., The cyto-taxonomy of Coleoptera. Can. Entomol. 82 58-68 (1950 b).

Smith, S. G., Cytology of some tenebrionid beetles (Coleoptera), J. Morphol. 91 325-363 (1952).

Smith, S. G., Chromosome numbers of Coleoptera. Heredity 7 31-48 (1953).

Smith, S. G., The cytogenetic basis of speciation in Coleoptera. Proc. !11t. Congr. Genet. 10th Meeting, Montreal .• Que. 1 444-450 (19:'9).

Smith, S. G., Chromosome numbers of Coleoptera. II. Can. J. Genet. Cytol. 2 66-88 (1960).

Stevens, N. M., Studies in spermatogenesis, with special reference to the accessory chromosome. Carneg. Inst. Wash., 1905, Carneg. Inst. Publ. No. 36, pt. 1 3-32.

Takenouchi, Y ., The chromosomes of three species oftenebrionid beeltles. J. Fae. Sci. Hokkaido Univ. Ser. 6 Zoo!. 13 315 -319 (1957).

EXPLANATION OF PLATE I

Fig11res 1-3. Meiotic stages in Platynotus exavatus. (1) Spermatogonial metaphase · (2) Primary spermatocyte (Polar view); (3) Primary spermatocyte (Side view). '

Figures 4-6. Meiotic stages in Gonocephalum depressum. (4) Spermatogonial metaphase (5) Primary spermatocyte (Polar view); (6) Primary spermatocyte (Side view).

Figures 7-9. Meiotic stages in P achycera arta. (7) Spermatogonial metaphase · (8) Primary spermatocyte (Polar view); (9) Primary spermatocyte (Side view). '

Figures 10-12. Meiotic stages in Himatismus fasciculatus (10) Spermatogonial meta­phase; (11) Primary spermatocyte (Polar view); (12) Primary spermatocyte (Side view).

Flg11res 13-15. Meiotic stages in Hyperops coromendelensis. (13) Spermatogon ia1 meta· pt\~se; (14) PtiQ\arr s~ertl\atocyte. (Pol~r view); (15) Pri~arr sper~atocyte (Side view).